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Research and development of herbaceous perennials as new potted plants for commercial floriculture :… Roberts, Christia M. 1995

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RESEARCH AND DEVELOPMENT OF HERBACEOUS PERENNIALS AS NEW POTTED PLANTS FOR COMMERCIAL FLORICULTURE: CASE STUDIES WITH LEWISIA SEED BIOLOGY AND DICENTRA POSTPRODUCTION PERFORMANCE by CHRISTIA M. ROBERTS B. Sc. (Agr.) (Hons.), The University of British Columbia, Canada, 1992 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Plant Science) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 1995 © ChristiaM. Roberts, 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada Date g3.fr "D-gC-g-wyW^ H ^ g T DE-6 (2/88) ABSTRACT Commercial development of new flowering potted plants is stimulated by overproduction of major crops worldwide and consumer demand for new products. The process of product development was critically examined and the role of modern plant biology research in the development process was investigated using new, non-commercial plant genera for case studies in seed biology and postproduction longevity. This examination included a review of the history of ornamental plant cultivation and the scientific literature, and observation of projects in a major, international floriculture production centre. Development work was most often undertaken by private, international breeders and propagators of new crop cultivars. Some private producers conducted their own breeding programs and successfully introduced new products. Product development consultants and discipline-oriented scientists had a significant role in development work. Crucial components of the process included identification of a plant species with potential in floriculture, active involvement of flower producers, confidentiality and product promotion. One case study investigated the mechanism of seed dormancy, and seed treatments were tested to improve germination of Lewisia tweedyi and Lewisia cotyledon. These two lewisia species were found to have dramatically different percent:; and rates of germination under axenic conditions and in laboratory experiments. Decoating increased germination from 0 to 87% in L. tweedyi which suggests that the seed coat imposes dormancy in this species. The role of the coat in seed dormancy was supported by measurements of seed coats in transverse section under a scanning electron microscope. The L. t\v eedyi seed coat was found to be 22% thicker than the L. cotyledon coat. Scarification of seeds with liquid nitrogen, infusing gibberellic acid, and an 8 or 12-week stratification improved germination in both ii species. Another case study determined the display life of potted plants of Dicentra eximia, Dicentra formosa, and Dicentra spectabilis. More flowers opensd in a simulated interior environment room if the plants were treated before harvest with an anionic silver thiosulfate complex. This increase in flower number resulted in a 75% increase in the display life of D. eximia (to 14 days) and a 65% increase in the display life of D. formosa (to 28 days). A similar effect was achieved by producing the plants under supplemental irradiance which also increased plant height and decreased production time. Height of D. spectabilis could be controlled by the application of daminozide which had no effect on forcing time, flower number or display life of the plants. in T A B L E OF CONTENTS Page ABSTRACT ii LIST OF TABLES v LIST OF FIGURES vi ACKNOWLEDGEMENTS vii FORWARD viii 1.0 INTRODUCTION TO PRODUCT DEVELOPMENT IN FLORICULTURE 1 2.0 RESEARCH AND DEVELOPMENT OF NEW FLOWERING POTTED PLANTS 6 2.1 Origins of ornamental plant products 6 2.2 Sources of new potted plants 9 2.3 International centres of product development 10 2.4 Scientific investigations in plant biology 15 2.4.1 Plant search 15 2.3.2 Plant breeding and propagation 16 2.3.3 Growth control 17 2.3.4 Postproduction performance 18 2.5 Development of commercial products 19 2.5.1 Systematic methods in public development 19 2.5.2 Stages in private development 20 3.0 CASE STUDY: INVESTIGATION OF SEED COAT-IMPOSED DORMANCY AND SEED TREATMENTS TO IMPROVE GERMINATION IN LEWISIA SPECIES GROWN AS FLOWERING POTTED PLANTS 23 3.1 Abstract 23 3.2 Introduction 24 3.3 Material and Methods 27 3.4 Results 31 3.5 Discussion 37 4.0 CASE STUDY: APPLICATION OF SILVER THIOSULFATE AND SUPPLEMENTAL IRRADIANCE TO IMPROVE THE DISPLAY LIFE OF DICENTRA SPECIES FORCED AS FLOWERING POTTED PLANTS . . . 41 4.1 Abstract 41 4.2 Introduction . . . . 42 4.3 Material and Methods 43 4.4 Results 45 4.5 Discussion 52 5.0 SUMMARY AND CONCLUSIONS 55 6.0 REFERENCES 57 iv LIST OF TABLES Page 2.1 Potted plant taxa in commercial production with representative floriculture crops. . 8 2.2 Commercial potted plants rank in sales value in British Columbia, Denmark, and Holland 13 3.1 Percent germination and mean time to germination in Lewisia cotyledon, Lewisia tweedyi, Lewisia tweedyi 'Alba', Lewisia tweedyi 'Rosea', and Lewisia tweedyi 'Elliot's Variety' after 32 weeks under axenic conditions. Seeds were evaluated in a growth room at constant 19°C with a 16-hr photoperiod or after a 4-wk chilling at 4°C in the dark before transfer to the growth room 32 3.2 Percent germination and mean time to germination in Lewisia tweedyi and Lewisia cotyledon after 10 weeks in a growth cabinet at IS ± 2°C with a 16-hr photoperiod 33 3.3 Percent germination in Lewisia tweedyi and Lewisia cotyledon scarified in liquid nitrogen (LN2) or non-scarified control, and soaked for 24 hours in 0, 1.0 or 10.0 mM gibberellic acid (GA3) in acetone after pre-chilling at 3 ± 0.5°C for 0, 2, 4, 8 or 12 weeks. Seeds were evaluated over 10 weeks at 18 ± 2°C with a 16-hr photoperiod 34 3.4 Mean weeks to germination in Lewisia tweedyi and Lewisia cotyledon scarified in liquid nitrogen (LN2) or non-scarified control, and soaked for 24 hours in 0, 1.0 or 10.0 mM gibberellic acid (GA3) in acetone after pre-chilling at 3 ± 0.5°C for 0, 2, 4, 8 or 12 weeks. Seeds were evaluated over 10 weeks at 18 ± 2°C with a 16-hr photoperiod 35 4.1 Effects of natural irradiance or natural 8 to 10-hr photoperiod supplemented with 50 umol m"2 s"1 of artificial light on Dicentra eximia and Dicentra formosa 'Bachanal' mean plant height at harvest and duration of forcing at 10.3°C mean temperature 46 4.2 Effects of daminozide on Dicentra spectabilis mean plant height at harvest and duration of forcing at 10.3°C mean temperature under natural irradiance. . . 53 v LIST OF FIGURES Page 3.1 Scanning electron micrographs of lewisia seed, (a) Lewisia tweedyi seed. Scale bar = 1 mm. (b) L. tweedyi arilloid seed appendage and seed coat surface. Scale bar = 200 um. (c) Lewisia cotyledon seed. Scale bar = 1 mm. (d) L. cotyledon hilar region and seed coat surface. Scale bar =100 um 26 3.2 Close up of Lewisia tweedyi seed coat surface scarified by (a) a 15 minute immersion in liquid nitrogen or (b) non-treated control. Scale bars =10 um. . . 29 3.3 Number of weeks to germination after moist pre-chilling at 3 ± 0.5°C for 0, 2, 4, or 8 weeks in Lewisia cotyledon and 0, 2, 4, 8, or 12 weeks in Lewisia tweedyi. Seeds were evaluated over 10 weeks at 18 ± 2°C with a 16-hr photoperiod 36 3.4 Centrospermae seed structure and seed coat thickness in lewisia. (a) Lewisia tweedyi transverse section showing peripheral embryo and centrally-located perisperm. (b) Close up of L. tweedyi seed coat showing diameter (arrows) of 73 um. (c) Lewisia cotyledon transverse section, (d) Close up of L. cotyledon seed coat showing diameter (arrows) of 57 um. Scale bars of whole sections = 1 mm; scale bars of coat diameters = 100 um 38 4.1 Number of open flowers per plant in Dicentra eximia after greenhouse forcing under natural irradiance (NI) or natural 8 to 10-hr photoperiod supplemented with 50 umol m"2s_1 of artificial light (HPS) at 10.3°C mean temperature 47 4.2 Whole-plant display life of greenhouse-forced Dicentra eximia, Dicentra formosa 'Bachanal', and Dicentra spectabilis treated with 0.1 or 1.0 mM silver thiosulfate (STS) or non-treated control 48 4.3 Number of open flowers per plant in Dicentra eximia (a), Dicentra formosa 'Bachanal' (b), and Dicentra spectabilis (c) treated with 0.1 or 1.0 mM silver thiosulfate (STS) or non-treated control 49 vi A C K N O W L E D G E M E N T S Each member of my graduate committee has supported and encouraged my interest in floriculture while sharing their expertise and providing guidance for this work. I thank Dr. Gerald B . Straley for sharing his knowledge and love of ornamental plants with me, and for always being generous with his time. Mr . George Ravenek has advised me regarding commercial floriculture standards and facilitated collaborative projects with flower growers. I appreciate his serving as industrial supervisor for the United Flower Growers Co-op Association, sponsors of my Science Council of British Columbia G .R .E .A .T . Scholarship. I thank Dr. F. Brian H o l l for keeping my interests in floriculture in the forefront while ensuring that I met University requirements and standards. Faculty members, staff, and students in the Department of Plant Science have offered assistance and encouragement. Dr. George W. Eaton helped with statistical analysis and has been a stimulating instructor of horticulture and experimental design. I first considered undertaking a Master of Science degree program following the recommendation of Dr. Brian E. Ell is . I appreciate his encouragement. The trust and hospitality of growers and scientists at international development institutes, particularly in Denmark, have allowed me a unique opportunity to observe and participate with leaders in product development. Dr. Arne Skytt Andersen supervised my work at The Royal Veterinary and Agricultural University in Copenhagen and promoted collaborative research with Dr. Margrethe Serek at the K V L Horticulture Section, Dr. Linda Noack at Team Grow-how, and Dr. Kirsten Brandt at the Research Centre for Horticulture. Drs. Andersen and Noack, Henny Andersen, and Dorte K . Rhode Nissen introduced me to many accomplished Danish greenhouse growers. I am grateful to each one of these individuals for sharing their laboratories, their time and answering my questions. The love and respect extended by my family has provided me with an opportunity to pursue an education as an adult. During these years, my husband, Hans Wyngaarden, and sons, Sam and Duff Roberts, have joked about never knowing what country I would be visiting on any one day. Meanwhile, Hans has made an exquisite copper lantern, among other things, and become a gourmet cook; Sam earned a degree in Engineering-Physics; and, Duffy stopped by regularly to rescue my garden and transplant another shrub. Thank you. vu FORWARD A portion of the material presented in section 4 of this thesis describing the postproduction performance of Dicentra has been published as "Supplemental irradiance and STS improve the display life of Dicentra species forced as flowering potted plants" by Christia M. Roberts, Margrethe Serek, and Arne Skytt Andersen in Scientia Horticulturae 62:121-128 (1995). The senior author initiated the investigation and wrote the manuscript for journal submission. Al l work was performed under the direction of Drs. Serek and Andersen in the greenhouse and simulated interior environment facilities at The Royal Veterinary and Agricultural University, Copenhagen, Denmark. Christia M. Roberts Dr. Margrethe Serek Dr. Arne Skytt Andersen viii 1.0 INTRODUCTION TO PRODUCT DEVELOPMENT IN FLORICULTURE Floriculture is a highly-competitive, international industry that produces a variety of high quality plant products. Worldwide sales exceed US$16 billion (Can$22 billion) annually at farmgate with more than 189,000 hectares in production (HPP, 1994). Among the various horticulture industries, greenhouse floriculture is characterized by highly controlled environments using mechanization, computer control, advanced plant cultural techniques, and sophisticated marketing and distribution systems for the highly perishable floral products. Production and distribution infrastructures are capital intensive. Investment in them is justified only by year-round production and sale of high-quality plant products. Product development is an inclusive term used to describe the initial concept and subsequent activities leading to the introduction of new commercial products. More specifically, product development in floriculture refers to the biological research and promotion required to introduce new products to commercial greenhouse production. Aspects of research in plant biology would typically include the search for new ornamental plant genera and species with commercial potential, plant breeding, investigation of propagation methods, determination of cues promoting floral induction, optimization of cultural requirements, and evaluation of postharvest performance. The plant search, assessment, and improvement may be conducted and financed by individual greenhouse growers, who are generally assisted by consultants and scientists on contract, by private or public interdisciplinary teams, or as joint ventures between large-scale organizations. Ornamental Plant Species in Cultivation There are approximately 350 families of flowering plants in the world representing about 250,000 flowering species (Stebbins, 1974). Ninety percent of all flowering plants 1 cultivated in temperate areas are found in fewer than 50 of these families. While hundreds of ornamental plants are grown as minor floriculture crops, only a few species represent most of the commercial