Abstract:

To study the effects of nitrogen application on the metabolic difference of active oxygen in leaves and roots of winter wheat, ‘Bainong207’ was used as material, a rhizobox experiment was conducted with seven nitrogen application levels (N0-no nitrogen application, N1-120 kg/hm ², N2-150 kg/hm ², N3-180 kg/hm ², N4-240 kg/hm ², N5-270 kg/hm ², N6-300 kg/hm ²). The relationships between malondialdehyde (MDA), soluble protein (WSP), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) in leaves and roots of winter wheat at the early growth stage and the characteristics of roots growth were analyzed. The results showed that at the early growth stage, MDA contents in leaves and roots were the highest under low nitrogen levels. With the increase of nitrogen level in certain range, WSP in leaves and roots was the highest with N2 treatment. T-AOC was up to the highest level in N6 treatment. Roots were more sensitive to environment stress than leaves. Nitrogen improved the root activity, reduced the root cap ratio, and increased the leaf and root biomass. MDA contents in roots and leaves and APX activity in roots decreased with the increasing nitrogen fertilizer. T-AOC in roots and leaves, CAT activity in leaves and SOD activity in roots increased with the increasing nitrogen fertilizer. These results demonstrated that enzymatic reaction mechanism of root and leaf was independent and collaborative with different nitrogen amounts. The inhibition of high nitrogen on an antioxidant system influenced partially the activity of antioxidase. The comparatively optimal condition for antioxidase activity is medium nitrogen (150-240 kg/hm ²nitrogen application), which is beneficial to the growth and development of winter wheat at earlier stage and accords with the principle of decreasing fertilizer and enhancing efficacy.

Key words: winter wheat, root, nitrogen, malondialdehyde, soluble protein, enzyme activity