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UBC Theses and Dissertations

Studies on early development and endogenous gibberellins in red alder (Alnus rubra Bong.) Elliott, Dave Michael

Abstract

The thesis is presented in five parts. In the first, our present knowledge of red alder {Alnus rubra Bong.) is summarized and shows a lack of specific knowledge about its seed and reproductive biology. The aims of the first study were (1) to determine the occurrence and (if present) the nature of seed dormancy; (2) to determine whether seed vigour was related to geographic location of different provenances; and (3) to examine the influence of stratification and presoaking on seed germination. Germination tests were carried out on stratified, presoaked and untreated seeds collected from several locations throughout the species' range. With one exception (seed from Haney, B. C. collected in 1976), dormancy was not a significant factor in preventing germination of untreated seeds. Germination of these exceptional seeds was improved by cold stratification for eight days and to a lesser extent, by presoaking in tap water for 2h hours. Seed collected from the same area before and after these tests showed no dormancy. Germination percent was relatively high for treated and untreated seeds of other provenances and showed few differences between provenances. There were more pronounced differences in seed vigour, as measured by germination value, between provenances. There appeared to be no direct relationship between the differences observed and geographic factors, as found in many wide ranging species native to western North America. The aims of the second study were (1) to examine the effects of fertilization and different soil types on root and nodule development, height growth, dry weight accumulation and root-shoot dry weight ratio of seedlings of red alder from different locations in its natural distribution; and (2) to relate observed differences between provenances to their geographic location. Early seedling development in fertilized and unfertilized seedlings front several sources and grown in different combinations of sand and a loamy soil, was examined. Root development was influenced by the type of growth medium and the nutrient status of the same. Nodulation, however, was little affected by these factors. Nodule development was more extensive on upper root branches than on lower ones. Fertilization increased height and dry weight, and lowered root-shoot dry weight ratio of seedlings. Height growth and dry weight accumulation were greater, and root-shoot ratio was lower in loam and in a loam-sand mixture (1:1 w/w) than in sand. Height growth did not differ between provenances. There were differences in dry weight and root-shoot ratio between provenances but these differences were not correlated with any geographic factor. In the last study, an attempt was made to identify endogenous gibberellins extracted from quiescent vegetative, male and female buds of red alder. Following fractionation of the extracts by silica gel partition chromatography, positive growth responses were obtained in the dwarf rice bioassay of several of the fractions. In gas-liquid chromatography, various fractions produced peaks with retention times similar to those of standard gibberellins. Although some qualitative indications were noted, it was not possible to confirm the presence and identity of gibberellins using combined gas-1iquid chromatography-mass spectrometry. Inadequate purification of extracts and low concentrations of endogenous gibberellins in the extracts were thought to be mainly responsible for this failure. The impact and implications arising from the results of these studies and -possible future directions for research are discussed in the final chapter.

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