turnover at auctions. For example, 150 cut flower crops are sold at Bloemenveiling Aalsmeer, the Dutch Flower Auction, but 80% of the total turnover is based on only eight; forty percent is represented by rose and chrysanthemum (Noordegraaf, 1993). These major commercial plants have been improved by decades of intensive research. Their development is ongoing as new cultivars are released, and plant culture is optimized. However, market saturation has led to highly competitive prices for industrial-scale floriculture crops (Griffin, 1995). One possible response to this competition is to develop "new plants" as high value crops. Interest in extending the range of plant species commercially available is driven by consumer demand for new products resulting in favourable returns to growers. Product development has been successful with both industrial-scale crops and smaller-scale specialty products. There are many examples of successful new flowering potted plants. A few recently introduced products include: Rosa mini-hybrids, currently leading potted plant sales in Denmark; potted A nigozanthos, the kangaroo paw, from Australia which has become widely available in florist shops; and Osteospermum ecklonis hybrids, predicted to capture the market of the familiar marguerite daisy, Argyranthemum frutescens. Herbaceous Perennials as New Potted Plants Consumer interest in herbaceous perennial plants has increased dramatically in Europe and North America over the last decade. In response, innovative members of the greenhouse industry have begun to propagate, produce and market perennials as specialty cut flowers, bedding plants, and as potted plants. Enterprising flower producers are growing perennials 2 in the greenhouse as potted plants (Asternovi-belgii), or forcing perennials in the greenhouse (Campanula carpatica) after vernalization in the field. Some are growing hardy perennials, including Saxifraga and A ubrieta, in the field for their entire production cycle. Standard floriculture practices, including environmental control and cultural techniques to control weeds and to fertigate pots, are employed in their production. These practices, along with associated marketing systems that facilitate rapid selling of plants, result in high quality potted perennials: crops are uniform, foliage covers the pot rim, and flowers cover the foliage. International floriculture breeders and propagators are beginning to enter the perennial market making select cultivars of perennial plants more widely available for potential introduction by greenhouse flower growers. For example, Benary Seeds introduced Campanula carpatica 'Dark Blue Clips' and C. carpatica 'Light Blue Clips' in 1995, and Goldsmith Seeds is presently selecting columbine (Aquilegia vulgaris) with no requirement for vernalization. Yoder Brothers, Inc., a major breeder and propagator of potted and cut chrysanthemum (Dendranthema xgrandiflorum) based in the United States, has entered into a joint venture with a major perennial breeder in the United Kingdom, Blooms of Bressingham. Yoder will propagate and distribute cuttings of Eilooms' cultivars to North American greenhouse growers. The Floriculture Industry in British Columbia The British Columbia floriculture industry is highly regarded in North America for the quality and variety of plant products, as well as for advanced greenhouse technology. Annual flower sales between $85 (BCMAFF Annual Report, 1994) and $140 million (Minister of Industry, 1995), 92 hectares of greenhouses, and 4,300 employees were reported by Statistics Canada and the British Columbia Ministry of Agriculture, Fisheries and Food. These figures 3 represent only the actual farmgate value and employment levels which are estimated to double or triple when associated merchandising sectors are considered. Although these British Columbia floriculture statistics are impressive, there are some incentives for innovation in the industry. Overall growth has slowed from 12% per annum in the 1980's to the current rate of 5%. Export sales are reported by Statistics Canada at 4.4% of total flower sales value (Minister of Industry, 1995). In contrast, Denmark exports 92% of their potted plants. Their export figure reflects the leading position of the Danish floriculture industry in potted plant quality and in product research and development. Achievements of the British Columbia industry have been based, in large part, on plant biology research and engineering technology imported from Europe. This strategy proved very effective to bootstrap a developing industry. British Columbia growers have benefitted from international work funded by very large-scale floriculture centres, even though crops and production technologies needed to be adapted to the local climate and markets. The dramatic contrast in scale between The Netherlands with more than 7000 hectares under glass versus approximately 100 hectares in British Columbia provides an example of their relative potential for research. Potted plants introduced in British Columbia are most often developed in European floriculture centres; there is little history of local development of new products. This reliance on imported plant products and greenhouse technology forces the British Columbia floriculture industry to follow the European leaders, unnecessarily in some cases. For example, while the British Columbia industry may not have the resources to compete with international companies on long-range breeding efforts for new cultivars of industrial-scale flower crops, local flower growers and scientists may be able to work together to 4 develop and introduce some perennial plants in great demand in the Pacific Northwest. Research Objectives It is with an appreciation of the extent and integration of expertise required for the successful introduction of new potted plants, that this thesis focuses on certain disciplines in applied biology research which are important components of product development. Plant product development is typically interdisciplinary in the broadest sense. Teams of discipline-oriented scientists, such as plant breeders and physiologists, collaborate with product development consultants who coordinate projects and promote new plants. These scientists and consultants liaise with growers who must evaluate the economic costs of each project, contribute to solving cultural problems, and assess the market potential for each new product. The objectives of this research were: 1) To examine the process of research and development of new potted plants in international floriculture centres; 2) To investigate seed dormancy and seed treatments to improve germination in Lewisia tweedyi and L. cotyledon; and, 3) To determine the effects of supplemental irradiance, silver thiosulfate and daminozide on the postproduction performance of Dicentra formosa, D. eximia and D. spectabilis. Information derived from these experiments with Dicentra and Lewisia is required to proceed with the commercial development of each species. In a broader sense, familiarity with the process of product development may facilitate local research and development of new flowering potted plants. Consumers are interested in herbaceous perennial plants. There are skilled local producers, and expertise in applied plant biology at local universities. The Provincial government has demonstrated support for innovative, collaborative floriculture projects. Al l these factors may indicate increasing opportunities for the development of herbaceous perennials as new potted plants in British Columbia. 5 2.0 RESEARCH AND DEVELOPMENT OF NEW FLOWERING POTTED PLANTS 2.1 Origins of ornamental plant products Domestication of food plants began 10,000 years ago, long before the cultivation of ornamental plants (Evans, 1993; Smith, 1995). Cereal grains were the earliest agricultural crops followed by legumes and root crops, vegetables, and fruits. Cultivation of plants for forage, ornament and as drug sources began only in the last 4,000 (Darlington, 1973) to 2,000 years (Hancock, 1992). It has been generally assumed that a surplus of food was required before societies or individuals allocated time and resources to the cultivation of ornamentals. Despite the relatively late emergence of cultivated ornamental plants in human history, flowering plants have become very important for display and in commerce. How and why wild ornamental species have been taken into cultivation describes the history of product development in floriculture. The lore of the great plant hunters and the images of the great glass conservatories are part of our gardening heritage. Trade in ornamental plants and development of production greenhouses have been continuous from their beginnings in western Europe until the present-day, worldwide floriculture industry. Domestication and selection of plants Selection of domesticated crops over the millennia has affected their genetic makeup. Harlan (1992) suggests that automatic selection, the unintentional improvement of plants, was routinely practiced during early domestication of crop plants. For example, seed dormancy and non-synchronous flowering are associated with wild plants, and rapid germination and synchronous flowering with domestication. Automatic selection continues to improve the germination of ornamental species in cultivation, as cultivation genetically modifies the morphology, as well as the physiology of flowering plants (Stebbins, 1974). Systematic 6 selection, the conscious practice of domesticating wild plants and improving specific traits, began only 200 years ago in a few technically advanced countries (Hancock, 1992). China: Development from wild ornamental plants to cultivated ornamental plants Gardening has a 2,000 year history in China where it was most highly developed in the 11th Century of the Sung dynasty (Gorer, 1970). Ornamental plants introduced to Europe in the 16th through the 19th Centuries include peony (Paeonia lactiflord), chrysanthemum (Dendranthema indicum and D. morifolium), azalea {Rhododendron simsii), rose (Rosa chinensis), and primula (Primula sinensis), as well as, the annual China aster (Callistephus chinensis) and China pink (Dianthus chinensis). Cultivars and hybrids of these species have become important, contemporary floriculture crops. Holland: Development from cultivated ornamental plants to commercial plant products Selected forms of local wild flowers, particularly bulbous plants, in the Middle East and Turkey were another early source of cultivated ornamental plants. The tulip was introduced to western Europe in 1578, and many named cultivars of hyacinth (Hyacinthus orientalis) were listed by 1768 (Darlington, 1973). These plants were highly developed in The Netherlands and formed the basis of the Dutch floriculture industry. Although China and the Middle East were early centres of cultivation, the origins of modern flower crops are now geographically diverse (Klougart, 1987) and represented by diverse plant families (Table 2.1). This history describes new relationships between human societies and the plants they domesticated (Smith, 1995). It points to some essential components of the process of product development: breeding, cultivation and marketing ornamental plant products. The process has become greatly accelerated in the modern world by the application of techniques in plant biology and by commercial opportunities in the marketplace. 7 Table 2.1. Potted plant taxa in commercial production with representative floriculture crops. Compiled from Danish Potted Plants (Anonymous, 1994); and Plants from British Columbia, Canada (United Flower Growers, 1994) catalogues. Family Cultivated genera Floriculture Crops Acanthaceae 11 Aphelandra squamosa; Beloperone guttata; Crossandra infundibuliformis Araceae 11 Anthurium hybrids; Spathiphyllum wallisii; Zantedeschia species Asteraceae 9 Aster novi-belgii; Dendranthema xgrandiflorum; Gerbera hybrids; Osteospermum ecklonis Begoniaceae 1 Begonia xhiemalis hybrids Bromeliaceae 6 Aechmea fasciata; Guzmania dissitiflora Cactaceae 5 Rhipsalidopsis hybrids; Schlumbergera hybrids Campanulaceae 2 Campanula carpatica; Platycodon grandiflorus Crassulaceae 7 Crassula coccinea; Kalanchoe blossfeldiana Ericaceae 3 Erica gracilis; Rhododendron simsii Euphorbiaceae 3 Acalypha hispida; Euphorbia pulcherrima Gentianaceae 2 Exacum affine; Eustoma grandiflorum Gesneriaceae 9 Achimenes hybrids; Aeschyanthus hybrids; Saintpaulia ionantha; Sinningia hybrids Liliaceae 5 Lilium longiflorum; Hyacinthus orientalis Malvaceae 3 Abutilon hybrids; Hibiscus rosa-sinensis Orchidaceae 3 Dendrobium; Paphiopedilum;md Phalaenopsis hybrids Primulaceae 2 Cyclamen persicum; Primula vulgaris Rosaceae 1 Rosa mini-hybrids Rubiaceae 6 Gardenia jasminoides; Ixora hybrids Scrophulariaceae 2 Calceolaria hybrids; Hebe hybrids Solanaceae 4 Capsicum annuum; Solanum pseudocapsicum 8 2.2 Sources of new potted plants Product development begins with the identification of a potential, new plant product. Sources of new ornamental plants in modern floriculture include new cultivars, new discoveries and forgotten plants. However, most often "new" refers to a new cultivar of a major flower crop. One hundred products featured in the New Flower and Plant Showcase of the trade journal FloraCulture International (Layton, 1995) were new cultivars of industrial-scale products. A yellow Miltoniopsis orchid for potted culture (Floricultura BV, The Netherlands) and a dwarf petunia 'Pink Morn' (Goldsmith Seeds, United States) were exceptions. There are commercial incentives for improving major flowering plants which are in demand with both flower