The synergistic effects of hydro and hormone priming on seed germination, antioxidant activity and cadmium tolerance in borage
In this research, the effect of priming with water for 24 hours and hormone-priming with different concentration of Gibberellic acid (GA3) (50, 100, 150 mg L-1) for 24 hours and hydro and hormone priming techniques either alone or in combination on germination, growth and biochemical properties of borage seedlings under cadmium stress conditions were investigated. The results showed that cadmium stress reduces seed germination and seedlings growth indices. Seed priming led to the significant increase in the germination percentage and rate, seedling dry weight and length, seedling vigor indices, and as well as the catalase and peroxidase activity of borage seedlings under both cadmium stress and non-stress conditions. Among the priming treatments, the combination of hydro and hormone priming showed the highest effects on the improvement of germination and seedling growth under cadmium conditions, which was significantly higher than those of the individual use of the hydro or hormone priming. At all levels of cadmium stress utilization of the combined hydro and hormone priming led to the 0.9 to 11.53-fold, and 0.95 to 2.63-fold increase in the seedlings dry weight compared with the control treatment and individual use of hydro or hormone priming, respectively. The highest activity of catalase and peroxidase enzymes in borage seedling was obtained from the seeds primed with the combination of hydro priming with 150 mg L-1 GA3, which was significantly higher than those of the other treatments. Generally, at all levels of cadmium stress, the combined hydro and hormone (specially 150 mg L-1 GA3) priming had the most positive effects on seed germination, growth and biochemical properties of borage seedlings.