氮、钾、甜菜碱对水分胁迫下夏玉米叶片膜脂过氧化和保护酶活性的影响

采用盆栽试验研究了水分胁迫和适量供水条件下，氮、钾和甜菜碱对2种不同基因型夏玉米陕单9号（抗旱品种）和陕单911（不抗旱品种）各生育期叶片膜脂过氧化和保护酶活性的影响，旨在揭示这些因子通过提高上述酶活性而增强作物抗旱性的生理功能。结果表明，水分胁迫下夏玉米超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性显著降低,不抗旱品种更甚；而丙二醛(MDA)含量有不同程度升高，抗旱品种的MDA含量和变幅小于不抗旱品种。苗期2个品种对水分胁迫响应较弱，SOD、POD、CAT和MDA均较低；拔节和抽雄期响应强烈，酶活性增高。SOD和POD达到最大值的时间比CAT晚，MDA在全生育期中呈现“升—降—升”的变化规律。施用氮、钾肥和甜菜碱能不同程度地提高夏玉米SOD、POD和CAT活性，降低MDA含量，减缓水分胁迫下膜脂过氧化作用。不抗旱品种施用氮肥增强了水分胁迫条件下叶片SOD、POD、CAT活性，降低了MDA含量，氮肥用量的影响有显著差异；抗旱品种施用低氮效果显著，施用高氮则降低了生育前期酶活性，增加了MDA含量，但生育后期氮肥用量的影响间无显著区别。钾肥和甜菜碱对受水分胁迫的夏玉米表现出比氮肥更突出的效果。而对适量供水条件下的夏玉米，氮、钾肥的作用明显下降，甜菜碱的效果甚至消失。说明施用氮、钾肥和甜菜碱对改善水分胁迫下玉米叶片膜脂过氧化作用和提高保护酶活性有重要贡献。

Effects of Nitrogen, Potassium and Glycinebetaine on the Lipid Peroxidation and Protective Enzyme Activities in Water-Stressed Summer Maize

A pot experiment was conducted under water stress and adequate water-supplying conditions with two cultivars of maize Shaandan 9(drought-resistant) and Shaandan 911(non-drought-resistant) to study the effects of nitrogen,potassium,and glycinebetaine on lipid peroxidation and protective enzyme activities in maize leaves at different growing stages for revealing their biological functions in the rise of crop resistance to drought by raising activities of these protective enzymes.Results showed that under the water stress condition,activities of superoxide dismutase(SOD),catalase(CTA),and peoxidase(POD) in leaves were significantly reduced while malondialdehyde(MDA) content was increased for both cultivars,but the decline was more obvious for the non-drought resistant one.Activities and variation of SOD,CTA,and POD were higher while MDA content was lower for the drought resistant cultivar(Shaandan 9) than those for the non-drought resistant cultivar(Shaandan 911).The lower activities of SOD,CTA,and POD at seeding stage than those at elongation and heading stages showed that the response of two cultivars to water stress was weaker at earlier than at later stages.Of these protective enzymes,activities of SOD and POD reached their peak later than that of CTA.MDA content followed a changing pattern of "rise-fall-rise" in the entire maize growth period.Applications of nitrogen,potassium, and glycinebetaine raised the activities of SOD,CTA,and POD while decreased the MDA content,and thus alleviated water stress effect.Under the water-stressed condition,addition of N fertilizer significantly increased activities of SOD, CTA,POD and decreased MDA content for the non-drought resistant cultivar with a significant difference among N rates.The significant response of drought resistant cultivar to N addition was merely found at low N rate.For high N rate, activities of SOD,CTA and POD were significantly decreased whereas MDA content was increased at earlier growth stage.However,at later growth stage,there was no significant difference between two N rates.Glycinebetaine and K fertilizer exhibited more significant biological function than N fertilizer in the rise of protective enzyme activities under the water stress condition.In contrast,with adequate water supply,effects of N and K fertilization significantly decreased,and the function of glycinebetaine even vanished.All the results suggest that addition of nitrogen,potassium,and glycinebetaine make a great contribution to improvement of the protective enzyme activities and lipid peroxidation metabolism.