Effect of Gibberellic Acid on Glutamine Synthetase Activity in Two Varieties of Lettuce Seeds, New York 515 and Grand Rapids

摘要

Gibberellic acid (GA) increased glutamine synthetase (GS) activity during imbibition by lettuce seeds. The effect of GA was more remarkable in the dark than under red light. The increase in GS activity induced by GA was inhibited completely by cycloheximide (1 mm). No promotive effect of GA on dark germination was observed in the presence of L-methionine-DL-sulfoximine, a specific inhibitor of GS. Therefore, GA has its promotive effect on the dark germination of lettuce seeds mainly through GS activity. The GS activity present in the embryonic axes of Grand Rapids seeds was about half that in New York 515 Improved, also the promotive effect of GA on dark germination was lower in Grand Rapids. This difference between dark germination in the New York and Grand Rapids seeds was interpreted as being the difference in the amount of GS activity in the embryonic axes of the dry seeds.