Effect of saline irrigation during grain-filling period on dry-matter increase of hulled rice

The effect of salinity stress on grain filling was studied in two rice varieties (Kala-Rata 1-24 and IR28) with different resistances of yield to salinity. Plants were subjected to saline irrigation (150 mM sodium chloride) during the grain-filling period in combination with the primary rachis-branch clipping. Saline irrigation decreased whole plant dry-matter production during the grain-filling period. A dry-matter increase of hulled rice was retarded because of the insufficient supply of dry-matter during the mid grain-filling period by saline irrigation;however it later recovered because of an increase in the compensatory translocation of stem reserves to the panicle. The final panicle dry weight did not decrease because of saline irrigation. The retardations of the dry-matter increases of hulled rice were markedly in the inferior spikelets of plants with intact primary rachis-branches, but not in the plants with half primary rachis-branches. The dry-matter increase of hulled rice that was retarded by saline irrigation recovered after the saline water was removed. These results indicated that the potential of grain growth and the carriage of assimilates might nor be affected by saline irrigation. The insufficient supply of dry-matter to hulled rice during saline irrigation may have resulted from a decrease in the production of low-molecular sugars for translocation because of the suppression of carbohydrate metabolism under salinity.