| Vallisneria natans(Lour.)Hara is a common engineering plant in polluted water restoration,and arsenic(As)is a common pollutant in polluted water.This study focusses on understanding the effects of different growth substrates and arsenic pollution on the growth of V.natans,identifying the main controlling factors,and analyzing the physiological mechanism behind.On the one hand,a long-term indoor culture experiment was conducted to study the growth status,resource allocation,and the interaction between V.natans growth and physiochemical properties of the substrate.On the other hand,the impact of As concentration and phosphorus deficiency on the growth of V.natans were studied in the aspects of individual level,organ level,plant tissue level and physiology level.The main results of this experiment are the following:1.There was no significant difference in total nitrogen content between red soil and sediment,but there were significant differences in total phosphorus,available phosphorus and redox potential(p<0.01).The growth index of V.natans in the sediment was better than that in the sand.The multivariate correlation analysis showed that the total phosphorus and available phosphorus were positively correlated with the number of branches,leaf length and total dry weight of V.natans(p<0.05),and the ammonium nitrogen content was negatively correlated with the number of branches,leaf length,root length and total dry weight of V.natans(p<0.05).In terms of resource allocation,concentrations of the total nitrogen and total phosphorus in the leaves and roots of V.natans were not affected by the growth substrate,but the content of soluble sugar in the leaves of V.natans growing in red soil was significantly higher than that in the roots(p<0.05).2.Under long-term semi-static As exposure(28 days exposure,exposure As concentration of 0 mg / L,0.05 mg / L,0.10 mg / L,0.50 mg / L,1.00 mg / L),the As content in roots and leaves of phosphorus deficiency group was significantly higher than that of phosphorus treatment group(p<0.01),and the presence of phosphorus effectively reduced As uptake by V.natans.The change trend of As content in different parts of V.natans was root > stem > leaf,and that of phosphorus content in different parts of V.natans V.natans was leaf > root > stem(phosphorus deficiency treatment group)and root > leaf > stem(phosphorus normal group).The relative electron transfer rate of leaves decreased significantly(p<0.01),and the concentration of dissolved oxygen consumed by roots increased.3.Under the short-term semi-static As exposure(7 days exposure,exposure As concentration of 0 mg / L,0.5 mg / L,1.0 mg / L,1.5 mg / L,2.0 mg / L,2.5 mg / L),the presence of phosphorus effectively reduced the As absorption of V.natans.The change trend of As content in different parts of V.natans was root > stem > leaf,and that of phosphorus content in different parts of V.natans was stem > root > leaf(P deficiency treatment group)and root > leaf > stem(P normal group).The indexes of photosynthesis decreased with the increase of As concentration,and the dissolved oxygen consumed by roots increased first and then decreased.Phosphorus supply can effectively increase As exposure tolerable concentration of SOD and GSH,and reduce the MDA concentration indicating cell membrane damage.This study can provide basic data for remediation projects of As polluted water body with V.natans engineering plant,and speculate the influence of matrix physical and chemical properties,phosphorus and As concentration on the remediation effect of water body. |
