苜蓿的弹花现象及花对传粉者觅食行为的操纵

Tripping of alfalfa and manipulation of pollinator foraging behavior by flowers

【目的】阐明弹花现象的发生机制及花在此过程中的角色与地位,对探讨植物多样化的散粉机制具重要意义。【方法】以‘新牧4号’紫花苜蓿为研究对象,进行弹花现象与传粉者访花行为的野外观测、花粉传递的控制实验及花结构的解剖学观察等。【结果】翼瓣与龙骨瓣边缘的特化结构相互嵌套形成了苜蓿触敏性的花结构,该结构不仅对传粉者具有较高的选择性,而且可通过弹花前后蜜孔位置的变化操纵传粉者的访花行为。龙骨瓣一旦被弹开,约90%的花粉被散出,雌雄蕊将不再回到原本位置,花当天即可闭合,反之,将持续开放5~6 d,为一次性的花粉释放机制;弹花效率不受昆虫体型大小的影响,它与访花频率共同决定了昆虫的弹花贡献率;昆虫的二次访花不能增加花药中剩余花粉的移出和柱头花粉的沉积。【结论】苜蓿特殊的花结构及花对传粉者觅食行为的操纵促进了弹花现象的发生和雄性适合度效益的最大化。

[Objective]Elucidating the tripping mechanism and the role and status of flowers in this process are of great significant to explore the diverse pollen dispersal mechanism.[Methods]Alfalfa(Medicago sativa L.)‘Xinmu No.4’was used as the research object to observe the flower tripping phenomenon and pollinator visiting behavior,pollen transfer control experiment,and anatomical observation of flower structure.[Results]The specialized structure of wings and keel edge were nested with each other and form the touch-sensitive flower structure of alfalfa.The“sensitiveness”structure not only had high selectivity to pollinators,but also could manipulate pollinatorsvisiting behavior by changing the location of honey hole before and after tripping.Once the keel flap was tripped,about 90%of the pollen in the anther was dispersed,and the gynostemium did not return to the original position.The flower closed on the same day,or it continued to open 5-6 d,which was a one-time pollen release mechanism.Tripping efficiency of insects,being not related to the insects size,determined the tripping contribution rate together with its visiting frequency.The insects second visiting did not increase the removing of residual pollen from anthers and pollen deposition on stigma.[Conclusion]The special flower structure and its regulation of pollinatorsforaging behavior promote the occurrence of tripping phenomenon,and benefits the male fit-ness in alfalfa.