Ethylene - Plant Growth Substances
This hydrocarbon C2H2 is a gas and is unbelievably a small and simple molecule to be accepted as a hormone. Ethylene is not produced by animals. The role of ethylene in the inhibition of growth and in geotropism was observed in 1901. Denny observed that ethylene can promote fruit ripening. Wallace observed the role of ethylene in leaf abscission. Gane noted that ethylene was actually produced by ripening fruit in 1934. Improvement in techniques like gas chromatography had immensely helped us in estimating the minute quantities of ethylene produced in plants.