The effects of sodium chloride on ion transport in potassium-deficient tomato

When tomato (Lycopersicon esculentum Mill. cv. Daniela) plants were grown in a potassium-deficient nutrient solution (0.5 mmol/L K+), growth was severely decreased in comparison with K+-replete plants (grown with 4.5 mmol/L K+). Supplying 1 or 5 mmol/L NaCl, but not 15 or 30 mmol/L NaCl, virtually restored growth to that of K+-replete plants. One factor which was probably involved in this growth increase was an accumulation of Na+ in the roots. This may have stimulated root growth, by releasing vacuolar K+ to the cytoplasm of growing cells, and thus K+ uptake and transfer to the shoot. There was no evidence to support previous suggestions that, under K+-deficiency, Na+ may directly stimulate root uptake of K+ or NO3−.