Physiological Responses And Lead Resistance Of Red Ardisia And Green Ardisia Under Lead Stress

Ardisia mamillata Hance attributes to Myrsinaceae,Ardisia,it is a kind of small shrubs with high ornamental and medicinal value.It is attributes include being able to survive in shade and warm environment.Using cuttage saplings of red ardisia and green ardisia as materials in the study.There are six lead treatment gradients of 0,250,500,750,1000,1250mg·kg^-1 and three different periods of 15d,30d,45d were set up.The indicators of photosynthetic characteristics,pigment content and physiological response under lead stress of the two varieties of Ardisia mamillata Hance were analyzed.The growing environment of red ardisia and green ardisia was determined and physiological response mechanism under the lead stress was studied in order to provide the scientific basis for plant resistance research and landscape application.The results are as follows:（1）in terms of photosynthetic characteristics,The light-response curves of red ardisia and green ardisia increased rapidly under low photosynthetic effective radiation（≤200 mol/m²·s）,and then gradually stabilized at 30d.The maximum net photosynthetic rate increased first and then decreased.low concentration of lead(≤500mg·kg^-1)was able to promoted the net photosynthetic rate,stomatal conductance and transpiration rate of red ardisia and green ardisia.The daily mean value of the three indexes was lower than the control group,and the growth of plants were inhibited when the lead concentration is 1250mg·kg^-1.The decrease of photosynthetic capacity is caused by non-stomatal factors.（2）With the extended of treatment time,The content of chlorophyll and anthocyanin decreased and it is lower than the control grop when the lead concentration is 1250mg·kg^-1,phenylalanine ammonia-lyase activity associated with anthocyanin synthesis was also reduced at 45d.Low concentration of lead stress could promote the accumulation of chlorophyll and anthocyanin,but the lead concentration of 1250mg·kg^-1 would affect the ornamental value.（3）With the increased of soil lead contents and the extended of treatment time,the cell membrane of red ardisia and green ardisia was seriously damaged,and the content of MDA continued to rise.The activity of SOD and POD increased first and then decreased,indicating that high concentration of lead inhibited the activity of antioxidant enzyme at 15d,30d,45d.The soluble sugar content of red ardisia decreased first,then increased and last decreased,while the content of green ardisia varied in the three lead stress stages.When the lead concentration was less than 750mg·kg^-1,the contents of soluble sugar and soluble protein increased and the soluble protein was lower than the control group at 45d.（4）In general,when the soil lead concentration was lower than 750mg·kg^-1,red ardisia and green ardisia grew well,and the normal growth of the plants would not be affected when the lead concentration below 1000mg·kg^-1.Therefore,in order to maintain the ornamental value of plants,it is recommended to select the area with soil lead concentration less than 750mg·kg^-1 for planting.Red ardisia and green ardisia had certain resistance to lead stress,and the resistance of green ardisia was slightly greater than red ardisia.However,above a certain lead concentration,red ardisia and green ardisia would cause toxic effects.