Effects of Polyamines on Morphophysiological Traits of Calendula officinalis L. under Salinity Stress Caused by Potassium Chloride and Sodium Chloride Salts

To evaluate the effects of polyamine foliar application on growth indices and physiological traits of Calendula officinalis L. under salinity stress, a factorial experiment was arranged in a completely randomized design with three replications. The experiment was conducted in a commercial greenhouse in Pakdasht, Iran, in 2021. The treatments included salinity stress induced by NaCl and KCl salts (0, 50 and 100 mg l-1). The salts were applied Ten days after relocating the transplants once in every three days. Putrescine and spermine foliar applications (1 and 2 mM) were applied at three stages, with intervals of 20 days, including at the six-leaf stage, full tillering and first bud emergence. The results showed that the treatments had a significant effect on the measured variables. The highest fresh and dry shoot weight, plant height, number of leaves and flowers were observed in the control. The highest root fresh weight and root volume were obtained in response to NaCl 50 mg l-1+spermidine 2mM. The effects of NaCl 50 mg l-1+putrescine 2 mM led to the highest root dry weight. The highest carotenoid content was obtained in response to KCl 50 mg l-1+spermidine 2 mM. The highest chlorophyll content was caused by NaCl 50 mg l-1+spermidine 2 mM. The highest superoxide dismutase enzyme activity and proline were obtained in response to NaCl 50 and 100 mg l-1, respectively. The results showed that polyamine foliar application, especially spermine, caused the most significant increase in growth indices and physiological traits of pot marigold under salinity stress.