Salt Exclusion Rate in Rice Roots in Relation to Ion Species

We investigated the exclusion rate of some ion species in order to discover the features of salt exclusion in rice roots. TSCF of each cation was negatively correlated with the transpiration rate as in the case of Na+. These results indicated that ion exclusion rates change with the transpiration rate. At the same transpiration rate, TSCF of IR28 was lower than that of KR1, which indicated that exclusion efficiency was essentially higher in IR28. The differences in TSCF of K+, Ca2+ and Mg2+ between both varieties were relatively small compared with those of Na+ and Li+. These results indicated that the difference in exclusion rate between varieties was affected by ion species. TSCF at the same transpiration rate seemed to be larger with the decrease in radius of hydrated ion. From these results, it was suggested that the exclusion system of Na+ in rice under saline conditions also works for K+, Li+, Ca2+ and Mg2+, and is driven by transpiration. It was also noted that exclusion may be affected by the radius of hydrated ion.