UV-B辐射增强下施氮对大麦根际土壤酶活性的影响

Effect of Enhanced Ultraviolet-B Radiation and Nitrogen Levels on Enzymatic Activities in Barley Rhizospheric Soil

在大田条件下,研究了UV-B辐射增强及不同施氮水平下,大麦不同生育期根际和非根际土壤纤维素酶、碱性磷酸酶和脲酶活性的动态变化。UV-B辐射设2水平,即对照(CK,自然光,12.0 kJ m-2d-1),增强20%(Elevated,14.4 kJ m-2d-1)。施氮量设3水平,即30、150和300 kg hm-2。结果表明:与对照相比,UV-B辐射增强对大麦根际土壤纤维素酶、碱性磷酸酶和脲酶活性的影响,因生育期和施氮量而异。中高氮下,UV-B辐射增强可降低根际土壤纤维素酶、碱性磷酸酶和脲酶活性,而低氮下UV-B辐射增强则提高相应酶活性,但UV-B处理间差异大多不显著。在UV-B辐射增强下,随施氮量增加,根际土壤纤维素酶活性下降,而碱性磷酸酶和脲酶活性呈先降后升趋势,但施氮量处理间差异大多不显著。根际土壤酶活性与非根际土壤相比,既有升高也有下降。研究认为,UV-B辐射增强尚不足以对大麦根际土壤纤维素酶、碱性磷酸酶和脲酶酶活性产生显著影响,这可能与设定的UV-B辐射强度、试验方法及采样方法有关。

The stratospheric ozone lay er formed a protective atmospheric filter against biologically harmful solar ultraviolet （UV） radiation. Anthropogenie emissions of chlorofluoroearbons and nitrogen oxides resulted in depletion of ozone layer. Consequently, enhanced levels of UV-B radiation （280 - 320 nm） 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 flee, 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 q）, 3 levels of N supply, i.e. 30, 150 and 300 kg N hm-2 and 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.