Some physiological characteristics of nitrogen metabolism under water-saving cultivation condition in rice

Field experiments were conducted to evaluate the effects of water-saving cultivation on some nitrogen nutritional physiology traits of rice taking traditional flooding cultivation (TF) as check. The results showed that the rice grain yield of non-flooded film mulching cultivation (PM) was significantly declined below TF, and markedly increased over non-flooding unmuching cultivation (UM). The patterns of the free amino acid (AA-N) and nitrate concentrations (NO3--N), nitrate reductase (NR), glutamine synthetase (GS), glutamic oxalacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activities were analogously characterized by higher concentrations/activities at early growth stages than later stages especially the four enzymes. Compared with TF, PM had some positive influence on AA-N, NO3--N, NR and GS in rice leaves at early growth stages, and decreased GOT but increased GPT in leaves during the growing season. Compared with UM, PM increased AA-N, NO3--N, NR, GS, GOT and GPT activities in leaves. Soil water-stress had a negative effect on nitrogen metabolisms in rice leaves and subsequent straw and grain yields, however, PM system tend to alleviate the negative effect even promote them. Nitrogen can improved the traits of PM treatments especially at early growth stages.