【摘要】 小黑桫椤(Alsophila metteniana)被列为我国国家二级保护植物。为探讨其种群数量下降原因,作者采用无菌培养方法和显微观察技术,在实验条件下研究了光照强度、光质、温度和pH值对小黑桫椤孢子萌发及早期配子体发育的影响。结果表明:孢子萌发和配子体发育的最适光照强度为40-70μmol·m-2·s-1,全黑暗时孢子不萌发;白光、红光、黄光和蓝光下的萌发率分别为68.78%、65.66%、63.74%和7.51%;白光和蓝光下配子体可以形成正常的心形原叶体,红光和黄光下配子体发育一直处于丝状体阶段。孢子萌发和配子体发育需要在酸性土壤进行(pH值在3.7-6.7);孢子萌发的适宜温度为20-30℃。从孢子接种到心形原叶体形成需要55d左右。根据上述结果,我们认为光照强度是小黑桫椤孢子萌发的必需条件,光质是限制小黑桫椤孢子繁殖的重要原因;光质、温度和pH值等环境因子的作用和配子体发育时间等是导致小黑桫椤种群数量日趋减少的主要原因。更多还原

【Abstract】 Alsophila metteniana is a wild species under second class state protection in China. To explore possible reasons for population declines, we collected spores of A. metteniana from Emei Mountain, Sichuan Province and experimentally cultured them in sterile conditions. We determined the effects of light intensity and quality, temperature, and pH on spore germination rates and early gametophytic development. The opti-mal light intensity for spore germination and early gametophytic development was 40–70 μmol·m–2·s–1, while spore germination was completely prohibited in darkness. Under the different light spectra tested, viz. white, red, yellow and blue light, spore germination percentages were 68.78%, 65.66%, 63.74% and 7.51%, respec-tively. When growing under white and blue light, gametophytes developed into normal cordate-shaped prothallus. When growing under red and yellow light, however, gametophytes developed into uniseriate fila-ments consisting of mostly elongated cells. For spore germination and gametophytic development, the opti-mal temperature is from 20℃ to 30℃, the suitable pH is from 3.7 to 6.7. The mature prothallus appeared 55 days after spore sowing. We conclude that light intensity was not a major but necessary factor for germina-tion and development of A. metteniana spores, and light quality may be an important factor limiting spore re-production. In conclusion, long period of gametophytic development and habitat factors such as light quality, temperature, pH may contribute to declines of wild populations.更多还原