Effects of selenium on enzymatic changes and productivity of garlic under salinity stress

Abstract

There is a lack of information pertaining to garlic growth under increasing levels of salinity. This research was conducted to assess the effects of NaCl level on growth, lipid peroxidation and antioxidant activity of marketable garlic (Allium sativum L.) in a hydroponic greenhouse experiment. Garlic plants were treated with NaCl (0, 30, 60 and 90 mM) and Na2SeO4 (0, 4, 8 and 16 mg Se L−1). The results showed that selenium application without salinity significantly increased the fresh and dry weights of bulb, number of clove per bulb, bulb diameter and bulb height compared to the control plants. Also, salt stress (30 mM) without selenium caused a drastic increase in garlic fresh and dry weights of root and bulb, bulb diameter and bulb height. Exogenous Se supply at 8 and 16 mg L−1 significantly increased Chl “a” under levels 60 mM of salinity. Also, Se supplementation at 16 mg L−1 in combination with salt stress (30 and 60 mM NaCl) significantly increased Chl “b” and total Chl. However, application of Se significantly decreased the level of malondialdehyde. Se supply (8 mg L−1) at 30 mM NaCl significantly decreased the electrolyte leakage by 58%. Low Se supply (4, 8 mg L−1) induced accumulation of total phenolic content at 90 mM NaCl, but this diminished at higher supply. The results show that garlic plants have high antioxidant activity against salinity stress without treatment with selenium compared to treated. Under salinity conditions of 30 mM NaCl, the superoxide dismutase and catalase activities increased with increasing the level of Se treatment. Addition of Se at 16 mg L−1 in combination with salt stress (60, 90 mM NaCl) significantly increased the level of ascorbate peroxidase activity. These results indicated that salt stress had a positive physiological effect on some growth parameters of garlic which is in contrast to previous reports. In addition, application of Se made garlic plants more tolerant to salt stress-induced oxidative damage by enhancing their antioxidant defense systems.