Photosynthesis And Water Characteristics Of Platycladus Orientalis And Sophora Japonica Seedling Under Lead And Drought Stress

In order to select the plants not only lead resistance but also drought tolerance and provide theoreticalbasis for ecological environment construction and vegetation restoration in arid and semi arid regions andheavy metals pollution area of our country,we combine the drought stress and lead stress to research thevariation law of Photosynthesis,WUE,Chlorophyll,Electrical conductivity and Leaf water potential of oneyear Sophora japonica and Platycladus orientalis under both drought stress((the relative soil water contentwere100%,80%,60%and40%) and Lead stress(the soil Pb content were0,300,500,1000,2000,4000,6000,8000,10000and12000mg/kg),to reveal the lead resistance and drought tolerance of Sophora japonica andPlatycladus orientalis.The results were as follow:1.Different Pb content in soil had significantly different effect on net photosynthetic rate of Sophorajaponica and Platycladus orientalis.300mg/kg Pb content in soil can promote the Photosynthesis of Sophorajaponica,but when Pb content in soil was higher than300mg/kg, the Photosynthesis became more and morelower with the increase of Pb content in soil.Different relative soil water content had significantly different effecton net photosynthetic rate of Sophora japonica.60%and40%relative soil water content had significant effecton net photosynthetic rate of Platycladus orientalis,80%relative soil water content had no significant effect onnet photosynthetic rate of Platycladus orientalis.2.Lead of low concentration had no significant effect on Chlorophyll content of Sophora japonica andPlatycladus orientalis. Lead of high concentration had remarkable effect on Chlorophyll content of Sophorajaponica and Platycladus orientalis. Chlorophyll a,Chlorophyll b and the total Chlorophyll content of Sophorajaponica and Platycladus orientalis decreased with the relative soil water content decline. Sophorajaponica's Chlorophyll had no significant change under80%relative soil water content,but had significantchange under60%and40%relative soil water content. Platycladus orientalis's Chlorophyll had significantchange under80%and40%relative soil water content,but had substantial change under60%relative soilwater content. Chlorophyll a/b of Sophora japonica was generally higher than Platycladus orientalis underPb stress and drought stress.3.Different Pb and drought stress levels had a more significant effect on electrical conductivity inPlatycladus orientalis than in Sophora japonica.The more Pb content in soil and the bigger droughtdegree,the more destroy on cell membrane permeability.The electrical conductivity of Platycladusorientalis was higher than Sophora japonica's under both lead and drought stress. Platycladus orientalis were affected least in the initial growth period by lead stress,while were affected largest in the late growthperiod. Sophora japonica were affected largest in the initial period by Pb stress,while were affected slightlyin the middle and late period.4.The leaf water potential of Platycladus orientalis were affected significantly by lead factor,drought factorand their interaction. The more Pb content in soil and the bigger drought degree,the more destroy on leaf waterpotential. The leaf water potential of Sophora japonica were affected not obviously by lead factor,but affectedsignificantly by drought factor and their interaction. The more Pb content in soil,the lower the leaf waterpotential was. Platycladus orientalis were affected largest in the initial growth period by lead stress,themiddle growth period less, the late growth period least. Sophora japonica showed little difference amongthe three growth periods under lead stress.5.The same Pb reagent had significantly different effect on different plants. Platycladus orientalis andSophora japonica could sustain the normal growth under lead and drought stress of highconcentration,showed that both of the two had stronger lead resistance and drought tolerance. Sophorajaponica showed stronger lead resistance than Platycladus orientalis in all physiological index researchedof this paper.However, there was not a rule on drought tolerance of Sophora japonica and Platycladusorientalis, both of the two had their own advantages and disadvantages.