Effect of selenium on growth and some physiological parameters of Allium iranicum Wendelbo. and Allium ampeloprasum L

Selenium as a metalloid and useful element has different effects on plants. It enhances plant growth at low concentrations while high concentrations of this element can cause stress in plants. The aim of this study was to investigate the effect of different concentrations of selenium (0, 20, 40, 120 and 240 µM) equivalent to (0, 2, 4, 11 and 22 mg/L), at the 4-leaf stage, on shoot and tuber growth and some physiological parameters of the Allium iranicum Wendelbo and Allium ampeloprasum L..The results showed that with increasing concentrations of selenium, the growth rate (height, weight gland and the aerial parts as well as chlorophyll content) of two species significantly decreased which the most reduction was occurred in plants grown at 22 mg/L treatment. Malondialdehyde content was increased in treatments of more than 2 mg/L compared to the control group. With increasing levels of selenium in the medium, catalase activity decreased, while antioxidant compounds content such as carotenoids, carbohydrates and protein increased. The results showed that low selenium concentrations (0-2 mg/L) promote the growth by increasing the amount of chlorophyll as well as the synthesis of carbohydrates, but higher concentrations of selenium (4-22 mg/L) reduced the growth due to the production of reactive oxygen species and reduces the biomass. The overall results of this study showed that different levels of selenium concentration, affect morphological and physiological characteristics of tuber and shoot of two species. The important morphological symptoms of selenium toxicity were tuber and aerial growth reduction and chlorosis of young leaves.