Gibberellin and ascorbic acid applications to mitigate seed deterioration damage in sunflower (Helianthus annuus L.) before and after seed aging conditions

Because of high levels of fatty acids, sunflower seed is susceptible to deterioration and damages caused by deterioration will reduce the quality of seed and seedling. To compare the effect of sunflower seed (cv. Barzegar) priming with gibberellin and ascorbic acid under two conditions, i.e. before and after the seed deterioration, an experiment was conducted in 2016 in the greenhouse of the Faculty of Agriculture, Lorestan University. The factorial pot experiment was performed based on a randomized complete block design with three replications. The first factor was the application time of priming in two levels (priming before and after seed deterioration) and the second factor was priming treatments in six levels (hydropriming, 50 and 75 ppm of gibberellin, 100 and 150 ppm of ascorbic acid, gibberellin 50 ppm + ascorbic acid 100 ppm and none primed control). Accelerated aging (72 h at 43 °C and 100% RH) was used to deteriorate the seed. The results showed that priming after seed deterioration in comparison with priming before deterioration was more efficient to improve traits such as seedling emergence and growth rate and seedling dry weight (p<0.05). However, for other traits such as emergence and seedling root length, there was an interaction between priming time and treatments; for these traits, priming after seed deterioration was generally more effective than priming before deterioration (p<0.05). Hydropriming after seed deterioration significantly improved percentage and rate of seedling emergence; and 75 ppm of gibberellin could improve seedling growth rate and dry matter accumulation. Therefore, 75 ppm of gibberellin and hydropriming are suggested for improving the quality of sunflower deteriorated seeds.