海滨锦葵花内五柱头裂片弯曲的独自调节

Independent regulation of curvature of five stigma lobes within Kosteletzkya virginica flowers

关键词:  海滨锦葵  独自调节  柱头裂片弯曲  花粉－胚珠比  混合交配系统  繁殖保障

Key words:  Kosteletzkya virginica  independent regulation  stigma lobe curvature  pollen ovule ratio  mixed mating system  reproductive assurance

摘要:

海滨锦葵花柱有5柱头裂片，若传粉失败，柱头裂片向下弯曲使柱头与自身花粉接触，发生延迟自交。传粉不足条件下发生的延迟自交可能提供繁殖保障。该研究定量分析了花粉搁置和授精胚珠数对花内未授粉柱头裂片运动的影响，并测定了花粉－胚珠比及柱头可授性和花粉生活力。结果表明，花内未授粉柱头裂片的弯曲不受其他柱头接受花粉量及授精胚珠数的影响，仅响应于其自身是否接受到花粉；花粉－胚珠比值显示海滨锦葵交配系统属兼性异交；未授粉柱头经弯曲与自身花粉授触时的强柱头可授粉和高花粉生活力为自交授粉的发生提供了可能。包括柱头裂片运动在内的多个花性状有机地展示了一种新花内混合交配系统，且花内柱头裂片弯曲的独自调节为从花水平验证被广泛接受的自交进化解释——繁殖保障假说提供了可能。

Abstract:

Kosteletzkya virginica has a pistil with five stigma lobes. If un pollinated，individual stigma lobes downward curve to bring them contact with a flower’s own anthers，possibly resulting in delayed selfing，which might provide reproductive assurance when pollinators are scarce. It was observed，but not experimentally tested，that each of the five lobes within flowers acts independently. Here，we quantitatively tested the effects of pollen loads and seed set on the curvature of un pollinated lobes within flowers，pollen ovule ratio and stigma receptivity and pollen viability. Results showed that the curvature of un pollinated lobes within flowers did not appear to be a response to the amount of pollen grains deposited on the adjacent stigmas and seed set，depending on if each received pollen. The value of pollen ovule ratio indicated that mating system belonged to facultative xenogamy. When un pollinated stigmas were in contacting with its own anthers via style movements，high stigma receptivity and pollen viability provided a possible for resulting in delayed selfing. Multiple floral traits including independent curvature of stigma lobes harmoniously exhibit a mixed mating system within flowers. Our data provided the first empirical demonstration that the curvature of the five stigma lobes within flowers regulates independently，which provides incentive for testing at the flower level the reproductive assurance widely accepted explanation for the evolution of selfing.