Dry‐matter yield and nitrogen‐15, Na+, Cl‐, and K+content of tomatoes under sodium chloride stress1

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Abstract
Crop yield and nutrient uptake are often impaired under salt, water, or both stress conditions. This study was designed to gather further information concerning NaCl stress effects on these components. Therefore, dry‐matter yield, nitrogen (total and 15N) uptake, Na+, Cl‐ and K+ content of leaves, stems, and roots of tomato (Lycopersicum esculentum Mill., cv. ‘Columbia') plants subjected to NaCl stress were studied in a greenhouse. Saline treatments consisted of 0.3 (control), 4.3, and 8.3 bars osmotic pressures. Plants were 80 days old at the start of salt and 15N treatments, and each plant was in a pot containing 1.8 kg of washed quartz sand. The 15N as K15NO3 solution was provided to plants at 10‐day intervals over a 30‐day period. Plants were harvested at 5‐day intervals during the 30‐day 15N treatment period. Dry‐matter production, total‐N, and 15N uptake at final harvests were significantly lower for saline treatments as compared with a control. There was a 46% reduction in leaf dry weights on day 20 due to NaCl stress. This value was 36% for roots and 25% for stems. Generally, similar reduction patterns resulted in total‐N and 15N uptake in plants due to NaCl stress. The Na+ and Cl‐ contents were substantially higher in stressed plants compared with the controls. The leaf K+ levels decreased with increased salinity. For most of the studied parameters, leaves were affected the most, roots were intermediate, and stems the least by salinity.