Winter wheat flag leaf aging and reactive oxygen species metabolism under different nitrogen and cultivation modes in dryland

The experiment was carried out to study the effects of three cultivation modes(flat planting,straw mulching,plastic sheet-mulching) and three different N levels(without nitrogen,120 N kg/hm2 and 240 N kg/hm2) on flag leaf aging of the winter wheat cultivar 'Xiaoyan 22'.The results showed that compared with flat planting(CK),straw mulching could increase the chlorophyll content of flag leaf(P0.05),slow the speed of flag leaf aging and the extent of declining metabolizability,increase the yield(P0.05).At the early filling stage,plastic sheet-mulching could increase the chlorophyll content of flag leaf,enhance POD,CAT activities,and lower malondialdehyde(MDA) content.At the late filling stage,there were a remarkable decline of leaf chlorophyll content,a quick leaf aging and a marked increase of MDA.Plastic sheet-mulching could increase the yield(P0.05).Nitrogen could enhance the chlorophyll content of flag leaf and the extent of active oxygen(POD,CAT),lower malondialdehyde(MDA) content.When the nitrogen was 120 N kg/hm2,the chlorophyll content of flag leaf was the most highest,the speed of flag leaf aging was slow,the extent of declining metabolizability was slow too.It is was of great benefit to wheat growth and filling at the late filling stage.