2.6. Ethylene Action and Methods for Inhibiting Ethylene Responses
Ethylene inhibitors reduce or eliminate the biological activity of ethylene.These compounds can be divided into two groups: inhibitors of ethylene
biosynthesis and inhibitors of ethylene action. The first are substances that interact with the ethylene biosynthesis pathway through inhibition of key enzymes, ACC
synthase, and ACC oxidase. The 1-aminoethoxyvinylglycine AVG and the amino-oxyacetic acid AOA are inhibitors of ethylene biosynthesis, while silver
thiosulfate STS, silver nitrate, and 1-methylcyclopropene 1-MCP are inhibitors of ethylene action Ferrante and Francini, 2008. Yang and Hoffman 1984
indicated that
aminoethoxyvinylglycine AVG and aminoethoxycetic acid AOA disrupt ACC synthase, while cobalt Co
2+
and α-aminois-butyric acid AIBA disrupt ACC oxidase.
Blocking ethylene effects at the receptor level is more effective as it will protect against both endogenous and exogenous ethylenes Serek and Reid, 1993.
The silver ion Ag
+
has proved to be a potent inhibitor of ethylene action in ornamentals. STS is generally applied as a pretreatment solution to cut flowers.
The persistence and mobility of STS allows very short pulse treatments. In potted plants STS is applied as an aqueous spray. Beneficial effects of STS are reported
for a great variety of cut flowers and potted plants. STS treatment prevents petal senescence induced by ethylene and prolongs the vase life Arora, 2008. 1-
Methylcyclopropene 1-MCP has been reported to be a non-toxic antagonist of ethylene action Sisler and Serek, 1997 that blocks the physiological action of
ethylene Sisler et al.,1996. Applications of 1-MCP to delay fruit ripening and extend the storage life have been extensively reported in both climacteric and non-
climacteric fruit Watkins, 2006 .
The use of 1-MCP for harvested fruits and vegetables represents a revolutionary advance in postharvest science and
practices. The gas works by attaching to a site receptor in fruit tissues that normally binds to ethylene. Binding of ethylene to these sites is how plant tissues
perceive that ethylene is present in the environment. If ethylene binding is prevented, ethylene no longer promotes ripening and senescence Huber et al.,
2003. 11
2.7. Cytokinin and its Physiological Effects
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