Physiological Responses And Drought Resistance Of Paeonia Rockii Under PEG-6000Simulated Drought Stress

Paeonia rockii is an endemic species to China and is endangered, which isespecially suitable for the cultivation in the northern cold and arid areas because of itscharacteristics: the tolerance to cold, drought, salt and poor, fewer pests and diseases,wide adaptability. P.rockii has ornamental, medicinal and oil value, and also with apromising prospect of broad application. At present, the research of P.rockii is mainlyfocused on taxonomy, breeding of new cultivars, reproduction technology, anatomicalstructures and cold resistance, but as for the study of P.rockii drought resistance it israrely reported.The experiment was to explore the optimum conditions of simulated droughtstress to the study of P.rockii drought resistance, using the hypertonic solution ofpolyethylene glycol (PEG-6000) to deal with experimental materials so as to simulatephysiological drought condition，and finally reach the aim of studing the effect ofphysiological indexes of P.rockii under drought stress. Using4-year old P.rockiicultivars ‘Shushengpengmo’ as materials, the experiment was carried out on thechanges of leaf water content, relative water content (RWC), relative electricconductivity (REC), contents of malondialdehyde (MDA), soluble sugar and freeproline under0,0.1,0.2,0.3kg/L of the polyethylene glycol (PEG-6000) simulateddrought stress to the4,6,8,10days. After significant difference analysis amongsamples by SPSS, the following conclusion can be drawn after integrating all factors:the optimum simulated conditions for the study of the drought resistance of P.rockiiisusing0.2kg/L PEG-6000to stress for8days. By this time, all physiological indexesof P.rockii are significantly different with control group.In addition, in order to compare the drought resistance of different cultivars ofP.rockii and screen the indexes of drought resistance，the experiment uses nine4-yearold P.rockii cultivars ‘Zibanfen’,‘Shushengpengmo’,‘Bingshanxuelian’,‘Hepinglian’,‘Lanhaiyinbo’,‘Honghaiyinbo’,‘Yanguanqunfang’,‘Ziloushanjin’ and ‘Helingbai’,and P.suffruticosa which is widely planted in Central China as materials, changes inleaf water content, relative water content (RWC), relative electric conductivity (REC),contents of malondialdehyde (MDA), soluble sugar, free proline and chlorophy a,chlorophy b, carotenoid, total content of chlorophyⅡ, and chlorophyⅡ a/b under the optimum simulated drought stress conditions which is screened from the first part ofour experiments (drought stress8days by0.2kg/L PEG-6000) were measured. Themethod of subordinate function was used to comprehensively evaluate the droughtresistance and compare its capabilities of drought resistance of different P.rockiicultivars and P.suffruticosa, and correlative degree analysis was used to screendrought resistance physiological indexes of P.rockii. The results are as follows: thedrought resistant capabilities of9P.rockii cultivars and P.suffruticosa were in adecreasing order of ‘Zibanfen’>‘Lanhaiyinbo’>‘Shushengpengmo’>‘Honghaiyinbo’>‘Bingshanxuelian’>‘Yanguanqunfang’>‘Ziloushanjin’>‘Hepinglian’>‘Helingbai’>P.suffruticosa; The correlative degrees of11measured indexes and average value ofsubordinative function were in a decreasing order of relative electric conductivity(REC)>chlorophy a>free proline>total content of chlorophyⅡ>soluble sugar>chlorophy b>relative water content (RWC)>malondialdehyde (MDA)>chlorophyⅡ a/b>carotenoid>leaf water content. As a result, the following conclusions can bereached: the drought resistance of P.suffruticosa which is widely planted in CentralChina is inferior to all P.rockii cultivars, it has the wrost aptability to drought, and isnot suitable for cultivation in arid regions. In nine P.rockii cultivars,‘Zibanfen’ hasthe highest drought resistance, while ‘Helingbai’ is the weakest. Therefore, it isintelligent to select P.rockii cultivars with higher drought resistance such as‘Zibanfen’,‘Lanhaiyinbo’ and ‘Shushengpengmo’, but it isn’t appropriate to selectP.rockii cultivars with lower drought resistance such as ‘Ziloushanjin’,‘Hepinglian’and ‘Helingbai’ while introducting new P.rockii cultivars to the arid regions. Besides,the relative electric conductivity (REC), chlorophy a, free proline, total content ofchlorophyⅡ and soluble sugar had significant influences on the drought resistance ofP.rockii against simulated drought stress, so they can be used as candidate indexes infurther studies to evaluate the drought resistance of P.rockii.