大叶补血草柱高二态维持机制及演化趋势的研究

Plants with hermaphrodite flowers are always in risk of conflict between male and female sexual function due to close proximity of sexual organs. Herkogamy,a spatial sexual segregation in sex-organ levels, is considered to be an adaptive strategy to avoide self-pollination，promote the precision of pollen transfer between morphs and alleviate interference between the male and female sex functions,including heterostyly,enantiostyly and stigma-height dimorphism. Stigma-height dimorphism, a distinctive heteromophic herkogamy, is a genetic floral polymorphism primarily characterized by two morphs with different style lengths but the anthers at the same level.. Currently, the maintain mechanism and evolutionary trend of reproductive strategies and in particular, sexual systems are still not well understood given stigma-height dimorphism is rare in angiosperms,although it is regard as a intermediate stage of heterostyly evolution by some scholars due to stigma-height dimorphism often appearing in some family with heterostylous species..Plumbaginaceae has been reported to have heterostylous species and our latest investigation has shown that the flowers of Limonium gmelinii has typical stigma-height dimorphism. Diverse breeding systems in Plumbaginaceae provide an ideal system in which to test hypotheses on the evolution of stigma-height dimorphism..To explore to the evolution of stigma-height dimorphism in the family and the maintain mechainsma of stigma-height dimorphism within Limonium gmelinii, in the project we plan to investigate various aspects of pollination biology and breeding system of Limonium gmelinii and sympatric species Limonium otolepis in the field populations in Xingjiang,including studies of the stigma-height dimorphism and ancillary character, pollination and mating patterns, incompatibility system and the test of several hypotheses on maintenance of stigma-height dimorphism. We also investigate the current selective pressure in Limonium gmelinii populations to track evolutionary trend of stigma-height dimorphism. All of these studies will be useful to clarify the pathway of occuring and evolution about stigma-height dimorphism, to better understand diverse breeding systems in angiosperms.

在被子植物中，两性花植物雌雄功能之间常存在着潜在的相互干扰。雌雄异位被认为是避免自交、促进花粉传递、降低雌雄功能干扰的一种适应。花柱高度二态性是一种独特的异型雌雄异位现象，其特别之处在于两种截然不同的柱头高度能够在同种植物中共存。因为柱高二态多出现在具有异型花柱的科中，被部分学者推测可能是二型花柱演化的中间阶段，但因为少见，至今，其维持机制和演化趋势仍不清楚。白花丹科Plumbaginaceae被报道是具有二型花柱植物的科，我们发现大叶补血草Limonium gmelinii具有典型的柱高二态现象。本项目计划以大叶补血为主要研究对象，以同域种耳叶补血草为对照，在多个野外居群调查柱高二态及相关花部性状的变异、传粉模式及交配系统，以期检验相关假说，探讨柱高二态的维持机制和演化趋势。发展对花进化动力的认识。为探索柱高二态植物的演化途径，理解柱高二态植物为什么以及如何在特定的科中发生提供依据。

同种植物不同个体有不同的花型，其中一个普遍的类型就是二型花柱。虽然有学者认为二型花柱的植物是由雌雄蕊等高的同型花植物进化而来，但驱使进化的选择因子仍不清楚。因同一物种或居群中缺少雌雄蕊等高的同型花做对照，难以评价二型花柱的适应与进化动力。前人根据花标本，确定了补血草属植物有较多二型花柱存在。为了发展对花进化动力的认识，我们对分布在新疆的一种有雌雄等高的同型花存在的补血草属植物---大叶补血草进行了研究。结果表明:大叶补血草大部分居群主要有长花柱（L型）、短花柱（S型）和雌雄蕊等高（H型）的三种花型构成，其中L型、S型花雌雄蕊长度具明显的交互性对应关系，H型花的雌雄蕊等长，介于L型和S型花雌、雄蕊之间。三种株型的花型频率在不同居群或在同一居群的不同年份不同。三种花型在花冠筒长、花冠开口直径、单花花粉量、胚珠数等花部参数上没有差异。但花粉纹饰、柱头乳突细胞形态表现出二型性，其中L型和H型的花粉纹饰、柱头乳突细胞形态一致，明显与S型花不同。对三种花型进行型间和型内授粉实验显示：三种花型型内和自花授粉均不亲和，而雌雄蕊长度具交互性对应关系或花粉纹饰、柱头乳突细胞形态具二型性的花型间授粉亲和。在没有交互性对应关系的花型间，柱头乳突形态和花粉纹饰间可能具有相互识别作用，进而促进非选型交配，使得自然居群三种花型的结实率没有差异。这与Dulberger（1975） 的“形态互补性假说”一致。这也是居群中雌雄蕊高度没有交互性对应关系的H型花柱得以维持的重要因素。依据L型和H型花具有相同的花粉、柱头形态以及型间的不亲和性可以推断，居群中雌雄蕊等高的H型花可能是L型花的变形。该居群的花型组合可能是大叶补血草二型花柱演化过程中的中间过渡类型。