Ethylene, or C2H4, is a gaseous plant hormone with a very simple structure. It affects the growth, development, ripening, and aging of all plants. This natural hormone can be produced from the seedlings, roots, leaves, stem, tubers, or fruits. If you’ve ever noticed leaves opening or a fruit ripening as days go by, ethylene is responsible for all this by being a natural plant hormone. In the picture of the orange below, ethylene is responsible for the orange coloring and the ripening. Ethylene is also used commercially in manufacturing different chemicals.