Effects of Foliar Application of Selenium and Nano-Selenium on Growth, Flowering, and Antioxidant Activity of Pot Marigold (Calendula officinalis L.) Under Salinity Stress Conditions

To investigate the comparative effects of selenium (Se) and nano-selenium (nano-Se) on the growth, physiological and biochemical properties of pot marigold (Calendula officinalis L.) under salinity stress, two separate greenhouse and field experiments were conducted. Treatments consisted of irrigation water salinity at two levels (1.1 dS m(-1) (control) and 6.1 dS m(-1)) and foliar spray at three levels (0 as control, Se and nano-Se at concentration of 10 mu M). The results demonstrated that salinity stress had adverse effects on the growth, reproductive, and physiological traits of pot marigold in both greenhouse and field conditions. However, the application of Se and nano-Se improved these parameters. Under salinity stress, the application of nano-Se increased dry weight of shoots in the greenhouse (77%) and field (116%) conditions compared to the control. Foliar spray of Se and nano-Se increased dry weight of flowers by 34% and 69% compared to the control, respectively, in the field experiment. The results of field study also illustrated that the application of nano-Se significantly increased the antioxidant activity of leaves and flowers under non-saline (30 and 4%) and saline (12 and 22%) conditions compared to the control, respectively. Under salinity stress, supplemental nano-Se enhanced the activity of catalase in the greenhouse (75%) and field (46%) conditions compared to the control. In general, foliar spray of Se and nano-Se mitigated adverse effects of salinity stress on the growth and yield of pot marigold in both greenhouse and field experiments. However, nano-Se was more effective than Se.