Ethephon is the trade name of a plant growth regulator (basic manufacturer Rhône-Poulenc). Upon metabolism by the plant, it is converted into ethylene, a potent regulator of plant growth and maturity. It is often used on wheat, coffee, tobacco, cotton and rice in order to help the plant's fruit reach maturity more quickly. In cotton, which initiates fruiting over a period of several weeks, ethephon is used to make all bolls open simultaneously in order to enhance harvest efficiency.
Although many environmental groups worry about toxicity resulting from use of growth hormones and fertilizers, the toxicity of ethephon is actually very low, and any ethephon used on the plant material is converted very quickly to ethylene.