探究非管状花的二型花柱植物维持传粉精确性的机制

Distyly is characterized by reciprocal herkogamy, that individual phenotypes of the same species have two floral morphs (long- and short-styled flowers) within a population. Previous studies assumed that heterostyly was possibly adaptive to avoid male-female sexual interference, and/or promote accurate pollination between floral morphs. Darwin once inferred that pollen grains from the two morphs could be deposited on different parts of a pollinator's body, thus reducing a mixture of heteromorphic pollen, and facilitating intermorph pollen transfer. This hypothesis is based on most heterostylous plants with specialized tubular flowers, however, it remains unclear how heterostylous species with non-tubular flowers maintain pollination accuracy. Our previous investigations showed that flowers of distylous Fagopyrum esculentum are non-tubular and pollinated by insects. To understand how distylous species with non-tubular flowers achieve pollination accuracy, we plan to combine field site experiments and artificial simulations to examine the effects of floral characteristics on compatible pollination in Fagopyrum esculentum. By stressing the interaction of plant-pollinator-plant, this project will quantify the contact sites on pollinator bodies and contact frequency on pollen and stigmas, the number of ratio of pollen grains from two morphs carried on different sites of the pollinator; then analyze how the pollinator and the degree of reciprocity between morphs affect pollen removal and deposition, and further reproductive success. This proposal aims to provide new evidence for the adaptive strategy of distylous flowers, and a better understanding of the reproductive ecology of the buckwheat crop resources.

二型花柱是一种互补式雌雄异位现象，即同种植物在居群中不同个体有长花柱短花药、短花柱长花药两种花型，其雌雄蕊位置交互对应，其适应性意义可能在于避免雌雄功能干扰、促进花型之间精确传粉。达尔文曾推测两种花型可将花粉分别落置于传粉者身体的不同部位，以减少两型花粉混杂、促进型间亲和传粉，即携粉位置分化假说；但该假说是基于较特化的管状花异型花柱植物，而对非管状花异型花柱植物是如何实现传粉精确性的,仍缺乏证据。本项目拟以前期调查的虫媒二型花柱植物甜荞为研究对象，结合定点研究和人工模拟，探究非管状花二型花柱植物维持传粉精确性的可能机制。本研究的切入点是植物-传粉者-植物间的互作，通过定量传粉者与花药柱头的接触部位和频率、传粉者不同部位携带的二型花粉数量及比例，分析传粉者和型间互补程度对二型植物个体的花粉移出落置及生殖成功的影响。以期为二型花柱的适应策略提供新的证据，并为深入了解荞麦属作物繁殖特性提供基础。

二型花柱是一种互补式雌雄异位现象，即同种植物在居群中不同个体有长花柱短花药、短花柱长花药两种花型，其雌雄蕊位置交互对应，其适应性意义可能在于避免雌雄功能干扰、促进花型之间精确传粉。前人认为二型花柱可以促进型间花粉传递，以维持二型花柱居群型比。本研究通过对中国西南地区7种荞麦属植物的花形态和柱头花粉落置模式的研究，验证了性器官相互作用与合法花粉落置有关的假说。我们使用适应性精确性概念来评估互补水平，并将性器官位置的不精确性与柱头上的合法花粉落置相关联。调查的七种荞麦属植物均表现出偏离完美互补，总不精确指数在3.1%到12.6%之间。在荞麦属中，偏离完美互补的现象很普遍，并对合法花粉落置产生影响。在二型花柱植物中，达尔文曾推测两种花型可将花粉分别落置于传粉者身体的不同部位，以减少两型花粉混杂、促进型间亲和传粉，即携粉位置分化假说；但该假说是基于较特化的管状花二型花柱植物，而对非管状花二型花柱植物是如何实现传粉精确性的，仍缺乏证据。本研究以前期调查的虫媒二型花柱植物甜荞为研究对象，定量了传粉者的访花频率、传粉者不同部位携带的二型花粉数量及比例。结果发现，传粉者在头部落置更多比例的短柱型花粉，而吻部落置更多的长柱型花粉，说明在较为开放的二型花柱植物中，两种类型的花粉也能通过落置到传粉者的头部和吻部，从而实现型间花粉的精确传递。.本项目拟以前期调查的虫媒二型花柱植物甜荞为研究对象，结合定点研究和人工模拟，探究了非管状花二型花柱植物维持传粉精确性的可能机制。本项目为二型花柱的适应策略提供新的证据，并为深入了解荞麦属作物繁殖特性提供基础。