producers and flower buyers. Propagules of the new cultivar are made available to producers along with complete cultural recommendations, as well as promotional materials. This type of development work is generally confidential within private floriculture companies (Mikkelsen, 1987). Major breeders and propagators of industrial-scale floriculture crops have extensive resources to improve product quality. However, their dominance also limits the selection of flowering plant species in commerce, and exacerbates overproduction. New cultivars are introduced on a regular basis, but introduction of a new species or genus is far less common (Suda, 1987). Development of new cultivars represents the incremental improvement of existing successful products. Another technique is to take a plant which is not currently a product and make it one. Enterprising members of the floriculture industry have investigated other sources of new potted plants. These sources include crops which may be new to the local industry, new from the garden, new from nature, or have new value added (Armitage, 1987; 9 Klougart, 1987; Andersen, 1989). The degree of difficulty in development of a commercial plant product is partly related to the source of the new plant. Transfer of propagules with cultural instructions from an international developer to a local producer is relatively easy, while development of wild ornamental species as new potted plants is far more challenging. A new species or genus typically requires at least five to eight years for development and commercialization even by a large, interdisciplinary team. 2.3 International centres of product development Development of new flowering plants for commercial production is characteristic of many leading international greenhouse centres. These industries are motivated to supply new plant products that satisfy the changing quality standards of the marketplace and challenge increasing foreign competition. Since proactive projects have proven to be a source of industry success, there is a well-established tradition for collaborative plant research and development by the producers and the scientific community. Keynote speakers at recent Symposia have represented international centres active in product development. The speakers at the New Ornamental Crops and Market for Floriculture Products section of the XXIVth International Horticulture Conference held in Japan in August, 1994, were: W. -U von Hentig, New ornamental crops in Europe; R. B. Jones, New ornamental crops in Australia; Min-Chang Huang, New ornamental crops in Asia; R. H. Lawson and M. S. Roh, New crops development in the USA; and P. J. Jansen van Vuuren, New ornamental crops in South Africa. Each of these centres has characteristic foci and strengths which are supported by their research and development groups. Australia, for example, is known for development of its unique flora (Considine, 1993). Geraldton wax (Chamelaucium uncinatum) has been exported 10 in large volumes as a filler in flower arrangements since the early 1980's. Christmas wax (Chcanelaucium uncinatum x C. floriferum) is currently being developed for potted culture. New, dwarf selections of kangaroo paw (Anigozanthos) are reported to flower in 16 to 18 weeks from tissue culture plugs (King and Angus, 1995). Certain species, such as riceflower (Pirn elect ferrugined), are also commercial products in Israel, since cultivation of Australian plants is suited to arid areas with high light levels. South Africa also has a rich ornamental flora that is relatively unexplored (van Vuuren et al., 1993). Botanists in that country are proposing an exchange of plants and collaborative research with European centres (A. S. Andersen and J. Van Staden, personal communication). The United States Department of Agriculture has supported a new floriculture crops program in cooperation with national floral societies (Roh and Lawson, 1993). Among all the international floriculture centres, the development of new potted plants in Denmark merits close examination as a model for potential product development in British Columbia. There are similarities between these two industries. Both are relatively small-scale in area, yet located on the edge of large markets, and they have reputations for producing a wide variety of high-quality plant products. More importantly, Denmark is the only country to the author's knowledge where private growers have successfully introduced new potted plants. Floriculture growers in British Columbia might benefit from the experience of product developers in Denmark. Denmark The floriculture system in Denmark is highly developed: the research sector has an international publication record; there is a strong tradition for both university and vocational education; an advisory system is well established; and the production sector operates with 11 very high productivity, quality, and with an emphasis on export. Trading partners are located in the European Union (EU) and Scandinavia. Potted plant sales are reported to have an annual value of Can.$455 million (Dansk Erhvergartnerforening, Odense, 1994). International Floriculture Trade Statistics (Anonymous, 1993) ranks Danish potted plant export second in the world after The Netherlands. Denmark is located just north of Holland, so the greenhouse producers are forced to compete with the largest floriculture centre in the world for EU trade. Breakdown of production costs and profits for different greenhouse commodity groups has demonstrated that overall costs of production and growers' profits were highest with potted plants in comparison to cut flowers or vegetables (Andersen, 1989). As a result, production shifted rapidly from a 20% potted plant share of greenhouse commodities in 1960 to 82% of production in 1992 (Danmark Statistiks, 1993). The small flowering plants are referred to as "bouquets on roots". Despite the relatively small scale of the Danish greenhouse industry in area (375 hectares), national characteristics of teamwork and innovation (Fivelsdal and Schramm-Neilsen, 1993), in combination with floriculture expertise and cooperative marketing (Andersen, 1989) have made Denmark a leader in product development. Many of their plant products are standard floriculture crops, but a few are new and developed in Denmark. The rank in sales value of miniature rose, campanula, heather, exacum and hebe verify highly successful, industrial-scale production of new potted plants (Table 2.2). Decorated Pinus pinea is also produced in large volume, and osteospermum may join the top ranks in the near future. Many other new crops, such as A ster novi-belgii and Muehlenbeckia species, are successful in smaller volumes. New products continue to be developed by private growers, private consultants, sales organizations, and by publically-funded research groups 12 Table 2.2 Commercial potted plants rank in sales value in British Columbia, Denmark and Holland. Products developed in Denmark and introduced during the last 15 years are shaded. Compiled from 1994 United Flower Growers Co-Op Association (UFG), 1993 Danish Growers' Association (DEG), and 1995 FloraCulture International statistics. Crop Rank (Sales Value) Floriculture Production Centre British Columbia Denmark Holland 1 Dendranthem a Rosa mini-hybrids Kalanchoe 2 Euphorbia Kalanchoe Begonia 3 Begonia Dendranthema Dendranthema 4 Cyclamen Begonia Saintpaulia 5 Gerbera Euphorbia A zalea 6 Kalanchoe Campanula Hydrangea 7 Saintpaulia Hibiscus Euphorbia 8 Lilium Schlumbergera Cyclamen 9 Hibiscus Exacum Phalaenopsis 10 Gloxinia Prim ula Rosa mini-hybrids 11 Rosa mini-hybrids Erica Hyacinthus 12 A zalea Hebe Guzmania 13 at universities and experiment stations. A major growers' sales cooperative, GAS A Aarhus, founded a product development section in 1986 which receives 40% support from the Product Development fund of the Danish Agricultural and Veterinary Research Council, and 60% from cooperative members. The product development group at GASA Aarhus survived cutbacks during the major reorganization in 1994. All growers invest in this group, since new plants attract buyers of new products to the entire system. Christensen and Friis (1987) described the systematic research and development process at the Institute of Glasshouse Crops Research in Denmark to introduce new potted plants to commerce. Plants were first collected in botanical gardens. Then, morphological and physiological problems were identified and solved. Finally, cultural techniques were recommended to growers. Research based on the initiation of projects by scientists was terminated in 1988 in favour of discipline-oriented research support for grower-initiated projects (Bredmose and Geertsen, 1988; Christensen and Friis, 1987). Breeding of aster, breeding and propagation of campanula and alstroemeria, axenic culture of native orchids with associated fungi, and postproduction testing of many potted crops are some current research projects with new plants. Many Danish growers have proven that conducting their own breeding programs (Miniature roses at Poulsen Roser/Rosanova; Gerbera hybrida 'Hummingbird' at Gartneriet Naeldebakken ApS), and introducing new species as potted plants (Campanula carpatica at Gartneriet PKM ApS; Helleborus orientalis at Simon Andersen Gartneriet ApS; Lewisia cotyledon at Gartneriet Timmermann A/S) can be profitable. Consultants and scientists have demonstrated organizational support and solved plant problems for the producers. These examples of cooperative endeavors illustrate the importance of innovation and teamwork in 14 the development of excellent floriculture products. 2.4 Scientific investigations in plant biology Application of basic research is critical for the commercialization of highly desirable herbaceous species as flowering potted plants (Armitage, 1990) Extremely high quality standards for potted plants require research to improve the plant species, and high greenhouse production costs necessitate optimization of plant culture. Selection and adaptation techniques have been investigated and cultivation optimized for the major greenhouse crops, but basic scientific and cultural information is lacking for new plants. Flowering plants with potential can be adapted to pot culture by a combination of breeding and crop management. A wide range of disciplines in plant biology are available to solve morphological problems, such as growth control, and physiological problems, such as propagation requirements and postharvest longevity during display in interior environments. 2.4.1 Plant search New plants are often identified in botanical gardens (Christensen and Friis, 1987) where a large variety of plants may be easily observed in a relatively small space over the growing year. They can also be identified by specialty growers and amateur breeders. Botanists are often familiar with propagation and cultural requirements of ornamental plants, and they have recommended some species with garden potential. Straley (1988) comments on the showy, semi-parasitic Indian paintbrushes (Castilleja species) of Western North America, yet cautions that they are considered difficult in the garden. Botanical interest does not necessarily indicate commercial potential. Selection, breeding and propagation of native herbaceous perennials or other perennials discovered in botanical gardens are required to benefit commercially from the potential 15 diversity and ornamental qualities of these plants. New Guinea impatiens, for example, were collected in 1970 in the wild (Mikkelsen, 1987). They have become a major potted crop only after extensive breeding and propagation. Clerodendrum ugandense was located in a botanical garden and considered as a flowering potted plant. In addition to its propagation requirements, growth regulation and postproduction performance have been investigated which led to its introduction as a commercial product (Andersen et al., 1993). Garden perennials have also been a source of new potted plants (lies and Agnew, 1995; Masvidal, 1993; Kristensen, 1989). Many cultivars of perennials are often available, but postproduction longevity of these plants in warm interior environments may be unsatisfactory (Christiansen, 1988; Fortgens and Molenaar, 1986). 2.4.2 Plant breeding and propagation Breeding has improved the ornamental qualities of new herbaceous plants and solved cultural (Langton, 1991), disease (Dons et al., 1991), and longevity problems (Woodson, 1991). Although most flowering potted plants are propagated clonally to retain horticultural traits, sexual propagation during development of new herbaceous perennials may provide a source of genetic variation, plants for early investigations, and easily disinfested explants for tissue culture (Sulaiman and Babu, 1993). Seed dormancy is a common and adaptive attribute of wild plants (Evans, 1993), but undesirable in cultivated plants. Dormancy of threatened, ornamental Himalayan poppy has been investigated (Sulaiman, 1993). Temperature regimes (Fay et al., 1993; Davis et al., 1993) and stratification (Bratcher et al., 1993) have increased germination percentages and decreased germination periods of perennial plants. Various method:? of vegetative propagation have been determined for new herbaceous potted plants, including armeria (Christensen et al., 16 1989) and hebe (Kristensen, 1989). In addition to conventional methods of propagation, biotechnology is used in floriculture to overcome crossing barriers in hybridization (Holsteijn, 1994), for large-scale in vitro multiplication to allow new species and cultivars into the marketplace quickly (Zimmerman et al., 1991; Murashige, 1990), and for obtaining disease-free propagules (Brandt, 1992). Micropropagation has become so important in floriculture breeding that some companies include in vitro culturability as a selection criterion. Worrall (1995) reported that embryo rescue techniques successfully overcame seed dormancy in an A nigozanthos breeding program. In vitro techniques are also required for propagation of orchids. In Denmark, successful axenic germination and culture of Dactylorhiza majalis with associated mycorrhizal fungi (Rasmussen et al., 1990) indicate some potential for using protocorms as orchid propagules in floriculture. 