Regulation of the expression of nitrate reductase genes in leaves of medical plant, Foeniculum vulgare by different nitrate sources

The effect of different sources of nitrate salts (ammonium nitrate, sodium nitrate and potassium nitrate) on nitrate reductase (NR) activity and nitrate reductase expression in the leaves of Foeniculum vulgare seedlings grown in pots containing perlite. Two week old seedlings were treated with 30, 60 and 120 mM aqueous solution of ammonium nitrate, sodium nitrate or potassium nitrate. After 21 days of nitrate supply, the leaves were harvest and kept in liquid nitrogen for analysis of nitrate/nitrite ratio, nitrate reductase activity and mRNA expression. Result showed that ammonium nitrate, sodium nitrate and potassium nitrate, as inducers, had significant effects on both nitrate reductase activity and nitrate reductase expression in some rates. In high ammonium nitrate, sodium nitrate and potassium nitrate supplies, nitrate reductase activity and nitrate reductase expressions were suppressed apparently due to nitrogen metabolite response inhibition and toxicity.