UV-B辐射增强下施氮对大麦根际土壤酶活性的影响

he stratospheric ozone layer formed a protective atmospheric filter against biologically harmful solar ultraviolet (UV) radiation. Anthropogenic emissions of chlorofluorocarbons and nitrogen oxides resulted in depletion of ozone layer. Consequently, enhanced levels of UV-B radiation (280~320nm) had been detected in the world. Enhanced UV-B radiation had been confirmed to negatively affect plant growth and development in higher plants. Barley is the forth most important worldwide cereal crop, after wheat, maize and rice, but very few studies have been conducted concerning its response to enhanced UV-B radiation. Field experiment with barley was conducted to investigate the dynamics of enzyme activities as affected by elevated ultraviolet-B radiation and N supply. The experiment was designed with two UV-B radiation levels, i.e. ambient (A, control, 12.0 kJ m -2 d -1) and elevated by 20% (E, 14.4 kJ m -2 d -1), 3 levels of N supply, i.e. 30, 150 and 300 kg N hm-2and performed at the Station of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing, China. The results indicated that, compared with control, the effects of elevated UV-B radiation on the activities of cellulose, alkaline phosphatase and urease in barley rhizosphere soil changed with growth stages and N supply. Under middle and high N supply, elevated UV-B radiation decreased the activities of cellulose, alkaline phosphatase and urease in rhizosphere soil, while increased the above enzymatic activities under low N supply, but in most cases, no significant differences between the treatments of UV-B radiation. Under elevated UV-B radiation, with increasing N supply, cellulose activity reduced, and the activities of alkaline phosphatase and urease decreased from low N to middle N and then increased from middle to high N in rhizosphere soil, but mostly no significant differences among the treatments of N supply. Compared with non-rhizospheric soil, the activities of the aforementioned enzymes either promoted or prohibited in barley rhizospheric soil. It is suggested that elevated UV-B radiation had a less significant effects on the activities of cellulose, alkaline phosphatase and urease in barley rhizosphere soil, which is likely related to the designed intensity of UV-B radiation, experimental and sampling methods.