DISTRIBUTION OF METABOLITES AND ENZYMES OF NITROGEN-METABOLISM BETWEEN THE MESOPHYLL AND PARAVENOUS MESOPHYLL OF NONNODULATED GLYCINE-MAX

The distribution of amino acids and key enzymes involved in nitrogen metabolism was determined in mesophyll cells (MC), mesophyll protoplasts (MP), and paraveinal mesophyll protoplasts (PVMP) isolated from fully expanded trifoliolate leaves of non-nodulated soybean. Qualitative and quantitative differences were found in the distribution of amino acids, with MP containing the highest concentrations. Activity of nitrate reductase, glycolate oxidase, glutamine synthetase and glutamate dehydrogenase was measured in both tissue types and differences in activities between the tissue types were seen. PVMP had high glutamate dehydrogenase activity when compared to MP. Activities of glycolate oxidase and glutamine synthetase were much higher in MP on a protoplast basis while nitrate reductase activity was similar between the two protoplast types. These results, on the distribution of metabolites and associated enzymes, are discussed as to their possible significance to nitrogen metabolism in the soybean leaf. © 1990 Oxford University Press.