水深、基质、光和去苗对菹草石芽萌发的影响

通过野调查，研究了水深对菹草石芽萌发率的影响，比较了梁子湖与湖北省其他四个不同水深的湖泊间菹草石芽明发率月动态；并通过萌发实验探讨了基质、光和去苗对菹草石芽萌发的影响。结果如下：无光环境下菹草石芽的萌发率较有光下的小，基质的有无及其类型对萌发率影响不大，去苗能使其萌发第二苗和第三苗的百分离分别从自然状态下的3．2％和1．0％提高至96．8％和64．0％（12月初）；五个湖泊的石芽均于7月初即开始萌发，相同月份不同湖泊石芽的平均萌发率基本与其平均水深成负相关关系，但12月初各湖泊的平均萌发率相近（＞95％）；同一湖泊水深越大，相同月份的萌发率越低，水深的增加能显著推迟萌发起始时间，但不改变其最终萌发率（12月初＞95％）。菹草石高萌发率的特征和极高的萌发第二、第三苗的潜力可能是其成为许多湖泊优势种的两个极其重要的维持机制。

EFFECTS OF WATER-DEPTH GRADIENTS, MATRICES, LIGHT AND REMOVAL OF PLANTLETS ON GERMINATION OF TURIONS OF POTAMOGETON CRISPUS L.

Potamogeton crispus L., as an important fodder source for herbivorous fish, can grow well in polluted lakes. However, seeds of the plant can rarely germinate in the nature, and thus sowing the plant turions has been considered as a major method for introduction of the plant. By field investigations and germination experiments, the authors investigated the effects of water depth gradients on the germination rates of the turions in Lake Liangzi in Hubei Province of China and compared the results with those obtained from other four lakes also in the province. The effects of matrices, light and removal of the initial plantlets on the germination were also examined in the present study. In the environment with light, the turions displayed higher germination rates than those in the absence of light. However, the effect of different bottom matrices was not observed. Moreover, removal of plantlets had an increase impact on the further germination rates. Germinations of the turions in the five lakes were recorded at the beginning of July, with the average germination rates varying inversely with the average water depth through until December. From July to December, the deeper the water in Lake Liangzi, the lower the germination rates observed, indicating that increased water depth may caused delays of the germination. But, at the early December high germination rates of more than 95% were observed in all areas of the lake with different water depths. It is suggested that the high germination rates and the potential of germinating a second or third plantlet are probably two important mechanisms to maintain the plant as a dominant species in lakes.