PLANT GROWTH REGULATORS INDUCED DROUGHT TOLERANCE IN SUNFLOWER (Helianthus annuus L.) HYBRIDS

Present study was conducted to investigate whether plant growth regulators viz. salicylic acid and ascorbic acid can alleviate the adverse effects of drought stress on germination and seedling growth of two sunflower hybrids (Hysun-33 and Hysun-38). Two (-0.06 MPa and -0.12 MPa) levels of drought stress were created by adding different concentrations of (PEG8000) polyethylene glycol in growth medium. Results indicated that increase in drought stress significantly decreased germination percentage, plumule length, germination rate and seedling fresh biomass, except radical length, while, in contrast non significantly increased mean germination time with respect to their control. The adverse effects of drought stress (-0.12 MPa) level were more severe than (-0.06 MPa). Both hybrids differed significantly but Hysun-33 was less affected compared to Hysun-38. However, seed treatment of both hybrids with salicylic acid and ascorbic acid at different concentrations (0, 100mg Land 200mg L) proved significantly effective in alleviating the adverse effects of drought stress and increased the values of all the attributes, whereas, non significant decrease was noted for germination time. Moreover, drought stress alleviative effects due to salicylic acid were higher compared to ascorbic acid. Over all, most effective concentration was 200mg L and maximum increase was recorded in Hysun-33.