Effect On Eco-Physiological Characters Of Mango And Dalbergia Odorifera T.Chen Under Water Stress

Water flooding and drought are the main environmental stress factors affecting plant growth.Nutrient loss under water flooding stress is one of the factors affecting the normal growth of plants.Plants in the reservoir falling area are often under drought stress after water flooding.In order to explore the effects of nutrients on the tolerance of plant water flooded and the effects of water flooded,water flooded drought alternate stress on plants,Mangifera indica Lin.and Dalbergia odorifera T.Chen were used as the research materials.Three experiments were set up in this study,experiment 1:taking one-year-old mango seedlings as the research material,the waterlogging tolerance of mango seedlings was studied through artificial simulation of waterlogging.Experiment 2:taking two-year-old D.odorifera seedlings as the research material,through the artificial simulation of eutrophic water flooding（setting four treatments:CK,H,W,WH）,to explore whether nutrient deficiency is the limiting factor of terrestrial plants’flooding tolerance,and whether eutrophic water flooding promotes terrestrial plants’flooding tolerance.Experiment 3:on the basis of Experiment 2,five treatments（CK,CD,HD,WD and WHD）were set to study the drought resistance of D.olbergia,and the effects of nutrients,flooding and eutrophic water flooding on the drought tolerance of D.odorifera.Through the measurement of plant growth morphology,physiology,photosynthesis and fluorescence index,the subordinate function analysis of the measured data was carried out,in order to provide scientific guidance for the selection of ecological restoration tree species of mango in special areas,and the reasonable application of D.odorifera in the water level area,riparian zone,polluted water and other special areas of vegetation restoration.The results are as follows:（1）Mango seedlings survived completely under 80 days of water flooding stress（10cm depth of water flooding）,and the leaves lost green and yellow,without shedding.The stem nodes elongated and the lenticels were enlarged,but no adventitious roots were produced.The relative water content and photosynthetic pigment content of leaves decreased significantly,while the relative electrical conductivity increased significantly.The content of soluble protein,soluble sugar and starch in mango leaves increased.The results showed that mango had a certain tolerance to flooding.（2）After 100 days of submergence stress,the survival rates of D.odorifera seedlings treated with W and WH respectively were 87.87%and 88.57%,and there was no significant difference.The results showed that both flooding stress significantly inhibited plant growth,promoted leaf yellowing and withering,significantly reduced net photosynthetic rate,Fv/Fm,primary root activity,chlorophyll content and dew point water potential,and significantly increased relative electrical conductivity,MDA,O₂.^-,H₂O₂ Content,soluble protein and antioxidant enzyme（SOD,POD,APX）activities of leaves Induction of adventitious root formation.The results showed that the chlorophyll a,total chlorophyll content,soluble protein content and root activity of WH plants were significantly higher than those of W plants,but the activities of SOD,POD and root activity of waterlogged adventitious roots were significantly lower than those of W plants;except for the above indexes,there was no significant difference in other physiological and biochemical indexes under the two kinds of waterlogging stress;there was no significant difference between the two kinds of waterlogged treatments,the mean value difference of membership function between the two flooding treatments is small.The results showed that nutrient supply could not alleviate the inhibition of waterlogging stress on D.odorifera,and eutrophic water could not effectively promote the waterlogging tolerance of D.odorifera.（3）Under 80 D drought stress,all D.odorifera seedlings survived,but the plant height was significantly inhibited,the leaves dropped and the biomass decreased.Drought stress significantly reduced net photosynthetic rate,Fv/Fm,water use efficiency,dew point water potential,root activity and soluble protein content.The relative electrical conductivity,H₂O₂and MDA content of leaves increased significantly under drought stress.The plant alleviated injury and resisted stress by increasing the activities of antioxidant enzymes（SOD,POD and APX）.The physiological responses of D.odorifera to drought stress were different in the early stage of applying nutrients and experiencing two kinds of flooding stress.However,the soluble protein content,SOD activity and root activity decreased significantly,and the relative conductivity increased significantly.The application of nutrients in the early stage promoted the growth of plant height and biomass accumulation in the late stage of drought stress,but the chlorophyll content decreased significantly and the carotenoid content increased significantly.In the early stage,the net photosynthetic rate was increased and the root activity was further decreased under two kinds of flooding stress.Compared with the drought group,the total chlorophyll content and POD activity increased significantly,the carotenoid and APX activities decreased significantly,and the relative conductivity increased significantly.There was little difference in the mean value of membership function among the four drought treatments.The results showed that the plant growth condition of drought group was poor after applying nutrients in the early stage,followed by the group of turning drought after flooding in the early stage,and the group of turning drought after flooding in the early eutrophic water body.The above results showed that mango and D.odorifera seedlings had a certain ability of water tolerance,and D.odorifera seedlings had a certain ability of drought tolerance.Nutrient supply could not alleviate the inhibition of D.odorifera in the flooding stage,and eutrophic water could not effectively promote the flooding tolerance of D.odorifera.Early flooding and eutrophic water flooding may enhance the ability of D.odorifera under late drought stress.Early application of nutrients and water flooding and eutrophic water flooding may also hinder the ability of tolerance to drought stress.In conclusion,mango and D.odorifera can be considered as special wetland ecological restoration tree species,so as to increase species diversity and improve landscape.