2.4.3 Growth control Chemical growth regulators are often aids in adapting new ornamental species that are naturally too large for potted plant culture (Holcomb and Beattie, 1 990; Davis and Andersen, 1989; Hentig, 1985). For example, ancymidol was applied to control the height of Clerodendrum ugandense (Andersen et al., 1993), uniconazole to osteospermum (Olsen and Andersen, 1995) and daminozide to Dicentra spectabilis (Lopes and Weiler, 1977b; Roberts et al, 1995). Various regulators were tested to adapt taller cultivars of godetia grown as cut flowers to potted plant production, but efficacy was of short duration (Anderson and Hartley, 1990) . In addition to regulation of plant height, growth retardants have been found to increase time to anthesis and reduce postharvest performance (Olsen and Andersen, 1995), and reduce the size of flowers (Gilbetz, 1992) in some herbaceous perennial species. 17 Plants may also be adapted for pot culture by control of the growing environment. The effect of photoperiod and forcing temperatures on potted Dicentra spectabilis (Lopes and Weiler, 1977a) and Physostegia virginiana (Beattie et al., 1989) have been determined. White et al. (1989) tested the interaction of chemical growth regulation and environmental factors on A quilegia cultivars to control plant form and flowering. Another environmental parameter, the difference between day and night temperature (DIF) is used commercially to regulate plant height, particularly in terminal flowering crops such as chrysanthemum and poinsettia. DIF has been tested with few new species, but it was insufficient to control the growth of clerodendrum (Andersen ec al., 1993) or campanula (Moe, 1990). 2.4.4 Postproduction performance Noordegraaf (1994) stresses longevity in the interior as an important quality characteristic of potted plants to the flower buyer. Postproduction testing of new commercial products is required to determine their interior performance (Nell and Barrett, 1989). Longevity of potted perennial plants in the interior may be influenced by preharvest conditions, such as irradiance (Serek, 1991), temperature (Lopes and Weiler, 1977a), and nutrient levels (Serek, 1990). Interior quality may also be affected by various postharvest treatments and environmental conditions. Postharvest performance of perennials has been improved by low postharvest temperature (Hoyer and Kristensen, 1991). Treatment with the anionic complex of the silver ion (STS) inhibits ethylene effects, including flower abscission (Cameron and Reid, 1983; Reid, 1985), on some ornamental plants (Woltering, 1987). STS increased the display life of potted rose (Serek, 1993) and campanula (Serek, 1991). A new, volatile 18 ethylene inhibitor improved the display life of potted rose and other flowering plants (Serek et. al., 1994a, 1994b). 2.5 Development of commercial products 2.5.1 Systematic methods in public development Systematic methods, such as the profile (Noordegraaf, 1987) and inventory (Sachs et al., 1976) methods, and overall schemes (Roh and Lawson, 1993) or systems (Armitage, 1986, 1990), have been proposed for the development of new plant products. However, development of many, successful new floriculture products has not conformed to reported, systematic methods. Experience has shown that systematic methods may be problematic in floriculture for various reasons. Available resources, including scientific and production expertise, market size, and the plant itself often dictate product potential and development methods. Plant selection, propagation and promotion have proved sufficient for the introduction of nursery crops (Macdonald, 1991), but not for development of new flowering potted plants (Christensen and Friis, 1987). Far more extensive research is required to meet floriculture quality standards, such as crop uniformity and postproduction longevity in interior environments, than nursery crop requirements. Capital-intensive controlled environments justify optimization of plant culture. For example, germination end rooting percentages of seeds or cuttings must be close to 100% in the greenhouse. Commercial floriculture is highly competitive, especially regarding the research and development of new flowering plant products. Confidentiality is required so that industrial partners can control supply and maximize economic returns to investments in new products. Intellectual property rights may be negotiated and assigned among collaborating partners in 19 plant development, and private companies often require signed statements of confidentiality from their staff. There are examples of successful development of ornamental plants. Attempts to determine generalized protocols for new potted plants should be based on the strategies and methods used by successful producers, researchers, and independent consultants who are current, international leaders in the field. Long-term research and development projects, in addition to confidentiality, make examination of commercial projects difficult. However, on-site visits to commercial firms and progressive greenhouses whsn possible, coupled with interviews of consultants and scientists active in product development, reveal current commercial procedures for development of new floriculture products. In all cases the author observed, potted plant research and development required a good idea, time and skills to solve problems, and an industrial partner. 2.5.2 Stages in private development Team Grow-how, a private plant research and development company based in Denmark, provides expert consultation to greenhouse flower growers. Dr. Linda Noack describes the following general stages of new potted plant development undertaken by her company with an independent grower as client. A new potted plant begins with a good idea. Innovative consultants observe fashion and consumer trends, analyze the market, and make projections. They have contacts and experience in floriculture production which allows them to integrate production and market information. A literature search of the plant's botanical characteristics and cultural information is an important early step. When a potential product is identified, the consultant must locate an interested grower with suitable facilities to proceed. If possible, the consultant 20 and industrial partner visit sites where the plant may be in limited production. Next, growers conduct greenhouse trials with new plants to determine their cultural requirements. Consultants or contract scientists conduct controlled experiments to solve cultural problems. Although, it is typical for problems to arise when learning to grow a new crop, this is a vulnerable stage in product development. For example, osteospermum was almost dropped from development because of disease problems in the early stages. Since the consultant and/or the grower may become discouraged, Team Grow-how reviews the progress of each project on an annual basis with their industrial partners before renewing a contract. A new potted plant requires introduction and promotion. A pilot introduction in a minor market can be used to identify postproduction, or other problems, with the product without lowering its reputation in a major market. Final introduction represents another vulnerable stage in the project. The producer must finance patents (Jondle, 1993; Wijnheijmer, 1989), marketing materials, and advertising without having had any return from their investment to date. Producers also know that there is no guarantee of success with the new plant. Team Grow-how, in cooperation with private flower producers, has successfully introduced industrial-scale potted plants in the last few years. Their new products include many campanula species, such as Campanula garganica 'Get Me' and C. cochlearifolia 'Elizabeth Oliver', the 'Sunny' series of Osteospermum ecklonis hybrids, Lavendula stoechas, and potted sunflowers (Helianthus annuus). They credit their success to the integration of production and scientific expertise, and to the large market for ornamental plants in Europe. 21 Although there is no formula or systematic method for successful development of new flowering potted plants, critical examination of the history of cultivated ornamental plants, scientific literature, and current commercial projects point to some essential components of the process, including the following: 1) identification of a plant species with potential based on its botanical characteristics, adaptability to cultivation, and consumer trends or marketing opportunities; 2) establishment of a strong industrial link for financial support of the project, assistance in determining the cultural requirements of the new plant, and production of the new commercial product; 3) application of techniques in modern plant biology to solve biological problems; 4) confidentiality during development and protection of intellectual property; and 5) promotion of the new plant product. 22 3.0 CASE STUDY: INVESTIGATION OF SEED COAT-IMPOSED DORMANCY AND SEED TREATMENTS TO IMPROVE GERMINATION IN LEWISIA SPECIES GROWN AS FLOWERING POTTED PLANTS 3.1 ABSTRACT The mechanism of seed dormancy was investigated in Lewisia tweedyi (A. Gray) Robinson and various seed treatments were tested in an attempt to improve the percent and rate of germination in both Lewisia tweedyi and Lewisia cotyledon (S. Watson) Robinson. Germination of naked embryos (86.9%) in L. tweedyi within four weeks of decoating suggested that the seed coat imposed dormancy in this species. Scanning electron micrographs of seeds in transverse section showed that the seed coat was 22% thicker (73 um) in L. tweedyi than in L. cotyledon (57 um). Unlike L. cotyledon, the testa of L. tweedyi was prominently sculptured. Maximum germination was 66.7% in L. tweedyi and 87.8% in L. cotyledon after 32 weeks under axenic conditions. Maximum germination in a factorial experiment was 59.0% in 0.3 weeks in L. cotyledon and 28% in 0.1 weeks in L. tweedyi after scarification in liquid nitrogen (LN2), soaking in gibberellic acid (GA3 10 mM), and pre-chilling at 3.2°C for 8 "or 12 weeks, respectively. Pre-chilling or GA 3 increased percent germination in both species, but LN 2 increased percent germination only in L. cotyledon. Time to germination was decreased by pre-chilling in both species, but GA 3 hastened germination only in L. tweedyi. Species seed quality and germination performance were variable. Seed treatments improved germination especially in L. cotyledon. In contrast, low percent germination over extended periods of time would limit production of L. tweedyi as a flowering potted plant. 23 3.2 INTRODUCTION Modern floriculture production goals and methods mandate rapid, uniform, and high percent germination of flower seeds. Generative propagation in highly controlled greenhouse environments is often automated for singulated sowing with the goal of producing one seedling for every one seed sown. Unsatisfactory germination of many herbaceous garden perennials and native plants, including Lewisia tweedyi and L. cotyledon, limit their introduction as flowering potted plants (Aelbrecht, 1989; Persson, 1993; Karlovich, 1995). Seed dormancies are characteristic of plants in nature where there is an adaptive advantage for low germination spread over time (Stebbins, 1974). Gutterman (1993) reports that seed strategies which "spread the risk" increase the chances of seedling survival by germinating at the right time in the right place. This is particularly important for plant species growing in extreme environments, such as deserts and mountainous regions, where great climatic changes occurring during the period between seed maturation in one season and germination in another affect the temperature and available moisture in the microhabitat of the seed. Lewisia tweedyi is an evergreen, herbaceous perennial restricted in nature to eastern spurs of the Cascade Mountains of northern Washington State and southern British Columbia (Mathew, 1989). The habitat and altitude range from rocky slopes at 2000 m in the Entiats to canyons and hillsides beneath pines at 450 m in the Wenatchee Range (Roger Simpson, personal communication). L. tweedyi is highly valued as an ornamental, but has a reputation for being challenging to grow. For this reason, the species has been cultivated only by alpine specialists (Colley and Mineo, 1985). The better known lewisia species, Lewisia cotyledon, is a minor commercial crop in some areas of Europe and western North America (Wicki-24 Friedl, 1990). In the wild, L. cotyledon is found between 150 and 1200 m in the Siskiyou Mountains of southern Oregon and northern California (Mathew, 1989). Lewisias (Portulacaceae) are members of the Centrospermae, a natural group of families in the order Caryophyllales (Bittrich, 1993). A linear peripheral embryo surrounds centrally located perisperm. Seeds in some members of the Portulacaceae have a seed appendage, or elaiosome, for myrmecochorous dispersal (Handel, 1978; Carolin, 1993; Boesewinkel and Bouman, 1995). Lewisia tweedyi is the only species in the genus with an arilloid (Fig. 3.1). Hershkovitz (1992) proposed a new taxonomic classification, Cistanthe tweedyi, based primarily on the seed appendage and valvate dehiscence from the capsule. Atwater (1980) and other authors have reported seed coat-imposed dormancies in the Centrospermae, including A maranihus retroflexus (Amaranthaceae) (Kigel et al., 1979), Beta vulgaris (Chenopodiaceae) (Santos and Pereira, 1989), and various Cactaceae (Bregman and Bouman, 1983). Impermeable seed coats may restrict water and/or oxygen to the embryo, mechanically restrain embryo expansion, and/or chemically inhibit the embryo (Ballard, 1973; Ralston, 1978; Werker, 1980/81; Bewley and Black, 1994). Germination will occur in decoated seeds having no embryo dormancy (Come and Corbineau, 1992). Very low percent germination over long periods of time in Lewisia tweedyi has been reported by specialty growers. Baulk (1988) observed L. tweedyi germination beginning a few weeks after sowing but concluding in the second season, or 15 to 18 months after sowing. Seed performance in L. cotyledon is not as problematic. However, germination recommendations for both species are inconsistent and imprecise. Methods are based on techniques suitable for the nursery trade or alpine hobbyists, such as stratification for unspecified periods in a garden cold frame, and not on commercial floricultural techniques. 