Physiological Response Mechanism Of Phyllostachys Heterocycla Var. Pubescens Seedlings Under Water Deficiency Stress

The membrane permeability,leaf water potential,Superoxide Dismatase (SOD),Atalase(CAT),Malondialdehyde(MDA),pigment content,photosynthetic parameters ,chlorophyⅡd ynamics and fluorescence imaging was conducted with the leaves of 1-year-old and 2-year–old Phyllostachys heterocycla var.pubescens under natural drought and re-watering and different water deficiency conditions (well watered(CK),little mild stres(sLS),moderate stress(MS),severelys stress(HS)),by pot culture method.The results were the same between conculusions of summer and autumnas,as follows:(1) From well watered to severely stress watered,the conductivity increased,leaf water potential decreased,and correlation is not significan(by regression analysis,R=0.054). Different gradient of water deficit stress treatment and natural drought,after rehydration The membrane permeability can recover after re-watering.(2)From well watered to severely stress watered and natural drought,the activity of SOD decreased 17.1639% at LS treatment,then increased;while the activity of CAT and MDA content increased gradually,then decreased after re-watering.The activity of SOD was not obvious in the process of natural drought and re-watering.( 3 ) By Spectrometry , chlorophyll content of bamboo seedlings were reliable( R=0.9994);while the variation of average of it is similar with other pigment content.by Extraction,increased the content of chlorophyll a,chlorophyll b and total chlorophyll were gradually decreased in the process of natural drought and from CK treatement to HS treatement. After re-watering,the content of chlorophyll a,chlorophyll b and total chlorophyll regained in natural drought and CK,LS,MS treatment,but HS treatment.(4)From well watered to severely stress watered,the net photosynthetic rate (A),transpiration rate(E),stomatal conductance (GH2O)were declined,and which mainly resulted from stomatal limitation.The water content around 50%-60% were suitable.(5)From NS treatment to HS treatment, Fm, Fv / Fm,Yield reduced,while Fo increased. The heterogeneity of chlorophyll fluorescence parameters Fo,Fm,Fv/Fm was significantly different . PSⅡapparatus damaged ( 1-year seeding at 17.68% water contentduring;2-year seedings at 51.33% water content)in the process of natural drought,and could restore after re-watering.