Effects Of Genotype On The Morphological And Physiological Traits Of Invasive Plant Hydrocotyle Vulgaris

Exotic plant invasion is an important topic in the field of ecology.Factors influencing the ability of invasive alien plants are not only affected by their own growth and physiological characteristics,but also by their genetic characteristics.Generally,plants with strong invasiveness have the ability of asexual reproduction,efficient resoiurce utilization and high phenotypic plasticity,and they can adapt to various environmental stresses.As plant genotype detection has become more and more efficient in recent years,the relationship between genotype diversity and plant invasion mechanism and ecosystem function has been paid more attention.Hydrocotyle vulgaris was one kind of clonal plants introduced in our country in the 1990s with a certain potential invasion risk,which has been widely spread in most southern provinces.Up to now,study on the risk of invasion of H.vulgaris mainly focused on the habitat adaptation and its relationship with ecological communities,and study on the invasion mechanism on the genetic level was relatively few.To study the effects of light and water condition on the morphological and physiological palsticity of H.vulgaris of different genotypes,12 different genotypes of H.vulgaris were subjected to three different treatments,i.e.,the control,flooding and shading.Results showed that the plasticity of the fitness(number of ramets,total biomass),the growth indexes(SIL,SLA)and physiological indexes(SOD,Pn,Gs,Ci)of H.vulgaris to the shading treatment differed significantly among different genotypes.Meanwhile,Results showed that the plasticity of the adaptive indexes(number of ramets,total biomass),the growth indexes(PL,SLA)and physiological indexes(soluble sugar,Pn,Gs,Ci,Ts)of H.vulgaris to the flooding treatment differed significantly among different genotypes.We found that there don't exist developmental instability costs in our study,however,we detected a certain range of developmental limits in the Ci index under shading and soluble sugar under flooding,which indicates the existence of costs and Iimits in the phenotypic plasticity responses of H.vulgaris to water and light condition.To identify the effects of genotype diversity on the morphological and physiological characters of H.vulgaris and the greenhouse gas emission under different water conditions,we constructed H.vulgaris populations at three levels of genotype diversity(1-,3-,and 6-genotypes)using six different genotypes chosen out of the total 12 genotypes,subjected to the control and flooding treatments.The results showed that under flooding treatment,genotype diversity has a significant impact on most growth(i.e.,leaf area,total biomass,stem biomass,root-shoot ratio,petiole biomass and root biomass)and physiological characteristics(i.e.,Pn?Gs?Ci?Ts)of H.vulgaris,cumulative emission of N2O and soil organic matter.With the increase in genotypic diversity,the growth indexes(i.e.,intemode length,petiole length,number of ramets,leaf area,total biomass,leaf biomass),the cumulative emissions of N2O under the flooding treatment showed a decreasing trend.Meanwhile,net effects of the genotype diversity of H.vulgaris were all found to be negative.Separating the net effect of diversity using the Loreau-Hector calculation method,we found the complementary effect to be negative.Genotype diversity might have exacerbated the competition among different genotypes,thus inhibiting the overall performance.The results indicated that H.vulgaris population tend to choose the growth strategy with single genotype when the space is limited.On the whole,there were certain phenotypic differences among different genotypes of H.vulgaris.When space is restricted,the genotype diversity had a negative effect on growth of H.vulgaris.This research would provide scientific theoretical basis and guidance for the landscape use and effective control of H.vulgaris.