Hyoscyamus is one of the medicinal plants, rich in tropane alkaloids. In this research the effects of nitrate and ammonium on production of secondry metabolites and other physiological parameters, were investigated. The results indicated that when nitrate and ammonium were both present in nutrient solution and ammonium concentration was lower than nitrate, dry and fresh weight of root and shoot increased. However, by increasing ammonium concentration, plant growth decreased. With increased concentra-tions of ammonium, root/shoot ratios were decreased. Nitrate reductase activity increased in both nitrate and ammonium fed plants. However, the higher ratio of ammonium to nitrate led to a decreased NRA. Alkaloid content (sum of hyoscyamine and scopolamine) increased in both nitrate and ammonium fed plants. However, the higher the ratio of ammonium to nitrate, the lower the alkaloid content.

Keywords: Ammonium, nitrate, Nitrate reductase, Alkaloid

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