AllEVIATION OF WATER STRESS ON SUNFLOWER PLANT BY SOME OSMOTIC REGULATORS

Abstract

Field experiments were carried out during two successive seasons of 2014 and 2015 to investigate the effect of CaCl2 (5 and 10 mM), ascorbic acid (AsA, 50 and 100 ppm) and putrescine (Put, 0.1 and 0.2 mM) as individual foliar applications on sunflower plants under two different irrigation levels: 55-65 and 25-35% of the field capacity (FC). In general, reducing the irrigation level widely caused multi physiobiochemical changes which reflected negatively on the growth and

yield of the produced seeds and ultimately on oil percentage. Physiobiochemical parameters

were investigated in term of leaf relative water content (RWC), leaf pigments (Chl a, Chl b, Chl a+b, Chl a/b, carotenoids, anthocyanins, and carotenoids/Chl a+b, leaf minerals (N, P, K and Ca), organic osmolytes (proline and soluble sugars) and phenolic related enzymes: phenylalanine ammonia lyase (PAL) and peroxidase (POD). Positive correlation between seed yield and water contents as well as essential macro- nutrient elements ( K and Ca ) was detected. Meanwhile, proline concentration had negative correlation with seed yield. The results indicated that all foliar treatments achieved progressive increases in the previous traits compared to the untreated plants under the same level of irrigation. In general, the highest significant (P≤0.05) increases were mostly obtained by the treatment of CaCl2 at 10 mM, Put at 0.2 mM and AsA at 100 ppm. The results of this study hypothesized that the foliar application of CaCl2, AsA, and Put at the ideal concentration may contribute to alleviate the negative effects of drought stress on sunflower plants by inducing some physio-biochemical changes which related directly or indirectly to drought tolerance mechanisms.