Catecholamine stimulation of the gibberellin action that induces lettuce hypocotyl elongation

Effects of catecholamines and their derivatives on gibberellicacid (GA)-induced lettuce hypocotyl elongation was studied,because catecholamines have a chemical structure similar tothe dihydroconiferyl alcohol that has been isolated from lettucecotyledons as a GA synergist. Epinephrine, norepinephrine, dopamineand 3,4-dihydroxymandelic acid synergistically enhanced thepromoting effect of GA on hypocotyl elongation. In contrast,metanephrine, normetanephrine, DOPA and 3-methoxy-4- hydroxymandelicacid did not enhance the GA effect. The action of catecholamineswas inhibited by trans-cinnamic acid which competitively inhibitedthe action of dihydroconiferyl alcohol; this suggests that thereceptor site for catecholamines is the same as that for dihydroconiferylalcohol. The basic ethyl acetate fraction from lettuce seedlingssynergistically enhanced the GA effect. TLC analyses of thisbasic ethyl acetate fraction revealed that the chromatographicarea corresponding to authentic catecholamines could enhancethe GA effect. From these results, a possible role for catecholamines in theregulation of lettuce hypocotyl elongation caused by GA wasposited, and is discussed here. (Received May 15, 1979; )