EFFECTS OF ZINC AND POTASSIUM NUTRITION ON SALINITY STRESS IN DIFFERENT WHEAT GENOTYPES: GROWTH AND NUTRITIONAL STATUS

To evaluate the role of zinc (Zn) and potassium (K) in alleviating the detrimental effects of salinity, two bread wheat (Triticumaestivum L.; Dagdas and ES-14) and two durum wheat (Triticum durum L.;Kunduru-1149 and Selcuklu-97)genotypes were grown in nutrient solution having different Zn (2x10(-8) M and 10(-6) M) and K levels (100 mu M and 2 mM), under controlled conditions. After 7 days, nutrient solution was salinized by three NaCl levels (0, 75 and 150 mM). Plants were harvested at the 15th day of growth. Increasing NaCl levels decreased dry matter production; these decreases were greater under Zn and K deficient conditions. Sodium concentrations of shoots and roots were increased with increasing NaCl levels while dry matter production, K, Ca and Zn concentrations, as well as K/Na and Ca/Na ratios were decreased. Supplemental Zn and/or K treatments increased the dry matter production and lowered the Na concentrations, especially at the highest NaCl level. Supplemental Zn led to decreases in IgNa ratios at 0 and 75 mM NaCl but to an increase in K/Na ratio at 150 mM NaCl level in the shoots. Supplemental K, both alone or in combination with Zn, increased the K concentration and K/Na ratio. In general, calcium concentrations of plants were decreased by Zn and/or K supplements at all salinity levels. Zinc concentrations were increased with the supplemental Zn but slightly decreased with supplemental K alone. Although the decreasing rates in dry matter production because of NaCl were more severe in durum than bread wheat genotypes, increases in dry matter production by supplemental Zn and K were higher in durum than bread wheat genotypes. The results showed that supplemental Zn and/or K enhanced salt tolerance in wheat genotypes which was ascribed to decreased Na and increased K concentrations with a resultant improvement in K/Na ratio.