水深梯度对钝脊眼子菜生长和繁殖的影响

Water depth is an important limiting factor affecting the growth and distribution of wetland plants. In this study, Potamogeton octandrus Poir. with typical heterophylly was selected as the research object. To investigate the adaptive mechanism and phenotypic plasticity of P. octandrus under different water depth conditions, the seedling growth, biomass, and reproduction strategies under the four water depth gradients of shallow water treatments (10 cm and 30 cm) and deep water treatments (50 cm and 70 cm) were studied. The results showed that heterophyllous leaves appeared after theplants transferred from underwater to aerial condition, and the relative growth rate decreased significantly, which was also positively correlated with the water depth gradient. The shoot height showed an explosive growth with theincrease ofwater depth, and thestem length in 10 cm water depth was significantly lower than those in other water depth treatments. The water depth also had a significant effect on the number of internodes, among which the number of internodes was the most in the 30 cm treatment, whiletheinternodelengthand biomass inthedeep watertreatments weresignificantlyhigherthanthos in the shallow water treatments. The number of branch showed significant differences among the four treatments, and showed a significant decrease with the increase of water depth. While the biomass and aboveground biomass allocation increased significantly with the increase of water depth. Water depth treatment had a significant effect on sexual reproduction indexes, and the increase of water depth inhibited the sexual reproduction. No inflorescence was formed under 10 cm treatment. The pollen production, P/O ratio and the number of inflorescence in 50 cm water depth were significantly higher than those in other treatments, moreover, the seed number and seed set of the deep water treatments were significantly higher than those of the 30 cm group. Comprehensive studies show that P. octandrus can be adapted to the water depth by adjusting the morphological plasticity and biomass allocation and adopting different reproduction strategies, and the optimum water depth rangeisabout50cm.