Alleviation of deleterious effects of salt stress by applications of supplementary potassium–calcium on spinach

The aim of the present study is to investigate the effects of salinity and the influence of supplemental K⁺ and Ca²⁺ on the alleviation of the deleterious effects of salinity stress in spinach plants. Spinach cultivars used were Green Gold, Larissa, Mikado, Ohio and Matador. In addition to four NaCl levels of 50, 100, 150 and 200 mM, the treatments were repeated with 10 mM K and 10 mM Ca at each NaCl level. The results revealed that Na⁺ and Cl⁻ concentrations were significantly increased and the K⁺, Ca²⁺ and NO₃ ⁻ concentrations were decreased with increasing NaCl concentrations in the growth medium. Being very important to the physiology and biochemistry of plants decreases in K⁺, Ca²⁺ and NO₃ ⁻ reduced both growth and the yield. The additions of K⁺ and Ca²⁺ reduced the Na⁺ and Cl⁻ concentrations in the plant tissues, increased the K⁺, Ca²⁺ and NO₃ ⁻ concentrations, resulting in an improvement in the marketable yield of the spinach plants. Even though the effects of supplemental K⁺ and Ca²⁺ were similar in some plants at different salt concentrations, the effect of additional Ca²⁺ alone was higher overall. Thus, the results of this study confirmed the principal effects of K⁺ and Ca²⁺ supplies in reducing the detrimental effects of salinity.