甘南红景天濒危的生殖生态学因素分析

为了寻找保护和恢复甘南红景天种群的有效途径,本文分析了甘南红景天的繁育系统、生殖过程、开花物候特征及影响生殖成功的主要因子.结果表明:甘南红景天为雌雄异株,雄花在花芽分化初期为两性植株,但随着花的不断发育,雌蕊的胚囊发育到一定阶段时败育,两性植株基本仅执行雄性功能,种群繁殖为异交,以风媒传粉方式为主,种群花期出现在全年降雨和气温较高的季节.6月初现蕾,6月中旬开花,7月上旬进入盛花期,花期在36 d左右,8月下旬果实成熟.两性植株略早于雌花开放,花期(10.2 d)大于雌性植株(8.4 d).由于部分雌花不易授粉,部分花蕾、胚珠损失,1~3年的幼龄植株几乎不开花结实,群落中只有11%的植株开花结实,种子自然繁殖率极低,约为2%.从花蕾到开花,雌性单株有20.0%～25.1%的花蕾损失; 从开花到结实,单株51.1%～65.0%的花败育;至种子成熟,仅10.1%～21.0%的胚珠发育成种子.雌性单株平均种子产量为158.1粒,人工条件下种子发芽率为81.5%,幼苗第一年的成活率为36.0%.表明种子质量不是导致甘南红景天濒危的原因,而花粉限制、种子产量和幼苗的成活率是真正影响其生殖成功和导致濒危的主要生殖生态学因素.

Analysis of reproductive ecological factors of endangered Rhodiola gannanica.

To find effective ways for protecting and recovering an endangered species Rhodiola gannanica in Gannan, an important distribution region of this species in the eastern Tibetan Plateau of China, the breeding system, reproductive process, flowering phenological characteristics and other reproductive controlling factors were investigated. The results showed that there was a unique breeding system in R. gannanica, which was dioecious, and male flowers were also bisexual plants in the early stage of flower bud differentiation. While the sac of pistil was aborted in a certain stage with the development of flowers, the bisexual plants only played the role of males’ functions. The outcrossing reproduction was observed, the pollination mode was mainly by wind, and the population flowering occurred in the season with abundant precipitation and high temperature. The bud satge appeared in early June, the florescence was in mid-June, and the flourishing florescence was in early July. The flo-wering duration of R. fastigiata was about 36 d, and the fruit ripening began in late August. The flo-wering time and the flowering duration of the bisexual plants were earlier than female plants. Due to the low pollination rate of the female plants, the buds and ovules were damaged and the 1-3 years young plants barely got flowering and fruiting, the rate of flowering and fruiting of the community only reached 11.0% and the rate of seed natural propagation was low (about 2.0%). 20.0%-25.1% buds of female plants were damaged from bud to flowering stages. 51.1%-65.0% flowers were aborted from flowering to fruiting stages. Only 10.1%-21.0% of ovules developed into seeds. The seed production of per female plant was 158.1, seed germination rate was 81.5% under artificial conditions, and seedling survival rate reached 36.0% in the first year. Our results revealed that seed quality was not the key ecological factor, while it was the pollen limitation, low seed production and the survival rate of seedling that resulted in the reproductive success and species endangered situation.