Antagonisms Between Amino Acids in the Growth of Spirodela Polyrhiza Due to Competitive Amino Acid Uptake

Abstract

The branched-chain amino acids L-leucine, L-valine and L-isoleucine can, when supplied to the medium, inhibit the growth of the duckweed Spirodela po/yrhiza. The responses to Lleucine and to L-valine could be described as all-or-none responses, that to L-isoleucine as a graded response. This information permitted unambiguous measurement of the growth responses. The relation between amino acid dose (initial concentration in the medium) and growth response was evaluated by means of probit analysis. Dose response curves were determined for each branched-chain amino acid when supplied singly to the medium. They were also determined when a second amino acid was added to the medium at a fixed initial concentration. It appeared that L-glutamic acid, glycine and L-alanine, in increasing order (1) antagonized, each to a distinct degree, the growth inhibitory action of irrespective which branched-chain amino acid and (2) inhibited the uptake rate of the branched-chain amino acids. D-valine, L-ornithine and L-lysine did not antagonize, nor did they inhibit uptake. Evidence is provided that the observed antagonisms result from inhibition of the uptake of the growth inhibitory amino acids.

Amino Acid Interactions in the Regulation of Nitrate Reductase Induction in Cotton Root Tips

“…The most effective antagonists were as follows: against glycine: leucine, phenylalanine, and histidine; against asparagine: leucine, valine, isoleucine, and proline; against glutamine: leucine, valine, and isoleucine. Glutamic and aspartic acids were effective against all three inhibitors, but they belong to a special category because 2 Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable. 467 Plant Physiol.…”

“…Inhibition of NR' induction by single amino acids can apparently be prevented by other amino acids (1, 5). Several explanations are possible for such antagonistic behavior, ranging from derepression to competition in amino acid uptake (2,6). In tobacco cell cultures, the most thoroughly studied higher plant system, threonine prevented independently the absorption of nitrate and the development of NR activity (8), but arginine reversed this inhibition without affecting threonine uptake (7).…”

Synthesis of the Aspartate Family and Branched-Chain Amino Acids

“…This possibility was eliminated during studies of the incorporation of the branched-chain amino acids into Spirodela (Borstlap, 1974). This possibility was eliminated during studies of the incorporation of the branched-chain amino acids into Spirodela (Borstlap, 1974).…”

Appendix: Supplementary Material

“…Ten years ago the paper of Nä sholm and co-workers (Nä sholm et al, 1998) renewed the discussion of the 60ties (e.g. Birt and Hird, 1958;McKee, 1962;Borstlap, 1974;Fokin et al, 1993) about direct uptake of organic nitrogen (N) by plants. Thereafter, an increasing number of studies were pointed on the possibility of direct uptake of organic N sources (mainly amino acids) by plants in various ecosystems.…”