Involvement of ethylene in the abscission of flowers and petals of Leptospermum scoparium

Excised vegetative and flowering shoots of Leptospermum scoparium Forst. emanate ethylene in a climacteric time course. Relatively high concentrations of applied ethylene were required to cause flower abscission. Flowers and petals dropped only if they were exposed to a high relative humidity, while at a low relative humidity the flowers dried out and shrivelled without abscission. Silver thiosulphate prevented ethylene‐induced, but not natural abscission of mature flowers. A rise in ethylene evolution followed treatment with silver thiosulphate in both young and mature flowers. Benzyl adenine prevented natural abscission and inhibited ethylene evolution, while ethylene‐induced abscission remained unaffected.