Effects Of Enhanced UV-B Radiation On Physiological Properties In Barley Cultivars

The stratospheric ozone layer formed a protective atmospheric filter against biologically harmful solar ultraviolet radiation. Anthropogenic emissions of chlorofluorocarbons and nitrogen oxides resulted in depletion of ozone layer. Enhanced UV-B radiation had been confirmed to negatively affect plant growth and development in higher plants. Barley is the forth most important worldwide crop, which is after wheat, maize and rice, but very few studies have been conducted concerning its response to enhanced UV-B radiation. Field experiment was conducted to investigate the effects of enhanced UV-B radiation on photosynthesis and transpiration physiological characteristics in different barley cultivars. The main results are as follows:(1) The decreases in plant height, number of green leaves, leaf area and biomass were observed under enhanced UV-B radiation, which was equal to the radiation intensity as 25% ozone depletion in Nanjing region.(2) Under enhanced UV-B radiation, total chlorophyll content, chlorophyll a and b content in barley leaves were generally declined. Significant differences were found at the heading stage. The content of carotenoid first decreased and then increased in the growth period. MDA content, which was the product in barley leaves, rapidly increased. Flavonoids content also rapidly increased. Soluble sugar showed a fluctuation decrease tendency. And soluble protein showed a fluctuation increase tendency.(3) Under enhanced UV-B radiation, net photosynthetic rate and stomatal conductance in barley leaves were declined. Intercullular CO2 concentration showed a fluctuation change tendency. Transpiration rate were declined.(4) The changing condition of the leaf area, photosynthetic pigment, net photosynthetic rate, physiological and biochemical had a close relationship with the selection of different function leaves in the different growth period.(5) Under enhanced UV-B radiation, It was obviously declined that contained grains per spike, theoretical yield, actual yield,1000-grain weight, setting rate, germination energy, germination percentage and so on.(6) Under enhanced UV-B radiation, differences existed in the sensitivity of different barley cultivars to UV-B radiation stress. Barley Su 4 had the strongest resistance against UV-B radiation stress, and Dan 2 had the least.