5种地黄花部综合特征与繁育系统的初步研究

生殖隔离是物种分化与延续的基础,地黄属植物是否存在生殖隔离仍不清楚。通过实地观测地黄属5个物种(天目地黄、湖北地黄、裂叶地黄、地黄和茄叶地黄)自然种群的花部形态、开花动态、花蜜体积、花蜜的糖浓度及其日变化、杂交指数、花粉-胚珠比等指标,结合人工授粉套袋,对地黄属植物的花部综合特征和繁育系统进行研究。结果显示:(1)地黄属植物的花为两性花,单花花期5～7 d,种群花期40～60 d;5种地黄在花序类型、花形态、花粉量、花粉-胚珠比等方面都存在差异,其中茄叶地黄的花粉完全败育。(2)5种地黄属植物的繁育系统属于异交,部分自交亲和,需要传粉者,不具有无融合生殖特性,地黄与茄叶地黄存在强烈营养繁殖。(3)5种地黄属植物的花朵基部有蜜腺可以产生糖浓度较高的花蜜,这也支持传粉者的存在,但除地黄确定为蜜蜂传粉外,其它地黄植物在野外并未观测到有效的传粉者,可能与地黄的散生特性、生境相互隔离以及传粉观测期气象条件恶劣有关。研究认为,5种地黄属植物较长的花期能有效弥补传粉者访问频率低的不足;除遗传屏障外,推测地黄属5个物种花展示方式的差异可能吸引不同的传粉者,加之地理、生态因素的作用导致了5种地黄属植物繁育系统的分化。

Preliminary Study on Floral Syndroma and Breeding System for Five Species of Rehmannia (Scrophulariaceae)

Reproduction isolation is the basis of species preservation and divergence,but little is known about the breeding system of Rehmannia.We studied the floral syndroma and reproductive characteristics of the five Rehmannia species (R.chingii,R.piasezkii,R.henryi,R.glutinosa,R.solanifolia) through investigating the following indices in field:flowering dynamics of natural populations,floral morphologies of flower organs,nectar volume and sugar concentration,out-crossing index,pollen-ovule ratio,pollination and bagging experiment.Our results indicate that:(1)Rehmannia species flowers are hermaphroditic.The flowering duration of a single florescence was 5-7 days,and the whole population flowering duration was 40-60 days.There are distinct difference among the five Rehmannia species in inflorescence types,floral characteristics,flower color,pollen amounts and P/O values.We found that R.solanifolia were pollen abortion.(2)The evidence of the out-crossing index,pollen-ovule ratio and hybridization experiment supported that the breeding system of Rehmannia was belonged to cross pollination system,partially self-compatible,with no apomictic ability,and pollinators required.We also found there was vegetative reproduction in Rehmannia,especially in R.glutinosa and R.solanifolia.(3)There are nectaries on the base of Rehmannia corolla and they can produce nectar with higher concentration of sugar,and this also supports the existence of pollinators.However,we did not observe any effective pollinators in Rehmannia species except in R.glutinosa with bees,which might be due to the scattered individual,isolated habitats and the bad weather conditions during pollination observation.Longer flowering duration could compensate for the insufficiency of pollinator visits.According to our results,we suppose that the different flowers display of five Rehmannia species possibly attracting distinct pollinators,together with genetic,geographic and ecological isolation,results in the differentiation of the breeding system in Rehmannia species.