微齿眼子菜与马来眼子菜对水深变化的适应性比较研究

ADAPTIVE COMPARISON OF POTAMOGETON MAACKIANUS AND P.MALAIANUS TO VARIOUS WATER DEPTHS IN AN EXPERIMENTAL STUDY

水深与水位波动是影响湖泊中沉水植被分布格局和物种多样性的重要因子。在洱海开展为期2个多月的原位实验,从大型浮台上悬挂吊盆模拟不同的水位梯度(2、4和6m)和水位变化模式(水位上升、水位下降和水位波动)对微齿眼子菜和马来眼子菜生长的影响。实验结果表明:水深梯度和水位变化模式对两种植物的生物量、株高、节数和叶片数具有显著影响,推测微齿眼子菜在洱海的临界生长水深约为5m,马来眼子菜的临界生长水深为3.5m;超过临界水深后两种植物生物量和叶片数下降、株高和节数不增长。在2m初始水深处光照相对充足,生物量随时间稳定增长,水深增加(20cm/6d×60d)对两种植物的生物量均未造成显著影响,株高和节数随水深显著增加,具有响应空间增长的潜力。在初始水深为4m时,进一步增加水深(20cm/6d×30d)会抑制微齿眼子菜生长,继后减少(-10cm/6d×30d)水深仍无法使其恢复生长;但先减少水深后增加水深可以小幅促进其生长。在初始水深为4m时,3种水位变化模式对马来眼子菜的生物量影响不大,但减少水深后增加水深可以小幅促进其生长。初始水深6m抑制两种植物的生长,并导致马来眼子菜死亡。实验结果表明,微齿眼子菜比马来眼子菜对弱光耐受性更好。

Water depth （WD） and water level fluctuation （WLF） play important roles in affecting diversity and distribution of submersed macrophytes in lakes. In this study, an in situ experiment was carried out on a floating platform in Lake Erhai to explore effects of various WD and WLF on submersed macrophytes Potamogeton maackianus and P. rnalaianus, by planting the plants in buttes and hanging the buttes at 2 m, 4 m and 6 m below water surface and adjusting WD of the buttes. We observed that the WD and WLF affected growth, shoot height, shoot knots and leaf number of the plants significantly, and that 3.5 m and 5 m were critical maximum colonizing WD of P. rnalaianus and P. rnaackianus, respectively. The plants had lower biomass and less leaf number and their shoots did not elongate at deeper WD than the critical WD. Increasing WD （20 cm/6 d× 60 d） did not affect biomass, but increased shoot height and shoot knots of the plants at the initial 2 m WD. Increasing WD （20 cm/6 d×30 d） deeper than 4 m inhibited growth of P. rnaackianus, which could not be reversed by the following decreasing WD （--10 cm/6 d ×30 d）; however, decreasing WD from 4 m and then increasing WD released stressful effects of 4 m WD on the plant. WLF did not affect growth of P. rnalaianus at 4 m WD, but decreasing WD from 4 m and then increasing WD released stressful effects of 4 m WD on the plant as compared to the stable 4 m WD. WD at 6 m inhibited growth of the two plant species and caused death of the plants. P. rnaackianus was more tolerated to weak light stress than P. malaianus.