The Physiological Responses Of Fruit Trees--Chinese Chestnut Etc To Water-Stress

Six two-year-old Chinese chestnut varieties and strawberry, apple grown in pots were adopted. The variation of physiological activated substance, such as betaine and Malondiadehyde in leaves etc.and diurnal variation of photosynthesis were measured. And drought-resistance of each variety was compared. Meanwhile, the variation of betaine content in leaves, stalks and roots under water-stress and. the effect of spraying exogenous betaine in different concentration on betaine content, MDA content and SOD activity under natural water-supply and water-stress were probed. The main results were as follows:1. Under natural water supply or water-stress, the photosynthetic rate, water use efficiency and carboxylation efficiency of HuaGuang and 10—14 was obviously higher than TaiLin 20 but transpiration rate lower than it. With water-stress degree increasing, the velocity of new branches slowered, leaf area became smaller, leaf relative water content and chlorophyll content decreased, the decreasing range of HuaGuang was the least, and then was 10-14, ShiFeng, Chu Shuhong, YanKui, TaiLin 20 was the greatest.The varying ranges among various varieties was obviously different. 2. During water- stress, the activity of SOD and POD increased firstly, then decreased; the decreasing range of TaiLin 20 was the greatest and HuaGuang was the least. betaine, and proline in leaves increased, Malondiadehyde content and Plasma mambrane permeality in leaves also increased, the differences among each variety were remarkable. The relation between betaine content in leaves and other physiological indexes was analyzed, the result showed that: Betaine content in leaves of Chinese chestnut was positivelycorrelative to drought resistance. Under different treatment with the same variety, betaine content was positively correlative to Malondiadehyde and Plasma mambrane permeality, and negatively to leaf relative water content. Biological and physiological indexes was analyzed synthetically, the order of their drought - resistance from better to weak was 10—14, HuaGuang, Shi Feng, Chu Shuhong, YanKui, TaiLin 20.3. There was some betaine in each tree under natural water supply, betaine content were various in different trees and organs with the same tree. Betaine content of Chinese chestnut was the most, apple was the least; with the same tree betaine content in leaves was the most and in roots was the least. Under water-stress betaine content of each tree increased greatly, the varying ranges of each tree were different, the varying trends of different organs in the same tree were similar. Under slight water-stress the increasing range of apple was greatest, then was strawberry, Chinese chestnut was the least; Under medium water-stress, the increasing range of Chinese chestnut was also greatest, but then was apple and strawberry. When under severe water-stress, betaine content of Chinese chestnut and apple continued increasing, strawberry almost didn't change.4. Whether under adequate water-supply or under water-stress, Chinese chestnut was sprayed exogenous betaine by 50,100 and 150mmol.L-1, Betaine content and SOD activity were evidently higher than contrast, MDA content was lower than contrast. In100 mmol.L-1, Betaine content and SOD activity were evidently higher than that in 50mmol.L-1, MDA content was lower.While in 150 mmol.L-1, three indexes almost didn't vary compared with that in 100 mmol.L-1. Therefore, 100mmol.L-1 was the optimal spraying concentration of. Compared with contrast the varying range of each indexes under water-stress was greater than that under natural water supply, which indicated exogenous betaine can better exerted its action as one kind of physiological drought resistant reagent under water-stress.