喀斯特湿地水葫芦(Eichhornia crassipes)生长及表型可塑性特征对不同富营养化水体的响应

Growth and phenotypic plasticity variability of Eichhornia crassipes in response to different eutrophic water in karst wetland

选择桂林会仙喀斯特湿地,以不同富营养化水体中生长时期为6月(生长旺盛期)和8月(暴发高峰期)的水葫芦(Eichhornia crassipes)为研究对象,探讨不同富营养化条件下水葫芦的生长及表型可塑性响应特征,以揭示水葫芦对不同富营养化水体的生态适应机制.结果表明:水葫芦的株高、根长和叶绿素含量均随水体富营养化程度的增加而降低,叶柄数、叶柄宽、叶片数、叶长、叶宽、匍匐茎数和分株速率随着水体富营养化程度的增加而升高;各性状参数在暴发高峰期均略高于生长旺盛期;根生物量、茎生物量、叶生物量和总生物量均随水体富营养化程度的加深而增加,茎生物量高于根生物量和叶生物量;水葫芦生物量的分配以及性状间的权衡关系(根生物量比、茎生物量比、叶生物量比和茎叶比等)因生长时期的不同而呈现差异性,表现出较强的表型可塑性特征;水体总有机碳、总氮、总磷、硝态氮、氨氮和叶绿素a浓度分别与水葫芦的茎生物量、叶宽、匍匐茎数和分株速率间存在显著的正相关关系,与根长、株高、叶生物量比和茎叶比间存在显著的负相关关系;水葫芦的表型可塑性指数在0.009~0.792之间,叶重比的可塑性指数最大,根冠比最小,重度富营养化水体下的可塑性指数最大.在会仙喀斯特湿地不同富营养化水体环境中,水葫芦通过外部形态结构调节和生物量的配比关系,产生了有利于其入侵和存活的较强的表型可塑性,是其生存繁殖的重要响应机制之一.

The invasion of an exotic species,Eichornia crassipes,has resulted in a series of ecological risks,with the potential consequence on the structure and function of natural ecosystems.In order to investigate the adaptive mechanism of E.crassipes in response to different environmental conditions,we conducted a field survey on phenotypic plasticity of E.crassipes under different eutrophic waters in the Huixian karst wetland.The results showed that there was a pronounced decrease in terms of plant height,root length,and chlorophyll content with the increase of eutrophicated water.The petiole number,petiole width,number of blades,leaf length,leaf width,stolon number,and growth rate all increased significantly in eutrophic state,which was higher at the peak of the E.crassipes invasion respectively.The total biomass,root biomass,stem biomass,and leaf biomass increased with the increase of eutrophicated water.The stem biomass was higher than that of the roots and leaves significantly.The distribution of E.crassipes biomass and the trade-off relationship among traits(root biomass ratio,stem biomass ratio,leaf biomass ratio,stem-to-leaf ratio,etc.)varied at different growth stages.There was a significant positive correlation among the total organic carbon,total nitrogen,total phosphorus,nitrate-nitrogen,ammonia-nitrogen,chlorophyll-a and stem biomass,leaf width,and stolon number of E.crassipes.It had a significant negative correlation among root length,plant height,leaf biomass ratio,stem-leaf ratio,etc.The phenotypic plasticity index of E.crassipes was ranging from 0.009 to 0.792,the leaf mass ratio was the highest and root/shoot of ramet was the smallest.The phenotypic plasticity was the highest in hypereutrophic water.The results indicated that E.crassipes can present a plastic adaptation in response to eutrophic water,with the improvement of the survival and behavior itself by adjusting the morphology and the relative biomass of reproductive organs to somatic biomass.We also suggest that the phenotypic plasticity of E.crassipes in the eutrophic water is one of the important mechanisms for its survival and reproduction,which might realize the spatial niche expansion and population regeneration.This study can enhance the understanding of E.crassipes invasive mechanisms in wetlands.