Ethylene is a plant hormone that differs from other plant hormones because it is a gas. Like Abscisic acid, it is the only member of its class. Of all the known plant growth substances, Ethylene has the simplest structure (Internet Source #5.) Ethylene gas (C2H4) is an odorless, colorless gas that exists in nature and can also be created by man (Internet Source #3.) Ethylene is a naturally occurring ripening gas but it is not easily detectable and it exists mainly where produce is stored. In nature, the largest producers are plants and plant products (such as flowers, vegetables and fruits) which produce ethylene gas within their tissues and release it into the air (Internet Source #2.) As some fruits and vegetables mature, they produce Ethylene gas, which continues the ripening process naturally. Without Ethylene gas, some items such as bananas would never ripen (Internet Source 4#.) Ethylene is also a by-product of man-made processes, such as combustion (Internet Source #2.).
As many great discoveries begin, Ethylene and its effects on produce were discovered quite by accident. Lemon growers would store freshly harvested green lemons in sheds. These lemons were kept warm by kerosene heaters until they turned yellow and ripened enough to take to the market for sale. When more modern heating systems were used, the lemons no longer turned yellow on time. Researchers soon found that the main factor in the ripening process. The concluded that a small amount of ethylene gas was given off by the burning of kerosene in the heaters (Internet Source #5.).
Ethylene is also known as the 'death' or 'ripening hormone" (Internet Source #1.) It plays an important role in many plant growth processes, development and eventually death. Among the many changes that Ethylene causes is the destruction of chlorophyll (Internet Source #6.) With the breakdown of chlorophyll, the red and/or yellow pigments in the cells of the fruit are unmasked and the fruit assumes its ripened color (Internet Source #6.