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 optimal 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%, respectively. 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 filaments consisting of mostly elongated cells. For spore germination and gametophytic development, the optimal 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 germination and development of A. metteniana spores, and light quality may be an important factor limiting spore reproduction. In conclusion, long period of gametophytic development and habitat factors such as light quality, temperature, pH may contribute to declines of wild populations.

Key words: Alsophila metteniana, light quality, spore germination, gametophytic development