Final answer:
Ethylene is a hormone that plays a key role in the ripening of fruits, affecting starch and acid conversion to sugars, and is involved in leaf and fruit abscission. It is a volatile gas, allowing it to diffuse through the air and impact nearby plants. Ethylene is also used in agriculture to control ripening times and prevent leaf drop in ornamental plants.
Step-by-step explanation:
Ethylene promotes the ripening of fruit by stimulating the activity of various enzymes, such as cellulase. This hormone is produced by aging tissues in plants, such as senescing leaves and stem nodes. One of the most prominent effects of ethylene includes the stimulation of the conversion of starch and acids into sugars, aiding in the ripening process. For example, placing avocados in a sealed paper bag can trap the ethylene they emit, encouraging the ripening of the fruit. Additionally, ethylene has roles beyond ripening; it is responsible for leaf and fruit abscission and also promotes the germination of certain seeds and the sprouting of bulbs.
As a volatile gas (C₂H₄), ethylene is unique among plant hormones. It can diffuse through the air and affect nearby plants. This property explains the adage about 'one rotten apple spoiling the whole barrel,' as over-ripening can be triggered by ethylene. In agriculture, ethylene's properties are exploited to control the timing of fruit ripening and prevent premature leaf drop in ornamental plants.
Historical observations even linked ethylene to changes in tree growth patterns near gas street lamps, where the released ethylene caused trees to develop twisting trunks and shed leaves prematurely. In modern times, fruit processors may use ethylene to hasten the ripening of fruits like tomatoes, though this method does not replicate the natural ripening process and may affect taste.