Effect of Seed Treatment on Physiological Traits of Two Safflower Cultivars under Defoliation

To evaluate the effects of priming and defoliation on some physiological traits of two safflower cultivars, a factorial experiment was conducted as a randomized complete block design with three replications in the research farm of Agricultural Sciences and Natural Resources University of Khuzestan in the crop years of 2017 and 2018.

The experimental factors consisted of two cultivars of safflower (Esfahan local and Sofeh cultivars) and three levels of priming with [Salicylic acid (SA) 0.9 milli molar, polyethylene glycol (PEG)- 6000 (-10 MPa)] and control at two defoliation levels (without defoliation and 50% defoliation in lower parts of plant).

The results showed that the defoliation and priming treatments had significant effects on chlorophyll a, chlorophyll b, and carotenoid content, in such a way that the priming with salicylic acid and polyethylene glycol was associated with a significant decrease in chlorophyll a (34.54%) and chlorophyll b (42.59%); although, the content of carotenoid increased in defoliation and priming with PEG (38.22), carotenoid was decreased in the treatment of defoliation and priming with salicylic acid. Defoliation treatment significantly (28.11%) increased the activity of ascorbate peroxidase in comparison to the control.

Generally, the results showed that the highest enzyme activity of ascorbate peroxidase (29.26%) was observed in the first year of priming with polyethylene glycol. The highest amount of catalase activity (27.45%) was also observed in Isfahan local cultivar and salicylic acid priming under 50% defoliation. The amount of Malondialdehyde decreased in priming with PEG, however, it increased (33.1%) in priming with salicylic acid and 50% defoliation treatment.