Effect of NaCl salinity on photosynthesis and dry matter accumulation in developing rice grains

We evaluated the effect of salinity on rice at the reproductive phase. From flag leaf stage to dough stage, potted rice plants were irrigated twice a week with saline water (0, 25, 50, 100, and 200 mM NaCl) at a volume of 1.5 times that of the soil. Photosynthesis and leaf biochemical constituents were measured at flowering (15 days after treatment establishment, DATE) and milking stage (25 DATE). Samples for grain dry matter and biochemical. analysis were collected at milking (25 DATE) and dough (37 DATE) stages. Reduction in photosynthesis in the salinized plants depended not only on a reduction of available CO2 by stomatal closure, but also on the cumulative effects of leaf water and osmotic potential, stomatal conductance, transpiration rate, relative leaf water content, and biochemical constituents such as photosynthetic pigments, soluble carbohydrates, and protein. The cumulative effects resulted in low concentrations of assimilates in the leaves. These low concentrations and poor translocation of assimilates from the source reduced grain dry matter. Grain growth was less sensitive to salinity at milking stage. This suggests that the plant is able to escape stress when the duration of salinity is short. (C) 1999 Elsevier Science B.V. All rights reserved.