Comparative Studies on the Sodium Potassium and Chloride Relations of a Wild Halophytic and a Domestic Salt-Sensitive Tomato Species

摘要

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.