Nitrogen Constituents in Manganese-Deficient Lemon Leaves

Total (Kjeldahl) nitrogen content of manganese-deficient lemon leaves was found to be about 40% higher (on a dry weight basis) than in the analog control leaves. The nitrate-N content rose in the deficient leaves from 18.2 mg/100 g to 95.6 mg/100 g dry weight. Among the N constituents studied, the free amino acids increased by about 42%, the protein amino acids by about 22%, and the total protein by more than 22%, all on a fresh weight basis. Acrylamide gel electrophoresis and ammonium sulfate fractionation showed qualitative differences in the various proteins. The increase of the protein fraction in the -Mn leaves may be attributed in part to the decrease of dry matter in these leaves (25.8% as compared to 30.7% in the control leaves) and in part to accumulation of apparent proteinous material in manganese-deficient tissues.