Ionic and Osmotic Effects of Salt on Leaf Membranes of Tomato Species

Potassium leakage from leaf discs was studied in the cultivated tomato, Lycopersicon esculentum, and its relatives, wild salt-tolerant species, L. peruvianum and L. pennellii. The discs were exposed to water or to iso-osmotic solutions of various salts and organic osmotica. The enhancement of leakage by NaCl, relative to water, was smaller in L. pennellii than in the other two species. The proportion of the osmotic effect of NaCl, as deduced from the comparison of the effects of sorbitol and mannitol with that of NaCl, was greater in L. pennellii than in the other two species. The ionic effect of Na⁺ seems stronger in L. esculentum than in the wild species and that of Cl^- weaker, as deduced from the replacement of either ion by another cation or anion. Leaf membranes of tomato were found more sensitive to SO²- than to Cl^-.