克隆植物乌菱对底泥磷含量及植株密度的表型可塑性响应

植物,尤其是克隆植物,能够通过表型变化来缓解外界压力,提高对环境的适应能力。该文研究了水生克隆植物乌菱(Trapa bicornis)对底泥磷含量(Sediment phosphorus concentration, SP)、植株密度(Plant density, PD) 及两者间交互作用的可塑性响应,探讨可塑性是否能促进其在富营养化环境中的生长。结果显示,底泥磷含量对乌菱的主菱盘叶数、同化根比根长、吸收根比根长以及叶、茎、同化根、吸收根与植株总磷含量等都有显著影响 (p<0.05),而植株密度对乌菱各生长及生理生态参数均无显著作用 (p>0.05);SP与PD的交互作用弱化了底泥磷含量对乌菱的效应。底泥磷含量和植株密度甚至改变了同化根、吸收根、茎、叶与总生物量之间的异速生长关系。研究结果表明:乌菱的表型可塑性变化主要受底泥磷含量的影响,乌菱通过器官生物量分配、形态结构及生理生态特征的调整来响应底泥磷含量的变化;同时,高的植株密度也可以提高其在富营养化生境下的生态适应性。

PHENOTYPIC PLASTICITY OF THE CLONAL PLANT TRAPA BICORNIS IN RESPONSE TO SEDIMENT PHOSPHORUS CONCENTRATION AND PLANT DENSITY

Aims Trapa bicornis is a clonal floating macrophyte that dominates several lakes in China. Due to eutrophication, the distribution of T. bicornis is shrinking, and T. bicornis has disappeared in some lakes. Our objectives were to investigate the effects of sediment phosphorus concentration (SP), plant density (PD) and their interaction on the plasticity of T. bicornis and examine whether plasticity could promote ecological adaptation in eutrophic environments. Methods In a controlled factorial experiment, we grew artificial populations of T. bicornis in low, medium and high PD (4, 8 and 12 individuals per container, respectively) under low, medium and high SP. We harvested all plants after six weeks and measured the dry mass for each plant part. Important findings SP significantly affected leaf, stem, green root, anchoring root and total plant phosphorus concentrations as well as number of main rosettes of trullate floating leaves, special green root length and special anchoring root length of T. bicornis, but PD did not significantly affect any growth or ecophysiological traits. With increasing SP, plant phosphorus concentration increased. Number of main rosettes of trullate floating leaves of T. bicornis was the largest at low SP and low PD, leaf mass ratio at medium SP and high PD, special green root length at high SP and medium PD, and special anchoring root length at high SP and high PD. SP, PD and their interaction altered some of the allometric relationships between leaf, stem, green root, anchoring root and total biomass. Morphological and ecophysiological traits mostly affected by SP and high PD may increase the ecological adaptability of T. bicornis under eutrophic conditions caused mainly by phosphorus.