Abstract:

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.

Key words: Nitrogen, Potassium, Glycine betaine, Water- stress, Summer maize, Lipid peroxidation metabolism, Protective enzyme activities