Study On Growth, Physiology, Biochemistry And Root Morphology Influence Of Malus Toringoides Under Drought Stress

Malus toringoides is a Rosaceae species, mainly located in the high altitude area of western Sichuan. The region obviously characterized by an arid climated and low rainfall. So this experiment took Malus toringoides biennis as test materials, and used the pot experiment method. physiological and biochemical index, growth index and root morphological index of Malus toringoides were determined under different degrees of drought stress. This experient set five moisture gradient as follows:the CK(control group: the soil volumetric water content of 28.2%), Tl(group 1:the soil volumetric water content of 22.4%), T2(group 2:the soil volumetric water content of 17.6%), T3(group 3:the soil volumetric water content of 12.8%) and T4(group 4:the soil volumetric water content of 8%). This paper discussed the influence of physiological, biochemical and growth in Malus toringoides under drought stress, and evaluated appropriate drought-resistant index. Theory guides were provided of Malus toringoides of their cultivation and propagation at arid high altitude regions. This research gave out main conclusions as follows:(1) With degree of drought stress increased, plant height,ground diameter, above ground dry biomass, root dry biomass and first lateral root number of Malus/oringoides grew slowly. But the ratio of root to shoot and Lateral root position first increased and then decreased, and They grew the fastest under the condition of soil volumetric water content of 17.6%.(2) Growth indicators analyzed by the PCA.According to the contribution rate of each principal component and the corresponding coefficient of growth indicators in the principal components, scored the comprehensive model was as follows: Y=-0.095X1+0.165X2+0.157X3+0.202X4+0.207X5-0.003X6+0.168X7As shown in the model,root dry biomass and the ratio of root to shoot are important growth indicators of studies on Malus toringoides drought resistance. (X1: first lateral root number, X2:ground diameter, X3:above ground dry biomass, X4:root dry biomass, X5:the ratio of root to shoot, X6:Lateral root position, X7:plant height)(3) With the increasing extent and duration of drought stress, the relative water content of leaf and chlorophyll content dropped significantly, proline and malondialdehyde content increased significantly; Soluble sugar content, SOD activity and POD activity conditions continued to rise in treatment group 1, but the varying trend Under the stress level was growing in drought at the early stage of stress and dropping sharply later in T2, T3 and T4.(4) physiological and biochemical analyzed by the PCA.According to the contribution rate of each principal component and the corresponding coefficient of physiological and biochemical in the principal components, scored the comprehensive model was as follows: Y=0.205X1-0.05X2-0.08X3+0.103X4+0.206X5+0.071 X6+0.201X7The model showed that POD activity, SOD activity and soluble sugar content are the important indicators of studies on Malus toringoides drought resistance.(X1:SOD activity, X2:the relative water content of leaf, X3:chlorophyll content, X4:MDA content, X5:POD activity, X6:proline content, X7:soluble sugar content)(5) With degree of drought stress increased, root total length, the most coarse lateral root length, root surface area, root volume, root tips and root forks of Malus toringoides decreased growth.But the growth of taproot long first increased and then decreased. The results showed that the growth of root was restrained under drought stress condition. But it promoted taproot development under a certain degree of drought.(6) Seven root morphological indexes are analyzed by the PCA. According to the contribution rate of each principal component and the corresponding coefficient of root morphology indexes in the principal components,scored the comprehensive model was as follows: Y=0.186X1+0.205X2+0.144X3+0.126X4+0.204X5+0.094X6-0.022X7The parameters of root surface area and root total length played a crucial role in the root morphology of Malus toringoides. Malus toringoides has a way of increasing thick roots length and thick roots surface area to adapt to drought conditions.(X1:root volume, X2:root surface area, X3:root tips, X4:root forks, Xs:root total length, X6: Taproot long, X7:the most coarse lateral root length)(7) Under a certain degree of drought, Malus toringoides seedlings had better regulating action to adapt to drought conditions. Compensatory growth reaction was found in group 1 and group 2. The growth of seedlings was restrained in groups 3 and group 4. So the appropriate soil volumetric water for Malus toringoides was more than 17.6%.