Effects Of Spraying Exogenous Abscisic Acid On Growth And Fruit Quality Of Apple

Apple is the largest fruit in China at present.Rainfall is less and uneven in Northwest China.Drought affects the normal growth and development of apples,resulting in low fruit yield and poor quality in many orchards.The effects of exogenous abscisic acid on drought resistance,fruit quality,defoliation and nutrient reflux of apple cultivars’Fuji Nagafu No.2’,’Qin Guan’and’Qinmi’in different growth periods were studied in order to provide technical basis for improving stress resistance and fruit quality of apple.The main results are as follows:1.The drought resistance of’Fuji Nagafu No.2’apples could be improved by exogenous abscisic acid treatment for a long time in the vigorous shoots of apples.Exogenous abscisic acid treatment with 50μmol/L,100μmol/L,150μmol/L and 200μmol/L concentration significantly reduced the transpiration rate and stomatal conductance of leaves,improved the ability of leaf water conservation,significantly increased the relative water content of leaves,and enhanced the ability of apples to adapt to water drought.Among them,200μmol/L concentration of exogenous abscisic acid treatment significantly reduced leaf area and autumn shoot length,which showed that high concentration of exogenous abscisic acid could inhibit the growth of fruit trees,while low concentration of exogenous abscisic acid treatment did not inhibit the growth of fruit trees.Abscisic acid treatment at 50μmol/L increased chlorophyll content and net photosynthetic rate of leaves and decreased transpiration rate of leaves,but had no inhibitory effect on fruit tree growth.2.Applying 400μmol/L exogenous abscisic acid at the turning stage of Apple could significantly improve the fruit quality of’’Fuji Nagafu No.2’and’Qin Guan’apples.Exogenous abscisic acid treatment with 400μmol/L concentration could significantly increase fruit firmness,soluble solids content and sugar-acid ratio of two apple varieties,increase fructose,glucose,galactose and sorbitol content,and reduce starch content,malic acid and sucrose content,so as to improve the intrinsic quality of fruit.The exogenous abscisic acid treatment of 400μmol/L significantly increased the a*value of apple fruit,decreased the H~0 value of apple fruit,increased the color of fruit,and improved the appearance quality of fruit.Exogenous abscisic acid treatment had no significant effect on fruit weight and fruit shape index.3.The application of exogenous abscisic acid at the defoliation stage of Apple significantly promoted the defoliation and nutrient reflux of’’Qinmi’apple.The defoliation rate of low concentration abscisic acid applied on windward slope was the same as that of high concentration abscisic acid applied on leeward slope.Exogenous abscisic acid treatment at 450μmol/L concentration could significantly promote N,P,K nutrient reflux in leaves,and promote K>P>N.