Effects Of Exogenous Melatonin And Ascorbic Acid On Physiological Characteristics Of Apple Rootstock M9T337 Under NaCl Stress

Soil salinization is an unavoidable problem today.Under the influence of various natural and human factors,the global saline land area is constantly expanding.The impact of saline-al kali land on agriculture is very large.Soil salinization in many areas has led to a decline in agr icultural product output,poor product quality,and even extinction or plant death.Facing the i ncreasingly serious soil salinization,more and more researches on how to alleviate the damag e of plants under salt stress have been made,and it is very serious to solve the planting proble m of saline-alkali soil.Secondary metabolites are important aspects of plant metabolism.Man y studies have found that secondary metabolites such as salicylic acid and melatonin can impr ove the resistance of plants to stress.This experiment explored the effects of exogenous applic ation of melatonin and ascorbic acid on apple M9T337 under salt stress.These two substances have effects on the physiological and biochemical changes of apple seedlings.The findings are as follows:The maximum salt concentration that M9T337 seedlings can withstand is 150MmNaCl s alt solution.Although the seedlings receive severe salt stress damage,they are not lethal and t he damage received is reversible.SOD,POD,CAT and other antioxidant enzyme activities re ached the highest,H₂O₂ and MDA content is very high,the leaves are yellow in a large area.Exogenous application of melatonin solution under 150mmol/L NaCl solution stress ca n effectively alleviate salt stress and enhance stress resistance of seedlings.The optimal conce ntration of melatonin applied is 100?mol/L.At this time,the content of harmful substances i n apple leaves is low,the antioxidant enzyme activity is high,the chlorophyll content is high,the physiological activity is good,and the damage caused by salt stress is minimal.Under 150 mmol/L NaCl solution stress,exogenous application of 100?mol/L melato nin and different concentrations of ascorbic acid can achieve better anti-stress effect.At 20 m g/L ascorbic acid,the physiological indexes of apple seedlings reached their peaks,the conte nt of harmful substances decreased,the antioxidant enzyme activity increased,and the physiol ogical state was the best.Under 150 mmol/L NaCl solution stress,the combined effect of 100?mol/L melatonin and 20 mg/L ascorbic acid had the best effect on alleviating salt stress i n seedlings.Under 150 mmol/L NaCl solution stress,100?mol/L melatonin and different concentr ations of GA3 were applied exogenously.Compared with the application of only 100?mol/L melatonin,after adding GA3,the content of harmful substances does not change much,the antioxidant enzyme activity decreases,the chlorophyll content changes little,and the damage to apple seedlings has not weakened,so melatonin alone The effect is better than the combine d effect with GA3,and the addition of GA3 did not better alleviate salt stress.