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Name: Sarah
Status: student
Grade: 9-12
Location: KY
Country: N/A
Date: 1/20/2005


Question:
Ethylene gas accelerates the ripening process of a banana, but why?


Replies:
Ethylene produced naturally by the plant accelerates ripening and maturation of the fruit.

http://www.biologie.uni-hamburg.de/b-online/e31/31g.htm

http://www.turbana.com/produ_recipes/prodbanana.htm

Anthony Brach Ph.D.


Plants use ethylene (C2H4, also called ethene) as a hormone. It is a very small, simple molecule that exists as a gas at biological temperatures. Thus, when a plant releases ethylene, it diffuses quite quickly in the air.

Different kinds of plants use ethylene differently; among the uses are the promotion of fruit development and ripening, release of buds from dormancy in springtime, stimulation of leaf and fruit abscission (dropping), causing some plants to become female, stimulation of leaf senescence, induction of flowering, etc.

Bananas use ethylene to stimulate fruit ripening. A bunch of bananas will stay green for a long time until the ethylene concentration in the air around them becomes high enough. When that happens, then they begin ripening and they begin releasing more ethylene, which makes them ripen faster and release more ethylene, etc. In this way, all of the bananas will ripen very suddenly and simultaneously. Keeping bananas in a plastic bag will make them ripen much more quickly than if you leave them out in the open, because the plastic bag traps the ethylene and thus makes its concentration rise more quickly.

Many other fruits - including apples and tomatoes, which are related to bananas only very distantly - use the same mechanism. If one apple in a barrel starts to ripen quickly (i.e. "goes bad"), it will cause all of the surrounding apples to do likewise. One bad apple spoils the bunch. Fruit distributors often take advantage of this effect by picking fruit well before ripening and then shipping fruit to grocers while it is still green. Then, just before delivery, the fruit is gassed with ethylene to kick-start the ripening process. This helps make sure none of the fruit will ripen too early, which would be problematic at the grocery store.

Here is a good web site:

http://www.plant-hormones.info/ethylene.htm

Christopher Perkins



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