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Role of environmental factors and plant growth regulators on the floral transition of Exacum Styer group Krishnasamy, Rani
Abstract
Exacum Styer Group exhibit many outstanding characteristics that make this crop suitable as a new flowering pot, bedding or cut flower crop. One requirement for a new crop's commercial success is a reliable system to predict or control flower initiation and development. Therefore, this study focuses on evaluating the role of environmental factors on the transition from vegetative to reproductive growth. Light treatments, based on a combination of shade nets and supplemental lights were designed to deliver between 1152 moles and 5211 moles of light over a 36 week period. Visual inspection of plants occurred daily with the dates of first visible bud and anthesis recorded from each individual within all populations (i.e., genetically related seedlings). Average number of days to visible bud and average number of days to anthesis for individual populations ranged from 170-218, and 237-280, respectively. Average number of days to anthesis for individual treatments were as follows: Treatment 1 (ambient light + 65% shade) 272 days; Treatment 2 (ambient light + 35% shade) 278 days; Treatment 3 (ambient light) 273 days; Treatment 4 (ambient light + supplemental light) 238 days. Analysis of variance results indicate significant effects (P<0.05) on days to visible bud and days to anthesis for population, treatment, and their interaction. These sources of variation are partly attributed to the high level of heterozygosity within these populations reflective of their interspecific background. Changes in meristem structure associated with floral initiation were characterized across populations of Exacum Styer Group. Meristem anatomy and morphology were characterized from tissue harvested weekly and were based on light (i.e., anatomy) and scanning electron (i.e., morphology) microscopy. Structural changes associated with floral initiation were consistent across all individuals and populations and were successfully sub-divided into six relatively distinct stages. In Stage 1, the shoot apical meristem (SAM) is dome to conical shaped with a height to width ratio of 0.90 and without visible structures. In Stage 2, the apical dome becomes flattened as development progresses with the height to width ratio changing to 0.43 and remaining without visible structures. In Stage 3, five sepal primordia are initiated around the apex that resembles foliage leaves in both position and development. During Stage 4, the apex continues to flatten and broaden with a height to width ratio further reducing to 0.09, and with five petal primordia arising simultaneously alternate to the sepals. In Stage 5, initiation of the stamens occurs with their first appearance as short structures alternate to the petals. Finally, in Stage 6, the ovary is initiated. These observations on meristem transition are consistent with previous reports for many other angiosperm species and support these six stages of transition as fundamental in angiosperm development. Meristem width and height were used in allometric analyses and associated with environmental treatments (i.e., light unit sum, heat unit accumulation, time). Coefficients of determination obtained from simple allometric regression ranged from 0.468 (Population 02-65) to 0.980 (Population 02-62). To include additional sources of variation over that of the simple allometric regression (i.e., interactions between both the environment (i.e., treatments) and genotype (i.e., both within and among individual families)), an expanded power function model was developed. The best subset regression procedure was performed with the expanded allometric model to determine which independent variables were most appropriate to include in the multiple regression model. The models that displayed a low Mallow's Cp value, a low variance inflation value and a high R2 were selected as the most useful. Direct comparisons between the two allometric models were based on the magnitude of the partial regression coefficients for each parameter in the best subset models. Using the best subset regression results, significant standard partial regression coefficients were observed for light sum (11 of 13 populations) and days (7 of 13 populations) indicating these two parameters significantly affected floral initiation.
Item Metadata
Title |
Role of environmental factors and plant growth regulators on the floral transition of Exacum Styer group
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2007
|
Description |
Exacum Styer Group exhibit many outstanding characteristics that make this
crop suitable as a new flowering pot, bedding or cut flower crop. One requirement for a
new crop's commercial success is a reliable system to predict or control flower initiation
and development. Therefore, this study focuses on evaluating the role of environmental
factors on the transition from vegetative to reproductive growth.
Light treatments, based on a combination of shade nets and supplemental lights
were designed to deliver between 1152 moles and 5211 moles of light over a 36 week
period. Visual inspection of plants occurred daily with the dates of first visible bud and
anthesis recorded from each individual within all populations (i.e., genetically related
seedlings). Average number of days to visible bud and average number of days to
anthesis for individual populations ranged from 170-218, and 237-280, respectively.
Average number of days to anthesis for individual treatments were as follows:
Treatment 1 (ambient light + 65% shade) 272 days; Treatment 2 (ambient light + 35%
shade) 278 days; Treatment 3 (ambient light) 273 days; Treatment 4 (ambient light +
supplemental light) 238 days. Analysis of variance results indicate significant effects
(P<0.05) on days to visible bud and days to anthesis for population, treatment, and their
interaction. These sources of variation are partly attributed to the high level of
heterozygosity within these populations reflective of their interspecific background.
Changes in meristem structure associated with floral initiation were characterized
across populations of Exacum Styer Group. Meristem anatomy and morphology were
characterized from tissue harvested weekly and were based on light (i.e., anatomy) and
scanning electron (i.e., morphology) microscopy. Structural changes associated with floral initiation were consistent across all individuals and populations and were
successfully sub-divided into six relatively distinct stages. In Stage 1, the shoot apical
meristem (SAM) is dome to conical shaped with a height to width ratio of 0.90 and
without visible structures. In Stage 2, the apical dome becomes flattened as
development progresses with the height to width ratio changing to 0.43 and remaining
without visible structures. In Stage 3, five sepal primordia are initiated around the apex
that resembles foliage leaves in both position and development. During Stage 4, the
apex continues to flatten and broaden with a height to width ratio further reducing to
0.09, and with five petal primordia arising simultaneously alternate to the sepals. In
Stage 5, initiation of the stamens occurs with their first appearance as short structures
alternate to the petals. Finally, in Stage 6, the ovary is initiated. These observations on
meristem transition are consistent with previous reports for many other angiosperm
species and support these six stages of transition as fundamental in angiosperm
development.
Meristem width and height were used in allometric analyses and associated with
environmental treatments (i.e., light unit sum, heat unit accumulation, time). Coefficients
of determination obtained from simple allometric regression ranged from 0.468
(Population 02-65) to 0.980 (Population 02-62). To include additional sources of variation
over that of the simple allometric regression (i.e., interactions between both the
environment (i.e., treatments) and genotype (i.e., both within and among individual
families)), an expanded power function model was developed. The best subset regression
procedure was performed with the expanded allometric model to determine which
independent variables were most appropriate to include in the multiple regression model. The models that displayed a low Mallow's Cp value, a low variance inflation value and a
high R2 were selected as the most useful. Direct comparisons between the two allometric
models were based on the magnitude of the partial regression coefficients for each
parameter in the best subset models. Using the best subset regression results, significant
standard partial regression coefficients were observed for light sum (11 of 13 populations)
and days (7 of 13 populations) indicating these two parameters significantly affected floral
initiation.
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Genre | |
Type | |
Language |
eng
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Date Available |
2011-02-22
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0100686
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.