25 Fig. 3.1 Scanning electron micrographs of lewisia seed, (a) Lewisia tweedyi seed. Scale bar = 1 mm. (b) L. tweedyi arilloid seed appendage and seed coat surface. Scale bar = 200 um. (c) Lewisia cotyledon seed. Scale bar = 1 mm. (d) L. cotyledon hilar region and seed coat surface. Scale bar =100 pm. 26 The objectives of this investigation were: 1) to determine if dormancy in Lewisia tweedyi is imposed by the seed coat; and 2) to test the effects of gibberellic acid, moist pre-chilling, and scarification in liquid nitrogen on percent germination and mean time to germination in L. tweedyi and L. cotyledon. 3.3 MATERIALS AND METHODS Seed source and seed viability — Seeds of Lewisia tweedyi, three selected forms of L. tweedyi, and L. cotyledon were obtained in 1993 from Ash wood Nurseries, the United Kingdom, and sown immediately in the axenic germination trial. All other experiments and microscopy used L. cotyledon seed supplied in 1994 by Jelitto Staudensamen, Germany, and L. tweedyi seed supplied in 1994 by an alpine specialist, W. F. Lichti at The Butterfly Conservation and Breeding Farm in Ontario, Canada. Viability of seeds in packets of Lewisia tweedyi (seed number = 75) and L. cotyledon (seed number = 70) (Ashwood), and L. tweedyi 'Lovedream' (seed number = 37) (Jelitto) was tested in 1994, 6 months after harvest. Seed of L. tweedyi (seed number = 100) from the alpine specialist was tested in 1995, 12 months after harvest. Seeds were soaked for 24 hours in a 1% solution of tetrazolium tricloride (TTC) after lifting a section of the seed coat to expose the embryo (Moore, 1973). TTC reacts with hydrogen atoms released by respiring embryos to form a red pigment. Number of seeds with red-coloured embryos was recorded as a measure of viability. Axenic germination — Lewisia cotyledon, L. tweedyi, L. t. 'Alba', L. t. 'Rosea', and L. t. 'Elliot's Variety' were surface disinfested with 7.5% NaOCl for 15 minutes and rinsed 3 times with sterile distilled water. One hundred seeds of each species and selected forms were sown 27 individually in 30-ml test tubes filled with 15 ml of one-tenth MS (Murashige and Skoog, 1962) agar medium and pH adjusted to 5.5. Sugar or hormones were not added to more closely simulate in vivo germination conditions. Forty seeds of each type were placed in a growth room set at constant 19°C with a 16-hr photoperiod. The remaining seeds were chilled at 4°C in the dark for 4 weeks before transfer to the growth room. Germination was periodically monitored and number of seedlings recorded on weeks 0 - 8, 18, 28, and 32 after sowing. Percent germination (PG) and mean time to germination (MTG) were calculated. The weighted mean was calculated according to the formula: MTG = Enx / £n where n was the number of seeds germinated; and x was the number of weeks between sowing and germination. Germination of naked embryos — Seeds of Lewisia tweedyi were surface disinfested in 15% NaOCl for 10 minutes, then rinsed in 70% alcohol for 5 minutes and washed 3 times in distilled water. The entire testa was carefully removed with a dissecting needle. Whole, untreated seeds were sown as a control. Three 25-seed replicates of each treatment were sown in 10-cm petri dishes on 3 layers of Whatman No.l filter paper moistened with 5 ml distilled water. Dishes were completely randomized and incubated in the dark at 22°C for 4 weeks. Distilled water was added as required. Seeds with a radicle > 1 mm were considered germinated. PG was calculated and a t-test used to compare the difference between the two treatment means. Seed treatments to improve germination — Lewisia tweedyi seed was immersed in liquid nitrogen (LN2) (- 196°C) for 15 minutes and L. cotyledon seed for 10 minutes to surface scarify the testa (Fig. 3.2) (Come and Corbineau, 1992). Different times of immersion were 28 Fig. 3.2 Close up of Lewisia tweedyi seed coat surface scarified by (a) a 15 minute immersion in liquid nitrogen or (b) non-treated control. Scale bars = 10 um. 29 based on different seed-coat thicknesses in the two species. Acetone was used for making solutions of gibberellic acid (GA3) (Sigma) at concentrations of 0, 1.0 or 10 m M based on improved germination in some perennial species after organic infusion of GA 3 (Persson, 1993). Scarified seeds were immersed for 24 hours in covered beakers containing the GA 3 solutions at room temperature. Decanted seeds were sown in 10-cm petri dishes on 3 layers of Whatman No.l filter paper moistened with 5 ml distilled water. Lewisia tweedyi seed was pre-chilled (3 ± 0.5°C) for 0, 2, 4, 8, or 12 weeks and L. cotyledon for 0, 2, 4, or 8 weeks. Germination of L. cotyledon before 8 weeks of pre-chilling obviated extending the pre-chill to 12 weeks. Seeds were periodically removed to a growth chamber at 18 ± 2°C with 16-hr photoperiod. Distilled water was added as required. Petri dishes containing 25 seeds each were randomly arranged in separate plastic containers representing blocks during pre-chilling and re-randomized in blocks during germination in all combinations of factors and levels (2 plant species * 3 levels of GA 3 x 2 levels of L N 2 x 4 or 5 levels of pre-chilling x 2 blocks x 2 replicate dishes). Number of germinated seeds (radicle > 1 mm) was recorded at the time of removal from the pre-chill and then weekly for 10 weeks. PG and MTG were calculated and data analyzed using the PC-SAS software package (SAS Institute, 1985). The variance of experimental data was tested using non-orthogonal contrasts to examine differences between means. Scanning electron microscopy — Whole, untreated seeds or transverse sections of Lewisia tweedyi and L. cotyledon were mounted on aluminum stubs and coated in a thin layer of gold using a Nanotech Semprep sputtering device before examination with a Cambridge 250T scanning electron microscope (SEM). The same methods were used to examine the testa of L. tweedyi immersed in L N 2 for 15 minutes immediately before SEM preparation. 30 3.4 RESULTS Seed viability — Lewisia tweedyi, L. t. 'Lovedream' and L. cotyledon seed from commercial sources were 58, 57, or 80% viable, respectively. Seed of L. tweedyi supplied by the alpine specialist was 85% viable. Axenic germination — Individual seeds of Lewisia cotyledon, L. tweedyi, and selected forms of L. tweedyi sown under sterile conditions germinated periodically during the entire test period of 32 weeks. Overall germination was 77.9% in L. cotyledon and 61.4% in L. tweedyi. A 4-wk chilling before transfer to the growth room increased PG in L. cotyledon and in all selections of L. tweedyi, but not in L. tweedyi. Chilling reduced MTG only in L. tweedyi 'Alba' (Table 3.1). Naked embryo test — Mean PG (3 25-seed replicates) was 86.9% for decoated Lewisia tweedyi seed and 0% in the control (P= 0.001). Seed treatments — PG and MTG were different (P=0.001) in Lewisia tweedyi and L. cotyledon (Table 3.2). Maximum germination was 59.0% in 0.3 weeks in L. cotyledon (P - 0.05) and 28% in 0.1 weeks in L. tweedyi (P = 0.01) after treatment with all factors at the highest levels. Scarification with L N 2 increased PG only in L. cotyledon (Table 3.3), and did not decrease MTG in either species (Table 3.4). Pre-chilling increased PG and decreased MTG in both species, however the effect on MTG was greater in L. tweedyi (Fig. 3.3). GA 3 increased PG in both species (Table 3.3), but decreased MTG only in L. tweedyi (Table 3.4). Scanning electron microscopy — Examination of Lewisia tweedyi seeds showed pronounced surface sculpturing of the testa, a micropylar hook, and a fleshy seed appendage (Fig. 3.1a and b). In contrast, the appendage was absent in L. cotyledon and the micropylar hook and surface sculpturing less pronounced (Fig. 3.1c and d). Cracking in the L. tweedyi testa was 31 Table 3.1 Percent germination and mean time to germination in Lewisia cotyledon, Lewisia tweedyi, Lewisia tweedyi 'Alba', Lewisia tweedyi 'Rosea', and Lewisia tweedyi 'Elliot's Variety' after 32 weeks under axenic conditions. Seeds were evaluated in a growth room at constant 19°C with a 16-hr photoperiod or after a 4-week chilling at 4°C in the dark before transfer to the growth room. Germination (%) Mean time to germination (weeks) Species Chilling 4°C Constant 19°C Chilling 4°C Constant 19°C L. cotyledon 87.8 62.9 6.3 5.8 L. tweedyi 57.9 66.7 14.9 7.7 L. tweedyi 'Alba' 35.1 17.5 15.2 17.1 L. tweedyi 'Rosea' 38.9 17.9 17.2 15.3 L. tweedyi 'Elliot's Variety' 55.9 40.0 13.4 16.4 32 Table 3.2 Percent germination and mean time to germination in Lewisia tweedyi and Lewisia cotyledon after 10 weeks in a growth cabinet at 18 ± 2°C with 16-hr photoperiod. Species Germination (%) Mean time to germination (weeks) L. tweedyi 10.3 2.2 L. cotyledon 38.9 1.1 Significance *** *** *** P=0.001 33 Table 3.3 Percent germination in Lewisia tweedyi and Lewisia cotyledon scarified in liquid nitrogen (LN2) or non-scarified control, and soaked for 24 hours in 0, 1.0 or 10.0 mM gibberellic acid (GA3) in acetone after pre-chilling at 3 ± 0.5°C lor 0, 2, 4, 8 or 12 weeks. Seeds were evaluated over 10 weeks in a growth chamber at 18 ± 2°C with 16-hr photoperiod. Plant species Treatments L. tweedyi L. cotyledon L N 2 scarification no yes Significance Pre-chilling (weeks) 0 2 4 8 12 Significance GA 3 in acetone (mM) 0 1.0 10.0 Significance NS, *** Nonsignificant or significant at P=0.001, respectively. 9.5 11.0 NS 33.6 44.2 4.7 4.2 9.3 13.8 19.3 *** 34.2 35.3 37.7 43.3 *** 6.6 9.4 14.8 * * * 36.8 33.0 41.9 34 Table 3.4 Mean weeks to germination in Lewisia tweedyi and Lewisia cotyledon scarified in liquid nitrogen (LN2) or non-scarified control, and soaked for 24 hours in 0, 1.0 or 10.0 mM gibberellic acid (GA3) in acetone after pre-chilling at 3 ± 0.5°C for 0, 2, 4, 8 or 12 weeks. Seeds were evaluated over 10 weeks in a growth chamber at 18 ± 2°C with 16-hr photoperiod. Plant species Treatments L. tweedyi L. cotyledon L N 2 scarification no 2.4 1.1 yes 2.1 1.0 Significance NS ' NS Pre-chilling (weeks) 0 4.3 1.8 2 3.6 1.3 4 2.5 0.8 8 1.3 0.3 12 0.3 — Significance * + * GA 3 in acetone (mM) 0 2.8 1.1 1.0 2.3 1.1 10.0 1.7 1.0 Significance * * * NS NS, *** Nonsignificant or significant at P=0.001, respectively. 35 Fig. 3.3 Number of weeks to germination after moist pre-chilling at 3 ± 0.5°C for 0, 2, 4, or 8 weeks in Lewisia cotyledon and 0, 2, 4, 8, or 12 weeks in Lewisia tweedyi. Seeds were evaluated over 10 weeks in a growth chamber at 18 ± 2°C with 16-hr photoperiod. Data are significant (P=0.01) for species x pre-chill. 36 visible after immersion of the seed in LN 2 , but not in the untreated control (Fig. 3.2). Micrographs of seeds in transverse section showed linear peripheral embryos with centrally located nutrient tissue (Fig. 3.4a and c) characteristic of Centrospermae. The seed coat was 22% thicker in L. tweedyi (73 pm) than in L. cotyledon (57 um) (Fig. 3.4b and d). 