Effects of nitrogen supply level on photosynthesis and chlorophyll fluorescence characteristics of rice under salt stress

The change of photosynthesis and chlorophyll fluorescence parameters of rice were studied in five nitrogen levels during tillering, booting, and heading periods under salt stress. The net photosynthetic rate (PN), stomatal conductance (gs), transpiration rate (E), apparent mesophyll conductance (AMC), effective quantum yield of PSII photochemistry (ΦPSII), electron transport rate (ETR), and photochemical quenching coefficient (qP) were significantly declined under salt stress and exhibited a lower magnitude of decline in the 2N, 1N, and 1/2N treatments respectively during tillering, booting, and heading periods. The stomatal limit value (Ls), Nonphotochemical quenching (NPQ) and plasma membrane permeability were significantly increased and exhibited a lower magnitude of increase in the 2N, 1N, and 1/2N treatments respectively during tillering, booting, and heading periods. The amount of nitrogen in the nutrient solution should be reduced 50% after the heading period to decrease salt damage to rice under salt stress.