AMINOLEVULINIC ACID-INDUCED CHANGES IN YIELD AND SEED-OIL CHARACTERISTICS OF SUNFLOWER (HELIANTHUS ANNUUS L.) PLANTS UNDER SALT STRESS

Effectiveness of a potential plant growth regulator, 5-aminolevulinic acid (ALA) on improving yield and regulating some potential physio-chemical attributes of seed and oil of two sunflower cultivars was examined in a greenhouse experiment. Four varying levels of ALA 20, 50 and 80 mg L-1 were applied foliarly to the two sunflower cultivars (Hysun-33 and S-278) grown under saline (150 mM NaCl) and non-saline (0 mM NaCl) conditions. Salt stress adversely affected the achenes/plant, total achene yield, 100-achene weight, seed moisture content, seed oil percentage, seed K+ and P concentrations of both sunflower cultivars, while in contrast, salt-induced increase in the accumulation of Cl- and Na+ in seed as well as alpha-tocopherols in oil of both sunflower cultivars. However, no significant change in seed organic and inorganic contents, oil refractive index (RI) and seed Ca2+ content was observed due to salt stress in both sunflower cultivars. Foliar-applied varying levels ALA remained ineffective in improving all yield variables, oil refractive index and seed inorganic nutrients (Na+, Cl-, K+ and P) of both sunflower cultivars under saline and non-saline regimes. However, a significant increase in seed oil concentration, accumulation of oil a-tocopherols and seed P of both sunflower cultivars was observed due to foliar-applied 20 and 80 mg of ALA under saline conditions. Overall, ALA was ineffective in ameliorating the salt-induced adverse effects on yield and different seed-oil characteristics except of seed P and oil alpha-tocopherols in sunflower plants.