Ethylene

• The gas ethylene is also known to function as growth hormone
• Earlier it was considered to be exogenous substances which regulates a large number of physiological processes in plants but now it has been kept under the categories of plant hormones

• This is only gaseous hormones of plants known
• Ethylene is actually a natural product of ripening fruit
• It is most powerful ripening hormone present in small quantity in plant tissues
• Ethylene is produced by fruits, flowers, seeds, leaves and roots
• Its chemical formula is CH 2 = CH 2
• Highly useful in inducing fruit ripening
• Ethylene is a natural product of ripening fruit
• Ethylene is a gas at temperatures under which a plant can live
• Auxins increase ethylene level in plants and auxin actions are attributed through ethylene such as increased percentage of female flowers and apical bud dominance

Role of Ethylene:

• Abscission: Principle accelerator of abscission – Capable of promoting changes associated with pre – abscission and aging of leaves, petioles, flowers and fruits
• Ethylene degreening is a commercial practice (5-10 ppm).
• Degreening occurs after ethylene treated are exposed to air – accelerates maturity and induces uniform ripening (Pine apple)

Fig : Biosynthesis of Auxin , Giberrelin , cytokinin , Ethylene and ABA.