Effects Of Waterlogging Stress On Growth And Physiological Characteristics Of Phoebe Zhennan Seedlings

Water is the primary factor affecting the productivity of ecosystem.Excessive（waterlogging）or insufficient（drought）water will interfere with the normal water physiology of plants to a certain extent.It will not only affect the growth and development of plants,but also affect their distribution and community structure,as well as the yield and product quality of trees.In agricultural and forestry production,although drought is more widespread,in some areas or in a particular period,the harm of waterlogging is no less than that of drought or even more.Therefore,in areas with excessive soil moisture,the study of waterlogging resistance of plants is one of the hot topics in academic circles.This research aimed to understand the effect of waterlogging on the photosynthetic physiology and growth characteristics of three-year P.Zhennan seedlings.The pot experiment was conducted with five levels of waterlogging treatments.The experiment was terminated when the leaves of seedlings of treanment H20 became wilting.The whole experiment lasted 51 days.And then the morphological characteristics（indexes）,The photosynthetic physiological indexes of functional leaves,physiological and biochemical indicators of absorbing and transporting roots were observed and determined.The results are as follows.（1）The contents of chlorophyll a,b and carotenoids decreased with the increase of waterlogging stress,full waterlogging stress,respectively,compared with the control was reduced by 62.7%、50.5%and 42.8%;（2）The net photosynthetic rate,stomatal conductance and transpiration rate decreased significantly with the increase of waterlogging stress（P<0.05）,compared with CK,full waterlogging stress decreased by 99.1%,96.2%and 94.7%respectively,and the intercellular CO₂ concentration decreased firstly and then increased,the full waterlogging stress increased by 101.7%compared with the control（P<0.05）;（3）With the aggravation of waterlogging,the plant height growth of P.Zhennan was significantly inhibited（P<0.05）,as the waterlogged degree aggravating,plant height net growth,respectively,compared with the control was reduced by 30.23%,76.7%,81.4%and 90.7%;（4）Under the condition of low light(PAR<600μmol·m^-2·s^-1)or low concentration of CO₂(the concentration of CO₂<600μmol·mol^-1),mild waterlogging has a positive influence on the photosynthesis of P.Zhennan;（5）Except for Full waterlogging stress（flooded with water）and CK,waterlogging stress caused the appearance of adventitious roots of P.zhenan,and the greater the degree of waterlogging stress,the fewer new adventitious roots;（6）The activity of transporting roots decreased significantly under waterlogging stress（P<0.05）,while the activity of absorpting roots decreased significantly after waterlogging stress was greater than moderate（H15,H20）stress（P<0.05）;（7）Compared with absorbing roots,transporting roots showed stronger waterlogging resistance,while absorbing roots were more sensitive to the changes of waterlogging environment compared with transporting roots.Waterlogging stress had significant effects on the photosynthesis,the resistant physiological characteristics,root growth and its metabolic function of Phoebe zhennan Seedlings.The growth of plant was severely inhibited or even death of plant was appeared.Therefore,it is inappropriate to develop the plantation of Phoebe zhenan in mountain valleys and low-lying areas.If the planting of Phoebe zhenan is necessary for special purpose,positive drainage and waterlogging prevention measures should be taken.