青藏高原东部橐吾属植物的花性分配和雌全同株系统

摘要

Gynomonoecy is the sexual system in which female and bisexual flowers occur on the same plant.Lit-tle attention has been paid to the adaptive significance of this sexual system.In this paper,we investigated 3 common species of the genus Ligularia (Asteraceae)in the eastern part of the Tibetan Plateau and examined the effects of flower head position,plant height and leaf removal on floral sex allocation.The results showed that plants of these three Ligularia genera were self-incompatible,and the intra-inflorescence variations in flo-ral traits were significant.Regardless of whether the racemes developed from top to bottom or in the opposite direction,the early-formed flowers within a raceme were larger and displayed female-biased sex allocation.The later-formed flowers had more ovules and displayed a male-biased sex allocation.Taller plants have a lager flower display and invest more resources in the female state.Raceme size and investment in ray floret biomass were significantly decreased in plants with leaves removed.However,plant height and leaf removal did not change the variation of floral traits within inflorescences.The adaptive significance of gynomonoecy in Ligu-laria lies in permitting flexibility in allocation of resources to male and female functions.Ecologically this be-havior may link seed set to resource availability and may assist with attracting pollinators,and may also reduce conflict between male and female functions.%雌全同株是指同一植株内同时拥有雌花和两性花的性系统，至今对该性系统的适应性研究较少。本文以青藏高原东部常见的3种橐吾属植物为材料，调查植株内头状花序的位置，植株高度和个体叶片去除对花性分配的影响。结果表明，3种橐吾均自交不亲和，并且花部特征存在显著的花序轴内变异，无论总状花序基向式发育还是顶向式发育，均表现出早期花有较大的花展示和偏雌的性分配，晚期花拥有较多胚珠和偏雄的性分配。较高的个体拥有较大的花展示，并在雌性功能上投入更多；被去除叶片的个体的花展示和雌花生物量投入均明显下降。然而，植株高度和叶片去除并不会改变花特征在花序内的变异。分析认为橐吾属植株的雌全同株系统的进化意义为资源的灵活分配和吸引传粉者，但无法排除减少雌雄功能冲突的可能。