Chromium is a heavy metal, this element is considered as an environmental hazard. .Toxicity effects of chromium on growth and development of plants including inhibition of germination process, decrease of growth and biomass of plant. The aim of this research is to study accumulation of Cr+3 and its effect on the growth of onion plant (Allium cepa cv. Hybrid). Thus, Onion seedlings grown in pots including soil and sand with raito 1:1 undergoing ,different treatments of Cr+3 (0, 5,10, 20, 40, 50, 100, 150, 200 mg/L). after 4 week seedlings were removed and morphophysiology parameters like root length, shoot length and dry weight of plants and accumulation of Cr+3 in roots and shoots were determined. The results indicated that the concentrations more than 150 mg/L chromium cause the reduction of morphophysiology parameters in the treatment plants rather than control plant and Cr3+ addition in the cultures caused enhancement of chromium content in roots and shoots of plant seedlings. It was also noted that accumulation of chromium in the roots were much higher than the shoots of the seedlings under treatment

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