ROLE OF POTASSIUM, ZINC AND GIBBERELLIC ACID IN INCREASING DROUGHT STRESS TOLERANCE IN SUNFLOWER (HELIANTHUS ANNUUS L.)

Nutrients and plant hormone are very essential and play a key role in drought stress tolerance. The current studies was conducted in pots, to investigate the role of potassium, zinc and gibberellic acid in biosynthesis of free proline, total phenolic, antioxidant compounds and drought stress tolerance in sunflower varieties. Plants were grown in glass house and foliar sprays of potassium Nitrate (KNO3), zinc sulphate (ZnSO4) and gibberellic acid GA(3) were applied. Varieties were evaluated for drought tolerance through leaf disc assay and polyethylene glycol PEG6000 was used to induce in-vitro drought stress. Zinc significantly increased the RWC% and maximum value was noted in HS-K6 followed by Rising Sun. Potassium increased the relative water content (RWC %) and the highest RWC % was found in Hysun-33 followed by Rising Sun, SMH-0907 and US-444. The biosynthesis of free Proline and total phenolic contents was significantly increased with Zn and K treatments. Superoxide dismutase, catalase, ascorbate peroxidase and ascorbic acid biosynthesis were significantly increased by Zn followed by potassium. The Zn treatment significantly reduced the MDA content in sunflower varieties. A significant positive correlation was found between RWC % with proline (R-2 = 0.92***) and total phenolic (R-2 = 0.95***) respectively. Antioxidant compounds also showed significant positive correlation with relative water content. Conclusively; drought tolerance in sunflower might be increased by foliar application of Zn, K and GA(3). Further investigation is suggested to study the effect of Zn, K and GA(3) on drought tolerant genes expression.