The Effects of Inflorescence Size and Flower Position on Biomass and Temporal Sex Allocation in <Emphasis Type="Italic">Lobelia sessiliflora</Emphasis> |
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Authors: | Tomoyuki Hiraga Satoki Sakai |
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Institution: | (1) Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan |
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Abstract: | To test the prediction of sex allocation theory that plants or flowers high in resource status emphasize the female function,
we explored the variation in both biomass (the number of pollen grains and ovules) and temporal (male and female durations)
sex allocation among and within plants of protandrous Lobelia sessilifolia in relation to plant size and flower position within plants. Among plants, the mean number of pollen grains and ovules per
flower of a plant increased with plant size, whereas the mean P/O ratio (number of pollen grains/number of ovules ratio) decreased
with plant size. The mean male duration, the mean female duration, and the mean ratio of male duration/flower longevity per
flower of a plant were not correlated with plant size. Thus, large plants emphasized female function in terms of biomass sex
allocation, which is consistent with the prediction of size-dependent sex allocation theory. The results for temporal sex
allocation, however were inconsistent with the theory. Within plants, the mean number of pollen grains and ovules per flower
at each position decreased from lower to upper flowers (early to late blooming flowers) and that of the P/O ratio increased
from lower to upper flowers. The mean male duration and the mean female duration per flower decreased from lower to upper
flowers, whereas the mean ratio of male duration/flower longevity increased from lower to upper flowers. The population sex
ratio changed from male-biased to female-biased. Thus, later blooming flowers emphasized the male function in terms of both
biomass and temporal sex allocation, consistent with the sex allocation theory, regarding the change in the population sex
ratio. |
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Keywords: | Pollen grain Ovule Male duration Female duration Protandry Sex allocation |
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