Ethylene, also known as the 'death' or 'ripening hormone' plays a regulatory role in many processes of plant growth, development and eventually death. Fruits, vegetables and flowers contain receptors which serve as bonding sites to absorb free atmospheric ethylene molecules. The common practice of placing a tomato, avocado or banana in a paper bag to hasten ripening is an example of the action of ethylene on produce. Increased levels of ethylene contained within the bag, released by the produce itself, serves as a stimulant after reabsorption to initiate the production of more ethylene. The overall effect is to hasten ripening, aging and eventually spoilage.