Effect of arsenate different levels on germination, growth and some physiological parameters of Alfalfa (Medicago sativa L.)

Mineral arsenic (As) is a pervasive peripheral carcinogen substance and consuming foods and drinking water contaminated  with this element can have consequences for human and animals health. Arsenic accumulates in surface soils in response to the weathering of rocks, cliffs, as well as human activities. Arsenic-exposed plants exhibit cytotoxic effects, such as growth retardation, cellular dysfunction and metabolism dysfunction. In the present research, effect of different concentrations of sodium arsenate solution (zero, 5, 10, 15 and 20 milligram per liter) was investigated on germination, growth and some physiological parameters of alfalfa in hydroponic medium. The results indicated that by increasing the concentration of arsenate, the percentage and rate of seeds germination, growth, concentration of photosynthetic pigments and concentration of root carbohydrates and aerial parts of alfalfa plants decreased. Also, the assessment of tension and growth indices (tolerance index, toxicity percentage, seedling vigor index and relative growth rate) confirmed these negative effects. According to the obtained results, it seems that arsenate, especially in high concentrations, appears to disrupt photosynthesis system, metabolism and inhibition of growth and development in the alfalfa plant, by inducing toxicity in plant and interfering with metabolic processes and mineral uptake.