Physiological and biochemical characteristics of salt stress tolerance in selected varieties of sunflower under various treatments of potassium, zinc and gibberellic acid

The effects of potassium, zinc and gibberellic acid foliar spray on salt stress tolerance, free proline, total phenolics, carbohydrates and chlorophyll contents in sunflower varieties were evaluated. Eight varieties of sunflower were grown in glass house and NaCl (150 mM) was added to roots alone and in combinations with KNO3, ZnSO4 and GA3 foliar spray. Different varieties were evaluated for salt tolerance through leaf disc assay (LDA). Various test solutions of NaCl were used to induce salt stress. T1 treatment (150 mM NaCl only) significantly decreased the greenness % in all of eight varieties of sunflower as compared to control C. The T2 treatment (150 mM NaCl + Potassium) enhanced the greenness % and maximum greenness % was observed in the SMH-0917 (76.00 %) followed by Ausigold-7 (75.50 %). The treatment T3 (150 mM NaCl + Zinc) and T4 treatment (150 mM NaCl + 100 ppm of GA3) retained the greenness % in leaf discs compared to control. The free proline and total phenolic contents significantly increased in all of eight varieties of sunflower when treated with K, Zn, GA3 and NaCl. Positively significant correlation was found between greenness % with proline (R2 = 0.86) and total phenolics contents (R2 = 0.83). Conclusively; salt tolerance could be increased by the application of K, Zn and GA3.