3.5 DISCUSSION Seed coat-imposed dormancy — Dormant seeds do not germinate when moisture, oxygen and suitable temperatures are available. There are many reports of seed dormancies in herbaceous perennial plants, but the mechanism of dormancy is unknown for most wild species (Salac and Hesse, 1975; Kelly et al., 1992). Impenetrable seed coats impose dormancy in many herbaceous plant families (Egley, 1989; Bewley and Black, 1994). This mechanism may be determined by decoating seeds (Come and Corbineau, 1992), developmental studies (Kelly et al., 1992), or micromorphological studies (Smith, 1988). PG of 86.9%) in Lewisia tweedyi within 4 weeks of decoating suggests that the covering structure imposes dormancy in this species. This type of dormancy, rather than a dormant embryo, is supported by SEM studies. Micrographs of L. tweedyi and L. cotyledon seeds in transverse section show a thicker seed coat with prominent surface sculpturing in L. tweedyi. These micro-morphological traits are characteristic of myrmecochorous seeds and of undomesticated plant species. The combination of thick coats and easily removed elaiosomes protects seeds from predation during dispersal by ants (Stebbins, 1974; Keeler, 1989). Seed coat thickness and surface texture are key morphological markers for seeds recovered in archeological sites. They are evidence of automatic selection for loss of seed coat dormancy during cultivation. Smith (1988) observed in SEM micrographs that testa of 37 Fig. 3.4 Centrospermae seed structure and seed coat thickness in lewisia species, (a) Lewisia tweedyi transverse section showing peripheral embryo and centrally-located perisperm. (b) Close up of L. tweedyi seed coat showing diameter (arrows) of 73 urn. (c) Lewisia cotyledon transverse section, (d) Close up of L. cotyledon seed coat showing diameter (arrows) of 57 um. Scale bars of whole sections = 1 mm; scale bars of coat diameters = 100 um. 38 2000 year old cultivated Chenopodium berlandieri (Centrospermae) are thinner than wild C. berlandieri. Germination treatments — The low percent germination observed in Lewisia tweedyi over extended periods of time is characteristic of plants growing in extreme habitats (Gutterman, 1993). In contrast, percent germination is higher and mean weeks to germination shorter in L. cotyledon whose native environment is not extreme. Seed dormancies are an advantage in nature, but they must be overcome in cultivation. Lewisia species require either selection or seed treatments to improve germination performance. Scarification, GA 3 , and stratification improve lewisia germination. Similar treatments were effective in other perennial species, including stratification in penstemon and asclepias (Allen and Meyer, 1990; Bratcher el al., 1993) and Echinacea (Javad Feghahati and Neil Reese, 1994), and GA 3 in ornamental Himalayan poppy (Sulaiman, 1993). Khan et al. (1992) discuss the role of GA in seed dormancy and germination. GA mimics moist chilling and moist chilling induces the production of GA. The hormone, thereby, integrates seed activities with prevailing environmental conditions. When the seed coat is impermeable to oxygen, Corbineau and Come (1995) repori; that chilling increases the oxygen supply to the embryo. The aqueous solution is more oxygenated and phenolic oxidation reduced during cold stratification. Commercial prospects — Propagation of herbaceous perennials from seeds is considered difficult (Karlovich, 1995). Producers are finding that although propagation by seed is low cost, many perennial species are difficult to germinate. Seed dormancy, poor seed quality, and unavailability are common problems. Seed quality in lewisia j.s variable, particularly for Lewisia tweedyi. Early harvest of unripe L. tweedyi seed capsules before valvate dehiscence 39 may be a common practice in small, commercial nurseries. After-ripening of seeds during a warm moist stratification at 19°C would explain higher PG in the reported axenic trial at a constant warm temperature than after a 4-wk chilling. These nurseries are also harvesting seed from mature plants which germinated over 2-yr periods as seedlings; they are not selecting for rapid germination, so the seed characteristics are not improved over time. Scarification with L N 2 and infusing GA 3 are possible commercial seed treatments, although seed companies are required to test the viability of each lot before sale. Viability might decrease more rapidly during storage of pre-treated seed (Alderson, 1987; Corbineau and Come, 1991). Poor seed performance in Lewisia tweedyi limits commercial development of this species as a flowering potted plant. It is an extreme example of seed quality, dormancy, and availability problems faced by commercial growers of herbaceous perennial plants that are not as highly selected as annuals and other major floriculture species. L. tweedyi, for example, is very variable in the rate of germination. Genetic variability is the basis of plant breeding. Although, germination of lewisias, especially L. cotyledon, is improved by seed treatments, seed characteristics may be more effectively improved by selection than by these seed treatments. As the demand for and development of herbaoous perennials continues, investigations of seed quality and germination requirements will steadily improve the seed characteristics of new floriculture species. 40 4.0 CASE STUDY: APPLICATION OF SrLVER THIOSULFATE AND SUPPLEMENTAL IRRADIANCE TO IMPROVE THE DISPLAY LIFE OF DICENTRA SPECIES FORCED AS FLOWERING POTTED PLANTS 4.1 A B S T R A C T The whole plant display life and total number of flowers per pot of Dicentra eximia (Ker-Gawl.) Torr., Dicentra formosa (Andr.) Walp. 'Bachanal', and Dicentra spectabilis (L.) Lem. were tested in a simulated interior environment after greenhouse forcing. During the display life, more flowers opened if the plants were treated before harvest with the anionic silver thiosulfate complex (STS). This increase in flower number resulted in a 75% increase in the display life of D. eximia (to 14 days) and a 65% increase in the display life of D. formosa (to 28 days). A similar effect was achieved by forcing the plants under supplementary irradiance (50 umol m"2 s"1 PPF), which also increased plant height and decreased production time. In contrast, the 10-day display life of D. spectabilis was not improved by treating with STS. Height of D. spectabilis could be controlled by a foliar spraj' of 5000 ppm daminozide (butanedioic 2, 2-dimethylhydrazide). This growth regulator had no effect on forcing time, flower number or display life of the plants. Postproduction longevity of D. formosa treated with 0.1 mM STS meets commercial"" floriculture standards. Although the display life of D. spectabilis and D. eximia were improved by preharvest treatments, these species do not meet commercial standards for longevity. Development of all species as flowering potted plants is limited by flower fading in interior display environments. 41 4 . 2 I N T R O D U C T I O N Research on the development of herbaceous perennials as new potted plants for greenhouse floriculture generally focuses on plant breeding (Masvidal, 1993) and cultural requirements (Beattie and Holcomb, 1983; Christensen et al., 1989; De Hertogh, 1987; White et al., 1989; lies and Agnew, 1995). There is little reported postharvest testing of new crops (Nell and Barrett, 1989), although postproduction performance is important for commercial success of flowering potted plants (Woltering, 1987). Dicentra species, or bleeding-hearts, are widely known garden perennials. The common bleeding-heart, D. spectabilis, is native to Japan and has racemes with pendent, rosy red or white, cordate flowers. It has been forced for greenhouse display (Dakers, 1938; Preston, 1951), and is recommended for Valentine's and Mother's Day florist sales despite having brittle foliage and fragile flowers (Smith, 1992; Weiler and Lopes, 1976). Because of its natural height, D. spectabilis must be treated with chemical growth regulators like daminozide to produce plants of acceptable size (Lopes and Weiler, 1977a,b). North American bleeding-hearts are not presently forced commercially despite their ornamental features and frost tolerance. Both the eastern D. eximia and western D. formosa have more numerous, though smaller, flowers than D. spectabilis, a long season of bloom, finely dissected foliage, and compact growth (20-40 cm) (Bluhm, 1988; Hansen and Stahl, 1993). Unlike the taller-growing (70 cm) common bleeding-heart, their potted culture may not require chemical growth regulation. In addition, breeding has resulted in availability of many D. formosa cultivars. Postproduction quality of potted perennials, as evaluated by the whole plant display life and number of flowers over the display life, may be reduced under warm temperatures 42 and low irradiance characteristic of interior display environments. Weiler and Lopes (1976) reported 100% flower abscission inD. spectabilis associated with 9000 lux light intensity and warm temperatures (15 and 22.5°C) during forcing. Silver thiosulfate (STS) has been shown to prevent flower abscission (Cameron and Reid, 1983), and extend the display life of ethylene-sensitive potted plants which may include herbaceous perennials (Christiansen, 1988). Postharvest quality of campanula has been improved with preharvest supplementary irradiance (Serek, 1991). The objectives in this experiment were: 1) to test whole plant display life and flower number per pot after treatment of D. eximia and D. formosa forced with supplementary irradiance; 2) to determine whether a preharvest spray of silver thiosulfate would improve the interior display of Dicentra species, including plants of D. spectabilis treated with daminozide during greenhouse forcing to control height. 4.3 MATERIALS AND METHODS Supplemental irradiance treatment— Plants of D. eximia and D. formosa 'Bachanal' in 10-cm (0.55-litre) pots were obtained from a commercial nursery and placed in an open cold frame for a 16 week vernalization period (3.5°C mean minimum; -6.2°C absolute minimum) initiated Week 37 of 1993 and terminated Week 1 of 1994. Vernalized plants (2.2 ± 0.5-cm height) were transferred to the university greenhouse and forced at 10°C day/8°C night under either natural irradiance and photoperiod (NI) that increased from 8 to 10 h (latitude 55°41'N), or natural daylight and photoperiod supplemented for 10 h day"1 at a photosynthetic photon flux (PPF) of 50 umol m"2 s"1 from SON-T high-pressure sodium lamps (HPS) (Philips, The Netherlands). 43 Actual mean greenhouse temperature recorded by the greenhouse climate computer data logger during the forcing period was 10.3 ± 0.1 °C. Plants were subirrigated with a standard complete nutrient solution (EC 1.0 mS cm'1) as required. When half of the flowers per raceme were open, height and flower number of replicate plants were determined. They were placed in a simulated interior environment room (IE) for determination of display life. STS treatment — HPS plants of D. eximia, D. formosa 'Bachanal' and D. spectabilis in the coloured-bud stage were sprayed to runoff («30 ml per pot) with distilled water, 0.1 mM, or 1.0 m M STS solutions containing 0.1% Sandovit surfactant (Argylene, Denmark). Each species was placed in the IE 5 days after STS treatment, when one-half of the flowers per raceme were open. They were watered with tap water from above as needed. Daminozide treatment— Field-grown, 10-cm potted (7.2 ± 2.5-cm height) D. spectabilis were selected at a commercial nursery and transferred to the university greenhouse for forcing under natural irradiance. Greenhouse conditions were 13 h photoperiod (05:30-18:30HR) with 12°C day/night temperature set points and ventilation at 15°C. Actual mean temperature was 15.3°C during the 17 day forcing period. Plants were sprayed until run-off with 0 or 5000 ppm daminozide (butanedioic 2, 2-dimethylhydrazide) when inflorescences started to elongate, and with STS (or distilled water for controls) when the basal flower of the racemes opened. Plants were evaluated for quality and display life when half of the flowers per raceme were open. Evaluation of quality and display life — Plant height, measured from the top of the pot to the highest part of the foliage, was recorded at harvest (Day 0). Number of open flowers per plant was counted on Day 0 and every subsequent two days in the IE. Plant longevity was considered to be the number of days from harvest to the day when all flowers either abscised, 44 or all remaining open flowers were senescent. Conditions in the interior environment room were: 20 ± 2°C, 60 ±5 % RH, light from cool-white fluorescent tubes at 12-h day"1 and 15 umol m"2 s"1 PPF. Plants were randomized in two blocks with 4-plant replications per treatment in each block for each species. Data were analyzed using the PC-SAS software package (SAS Institute, 1985). The variance of the experimental data was tested, and non-orthogonal contrasls were used to examine differences between means. 4.4 RESULTS Effects of supplementary lighting — Supplemental irradiance appeared to decrease the time to flowering and slightly increased plant height at harvest in Dicentra eximia and D. formosa (Table 4.1). In D. eximia plants forced with HPS irradiance, more flowers opened during simulated interior display (Fig. 4.1). The use of HPS during forcing did not affect D. formosa flower opening in the interior (data not shown). Effects of STS — Treatment with STS at a concentration of 1.0 mM extended the display life of Dicentra eximia by 75% to 14 days (Fig. 4.2); 0.1 mM STS had no effect on the display life of this species. The display life of D. formosa was increased by 65% to 28 days by both 0.1 and 1.0 mM STS (Fig. 4.2). The STS treatments enhanced flower opening during the display life of both D. eximia and D. formosa (Figs. 4.3a and b). Although the 10-day display life of D. spectabilis was not affected by STS treatment (Fig. 4.2), postproduction flower opening was also increased in this species (Fig. 4.3c). The colour of the flowers that opened in the IE was faded in all three species. Effects of daminozide — Daminozide had no effect on forcing period, but significantly 45 Table 4.1 Effects of natural irradiance or natural 8 to 10-hr photoperiod supplemented with 50 |amol m"2 s"1 of artificial light on Dicentra eximia and Dicentra formosa 'Bachanal' mean plant height at harvest and duration of forcing at 10.3°C mean temperature. Species Irradiance Forcing period (days) Plant height (cm) Dicentra eximia Natural 48 17.8 Supplemental 44 20.3 Significance - ** Dicentra formosa Natural 58 19.9 Supplemental 52 23.6 Significance - *** Significant at P=0.01 or P=0.001, respectively. 46 0 2 4 6 8 I D 1 2 T i m e ( d a y s ) Fig. 4.1 Number of open flowers per plant in Dicentra eximia after greenhouse forcing under natural irradiance (NI) or natural 8 to 10-hr photoperiod supplemented with 50 umol m"2 s"1 of artificial light (HPS) at 10.3°C mean temperature. Plants were evaluated over time in a simulated interior environment room. Source of variation: D. eximia NI (control) vs. HPS x L or Q L N S Q** L = linear, Q = quadratic. Ns'"Nonsignificant or significant at Pr=0.01, respectively. 