The picture above shows a group of bananas that have ripened. Ethylene is a colorless, flammable gas. It is also a hydrocarbon, and the simplest alkaline. Ethylene has many uses in the world today. Because it is a good natural plant hormone, it is used in agriculture to ripen bananas faster so they can be sold as produce. Other uses include faster coloring of citrus fruits, increasing growth rate of seeds, and to make plastics.