Effect of Different Sources and Levels of Selenium on Growth and Some Physiological Characteristics of Onion (Allium cepa L.)

Selenium (Se) is an essential element for humans and animals. However, its effects are less known on plants. In this study, the effect of different sources and levels of selenium was studied on growth and some physiological characteristics of onion in hydroponic system, it is done in order to have a good and an acceptable quality character, and does not have a problem for human and plant. The treatments included four levels of selenium nanoparticles (2, 5, 10 and 30 mgL-1) and three concentrations of sodium selenite (2, 4 and 8 mgL-1) and sodium selenate (1, 2, and 3 mgL-1), each treatment were separately performed in a completely randomized design with three replicates. Results showed that in seedling stage different levels of nano-selenium, sodium selenite and sodium selenate were significantly effected on leaf fresh weight, root fresh weight, root dry weight, pseudostem fresh weight and also bulb weight, bulb diameter and length of bulbs. Sodium selenite and sodium selenate were significantly effected on leaf chlorophyll content and total selenium bulb. The highest leaf chlorophyll content was observed at low levels of sodium selenite and sodium selenate by increasing selenium concentration in nutrient solution, leaf chlorophyll content were decreased in comparison with control. The content of total selenium bulb increased with increasing sodium selenite and sodium selenate concentration in nutrient solution, However increase in plants treated with sodium selenate was more than plants treated with sodium selenite.