Effects of PEG 6000 simulated drought stress on physiological and chlorophyll fluorescence characteristics of Dendrobium candidum seedlings
[Objective]The objective is to study the effects of PEG 6000 simulated drought on physiological and chlorophyll fluorescence characteristics of Dendrobium candidum,so as to provide reference for variety selection,industrial cultivation,and near wild cultivation of D.candidum.[Method]The seedlings of D.candidum'Jingpin No.1'were used as experimental materials and treated with PEG 6000 at different concentrations to simulate drought stress.The stem segment and leaf cell structure of D.candidum seedlings were observed,and the dynamic changes of peroxidase(POD),catalase(CAT)activity,malondialdehyde(MDA),soluble sugar,soluble protein,chlorophyll content and chlorophyll fluorescence parameters in D.candidum leaves were detected.[Result](1)The content of chlorophyll in the stem and leaf cells of D.candidum decreased after treatment with high concentration of PEG 6000(20％-30％).(2)PEG 6000 simulated drought stress significantly affected the content of soluble sugar and protein,MDA,POD and CAT activity of D.candidum seedlings.The soluble sugar content increased with the increase of PEG 6000 concentration and the extension of treatment time,reaching its highest value on the 12th day,while the soluble protein showed a downward trend.MDA content,POD and CAT activity increased first and then decreased with the increase of PEG 6000 concentration,reaching the peak at a PEG 6000 concentration of 20％.(3)PEG 6000 simulated drought treatment of D.candidum seedlings significantly affected chlorophyll fluorescence parameters such as maximum photochemical efficiency(Fv/Fm),photosynthetic efficiency(a),electron transfer rate(ETR),photochemical quenching coefficient(qp)and non-chemical quenching coefficient(qNP).With the extension of PEG 6000 stress treatment time and the increase of PEG 6000 concentration,a,ETR,Fv/Fm and qP showed a significant downward trend,while qNP showed a trend of first increasing and then decreasing.[Conclusion]20％PEG 6000 treatment for 12 days can be used as a method for screening drought resistant varieties of D.candidum,which can resist and adapt to a certain degree of drought stress by increasing the content of soluble sugar,reducing the content of soluble protein and improving the activities of defense enzymes such as POD and CAT.The maximum light energy conversion efficiency of D.candidum seedlings decreases,and the photosystem Ⅱ(PS Ⅱ)is damaged by stress,which seriously affect the photosynthesis of D.candidum seedlings.At the same time,D.candidum seedlings consume the excess light energy absorbed by the PS Ⅱreaction center by activating the qNP pathway to maintain normal photosynthesis.Therefore,soluble sugars and protein,POD and CAT,and chloroplast fluorescence parameters can all be used as indicators of drought resistance in D.candidum.[Ch,6 fig.44 ref.]
Dendrobium candidumdrought stressphysiology and biochemistry indicatorschlorophyll fluorescence parametersPEG
万方数据
