Anatomical and Physiological Effects of Silver Thiosulfate on Ethylene-Induced Abscission in Coleus

Abstract. Petioles of explants of Coleus blumei Benth. exposed to 20 ~1/1 ethylene abscised within 36 h. Pretreatment of explants with 4 mM silver thiosulfate (STS) inhibited ethylene-induced abscission. Delaying treat-ment with STS reduced its effectiveness in retarding ethylene-promoted abscission, suggesting that some events leading to abscission are initiated during the first hours of ethylene treatment. Microscopic study of abscis-sion zones of ethylene-treated xplants howed greatly increased amounts of rough endoplasmic reticulum, disruptions of the plasma membrane, and some cell separation i the region of the middle lamella. Pretreatment with STS prevented ethylene-induced reorganization of the endomembrane system and the subsequent middle lamellar dissolution. The correlation between ethylene and the promotion of fruit, floral, or foliar abscission has been recognized for over 80 years (Neljubow 1901, Abeles 1973). Elevated levels of ethylene in plar tissues may be the result of natural aging processes (maturation), environmental stress, invasion of pathogens, or th