Effects of water-nitrogen interaction on rice senescence and material transport and yield during grain filling.

Super hybrid rice Gangyou 527 was used to investigate the effects of three irrigation regimes [submerged irrigation(W1),dry cultivation(W3) and the treatment W2 that damp irrigation before booting stage,shallow irrigation at booting stage,wetting-drying alternation irrigation from heading stage to mature stage] and different amounts of N on net photosynthetic rate(Pn),activated oxygen(O-·2)and H2O2,malondialdehyde(MDA),osmotic regulators,antioxidant enzyme activities in flag leaves and bleeding intensity during grain filling.The correlation of the different physiological index and accumulation of dry-matter and transport was also determined.The results showed that compare with other treatments,W2 and suitable N application amount(180 kg/ha) delayed the increase of reactive oxygen species and MDA,had high Pn and promoted the accumulation of soluble protein content,etc.,and enhanced the superoxide(SOD),catalase(CAT) and peroxidase(POD) activities,consequently,promoted material accumulation and promote yield.Applying N(270 kg/ha) resulted in a negative effect of waternitrogen interaction.As for the treatment of dry cultivation of rice,applying N ranged from 90 to 180 kg/ha could alleviate the negative effect of water-nitrogen interaction,which has practical implications for drought regions.In addition,there was significant correlation between the physiological index,in which significant positive correlations was observed between O-·2,H2O2 and MDA,and a significant negative correlation between them with antioxidant enzyme activities,Pn and soluble protein content.Furthermore,in the process of leave senescence,underground was closely related to aboveground,and root vigor had high significant positive correlation with antioxidant enzyme activities,Pn and soluble protein,but it had high significant negative correlation with O-· 2 ,H2O2 and MDA.