弱光下不同铵硝配比氮素对大白菜幼苗生长和抗氧化的影响

Effects of Ammonium︰Nitrate Ratios on Growth and Antioxidant Enzyme Activities of Chinese Cabbage Seedling Under Low Light Intensity

以大白菜[Brassica pekinensis(Lour.)Olsson]中结球小的类型‘金娃娃’品种为试验材料,采用水培的方法,研究了正常光(200μmol·m^(-2)·s^(^(-1)))和弱光(100μmol·m^(-2)·s^(-1))下营养液中不同铵硝配比(0︰100、10︰90、15︰85和25︰75;总N浓度为5 mmol·L^(-1))氮素对幼苗生长以及叶片生理生化特性的影响。处理14 d后,正常光下,铵硝配比15︰85的处理植株长势最佳,较全硝态氮处理叶面积、株幅、鲜质量和干质量分别显著提高了33.8%、30.5%、77.9%和72.9%。弱光抑制了幼苗的生长,植株叶面积、株幅和干鲜质量均低于正常光下生长的植株。弱光下幼苗叶片丙二醛(MDA)、超氧阴离子、过氧化氢(H2O2)含量明显升高,植株遭受膜脂过氧化程度较高。铵硝配比10︰90处理较全硝态氮处理相比,植株叶面积、株幅、鲜质量和干质量分别显著提高了20.4%、14.9%、55.9%和36.5%,而且显著提高叶片的可溶性糖和可溶性蛋白含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性,降低MDA和超氧阴离子含量,有效地抑制了膜脂过氧化。正常光条件下,铵硝配比为15︰85时植株长势最佳;弱光下,铵硝配比为10︰90时植株长势最佳,可降低膜脂过氧化物质含量、提高抗氧化酶活性和渗透调节物质含量,进而提高幼苗耐弱光性。

Small type of Chinese cabbage[Brassica pekinensis（Lour.）Olsson]was used as material. The hydroponic experiment was conducted to study effects of ammonium：nitrate ratios（0：10,10：90,15：85 and 25：75;total nitrogen concentration 5 mmol · L^-1）on growth,osmotic regulation and antioxidant enzyme activities of Chinese cabbage seedling under normal（200 μmol · m^-2 · s^-1and low（100 μmol · m^-2 · s^-1 light intensity. After 14 days treatment,plants fertilized with ammonium：nitrate（15：85）under normal light intensity were the best in growth potential. The leaf area,growth range,fresh weight and dry weight of plants improved 33.8%,30.5%,77.9% and 72.9% compared with ammonium：nitrate（0：100）,respectively. The leaf area,growth range,fresh and dry weight of the plants in low light intensity were apparently lower than those of plants in normal light intensity,indicating that low light intensity suppressed the growth of seedlings. The malonaldehyde（ MDA）, superoxide anionand hydrogenperoxide（H2O2）contents of seedling leaves in low light intensity apparently rose up,resulting in higher membrane lipid peroxidationin plants. However,the leaf area,growth range,fresh weight and dry weight of plants fertilized with ammonium∶nitrate（10：90）improved 20.4%,14.9%,55.9% and 36.5% compared with ammonium∶nitrate（0：100）,respectively. Furthermore,ammonium∶nitrate（10：90）significantly improved the soluble sugar,soluble protein contents and superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）,ascorbate peroxidase（APX）activities in Chinese cabbage,decreased the reactive oxide species contents,and effectively suppressed membrane lipid peroxidation. In normal light intensity,the ammonium∶nitrate ratio（15：85）was beneficial for plant growth while the suitable ratio was 10：90 in low light treated plants. In conclusion,appropriate ammonium：nitrate（10：90）enhanced shading tolerance of Chinese cabbage seedling by decreasing the contents of membrane lipid peroxidation substances,and increasing theactivities of antioxidant enzymesand the contents of osmotic regulation substances.