Shibata Akari, Kudo Gaku
Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
AoB Plants. 2016 Dec 30;9(1). doi: 10.1093/aobpla/plw089.
In sexually dimorphic plants, resource allocation to reproduction often differs between sex morphs. In gynodioecious species, i.e. coexisting hermaphrodite and female plants within a population, females often produce more fruits than hermaphrodites. Since fruit production is costlier than flower production, hermaphrodites and females may regulate flower and fruit production differently in response to resource availability. To clarify the gender-specific strategies of reproductive allocation, we assessed sexual dimorphism in reproductive traits, size-dependent resource allocation, morphological traits, and photosynthetic capacity in a natural population of a gynodioecious shrub, Daphne jezoensis Hermaphrodites had larger flowers and increased flower number with plant size at a rate greater than females, but showed consistently smaller fruit production. Although females did not increase flower production as much as hermaphrodites did as their size increased, they produced 3.7 times more fruits than did hermaphrodites. Despite a large sexual difference in fruiting ability based on hand-pollination, total resource investment in reproduction (the sum of flower and fruit mass) was similar between sex morphs across plant sizes, and there was little sexual difference in the cost of reproduction, i.e. the negative effect of current reproduction on future reproductive effort, in the natural population. In addition, there were no sexual differences in the resource allocation to vegetative organs (leaf and root mass) and photosynthetic capacity (light response photosynthetic rates). Under natural conditions, pollen limitation strongly restricted the fruit production of females, resulting in similar cost of reproduction between hermaphrodites and females.
在具有性别二态性的植物中，不同性别形态之间用于繁殖的资源分配往往存在差异。在雌全同株植物物种中，即在一个种群中同时存在雌雄同体和雌性植株，雌性植株通常比雌雄同体植株结出更多果实。由于果实生产比花朵生产成本更高，雌雄同体和雌性植株可能会根据资源可利用性以不同方式调节花朵和果实的生产。为了阐明繁殖分配的性别特异性策略，我们评估了雌全同株灌木长白瑞香自然种群中繁殖性状的性别二态性、与大小相关的资源分配、形态性状和光合能力。雌雄同体植株的花朵更大，且随着植株大小增加，花朵数量增加的速率高于雌性植株，但果实产量始终较低。尽管雌性植株随着大小增加，花朵产量的增加幅度不如雌雄同体植株，但它们的果实产量是雌雄同体植株的3.7倍。尽管基于人工授粉的结果显示结果能力存在很大的性别差异，但在不同大小的植株中，不同性别形态之间用于繁殖的总资源投入（花朵和果实质量之和）相似，并且在自然种群中，繁殖成本（即当前繁殖对未来繁殖努力的负面影响）几乎没有性别差异。此外，在营养器官（叶片和根质量）的资源分配和光合能力（光响应光合速率）方面也没有性别差异。在自然条件下，花粉限制强烈限制了雌性植株的果实产量，导致雌雄同体和雌性植株之间的繁殖成本相似。
