白及的花部特征与繁育系统

Floral Syndrome and Breeding System of Bletilla striata

通过野外观察、授粉特性分析、杂交指数估算及人工控制授粉试验等方法对白及野生居群的花部特征和繁育系统进行了研究。结果表明:在自然条件下,白及4—5月开花,群体花期约44 d,群体盛花期约12 d,集中在4月29日—5月10日,单株花期11～27 d,单花花期6～8 d。总状花序上具两性花3～11朵。在花朵开放的整个过程中,花药始终高于柱头且两者之间存在隔离。花粉成熟时由粘性物质聚结成团,无法散落至柱头。开花后3 d内花粉活力和柱头可授性均较高。白及杂交指数为4。无论去雄与否,套袋后的花均不结实,说明其不能进行自然的自花授粉和无融合生殖。白及人工自花授粉、同株异花授粉和异株授粉的结实率分别为93.33%、90.00%和93.33%,自然条件下的结实率为5.26%。花粉成熟时由粘性物质聚结成团和缺乏有效的传粉媒介可能是白及自然条件下结实率低的主要原因。

Field investigation, out-crossing index estimation, pollination characteristics analysis and artificial pollination experiments were conducted on the floral syndrome and breeding system of Bletilla striata. The main results were as follows： Under natural conditions, the flowering stage of populations was approximately 44 days from April to May, and the majority of plants kept blooming in 29th April to 10th May. The flowering stage for individual plant was approximately 11 - 27 days and the life span of a single flower was about 6 - 8 days. The flowers of B. striata were bisexual, with 3 to 11 in a raceme. The anther always exceeded stigma during the whole flowering process. Mature pollen grains were grouped by viscous substances and couldn＇t disseminate to the stigma. The pollen viability and the stigma receptivity were both high within 3 days after blossoming. The out-crossing index was 4. Bagged flowers had no fruit setting regardless of emasculation or not, which indicated that there were no spontaneous autogamy and apomixis for B. striata. Fruit sets of manual self-pollination, goitonogamy and cross-pollination were 93.33%, 90.00% and 93.33% respectively, while fruit set under open pollination condition was only 5.26% It was concluded that mature pollen grains grouped by viscous substances and lack of efficient pollinator may be the major factor leading to low fruit set for B. striata in nature.