Re: can you elaborate how bananas are ripened with ethylene?

The book cited below gives a lot of details that I cannot provide here. Bananas 
are unusually responsive to ethylene and even half-grown bananas can be ripened 
with ethylene. Acetylene works but at least 100 times more acetylene is require 
compared to ethylene. 

Important factors in ethylene treatment are ethylene concentration (about 10 
microliters/liter), controlling humidity to prevent drying out of the fruit (85 
to 90% relative humidity), adequate ventilation to prevent buildup of carbon 
dioxide which slows ripening (keep below 1% carbon dioxide), optimal temperature 
(15 to 21 C) and both the stage of ripeness before treatment and the desired 
stage of ripeness after treatment which determines the time required. Because so 
much of world's bananas are ripened with ethylene, special ripening rooms are 
often built. 

Reference

Willis, R.B.H. et al. 1989. Postharvest: An Introduction to the Physiology and 
Handling of Fruit and Vegetables. London: Oxford Professional Books.