Effects Of Flooding Stress On Physiology And Ecology Of Mulberry Seedlings

In order to explore the effects of flooding stress on the physiological and ecological characteristics of mulberry seedlings,the method of simulating flooding was carried out to study the leaf morphology,plant height,ground diameter,the anaerobic respiratory enzymes and antioxidant enzymes activity in the leaves of two-year-old potted mulberry seedlings under different flooding time and flooding depths.And the 3-year-old potted mulberry seedlings were divided into three treatments:low flooding(15cm),half flooding(32cm)and full flooding(65cm).The leaf morphology of mulberry seedlings was observed and recorded regularly,while the FluorCam portable chlorophyll fluorescence imager was used to determine the fluorescence parameters and images of mulberry leaves.The main findings are as follows:(1)The damage degree of leaves under flooding stress was significantly as follows:deep flooding group>root flooding group,non-growing season flooding stress>growing season flooding stress.Among them,the leaves of mulberry seedlings in deep flooding group showed wilting and yellowing on the 15th day,and the leaves were basically rotted and shed by the end of flooding in non-growth season.In growing season,the leaves of mulberry seedlings in the deep flooding group began to appear wilting and shedding on the 30th day.While some of the leaves in the root flooding group remained healthy and intact after the flooding.(2)Flooding stress inhibited the growth of plant height and ground diameter of mulberry seedlings both in the non-growing season and growing season,however,this inhibition was more significant in the growing season.The inhibition under different flooding depths on plant height and ground diameter of mulberry seedlings were significantly as follows:deep flooding group>root flooding group>control group(P<0.05).(3)Under the same flooding time,the activities of anaerobic respiration enzyme and antioxidant enzymes in the leaves of mulberry seedlings showed a significant upward trend with the increase of flooding depth both in non-growing and growing seasons(P<0.05).Under the flooding stress in growing season,the activities of six enzymes in the leaves of mulberry seedlings showed a significant upward trend with the prolongation of flooding time(P<0.05).The SOD activity of mulberry seedlings increased significantly on the 60th day of flooding for in the non-growing season,that in the control group and the root flooding group decreased by 3.49%and 9.22%respectively on the 90th day.However,the activity of POD and CAT reached a maximum on the 90th day,the activities of the two enzymes in three treatments increased by 8.03%,15.7%,10.23%,and 12.05%,6.45%,9.15%higher than the 30th day of flooding respectively,the difference was significant(P<0.05).Increasing the activity of antioxidant enzymes and anaerobic respiration enzymes in leaves is the response of mulberry seedlings to the flooding stress in the growing season.Increasing the activity of anaerobic respiration enzyme and antioxidant enzymes with the synergistic effect of the three antioxidant enzymes are responses of the 2-year-old mulberry seedlings to the flooding stress in the non-growing season.(4)The Fo,Fm,QYmax,Fv/Fo and Rfd-Lss of mulberry seedlings in the three treatments were significantly reduced on the 4th day of flooding stress.The Fo,Fm and Fv/Fo in the half flooding and full flooding groups both decreased significantly on the 8th day,and then showed a relatively stable trend.The 1-qP-Lss of the mulberry seedlings in three different groups significantly increased by 13.25%,45.33%and 69.42%(P<0.05),and then showed a relatively stable trend.Under the flooding stress,the decrease of fluorescence intensity of mulberry seedlings firstly began with the tip of the blade and then gradually extended from the edge of the blade to the entire blade.The self-repairing of leaf photosynthetic system maintains its photochemical activity by forming external morphology such as reducing the amount of leaves and generating adventitious roots,which is the physiological and ecological response of the 3-year-old mulberry seedlings to resist to flooding stress.