47 Fig. 4.2 Whole-plant display life of greenhouse-forced Dicentra eximia, Dicentra formosa 'Bachanal', and Dicentra spectabilis treated with 0.1 or 1.0 mM silver thiosulfate (STS) or non-treated control. Plants were evaluated in a simulated interior environment room after harvest until flowers either abscised or became senescent. Source of variation: D. eximia D. formosa D. spectabilis Control vs. STS 0.1 mM NS *** NS Control vs. STS 1.0 mM *** *** NS STS 0.1 mMvs . STS 1.0 mM *** NS NS N b ' """'Nonsignificant or significant at P=0.001, respectively. 48 Fig. 4.3 Number of open flowers per plant in Dicentra eximia (a), Dicentra formosa 'Bachanal' (b), and Dicentra spectabilis (c) treated with 0.1 or 1.0 mM silver thiosulfate (STS) or non-treated control. Plants were evaluated over time in a simulated interior environment room. Source of variation: D. eximia Control vs. STS 0.1 mM x L or Q L N S Q N S Control vs. STS 1.0 m M x L or Q L*** Q** STS 0.1 mM vs. STS 1.0 mM x L or Q L*** Q* L=linear, Q=quadratic. N S ' *• """"Nonsignificant or significant at ^=0 05, P=0.001, respectively. 49 D. formosa D. spectabilis L « . Q N S L N S Q N S L « . Q N S L N S Q* L* Q N S L N S Q* 50 51 reduced plant height of Dicentra spectabilis (Table 4.2). Treatment of D. spectabilis with 5000 ppm daminozide during forcing did not affect flower number or display life, and no interaction between STS and daminozide was detected (data not shown). However, daminozide appeared to reduce individual flower diameter by 40% from 2.5 to 1.5 cm. 4.5 DISCUSSION AND CONCLUSION Silver is an inhibitor of ethylene biosynthesis and ethylene action in plants (Yang, 1985; Reid and W u , 1991; Serek and Reid, 1993). Since the discovery of the anionic silver thiosulfate complex (Veen and Van de Geijn, 1978), STS has been used in commercial floriculture to protect flowering plants from the harmful effects of endogenous ethylene and exogenous exposure to ethylene. Effects on ethylene-sensitive plants include flower, bud, and leaf abscission (Reid and Wu, 1992), epinasty, and leaf yellowing. These results indicate that STS prevents flower abscission in Dicentra species. Pretreatment of D. eximia and D. formosa with STS improves ilower opening during the interior display, and thereby the display life of the potted plants. Presumably, STS prevents abortion of buds in a similar fashion to its action in lilies grown under low-light conditions (Van Meeteren and De Proft, 1982). The display life of D. spectabilis does not meet accepted commercial flowering potted plant standards (3-4 weeks) and was not improved with STS under the conditions of this experiment. However, STS did prevent flower abscission. Environmental pollution due to silver-based products is controversial. STS treatment of various cut flowers, including Dicentra to prevent wilting of cut stems, is mandatory in Dutch flower auctions, but the STS solutions may not be brought into the auction buildings (Doom and Woltering, 1991). Spraying of STS on potted plants is: not permitted in Holland; 52 Table 4.2 Effects of daminozide on Dicentra spectabilis mean plant height at harvest and duration of forcing at 15.3°C mean temperature under natural irradiance. Daminozide (ppm) Forcing period (days) Plant height (cm) 0 17 5000 17 Significance '"Significant atP=0.001. 32.2 22.7 53 it is a common practice in Denmark. Alternative inhibitors of ethylene biosynthesis are commercially available for cut flowers (Nell, 1992), but they are only effective in ethylene-free environments (Staby et al., 1993). The first environmentally-safe alternative to silver is under development (Serek et al., 1994a,b). The new gaseous chemical, 1-methylcyclopropene (1-MCP), inhibits ethylene binding and prevents ethylene action in plants. The display quality of flowering potted plants, including Dicentra, may be improved in the near future by treatment with this compound. Growth regulators affect the display life and quality of plants. Sheldron and Weiler (1982) found that daminozide successfully controlled plant height in aquilegia but reduced flower size, and Gilbetz (1992) observed the same effects in chysanthemum treated with paclobutrazol or uniconizol. Dicentra spectabilis responds similarly. Although no effect of daminozide on the display life of D. spectabilis was detected in this experiment, growth regulators have been reported to decrease longevity of osteospermum (Olsen and Andersen, 1995). Supplementary light during production improves the display life of some potted herbaceous perennials such as campanula (Serek, 1991) and Dicentra eximia. High endogenous levels of ethylene in D. spectabilis are not affected by light or STS treatments. The heart-shaped flowers of Dicentra species make them highly desirable as tokens of affection on Valentine's Day. However, their success as flowering potted plants requires that display quality meets commercial standards which apply equally to major crops and to new introductions. Quality characteristics include the number of flowers per pot, flower colour that does not fade, and plant longevity (Noordegraaf, 1994). The display life of D. formosa meets commercial longevity standards. Development of potted Dicentra which may be planted in the garden is limited by postharvest flower fading in the interior. 54 5.0 SUMMARY AND CONCLUSIONS Development of new flowering plants for commercial production is characteristic of innovative growers in leading international greenhouse centres. These industries are motivated to supply new plant products that satisfy the changing quality standards of the marketplace and to challenge increasing foreign competition. Where proactive projects have proven to be a source of industry success, there is a well-established tradition for collaborative plant research and development by flower producers and the scientific community. The potential benefits of new herbaceous perennial products are numerous and varied: consumers are demanding novelty and variety; individual growers benefit from favourable economic returns; specialty plants provide a niche for new and smaller-scale growers; many potted perennial species extend the production period and provide revenue early in the season; and, new plants support sales of major crops and compete for export markets. Changing quality standards in floriculture are placing greater demands on science. Standards increasingly include consumer-oriented qualities determined by the flower buyer, in addition to production-oriented qualities required by producers. Ornamental traits, such as flower colour and plant form, have always been important to the flower buyer. More recently, consumers are also demanding interesting products, excellent postproduction performance, and good customer service. Scientific investigations in plant biology are required to solve production problems and meet quality standards. A wide range of disciplines are available to solve problems and commercialize highly desirable plants. Lack of basic scientific and cultural information provides research opportunities to develop new species, such as lewisia and dicentra, as 55 flowering potted plants. The major floriculture crops are great products: they are genetically diverse, adaptable and high yielding. The floriculture industry is skilled in the production and promotion of these familiar products. Nonetheless, new flowering potted plants have great appeal. However, the time and research required to turn a potential plant species into a commercial plant product should not be underestimated. New plants are not likely to out-perform established crops without extensive research and development. Risk is always associated with product development in floriculture. Quality standards for potted plants are extremely high, commercial growing facilities are capital intensive, and competition among growers is vigourous on both a local and international scale. To quote one highly successful and innovative European flower producer, "Development of a new, flowering potted plant doesn't have to be easy. If it were, then anybody could do it." This grower obviously welcomes the challenge and competitive edge associated with new plant products. Research and development of new potted plants would stimulate the floriculture production industry in British Columbia. Good science, good ideas, and funding during development would reduce the risk to producers. The role of product development specialists is to identify resources, and promote innovation and teamwork in floriculture. 56 6.0 REFERENCES Aelbrecht, J. 1989. The effect of different treatments on the germination of Lewisia hybrid seeds. Acta Hortic. 252:239-245. Alderson, P. G. 1987. Seed technology aspects of flower seed germination. Acta Hortic. 202:35-47. Allen, P. S. and S. E. Meyer. 1990. Temperature requirements for seed germination of three Penstemon species. HortScience 25:191-193. Andersen, A. S. 1989. Danish ornamental horticulture in greenhouses and the quest for new crops. Acta Hortic. 252:13-32. Andersen, A. S., T. Wingreen and L. Andersen. 1993. Clerodendrum ugandense Prain. propagation, retardation and post-production performance as an indoor potted plant. Acta Hortic. 337:31-42. Anderson, RG. and G. Hartley. 1990. Use of growth retardants on Satin flower, Godetia, for pot plant production. Acta Hortic. 272:285-292. Anonymous. 1993. International floriculture trade statistics 1993. Pathfast Publishing, Essex, UK. Anonymous. 1994. Danish potted plants. Gartneribrugets Afsaetningsudvalg (GAU), Valby, Denmark. Armitage, A. M. 1986. Evaluation of new floricultural crops: a systems approach. HortScience 21:9-11. Armitage, A. M. 1987. What is a new crop? Acta Hortic. 205:1-2. Armitage, A. M. 1990. New herbaceous ornamental crops research, pp. 453-456. In: Advances in new crops. Proceedings of the first national symposium New Crops: Research, Development, Economics. Eds. Janick, J. and J. E. Simon. Timber Press, Portland. Atwater, B. R. 1980. Germination, dormancy and morphology of the seeds of herbaceous ornamental plants. Seed Sci.Technol. 8:523-573. Ballard, L. A. T. 1973. Physical barriers to germination. Seed Sci. Technol. 1:285-303. Baulk, P. 1988. Lewisias. A cultural guide. Ash wood Nurseries publication, Kingswinford, West Midlands, U. K. 57 Beattie, D.J, CF. Deneke, E.J. Holcomb, and J.W. White. 1989. The effects of photoperiod and temperature on flowering of Physostegia virginiana 'Summer Snow' and 'Vivid' as potted plants. Acta Hortic. 252:227-234. Beattie, D.J. and E.J. Holcomb. 1983. Effects of chilling and photoperiod on forcing astilbe. HortScience 18:449-450. Bewley, J. D. and M. Black. 1994. Seeds. Physiology of development and germination. Plenum Press, New York. 445 pp. Bittrich, V. 1993. Introduction to Centrospermae. pp. 13-20. In: The families and genera of vascular plants. Eds. Kubitzki, K., J. G. Rohwer, and V. Bittrich. Springer-Verlag, Berlin. Bluhm, W.L. 1988. Native herbaceous perennials of the Pacific Northwest worthy of commercial production. Proc. Int. Plant Prop. Soc. 38:135-137. Boesewinkel, F. D. and F. Bouman. 1995. The seed: structure and function, pp. 1-24. In: Seed development and germination. Eds. Kigel, J. and G. Galili. Marcel Dekker, Inc., New York. Brandt, K. 1992. Micropropagation of Campanula isophylla Moretti. Plant Cell, Tissue and Organ Cult. 29:31-36. Bratcher, C. B., J. M. Dole, and J. C. Cole. 1993. Stratification improves seed germination of five native wildflower species. HortScience 28:899-901. Bredmose, N . and V. Geertsen. 1988. Final report for project: Development of new pot plants. Institute for Glasshouse Crops Research, Aarslev, Denmark. Bregman, R. and F. Bouman. 1983. Seed germination in Cactaceae. Bot. J. Linn. Soc. 86:357-374. Cameron, A.C. and M.S. Reid. 1983. Use of silver thiosulfate to prevent flower abscission from potted plants. Sci. Hortic. 19:373-378. Carolin, R. C. 1993. Portulacaceae. pp. 544-549. In: The families and genera of vascular plants. Eds. Kubitzki, K., J. G. Rohwer, and V. Bittrich. Springer-Verlag, Berlin. Christensen, O.V. and K. Friis. 1987. Research and development of unknown new pot plants. Acta Hortic. 205:33-37. Christensen, O.V., L.N. Kristensen, K. Friis, and O. Bovre. 1989. Propagation and forcing of Armeria maritima as a pot plant. Tidsskr. Planteavl 93:239-242. Christiansen, I. 1988. Primula vulgaris. Forbedret holdbarhed efter spr0jtning med Argylene. Gartner Tidende 104:59. 58 CoIIey, J. C, and B. Mineo. 1985. Lewisias for the garden. Pacific Hortic. 46:40-49. Come, D. and F. Corbineau. 1992. Environmental control of seed dormancy and germination, pp. 288-298. In: Advances in the science and technology of seeds. Eds. Jiarui, F. and A. Khan. Science Press, Beijing. Considine, J. A. 1993. Progress in selection and cultivation of Australian native plants for floriculture. Acta Hortic. 337:11-18. Corbineau, F. and D. Come. 1991. Seeds of ornamental plants and their storage. Acta Hortic. 298:313-321. Corbineau, F. and D. Come. 1995. Control of seed germination and dormancy by the gaseous environment, pp. 397-424. In: Seed development and germination. Eds. Kigel, J. and G. Galili. Marcel Dekker, Inc., New York. Dakers, J. S. 1938. The modern greenhouse. Cassell and Co., Ltd., London. 258 pp. Darlington, C. D. 1973. Chromosome botany and the origins of cultivated plants. George Allen & Unwin, London. 