Potassium, Zinc and Gibberellic Acid Foliar Application Enhanced Salinity Stress Tolerance, Proline and Total Phenolic Contents in Sunflower (Helianthus annuus L.)

Role of potassium (K), zinc (Zn) and gibberellic acid (GA ) in salinity tolerance, proline and total 3 phenolic contents in sunflower varieties were investigated. Eight varieties of sunflower (Rising Sun, SMH-0907, Ausigold-7, SMH-0939, US-444, Hysun-33, SMH-0917 and HS-K6) were obtained from National Agricultural Research Center Islamabad and analyzed for salinity tolerance. Different solutions of potassium (10 and 5 mg/L), zinc (1 and 2 mg/L) and gibberellic acid (100 ppm) were prepared and added to the plants through foliar sprays. Salt tolerance assessment carried through leaf disc assay using sodium chloride (NaCl) test solutions. Potassium and gibberellic acid significantly increased the salinity tolerance in sunflower varieties. The highest salinity tolerance was found in the Hysun-33 followed by US-444 at higher concentration of potassium foliar spray. In gibberellic acid treatment, the maximum salinity tolerance level was observed in the SMH-0917 followed by Hysun-33. The treatments of potassium, Zinc and GA significantly enhanced the free proline and 3 total phenolics content production in the leaves of sunflower. Significant positive correlation was found between greenness % with proline (R = 0.86) and total phenolics contents (R = 0.83), respectively. 22