Nitrate or ammonium nutrition in french bean

Summary

Bean Plants were grown in a greenhouse in sand irrigated with nutrient solutions containing either 2 mM NO ⁻₃ or 2 mM NH ⁺₄ . After 45 days fresh weight of NH ⁺₄ plants was half that of NO ⁻₃ plants. Cation concentration in NH ⁺₄ plants was 30% less than in NO ⁻₃ plants. Amino acids (SER, ASN, GLN) accummulated 3 to 10 times more in NH ⁺₄ plants. The concentration of organic acids (malic, malonic, citric) was 10 to 30 times higher in NO ⁻₃ plants. The ATP-costings for the synthesis of amino acids and organic acids in NH ⁺₄ plants was half that of NO ⁻₃ ones: therefore it could not account for the reduction of growth in the ammonium-fed plants.