关键词: 白及, 花部特征, 花粉活力, 柱头可授性, 杂交指数, 繁育系统

Abstract: 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.

Key words: Bletilla striata, floral syndrome, pollen viability, stigma receptivity, out-crossing index, breeding system