Changes revealed by a tracer technique in the amino acid metabolism of thermodormant and non-dormant New York lettuce seeds.

Abstract

The metabolism of glycerol-(14)C(U) in non-thermodormant New York lettuce seeds was compared with that in thermodormant ones in order to find metabolic changes and a possible osmotic substance(s) in the non-dormant seeds. The higher incorporation of radioactivity into cationic substances in the non-dormant seeds revealed rapid synthesis and large pool sizes for some amino acids, especially Gln and Glu, before radicle protrusion. The enormous accumulation of Gln and Glu in germinating seeds indicates that these amino acids may act as osmotic substances in the germination of New York lettuce seeds. There were no indications that an osmotic substance(s) is included in the neutral and acidic fractions of the 80%-ethanol extracts. Time course analyses of free amino acids showed changes in the metabolism of free amino acids, especially Arg and Asn, at the early stage (4 to 8 hr) of imbibition both in thermodormant and in non-dormant seeds. These data are evidence that the metabolism of amino acids in New York lettuce seeds was affected by temperature treatment from the early stage of imbibition.