ALLEVIATION OF ADVERSE EFFECTS OF SALT STRESS ON SUNFLOWER (HELIANTHUS ANNUUS L.) BY EXOGENOUS APPLICATION OF SALICYLIC ACID: GROWTH AND PHOTOSYNTHESIS

he present study was conducted to assess whether exogenously applied SA as a foliar spray could ameliorate the adverse effects of salt stress on sunflower plants. Two lines of sunflower (Hisun-33 and SF-187) were grown under normal or saline (120 mM NaCl) conditions. Different levels of salicylic acid (0, 100, 200, 300 mg L-1) were applied as a foliar spray. Salt stress reduced the growth of both lines, but both cultivars were equally responsive to the stress. Application of 200 mg L-1 of SA caused an increase in biomass of both lines under non-saline or saline conditions. Photosynthetic rate of both cultivars increased due to SA applied foliarly both under control and saline conditions, particularly in line SF-187. Furthermore, increase in growth of both cultivars due to exogenously applied SA may have been due to changes in photosynthesis. However, SA applied as a foliar spray did not change the sub-stomatal CO2 suggesting that stomtal factors were not the major controlling factors for photosynthesis. Overall, the adverse effects of salt stress could be alleviated by exogenous application of SA.