Ethylene is a simple gaseous plant growth regulator with a wide range of effects on plant physiology. Physiological Effects:
Fruit Ripening: It is the most widely known effect. Ethylene initiates and promotes the ripening process in climacteric fruits (e.g., bananas, apples, tomatoes), leading to changes in color, texture, and aroma.
Senescence and Abscission: It accelerates the aging (senescence) of leaves and flowers and promotes the formation of an abscission layer, leading to the shedding of leaves, flowers, and fruits.
Breaking Dormancy: It can break seed and bud dormancy in certain plants.
Flowering: While it generally inhibits flowering, it induces it in some plants like pineapples and mangoes.
Triple Response: In seedlings growing in the dark, ethylene causes a 'triple response' to mechanical stress: inhibition of stem elongation, promotion of radial swelling of the stem, and horizontal growth (diageotropism).
Applications:
Artificial Ripening: Ethylene is used commercially to ripen fruits that are harvested when green. A compound called Ethephon is often used, which releases ethylene when sprayed on plants. This allows for controlled ripening of fruits like tomatoes and bananas.
Inducing Flowering: It is used to synchronize flowering and fruit set in pineapple plantations.
Promoting Sprouting: Used to promote the sprouting of potato tubers.
Thinning Agent: It can be used as a thinning agent to reduce the number of fruits in crops like cotton, cherry, and walnut, leading to larger remaining fruits.