237 pp. Davis, T. D. and A.S. Andersen. 1989. Growth retardants as aids in adapting new floricultural crops to pot culture. Acta Hortic. 252:77-85. Davis, T. D., D. Sankhla, N. Sankhla, A. Upadhyaya, J. M. Parsons, and S. W. George. 1993. Improving seed germination of Aquilegia chrysantha by temperature manipulation. HortScience 28:798-799. De Hertogh, A.A. 1987. Forcing of selected ornamental Oxalis spp. as potted plants. Acta Hortic. 205:213-217. Dons, J. J. M., C. Mollema, W. J. Stiekema, and B. Visser. 1991. Routes to the development of disease resistant ornamentals, pp. 387-417. In: Genetics and breeding of ornamental species. Eds. Harding, J., F. Singh, and J. N. M. Mol. Kluv/er Academic Publishers, Dordrecht. Doom, W. G. v. and E. J. Woltering. 1991. Developments in the use of growth retardants for the maintenance of post-harvest quality in cut flowers and potted plants. Acta Hortic. 298:195-208. Egley, G. M. 1989. Water-impermeable seed coverings as barriers to germination, pp. 207-223. In: Recent advances in the development and germination of seeds. Ed. Taylorson, R. B. Plenum Press, New York. 59 Evans, L. T. 1993. Crop evolution, adaptation and yield. Cambridge University Press, Cambridge. 500 pp. Fay, A. M., S. M. Still, and M. A. Bennett 1993. Optimum germination temperature of Rudbeckiafulgida. HortTechnology 3:433-435. Fivelsdal, E. and I. Schramm-Nielsen. 1993. Egalitarianism at work: Management in Denmark, pp. 27-45. In: Management in Western Europe. Ed. Hickson, D. J. Walter de Gruyer, Berlin. Fortgens, G. and W. H. Molenaar. 1986. Containerized nursery production: new potplants for indoor use. Acta Hortic. 181:377-381. Gilbertz, D. A. 1992. Chrysanthemum response to timing of paclobutrazol and uniconazole sprays. HortScience 27:322-223. Gorer, R. 1970. The development of garden flowers. Eyre and Spottiswoode, Ltd., Norwich. 254 pp. Griffin, M. 1995. Challenging the tulip. Ceres 153, 27(3):41-43. Gutterman, Y. 1993. Seed germination in desert plants. Springer-Verlag, Berlin. 253 pp. Hancock, J. F. 1992. Plant evolution and the origin of crop species. Prentice Hall, Englewood Cliffs. 305 pp. Handel, S. N. 1978. New ant-dispersed species in the genera Carex, Luzula, and Claytonia. Can. J. Bot. 56:2925-2927. Hansen, R. and F. Stahl. 1993. Perennials and their garden habitats. Cambridge University Press, Cambridge. 164 pp. Harlan, J. R. 1992. Crops and man. Amercan Society of Agronomy and Crop Science Society of America, Madison. 284 pp. Hentig, W. U. v. 1985. Treatment of rarely cultivated pot-plants with growth regulators. Acta Hortic. 167:309-317. Hershkovitz, M. A. 1992. Leaf morphology and taxonomic analysis of Cistanthe tweedyi (nee Lewisia tweedyi; Portulacaceae). Syst. Bot. 17:220-238. Holcomb, E.J. and D.J. Beattie. 1990. Growth retardants for perennials. Proceedings of the Plant Growth Regulator Society of America, 17th Annual Meeting: 164-168.. 60 Holsteijn, H. M. C. v. 1994. Plant breeding of ornamental crops: Evolution for a bright future?! Acta Hortic. 355:63-70. Hayer, L. and K. Kristensen. 1991. Low post-harvest temperatures reduce the collapsing of Primula vulgaris 'Dania Skarlagen'. Acta Hortic. 298:287-295. HPP. 1994. World floriculture industry, part III. HPP Publishers, Amsterdam. Des, J. K. and N. H. Agnew. 1995. Forcing herbaceous perennials to flower after storage outdoors under a thermoblanket. HortTechnology 5:239-243. Javad Feghahati, S. M. and R. Neil Reese. 1994. Ethylene-, light-, and prechill-enhanced germination of Echinacea angustifolia seeds. J. Am. Soc. Hortic. Sci. 119:853-858. Jondle, R J. 1993. Legal protection for plant intellectual property. HortTechnology 3:301-307. Karlovich, P. T. 1995. The pros & cons of producing perennials from seeds. Greenhouse Management & Production Vol. 14 (No.7):37, 41-42. Keeler, K. H. 1989. Ant-plant interactions, pp. 207-242. In: Plant-animal interactions. Ed. Abrahamson, W. G. McGraw-Hill, New York. Kelly, K. M., J. Van Staden, and W. E. Bell. 1992. Seed coat structure and dormancy. Plant Growth Reg. 11:201-209. Khan, A. A., H. Xuelin, Z. Guangwen, and J. Pnisinski. 1992 Integration of hormonal controls of seed dormancy and germination with environmental demands, pp. 313-335. In: Advances in the science and technology of seeds. Eds. Jiarui, F. and A. Khan. Science Press, Beijing. Kigel, J., A. Gibly, and M. Negbi. 1979. Seed germination in Arnaranthus retroflexus L. as affected by the photoperiod and age during flower induction of the parent plants. J. Exp. Bot. 30:997-1002. King, R. and T. Angus. 1995. Australian plants in bloom - "potted color". GrowerTalks 59:104-110. Klougart, A. 1987. Exploration, adaptation, evaluation, amelioration. Acta Hortic. 205:3-12. Kristensen, L.N. 1989. Hebe cultivars as potential pot plants. Acta Hortic. 252:235-238. Lang ton, F. A. 1991. Selection for production traits in flower crops, pp. 135-155. In: Genetics and breeding of ornamental species. Eds. Harding, J., F. Singh, and J. N. M. Mol. Kluwer Academic Publishers, Dordrecht. 61 Layton, L. 1995. New flower and plant showcase. FloraCulture International 5(9): 12-14, 16, 18,20,22,24. Lopes, L.C. and T.C. Weiler. 1977a. Light and temperature effects on the growth and flowering of Dicentra spectabilis (L.) Lem. J. Am. Soc. Hortic. Sci. 102:388-390. Lopes, L.C. and T.C. Weiler. 1977b. Chemical growth regulation of Dicentra spectabilis (L.) Lem. HortScience 12:335. Macdonald, A.B. 1991. Planning and implementing a successful plant introduction program for the nursery industry. PlantSource 7:3-5. Masvidal, L. 1993. Development of new pot-plants from wild species of Aquilegia. Acta Hortic. 337:131-138. Mathew, B. 1989. The genus Lewisia. Timber Press, Portland. 151 pp. Mikkelsen, J. C. 1987. Commercial aspects of new crop development. Acta Hortic. 205:49-55. Minister of Industry. 1995. Greenhouse industry 1994. Statistics Canada Catalogue No. 22-202, Ottawa. Moe, R. 1990. Effect of day and night temperature alternations and of plant growth regulators on stem elongation and flowering of the long-day plant Campanula isophylla Moretti. Sci. Hortic. 43:291-305. Moore, R. P. 1973. Tetrazolium staining for assessing seed quality, pp. 347-366. In: Seed ecology. Ed. Heydecker, W. Butterworths, London. Murashige, T. 1990. Plant propagation by tissue culture: A practice: with unrealized potential, pp. 3-9. In: Handbook of plant cell culture, vol. 5. Eds. Ammirato, P. V., D. A. Evans, W. R. Sharp, and Y. P. S. Bajaj. McGraw Hill, New York. Murashige, T. and F. Skoog. 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15:473-497. Nell, T. A. 1992. Taking silver safely out of the longevity picture. GrowerTalks 56(2):35, 37, 39, 41-42. Nell, T.A. and J.E. Barrett 1989. Postproduction longevity of new flowering potted plants. Acta Hortic. 252:87-89. Noordegraaf, C. V. 1987. Development of new cutflower crops. Acta Hortic. 205:25-31. Noordegraaf, C. V. 1993. Changes in floricultural crops in Europe. Acta Hortic. 337:43-51. 62 Noordegraaf, C. V. 1994. Production and marketing of high quality plants. Acta Hortic. 353:134-148. Olsen, W. W. and A. S. Andersen. 1995. Growth retardation of Osteospermum ecklonis. Acta Hortic. 397:129-138. Persson, B. 1993. Enhancement of seed germination in ornamental plants by growth regulators infused via acetone. Seed Sci. Technol. 21:281-290. Preston, F. G. 1951. The greenhouse: A complete guide to the construction and management of greenhouses of all kinds, from the cold house to the tropical house; and to the cultivation of greenhouse plants, including orchids, cacti and hot house species. Ward, Lock & Co., Ltd., London. 640 pp. Rasmussen, H., T. F. Andersen, and B. Johansen. 1990. Temperature sensitivity of in vitro germination and seedling development of Dactylorhiza majalis (Orchidaceae) with and without its mycorrhizal fungus. Plant, Cell and Environ. 13:171-177. Reid, M. S. and M. J. Wu. 1991. Ethylene in flower development and senescence, pp. 215-234. In: The plant hormone ethylene. Eds. Mattoo, A. K. and J. C. Suttle. CRC Press, Boca Raton. Reid, M. S. and M. J. Wu. 1992. Ethylene and flower senescence. Plant Growth Regul. 11:37-43. Roberts, C. M., M. Serek, and A. S. Andersen. 1995. Supplemental irradiance and STS improve the display life of Dicentra species forced as flowering potted plants. Sci. Hortic. 62:121-128. Roh, M. S. and R. H. Lawson. 1987. Research and development of new crops in the United States Department of Agriculture. Acta Hortic. 205:39-48. Roh, M. S. and R. H. Lawson. 1990. New floricultural crops, pp. 448-453. In: Advances in new crops. Eds. Janick, J. and J. E. Simon. Timber Press, Portland. Roh, M. S. and R. H. Lawson. 1993. Progress of new crops research - A cooperative program between the government and industry. Acta Hortic. 337:146-152. Rolston, M. P. 1978. Water impermeable seed dormancy. Bot. Rev. 44:365-396. Sachs, R, M., A. M. Kofranek, and W. P. Hackett 1976. "Evaluating new pot plant species." Florists Rev. 159(4116):35-36, 80-84. Salac, S. S. and M. C. Hesse. 1975. Effects of storage and germination conditions on the germination of four species of wild flowers. J. Am. Soc. Hortic. Sci. 100:359-361. 63 Santos, D. S. B. and M. F. A. Pereira. 1989. Restriction of the tegument to the germination of Beta vulgaris L. seeds. Seed Sci. Technol. 17:601-611. SAS Institute. 1985. SAS/STAT guide for personal computers, version 6 edition. SAS Institute, Cary, N.C. Serek, M. 1990. Effects of pre-harvest fertilization on the flower longevity of potted Campanula carpatica 'Karl Foerster'. Sci. Hortic. 44:119-126. Serek, M. 1991. Effects of pre-harvest supplementary irradiance; on decorative value and ethylene evolution of Campanula carpatica 'Karl Foerster' flowers. Sci. Hortic. 48:341-347. Serek, M. 1993. Ethephon and silver thiosulfate affect postharvest characteristics of Rosa hybrida 'Victory Parade'. HortScience 28:199-200. Serek, M. and M. S. Reid. 1993. Anti-ethylene treatments for potted Christmas cactus -efficacy of inhibitors of ethylene action and biosynthesis. HortScience 28:1180-1181. Serek, M., M. S. Reid and E. C. Sisler. 1994a. A volatile ethylene inhibitor improves the postharvest life of potted roses. J. Am. Soc. Hortic. Sci. 119:572-577. Serek, M., E. C. Sisler, and M. S. Reid. 1994b. Novel gaseous ethylene binding inhibitor prevents ethylene effects in potted flowering plants. J. Am. Soc. Hortic. Sci. 119:1230-1233. Sheldron, K. G. and T. C. Weiler. 1982. Regulation of growth and flowering in Aquilegia xhybrida Sims. J. Am. Soc. Hortic. Sci. 107:878-882. Smith, B. D. 1988. SEM and the identification of micro-morphological indicators of domestication in seed plants, pp. 203-213. In: Scanning electron microscopy in archaeology. Ed. Olsen, S. British Archaeological Reports International Series, Oxford. Smith, B. D. 1995. The emergence of agriculture. Scientific American Library, New York. 231 pp. Smith, T. 1992. Culture notes: Bleeding heart. GrowerTalks 12:17. Staby, G. L., R M. Basel, M. S. Reid, and L. L. Dodge. 1993. Efficacies of commercial anti-ethylene products for fresh cut flowers. HortTechnology 3:199-202. Stebbins, G. L. 1974. Flowering plants: Evolution above the species level. Belknap Press, Cambridge. 397 pp. Straley, G. B. 1988. British Columbia's alpine and subalpine flora v/ith garden potential. Proc. Int. Plant Prop. Soc. 38:130-134. 64 Suda, S. 1987. Breeding and evaluation of Sakata's new flowers. Acta Hortic. 205:21-24. Sulaiman, I . M. 1993. Seed germination studies in three species of threatened, ornamental, Himalayan poppy, Meconopsis Vig. (Papaveraceae). Seed Sci. Technol. 21:593-603. Sulaiman, I . M. and C. R Babu. 1993. In vitro regeneration through organogenesis of Meconopsis simplicifolia - an endangered ornamental species. Plant Cell, Tissue and Organ Cult. 34:295-298. United Flower Growers. 1994. Plants from British Columbia, Canada. United Flower Growers Co-Op Association, Burnaby, British Columbia. Van Meeteren, U. and M. de Proft 1982. Inhibition of flower bud abscission and ethylene evolution by light and silver fhiosulphate in Lilium. Physiol. Plant. 56:236-240. Veen, H. and S. C. Van de Geijn. 1978. Mobility and ionic form of silver as related to longevity in cut carnations. Planta 140:93-96. Vuuien, P. J. J. v., J. Coetzee, and A. Coertse. 1993. South Afric;ui flowering plants with a potential as future floriculture crops. Acta Hortic. 337:65-71. Weiler, T. C. and L. C. Lopes. 1976. Photoregulated Dicentra spectabilis (L) Lem. as a potential potted plant. Acta Hortic. 64:191-195. Werker, E. 1980/81. Seed dormancy as explained by the anatomy of the embryo envelopes. Isr. J. Bot. 29:22-44. White, J.W., D.J. Beattie, and E.J. Holcomb. 1989. Flowering studies with Aquilegia cultivars. Acta Hortic. 252:219-226. Wicki-Friedl, P. 1990. Lewisia als topfpflanze interessant? GbGw 90(13):633-638. Wijnheijmer, E. H. M. 1989. Plant breeders' rights in The Netherl;inds. Acta Hortic. 252:91-95. Woltering, E.J. 1987. Effects of ethylene on ornamental plants: A classification. Sci. Hortic. 31:283-294. Woodson, W. R 1991. Gene expression and flower senescence, pp. 317-331. In: Genetics and breeding of ornamental species. Eds. Harding, J., F. Singh, and J. N. M. Mol. Kluwer Academic Publishers, Dordrecht. Worrall, R 1995. Breeding of dwarf kangaroo paw (Anigozanthos) for use as flowering pot plants. Acta Hortic. 397:189-196. 65 Yang, S. F. 1985. Biosynthesis and action of ethylene. HortScience 20:41-45. Zimmerman, T. W., F. T. Davies, Jr., and J . M . Zajicek. 1991. In vitro and macropropagation of the wildflower Dyssodia pentacheta (D.C.) Robins. HortScience 26:1555-1557. 66 

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