水深梯度对钝脊眼子菜生长和繁殖的影响

Influence of water depth on growth and reproduction of Potamogeton octandrus

关键词:  钝脊眼子菜, 表型可塑性, 水深, 异型叶, 繁殖策略, 湿地生态

Key words:  Potamogeton octandrus, phenotypic plasticity, water depth, heterophylly, reproduction strategy, wetland ecology

摘要:

水深是影响湿地植物生长和分布的一个重要限制性因子,该研究以具有典型异型叶性的钝脊眼子菜(Potamogeton octandrus)为对象,通过分析浅水处理(10 cm 和30 cm)和深水处理(50 cm和70 cm)4个水深梯度下幼苗生长、生物量及繁殖策略等,探讨钝脊眼子菜在不同水深条件下的适应机制和表型可塑性。结果表明,钝脊眼子菜植株到达水面后出现异型叶,相对生长率显著降低,且与水深梯度呈正相关。钝脊眼子菜的株高随着水深的增加呈现爆发式的增长,10 cm水深的总茎长显著低于其他水深处理。水深对节间数也有显著性影响,其中,30 cm组处理节间数最多; 而深水处理组的节间长和生物量均显著高于浅水处理组。分蘖数在4组处理之间均表现出显著性差异,随着水深的增加呈现显著性递减。生物量和地上生物量分配则随着水深增加而明显增加。水深处理对有性生殖指标有显著性影响,水深的增加抑制其有性繁殖。其中,10 cm条件下无花序形成,50 cm水深下的花粉量、P/O比和花序数显著高于其他处理组,且深水处理的结实数和结实率均显著高于30 cm组。这表明钝脊眼子菜可通过调整形态可塑性和生物量分配,并采取不同的繁殖策略,以达到对水深的最佳适应,其中最适水深生长范围在50 cm左右。

Abstract:

Water depth is an important limiting factor affecting the growth and distribution of wetland plants. In this study, Potamogeton octandrus 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 the plants 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 the increase of water depth, and the stem 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, while the internode length and biomass in the deep water treatments were significantly higher than those in the shallow water treatments. The number of branch showed significant diffe-rences 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 stu-dies indicate that P. octandrus can be adapted to the water depth by adjusting the morphological plasticity and biomass allocation to adopt different reproduction strategies, and the optimum water depth range is about 50 cm.