| Abstract: | Cucumber seedlings were grown in darkness on filter paper saturatedwith water, gibberellin (GA), growth-retarding chemicals (mainlyAmo-1618) or both GA and Amo-1618. The effects on oxygen consumptionand catalase activity were studied on cotyledons, radicles,and hypocotyl tips. GA increased respiration and catalase activity of hypocotyland cotyledons, decreased radicle respiration, and had no significanteffect on its catalase activity. Amo-1618 decreased respirationof hypocotyl and cotyledons and increased that of the radicles.It stimulated catalase activity in all three organs. The inverse effects of GA and Amo-1618 on oxygen uptake andcatalase activity were mutually antagonized when both compoundswere applied at concentrations counteracting their oppositeeffects on hypocotyl elongation. No stimulating effect on catalase activity was found with mostother growth-retarding chemicals. Some of them had no significanteffect on the enzyme, and one even decreased its activity. |
