束花石斛的繁育生物学特性

为了探究束花石斛（Dendrobium chrysanthum）的繁育生物学特性，对其开花习性、花粉活力、柱头分泌特性、人工授粉结实率、自然结实种子育性和贮藏特性进行研究，结果表明：（1）束花石斛花芽萌动期为19 d，现蕾期为23 d，群体花期为28 d，单花寿命10~15 d；（2）开花1~3 d花粉活力保持在90%左右，开花至第9天时花粉活力仅为23.7%，初始3 d开花的花粉活力与其他时间取样的活力差异均达极显著水平（P<0.01），花粉活力随开花时间延长呈由强到弱的趋势；（3）束花石斛的柱头腔从开花第2天开始有分泌物，第6 d时分泌物最多，柱头过氧化氢染色结果表明在开花5~6 d时柱头可授性最强，柱头可授性随开花时间延长呈由弱到强再到弱的趋势；（4）选取花朵开放4 d的花粉和柱头人工授粉，同株异花和同花授粉未见结实。野外结实果质量2.02~4.83 g，种子长0.628~0.845 mm，宽0.082~0.110 mm，长宽比为7.798，成胚率达97.35%，种子活力为90.80%，室温条件保存6个月的种子活力维持在73.20%。上述结果说明，束花石斛单花花期不长，开花初期花粉活力最高，柱头发育要滞后于花粉的发育；束花石斛不存在无融和生殖，人工同株自花授粉不育。但自然状况下能正常结实，种子发育良好，胚活力较高，干燥种子在自然条件下有一定的耐贮特性。本研究揭示了束花石斛的开花生物学特性和雌雄蕊异熟特点，其交配系统应为自交不亲和，为其野生种质资源的保育和人工精准授粉提供科学依据。

Reproductive Biological Characteristics of Dendrobium chrysanthum

In order to clarify the reproductive biological characteristics of Dendrobium chrysanthum， the flowering habits， the pollen vitality， the characteristics of stigma secretion， the fruit setting rate as well as the development and storage of seed were investigated. The results were listed as followed： （1）Its budding period and the emergence were 19 d， 23 d respectively. The population's flowering period was 28d， whereas the single flower span was from 10-15 d. （2）From the first day to the third day of flowering， the pollen viability was about 90% but decreased to 23.7% at the ninth day of flowering. The data of pollen viability significantly differed between at three former day and other latter time（P<0.01）， pollen viability varied from high to low level with the blooming. （3）The stigma of D. chrysanthum produced secretions from the 2nd day of flowering， and had the maximum yield at the 6th day， and stigma staining showed that the stigma receptivity was optimal at the 5-6 d of flowering， and stigma receptivity changed from weak to strong to and then to weak with the prolongation of bloom stage. （4）An artificial pollination was made at the fourth day after flowering. but no fruit was found after cross-pollination and same-flower pollination. In the field， the seedpod weight was from 2.02-4.83 g， seed length varied from 0.628-0.845 mm and its width was from 0.082-0.110 mm， and the ratio of length to width was 7.798 and the rate of embryo formation reached to 97.35%， and the seed vigor was 90.80%， and the seed vigor maintained at 73.20% at room temperature for 6 months. All results mentioned above indicated that the flowering period of D. chrysanthum was short， and the pollen vigor remained the highest after flowering， and the pollen matured earlier than stigma. There was no apomixis occurred in D. chrysanthum， and the artifical self-pollination caused sterile. Although it could bear well-developed seedpods under natural condition with a high seed vitality. Dried seeds could keep a good storage resistance under natural condition. This study confirms the biological characteristics of flowering and dichogamy of D. chrysanthum， and its breeding system belongs to self-incompatibility， and could provide the strategies for conservation of wild germplasm resources and a precise hand-pollination of D. chrysanthum.