Effects Of Exogenous Substances On Physiological Functions Of Malus Baccata Borkh. Leaves Under Temperature Stress

This experiment simulated the temperature change characteristics of early spring in Shenyang area,In Malus baccata seedlings of variable temperature stress and exogenous reagents?CaCl₂,alpha ketoglutaric acid,CsA,AsA,EGTA?treatments.After processing every 1 day sampling,a total of 11d is processed.By measuring the photosynthetic rate,chlorophyll fluorescence parameters,malondialdehyde content,membrane permeability,membrane potential,respiratory metabolism pathway,three carboxylic acid circulating metabolites,key enzyme activity,antioxidant enzyme activity,ascorbic acid-glutathione circulatory metabolite and key enzyme activity,etc.The response characteristics of the leaf mitochondria and chloroplasts to the rapid temperature change,as well as the regulation effect of calcium ions on the interaction of the two,were studied.The physiological basis of the adaptive expression of the temperature of the stator leaves under the variable temperature stress was discussed.The main results are as follows:1.In addition to EGTA treatment,other treatments protected the ability of leaf capture and utilization of light energy,and inhibited the reduction of photosynthetic pigments.Temperature stress resulted in Malus baccata leaf net photosynthetic rate?Pn?,stomatal conductance?Gs?and transpiration rate?Tr?decreased;The treatment of alpha ketopamyl diacid significantly increased Pn,Gs and Tr during the process of temperature variation;CaCl₂,ascorbic acid?AsA?and cyclosporin A?CsA?significantly increased Pn,Gs and Tr in the late stage of temperature stress treatment,while EGTA treatment significantly reduced the three photosynthetic parameters.The concentration of intercellular carbon dioxide?Ci?was higher under temperature variation stress,and the concentration of Ci in EGTA treatment was higher than that of variable temperature stress treatment,while other treatments were lower than that of variable temperature stress treatment.2.In the process of temperature variation stress,the content of hydrogen peroxide?H₂O₂?and the production rate of superoxide anion?O₂^-?increased as a whole,while the activity of antioxidant enzymes?SOD,POD,CAT,APX,GR,DHAR and MDHAR?and the content of antioxidants?AsA and GSH?decreased.The H₂O₂ content and O₂^-production rate of alpha ketone glutaric acid,AsA and CaCl₂ decreased significantly compared with that under temperature stress,and the activity of antioxidant enzymes increased significantly.EGTA treatment inhibited the increase of antioxidant enzyme activity and resulted in excessive accumulation of reactive oxygen species?ROS?.3.The total respiration rate under low temperature stress is at a low level.Except for EGTA and CsA treatments,the total respiration rate of other treatments is significantly higher than that of variable temperature stress.After EGTA treatment,the respiratory activity of TCA was inhibited and the respiratory activity of EMP was higher;the other treatments increased the respiratory activity of TCA in different degrees,and the treatment was more significant with CaCl₂ and alpha ketopamyl diacid.4.Compared with temperature stress,membrane permeability of CaCl₂,alpha ketone glutaric acid,CsA and AsA decreased,and EGTA treatment increased membrane permeability;the mitochondrial membrane potential is the opposite result.Under different temperature stress,CP activity decreased and AP activity increased.All treatments increased CP activity,while EGTA treatment decreased CP activity and AP activity.5.The relative growth rate of plants was reduced under temperature change,and EGTA treatment enhanced the inhibition of plant relative growth rate.Other exogenous reagents alleviated the inhibition effect of low temperature stress,which was most obvious with CaCl₂treatment.EGTA treatment accounted for the largest proportion of dry matter and the smallest leaf,indicating that calcium inhibitors inhibited plant growth under low temperature stress.