Physiological Response Of Three Typical Varieties Of Rape To Drought Stress

Taking Q2 of Brassica napus,Xinyou 9 of Brassica juncea and L14 of Brassica campestris as experimental materials,all the rapeseed varieties were cultivated in pots via normal water su pply(CK),moderate drought(MD),severe drought(SD)and other treatments separately.The p hysiological response of rape seedlings to drought was studied by analyzing its biological chara cteristics,measuring its morphological,physiological and biochemical parameters,and statistical analysis was carried out.The difference of drought resistance among three types of rape and its possible mechanism were revealed.The results of the experiment provide theoretical and techni cal support for the development of disaster resistance and disaster reduction measures and the p romotion of high and stable yield of rape.The main results are as follows:1.With the aggravation of drought stress,the total biomass of the three types of rapeseed de creased in different degrees,and the ratio of root to shoot increased in different degrees.of wh ich Q2 biomass decreased the most,reaching 49.5%,the root shoot ratio also increased the mo st significantly,which was 1.7 times of CK,followed by Xinyou 9,which was 1.6 times,and L14 by 1.2times.In addition,the relative water content of leaves and the rate of water loss of leaves in vitro decreased in different degrees.The rate of water loss of leaves in vitro was mo re sensitive to drought stress.In the whole process,Q2 was the fastest,L14 was the second,X inyou 9 was the slowest.At the same time,the relative water content of leaves in Xinyou 9 w as higher,showing better water retention capacity.2.Drought stress reduced the net photosynthetic rate,transpiration rate,stomatal conductance,maximum photochemical efficiency,PSII potential activity,actual photochemical efficiency and e lectron transfer rate of three types of rape leaves,of which Q2 decreased the most,Xinyou 9 decreased the less,showing a strong drought tolerance;The transmission electron microscope im ages of chloroplast showed that drought stress caused different degrees of damage to the chloro plast of three types of rape.Q2 was the most obvious damage,which was manifested in the b asic loss of cell morphology under severe drought,while Xinyou 9 was the least affected.3.The contents of soluble sugar,proline,soluble protein and the activities of peroxidase and superoxide dismutase in the leaves of three types of rape increased significantly with the aggra vation of drought stress,but the accumulation of organic solute was quite different.The accum ulation of proline and soluble sugar in Q2 increased to 12.37 and 2.58 times of the original,w hile that in Xinyou 9 and L14 increased respectively the proline and soluble protein increased t o 6.60 and 6.55 times respectively.In addition,the activities of antioxidant enzymes were also different.The activities of SOD and pod in L14 increased the most in the three materials,whic h were 2.92 and 4.14 times as much as before.4.According to the principal component analysis,each index is integrated into four independ ent comprehensive indexes(the cumulative contribution rate is 92.259%).Combined with the membership function analysis,the comprehensive evaluation D value of drought resistance is obta ined.The order of drought resistance of three kinds of rape is: Xinyou 9 > L14 > Q2,and th e D values were 0.749,0.691 and 0.253 respectively.Grey correlation analysis showed that wat er use efficiency,net photosynthetic rate,in vitro leaf water loss rate,malondialdehyde were cl osely related to the drought resistance of rape seedling,which could be used as the identificati on index of drought resistance of rape seedling.