Abstract:

Abstract: ① There is a close relation between nitrogen nutrition and senescence of wheat flag leaf. Treatment N3 (264kg ha-1) and N2 (165kg ha-1) remarkably increased the activity of SOD and POD compared with treatment N0, improved the balance of reactive oxygen production and scavenging, reduced the accumulation of peroxide in cells, and thus slowing down the processes of flag leaf senescence. No remarked differences in the activities of SOD and POD, MDA content and chlorophll content were observed between treatment N3 and N2, indicating that when the nitrogen application amount rose to a reasonable level, the flag leaf senescence can not be slowed down by continuous increase of nitrogen application. ② The process of senescence could be divided into two periods, i.e. slow-senescence phases and fast-senescence phases. In slow-senescence phases, the activities of POD and SOD, MDA content and chlorophll content in flag leaf increased slightly. At fast-senescence phases, the three physiological parameters decreased sharply, and the wheat showed obvious senescence characteristics. The inflection point of flag leaf senescence is 14 days after anthesis with flat planting and 21 days after anthesis with raised bed planting. ③ When 165 kg ha-1 of nitrogen applied, middle yield to higher yield can be obtained with the both planting models . On condition of nitrogen nutrition level 264 kg ha-1, the grain yield of 7845.7 kg ha-1 was achieved in raised bed planting, 9.6 % higher than that in flat planting.