Effects of enhanced UV-B radiation treatment on photosynthesis, yield and conventional quality of adult mango tree

ObjectiveEffects of enhanced UV-B radiation treatments on the photosynthesis,yield and conventional quality of adult mango trees were studied to provide theoretical reference to formulate cultivation technology of the resis-tance of mango trees to enhanced UV-B radiation.MethodTainong No.1 mango adult tree was used as experiment material and treated(under 20,40,80,120,160 and 200 W)by six enhanced UV-B radiation(irradiation by UV-B)ultraviolet lamp). And the sunlight irradiation was used as CK to measure and analyze the photosynthetic index of mature leaves, yield and ordinary quality of fruits.ResultAfter treated by enhanced UV-B radiation,the contents of chlorophyll and ca-rotenoid in the mature leaves of mango trees,net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance (Gs)of mature mango leaves decreased with the increase of enhanced UV-B radiation,showing accumulation effects and dose effects of enhanced UV-B radiation. The yield of mango tree under treatment 160 and 200 W were lower than that of CK,while the yield of mango tree under other treatments made no obvious difference from that of CK. Content of soluble sugar,the ratio of sugar/acid in fruits and vitamin C(Vc)content decreased with the increase of the enhanced UV-B radia-tion amount. Meanwhile,the ratio of sugar/acid in fruits under all treatments except for the second harvest under 200 W treatment,content of the soluble sugar in fruits under treatment over 80 W and content of Vc in fruits under treatment over 120 W were significantly less than those of CK(P<0.05,the same below). Content of titratable acids in fruits increased with the increase of the enhanced UV-B radiation intensity and was significantly more than that of CK when under the treatment over 80 W.ConclusionPhotosynthesis of the mature leaves in adult mango trees can be inhibited under en-hanced UV-B radiation,and content of soluble sugar,the ratio of sugar/acid in fruits and Vc content decrease. Accumulative effects and dose effects of enhanced UV-B radiation are presented which results in reducing yield and worsening fruit quality.