Effects of Water and Nitrogen Coupling on Chlorophyll Content and Photosythetic Rate of Winter Wheat Leaves

The effects of water,nitrogen and their coupling on the chlorophyll content and photosynthetic rate of two different types of winter wheat were studied on the field conditions during 2006-2007.The result showed that suitable nitrogen could evidently increase the chlorophyll content and photosynthetic rate.The water and nitrogen coupling had similiar effect.The chlorophyll content and photosynthetic rate of winter wheat leaves increased with the amount of nitrogen when irrigated one time during jointing stage.The demand of nitrogen that composing chlorophyll in flag leaves tend to decrease remarkably at the condition water two times at jointing and anthesis stage.The excessive nitrogen had a negative effect on chlorophyll and photosynthetic rate,especially on Shimai15(SM15).Anthesis water could delay the decompose of chlorophyll after 20 d after anthesis(daa).But the effect reduced with the nitrogen increasing,especially on SM15.SM15 had positive correlations between chlorophyll content and photosynthetic rate during 6-15 daa.Shixin 733(SX 733)had the highest chlorophyll content and the photosynthesis rate under 240 kilograms pure nitrogen per hectare at irrigation two times treatment;While for SM15 was 120 kilograms pure nitrogen per hectare at the same condition.