The ethylene is phytohormone which is in gas form and synthesized in fruits to ripe the fruits. The fruits are classified into two groups based on ethylene synthesis in the fruits. First group of fruits are called climacteric fruits in which ethylene synthesis increases at maturity and fruits ripe after harvesting at maturity such as mango, banana, apple and tomato. In second group of fruits ethylene synthesis does not increases at maturity and fruits do not ripe after harvesting if harvested even at maturity, these fruits are called non-climacteric fruits. Ethylene is natural hormone for ripening of fruits and synthesized into both climacteric and non-climacteric fruits but synthesis increases in climacteric fruits at maturity. The ethrel or ethephon is applied externally as source of ethylene to enhance the fruit ripening of climacteric fruits. The ethephon releases the ethylene gas around the fruits. The ethylene is non hazardous and recommended for fruit ripening.
The another chemical calcium carbide is used for ripening of fruits which is harmful for the health and not recommended for fruit ripening. The Calcium carbide burns at high temperature in the presence of oxygen and used in gas welding works. It reacts with water and releases acetylene gas which burning gives as high as 3000 degree Celsius temperature. The acetylene is hazardous and not a fruit ripening hormone and its use for fruit ripening is punishable offense in India.
