Supplementary Calcium and Potassium Improve the Response of Tomato (Solanum lycopersicum L.) to Simultaneous Alkalinity, Salinity, and Boron Stress

Irrigation water of poor quality that is high in salts, alkalinity-inducing compounds, and boron (B) threatens global agricultural production. The objective of the present study was to determine whether supplementary calcium (Ca) and potassium (K) ameliorate the response of tomato plants to a simultaneous combination of these stress conditions. Irrigation water high in alkalinity, salinity, and B reduced plant growth, which was associated with a partial impairment in the antioxidant system (reduction in catalase activity), impairment in water relations (reduced relative water content), decreased nutrient acquisition [lower nitrogen (N), phosphorus (P), K, Ca, and magnesium (Mg) content]; and specific toxicity due to the increase in shoot sodium (Na) and B. However, stressed plants exhibited partially improved growth when supplemented with greater concentrations of Ca and K, which were associated with enhanced P concentration, maintenance of chlorophyll a concentration, and/or partially restored N, P, K, Ca, and Mg uptake.