Regulative Mechanism Of Nitrogen Nutrition On Phyotosynthetic Efficiency Of Dryland Wheat

Water deficit and soil infertile is the main limited factor in arid agricultural production. Under rational cultivated, it was an important measure to resist drought and promote yield by applied additional nitrogen fertilizer on dryland, which could also improve water status and photosynthetic ability. But it was not completely clear about the conditions that yield was increased by applying fertilizer on arid fields and the mechanism of drought-resistance. So the theory for improve culture technologyand promote agriculture field productivity could be given by elucidated the regulative mechanism of nitrogen on crop development under water stress environment. The effect on winter wheat mass variation, physiological properties of leaf photosynthesis and water use efficiency (WUE) under different nitrogen treatments was studied and some conclusions were made as following:1. The leaf water potential and relative water content (RWC) were decreased with nitrogen supply increased in every developmental stage. But the ability of water conservation was enhanced by nitrogen nutrition.2. The leaf photosynthetic ability was increased firstly and then decreased with nitrogen supply increased. It indicated that the rational nitrogen quantity among a definite range could improve leaf photosynthetic ability. But photosynthetic ability was decreased when the nitrogen quantity was excessive.3. With leaf RWC progressively decreased, Fo rose continuously, Fv/Fm appeared not to be affected, while 'I'PS II, qP and qNP dropped. These indicated that the PS II reaction center was damaged. The photosynthetic apparatus such as light-harvesting apparatus and PS II central complexity were damaged by the active oxygen species which produced by the enhanced Mehler action.4. Fv/Fm, Fv/Fo, qP and qNP were improved significantly by nitrogen nutrition, which indicated that in one aspect nitrogen increased the proportion of light energy which used for photochemical electron transport, promoted light energy transformative efficiency and potential activation of PS II. In another aspect, nitrogen enhanced the non-photochemical dissipation of excessive light energy which was favor to protect photosynthetic apparatus against the destroy of environmental stress.5. WUE and yield were decreased firstly and then increased, which showed that excessive nitrogen was not benefit to highly efficient water use. The effect that yield was increased by fertilize lays was not only depend on itself, but more on the interaction with water.