Zhang Tao, Tan Dun-Yan
Xinjiang Key Laboratory of Grassland Resources and Ecology, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Urümqi 830052, China.
J Integr Plant Biol. 2009 Mar;51(3):316-24. doi: 10.1111/j.1744-7909.2008.00800.x.
The pollen donor and pollinator attractor hypotheses are explanations for the functions of the male flowers of andromonoecious plants. We tested these two hypotheses in the andromonoecious shrub Capparis spinosa L. (Capparaceae) and confirmed that pollen production and cumulative volume and sugar concentration of nectar do not differ between male and perfect flowers. However, male flowers produced larger anthers, larger pollen grains and smaller ovaries than perfect flowers. Observations on pollinators indicated that two major pollinators (Xylocopa valga Gerst and Proxylocopa sinensis Wu) did not discriminate between flower morphs and that they transferred pollen grains a similar distance. However, there were more seeds per fruit following hand pollination with pollen from male flowers than from perfect flowers. Individuals of C. spinosa with a larger floral display (i.e. bearing more flowers) received more pollen grains on the stigma of perfect flowers. Female reproductive success probably is not limited by pollen. These results indicate that male flowers of C. spinosa save resources for female function and that they primarily serve to attract pollinators as pollen donors.
花粉供体和传粉者吸引假说解释了雌雄同株植物雄花的功能。我们在雌雄同株的灌木刺山柑（ Capparaceae科）中对这两个假说进行了验证，证实雄花和两性花在花粉产量、花蜜累积量及糖浓度方面并无差异。然而，雄花产生的花药更大、花粉粒更大，子房比两性花的更小。对传粉者的观察表明，两种主要传粉者（黄斑蜂Xylocopa valga Gerst和中华拟黄斑蜂Proxylocopa sinensis Wu）对花的形态并无偏好，且它们传播花粉的距离相似。然而，用雄花花粉进行人工授粉后每个果实中的种子比用两性花花粉授粉的更多。具有更大花展示（即着花更多）的刺山柑个体在两性花的柱头上接受的花粉粒更多。雌性繁殖成功率可能不受花粉限制。这些结果表明，刺山柑的雄花为雌性功能节省了资源，并且它们主要作为花粉供体起到吸引传粉者的作用。
