Responses of two varieties of tomato to abrupt and gradual short-period sodium chloride exposure

Abstract

The relationship between osmotic adjustment and mineral retention by different plant parts were examined for two varieties of tomato (Lycopersicum esculentum L): Pritchard and Rogygross. Plants were grown in solution cultures and exposed at each stage of development either gradually to 0.05M NaCl increments for 6 hours each until 0.20M, or abruptly to increased NaCl levels for 24 hours. Both varieties of tomato survived gradual exposure to NaCl increments at all stages of development, while unable to survive abrupt exposure to 0.20M, and even Pritchard to 0.15M NaCl during the vegetative stage. With abrupt exposure to 0.15M and 0.20M NaCl both varieties showedi nitial wilting followed by rapid recovery during flowering. Although Pritchard showed lower tolerance with abrupt exposure it exhibited similar osmotic adjustment as Rogygross variety upon the gradual exposure to NaCl increments. Increased NaCl concentration in the root medium induced a gradual uptake of Na with a concomitant partial replacement of K, which was associated with increased Ca retention in the aerial parts. Gradual exposure increased the retention of the osmoregulatory cations K and Ca. It was suggested that gradual rather than abrupt changes in the internal osmotic pressure, which was associated with the increased retention of osmoregulatory cations, being itself not restrictive for essential metabolic processes.