Plant Water Relation and Silicon Concentration in Two Rice Varieties Differing in Salinity Tolerance

Abstract

Differences in salinity tolerance in rice varieties could not be explained by the tissue sodium concentration under saline soil conditions in some cases. This study was carried out to determine whether the plant water status and tissue silicon concentration were responsible for the varietal differences in salinity tolerance in rice. A salinity-sensitive variety Mangasa and a salinity-tolerant variety IR4595-4-1-13 were transplanted to pots filled with soil to which sodium chloride was added at a rate of 10g/pot and were compared with plants grown without addition of sodium chloride. Decrease in shoot dry matter and percentage of ripened grains due to soil salinity were conspicuous in Mangasa, resulting in a larger decrease in grain yield. Although the midday leaf water potential decreased by salinity, the degree of its reduction and osmotic adjustment did not differ between the varieties. Reduction of stomatal conductance due to salinity was larger in Mangasa. Potassium concentration in leaves and stems decreased under salinity in both varieties, whereas the sodium concentration in Mangasa increased slightly more than that in IR4595-4-1-13. There were no changes in the potassium and sodium concentrations in hulls due to salinity in the two varieties. Silicon concentration in IR4595-4-1-13 decreased under salinity in leaves and stems but did not change in hulls. In contrast, the reduction of the silicon concentration in Mangasa due to salinity was observed only in hulls. Therefore, it was concluded that Mangasa was sensitive to saline soil conditions as reflected in the lower dry matter production and lower percentage of ripened grains due to the larger reduction of stomatal conductance and the silicon concentration in hulls.