Selectivity and Partitioning of Potassium and Sodium in Sesame

Net uptake and partitioning of sodium (Na+) and potassium (K+) in plants of two sesame cultivars (Sesamum indicum cv. ‘PB-1’ and cv. ‘UCR’) exposed to 20 mM sodium chloride (NaCl) were studied over a period of 28 days. Both cultivars showed a marked discrimination between K+ and Na+ during uptake. The reduction of K+ in the plants caused by the NaCl treatment was of similar magnitude in the two cvs. The cv. ‘UCR’ showed lower Na+ concentrations in the shoot tissues than ‘PB-1’ and K+/Na+ selectivity ratios were higher in cv. ‘UCR’ than in cv. ‘PB-1’. At the last sampling on day 28 there was a marked decrease of shoot growth in cv. ‘PB-1’ in comparison to the cv. ‘UCR’. Leaves of cv. ‘PB-1’ showed clear toxic symptoms, while those of cv. ‘UCR’ did not. It is concluded that Na+ exclusion from the shoot contributes to salt tolerance of sesame, cv. ‘UCR’.