Effects Of Defoliants On Photosynthetic Physiology And Antioxidant System Of Greenhouse Grape

How to solve the problem of sleep,reduce fruit production cycle,production management has become a problem to be solved.In this experiment,seven-year-old’Zaoheibao’ grapes were used as the test material.Spray 0.2% ethephon and 6% urea on the leaves to explore the effects of defoliants on the photosynthetic physiology,antioxidant system,osmotic adjustment substances and carbohydrates of grape leaves.which provided a basis for the application of defoliants on fruit trees.The main results of the test are as follows:1.After spraying defoliant,the P_n,G_s and T_r of the leaves decreased,and the C_i decreased to the lowest point at the 15 th day after spraying.The effect of 0.2% Ethephon on net photosynthesis was greater and the inhibition of photosynthesis was stronger.2.After spraying defoliant,F₀ and NPQ increased,q_p and ETR decreased,F_v/ F_m and F_v/ F₀ increased first and then decreased,but the change was small and remained stable.The effect of 0.2% ethephon treatment on F₀ and q_p was greater at the later stage of spraying.3.After spraying defoliant,the changes of chlorophyll a,chlorophyll b and Carotenoid showed a trend of "down-up-down" Both chlorophyll a and chlorophyll b decreased to the lowest point on the 15 th day after applying defoliant,but the decrease of Carotenoid was not significant.0.2% Ethephon can reduce the chlorophyll content of leaves.4.After spraying defoliant,the activities of SOD,POD and CAT increased at first and then decreased.GSH defoliant treatment increased in different degrees,but 200 times ethephon treatment increased in the last stage,6% urea treatment was the opposite.6% urea treatment could reach the peak of antioxidant enzyme earlier,and the damage to leaves was faster.5.After spraying defoliant,the content of Pro and soluble protein in leaves increased continuously.6% urea treatment had higher accumulation of osmotic adjustment substances.6.After spraying defoliant,the content of soluble sugar decreased firstly and then increased,but the content of starch was the opposite.The treatment of defoliant had little effect on soluble sugar content of grape leaves.0.2% Ethephon had a higher accumulation of carbohydrate in the shoot.7.After spraying defoliants,the soluble sugar content of the leaves showed a trend of first decreasing and then increasing,and the starch content was the opposite.There was no significant difference in soluble sugar content between the defoliation treatment and the control.The soluble sugar content of the branches after 0.2% ethephon treatment was significantly higher than that of the control,and there was no significant difference between the 6% urea treatment and the control.No significant difference between the two branches of the starch content of the treated and control defoliants.In summary,0.2% ethephon treatment than 6% urea treatment on the leaf photosynthesis and chlorophyll inhibition,fluorescence increased more,can make the shoot accumulation more carbohydrates,increase the germination rate of the following year.After 6% urea treatment,the osmotic adjustment substances were more and the damage of reactive oxygen species was higher.So 0.2% Ethephon is the better defoliant.