通过野外观察,运用套袋授粉和联苯胺-过氧化氢法等实验方法对距瓣尾囊草开花物候以及种群的繁育系统特性进行研究.研究结果:1)距瓣尾囊草为两性花,聚伞状花序,花期较长,从头年12月持续到次年4月,单花花期持续8-15 d,种群花期可持续4个月左右.2)距瓣尾囊草在花朵未开放前花粉没有活力,花药开裂当天花粉活力达到94.8％,第2天为90.3％,第3天为81.6％,第4天为62.9％,此后其花粉活力明显减弱;柱头可授性于散粉后第3天开始出现,散粉后4-5天最强,散粉后第8天柱头失去可授性;柱头可授性和花粉活力有5d左右的重叠期.3)其花粉胚珠比P/O为938.5±250,按照Cruden标准划分,其有性繁育系统为兼性异交.4)按照Dafni的标准,距瓣尾囊草的OCI=4,即繁育系统为异交、部分自交亲和、需要传粉者.5)人工异花授粉结实率达80％以上,略高于自然结实率78.94％;直接套袋结实率为5.71％;去雄套袋和去雌套袋均不结实.以上结果表明,距瓣尾囊草繁育系统表现为异交为主、部分自交亲和并且不存在无融合生殖现象,其开花物候、花部特征和繁育系统为适应特殊的环境提供了一定的生殖保障,本次研究结果为距瓣尾囊草的迁地保护和种群的繁衍复壮提供理论依据.%The endangered and rare species Urophysa rockii belongs to a unique genus of seed plants that is only distributed in the Jiangyou area of Sichuan,China.Breeding system characteristics and flowering phenology are the most important factors influencing plant reproductive success.The flowering phenology,floral characteristics,and breeding system characteristics of U.rockii were investigated in Jiangyou,Sichuan.Analysis showed that:1) It is a bisexual flower with an umbel and a long flowering period.It lasted from December to April of the following year.The flowering period of one flower was 8 to 15 days,and the flowering period lasted for about 4 months.2) The flower of Urophysa rockii showed no pollen activity before the flower was opened.On the first,second,third,and fourth day of anther dehiscence,pollen activity was 94.8％,90.3％,81.6％,and 62.9％,respectively,and pollen viability obviously decreased.Stigma receptivity began the third day after pollen scatter,and reached the highest levels on the fourth and fifth day,then the eighth day after pollen scatter,stigma receptivity was lost.Stigma receptivity and pollen viability overlapped for about 5 days.3) The pollen-ovule ratio was 938.5±250,according to the Cruden standard and the sexual reproduction system was facultative outcrossing.4) According to the standard of Dafni (1992),the OCI =4,showing that the breeding system was out-crossing,partly self-compatible,and insect pollinator-dependent.5) The seed setting rate of palmification was above 80.0％,slightly higher than the natural seed setting rate of 78.9％.Direct bagged seed setting rate was 5.71％;emasculation by bagging and removing pistil bagging were mostly infertile.The results showed that in the breeding system of this species,out-crossing was predominant,partially self-compatible,and there was no apomixis,but it required pollinators.The floral characteristics,flowering phenology,and breeding system of Urophysa rockii provided some reproductive assurance and evolutionary potential for its ability to adapt to the special environment.The aim of this article was to provide the theoretical basis for the ex-situ conservation and rejuvenation of population reproduction of Urophysa rockii.
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