Glycine and L-Alanine as Antagonists of Growth Inhibition by the Branched-Chain Amino Acids in Spirodela polyrhiza

Growth inhibition of the duckweed Spirodela polyrhiza (L.) Schleidenby exogenously supplied L-leucine, L-valine, or L-isoleucinewas antagonized by simultaneously supplied glycine or L-alanine.Calculations, using the kinetic parameters for the uptake ofthese amino acids, indicated that the antagonisms to a considerabledegree resulted from competitive inhibition of the uptake ofthe growth-inhibiting amino acids. However, the antagonismsresulted partly from an interaction between growth inhibitorand antagonist inside the cells.