Comparative studies on the sodium, potassium, and chloride relations of a wild halophytic and a domestic salt-sensitive tomato species.

In long-term experiments with differentially salinized nutrient solutions, plants of Lycopersicon esculentum Mill cv. Walter failed at Na(+) concentrations of 200 millimolar or more but tolerated K(+) concentrations of that magnitude. The behavior of the wild, salt-tolerant Lycopersicon cheesmanii (Hook) C. H. Mull., accession number 1401, was diametrically different; it tolerated Na(+) at 200 millimolar, but K(+) at the same concentration proved toxic to it.Short-term comparative studies on the absorption and translocation of Na(+), K(+), and Cl(-) of the two species were carried out using radioactive tracers with excised roots and whole plants. These studies showed that, under high salt conditions (50-100 millimolar NaCl), the tolerant 1401 freely accumulated Na(+) in the shoot, while the salt-sensitive cultivar excluded it from the leaves, where it has been shown to be toxic.In experiments where K(+) was limiting, the salt-tolerant species could partially substitute Na(+) for K(+). Sodium stimulated growth even when K(+) was present at adequate concentrations. The domestic cultivar could not substitute Na(+) for K(+) and showed no similar growth stimulation when Na(+) was added in the presence of adequate K(+). The salt-tolerant 1401 was more efficient in K(+) absorption than was the domestic cultivar at both low and moderate ambient K(+) concentrations.The two species differed little in their chloride relations.