底泥高磷浓度提高了喜旱莲子草的入侵性

 植物通过改变自身的形态和生态生理特征对多变的环境因素做出响应，这种表型可塑性能增强外来物种的入侵能力。该文研究了入侵植物喜旱 莲子草（Alternanthera philoxeroides）对底泥磷浓度、植株密度以及二者间交互作用的可塑性响应，探讨可塑性是否能使其获得更高的入侵 能力。结果表明：低密度×底泥高磷浓度处理条件下的叶重、茎重、 总重、叶数、分枝数和茎长等明显高于低、中磷浓度处理；高密度×底泥 高磷浓度条件下的叶数、茎长和比茎长的值最大；植株的含磷量随底泥磷浓度的升高显著增加，说明喜旱莲子草响应底泥磷浓度变化时改变了 自身的形态与生态生理性状。泥底含磷量对叶重比、叶数、 茎长、茎磷含量、叶磷含量和植株总含磷量的影响都达到显著水平（p<0.05）；植 株密度对茎重、比茎长、叶磷含量和植株总磷含量的影响达到显著水平（p<0.05）。与入侵能力相关 的叶重比、叶数、茎长在底泥高磷浓度处 理中显著增加，说明底泥的高磷浓度增强了喜旱莲子草的入侵能力。

HIGH SEDIMENT PHOSPHORUS CONCENTRATION ENHANCED INVASIVENESS OF ALTERNANTHERA PHILOXEROIDES

Aims Plants show phenotypic plasticity in response to changing environments via variations of morphological and ecophysiological traits, and this plasticity can increase invasiveness. Plasticity, rather than genetic diversity, made Alternanthera philoxeroides more invasive, but its plasticity to sediment phosphorus concentration of invaded habitats was undocumented. This study addresses plasticity of A. philoxeroides to sediment phosphorus concentration and planting density and whether plasticity increases invasiveness. Methods In a controlled factorial experiment, we grew artificial populations of A. philoxeroides at low and high densities (four and eight individuals per container, respectively) under three levels (low, median, high) of sediment phosphorus concentrations. All plants were harvested after six weeks, and dry mass of leaves, stems and roots were measured. Important findings Under low planting density, leaf mass and number, stem mass and length, branch number, and total biomass of A. philoxeroides were larger at high than low or median sediment phosphorus concentration. Under high planting density, leaf number, stem length and special stem length were greater at high than at low or median sediment phosphorus concentration. Leaf, stem, root and total phosphorus concentrations in A. philoxeroides increased significantly with increasing the sediment phosphorus concentration. Leaf mass ratio was also affected by sediment phosphorus concentration, and stem mass, special stem length, leaf and total phosphorus concentration were significantly affected by planting density. Results imply that morphological and ecophysiological traits of A. philoxeroides were altered by sediment phosphorus concentration and that high sediment phosphorus may strengthen the invasiveness of A. philoxeroides.