灰楸的繁育系统

Breeding System of Catalpa fargesii

在自然居群中通过野外观察和人工授粉等试验,用杂交指数、花粉一胚珠比、套袋和人工授粉等指标对灰楸(Catalpa faygesii Bureau)的繁育系统进行了初步分析,并探讨了影响其生殖成功的因素。结果表明:灰楸总状花序伞房状排列,顶生。通常有完全花9.63朵(1～18),单花开放时间5～7 d,种群花期一般为4—5月。主要访花昆虫为蜂类。雌雄同花,异熟,使雌雄蕊时间上隔离。花开放过程中柱头始终高于花药,使雌雄蕊空间上隔离。杂交指数为4,判断繁育类型属于异交,部分自交亲和,存在自交衰退,需要传粉者。花粉—胚珠比为309,判断繁育类型属于兼性异交;结合套袋和人工授粉试验结果,认为灰楸属于以异交为主的繁育系统。

A study was conducted to analyze the breeding system of Catalpa fargesii in terms of outcrossing index and pollen-ovule ratio through bagging test and artificial pollination test on the natural populations of C.fargesii.The factors influencing the reproductive success of C.fargesii were discussed.Results showed that the raceme of C.fargesii is acrogenous and arranged in an umbrella shape.C.fargesii plants usually have an average of 9.63 complete flowers（1-18 complete flowers）.The flowering period of C.fargesii is between April and May.The life span of inflorescence is approximately 5-7 days.The most common floral visitors are bees.The flowers of C.fargesii are androgynous and dichogamous.Stigma always remains higher than the anther at anthesis.Stamen and pistil are separated in space（hercogamy） or time（dichogamy）.The outcrossing index of C.fargesii is 4.0.C.fargesii is a cross-pollinated species,which is partially self-compatible and needs pollinators.Inbreeding depression is commonly observed in C.fargesii.The pollen-ovule ratio is 309.The breeding system of C.fargesii reproduction is facultative xenogamy.Bagging test and artificial pollination test indicate that C.fargesii belongs to cross breeding system.