Differential accumulation of potassium results in varied salt-tolerance response in tomato (Solanum lycopersicum L.) cultivars

To quantify the effect of two potassium levels (4.5 and 9.0 mM) on salt tolerance, we conducted a solution culture experiment using salt-tolerant (Nagina) and salt-sensitive (Peto-86) Solanum lycopersicum (tomato) cultivars grown under NaCl stress (0, 75, and 150 mM). Potassium is known to minimize oxidative stress and enhance photosynthesis in salt-stressed plants. A 30-day treatment with potassium, differentially increased stomatal conductance and transpiration, decreased oxidative stress, lowered the activities of antioxidant enzymes (i.e., superoxide dismutase, catalase, and glutathione reductase), increased leaf K+ levels and the K+/Na+ ratio, and improved the membrane stability index in the salt-tolerant and salt-sensitive tomato cultivars exposed to salt stress. The salt-sensitive cultivar had significantly higher malondialdehyde (MDA) concentrations and lower antioxidant enzyme activity than the salt-tolerant cultivar. These results indicate that potassium can be used to alleviate salt-induced oxidative stress and photosynthetic limitations in tomato plants and ultimately improve survival under salt stress.