Ethylene: It is a group of plant growth regulators which are widely used for ripening fruits and for the production of more flowers and fruits. It is a small hydrocarbon, the colourless flammable gas which is denoted by a formula C₂H₄ or H₂C=CH₂. Ethene is the IUPAC name for ethylene. It has a “sweet and musky” odour when it is pure. It is the simplest alkene and also the second simplest unsaturated hydrocarbon C₂H₂.

It is abundantly used in the chemical industry, and the polyethene is extremely produced using ethylene. Further, ethylene is also used in agricultural practices to ripen fruits, germination of the seed, etc.

Formula of Ethylene

The IUPAC name for ethylene is ethene. It consists of two carbon atoms and four hydrogen atoms. The formula for ethene is C2H4 or H2C=CH2.

Ethylene as a Plant Hormone

Chinese used to burn incense to ripen fruits in ancient times. Similarly, Egyptians used gash figs for the same purpose. As said previously, ethylene hormone is the only gaseous hormone that plays an important role in:

• Hypocotyl elongation and root initiation.

• Promotes growth of root to increase the absorbing capacity for water and minerals.

• Promotion of Apo-geotropism during root development.

• Possible role in adventitious root development.

• Affect gravitropism.

• Stimulates stem growth.

• Plays an important role in bud outgrowth.

• Plays an essential role in stem branching.

• Stimulates bending of stem and branches in the direction of light.

• Promotes root and shoot differentiation in a triple response. 

• Interferes with the transport of other hormones like auxin.

• Prevents stem trichome formation in Arabidopsis.

• Promotes leaf growth.

• Promotes leaf area expansion.

• Involved in leaf development and leaf senescence.

• Dismantling of leaf cells and nutrient recycling from senescent leaves to other plant parts.

• Regulatory role in the transition from vegetative to reproductive phase of some plants.

• Sex determination of flower and production of female flower in male plants 

• Promotes flowering in pineapples.

• Induces flowering n Bromeliad.

• Induces the opening of flowers.

• Stimulates flower senescence.

• Breaks seed dormancy and promote seed germination.

• Induces epinasty.

• Rise in the respiration of some climacteric fruits.

• Fruit ripening.

• Change in color of the fruit during the ripening process.

• Promotes fruit senescence.

• It helps plants to respond to environmental conditions.

Function of Ethylene

• Growth: It stimulates horizontal growth and the swelling of the axis. It inhibits the growth in the longitudinal direction.
• Gravity: It reduces the sensitivity to gravity. The stems become positively geotropic and the leaves and flowers undergo drooping.
• Senescence: It speeds up the senescence of flowers and leaves.
• Abscission: It stimulates the abscission of flowers, leaves, fruits and other parts of the plant. It helps in the formation of hydrolases.
• Apical Dominance: It prolongs dormancy of lateral buds and promotes apical dominance.
• Breaking Dormancy: It breaks the dormancy of seeds, buds and storage organs.
• Ripening of Fruit: It induces artificial ripening of climacteric fruits such as banana, mango, apple, etc.
• Flowering: It induces flowering in plants like pineapple and mango. In some plants, it also causes fading of flowers.

Uses of Ethylene

1. It regulates a number of physiological processes and hence is used as a plant growth regulator.
2. It lamps are used for colour development and ripening of fruits such as banana, mango, apple, etc.
3. It induces a feminising effect in plants, i.e., it is used to increase the number of female flowers in a plant to induce fruiting.
4. It is applied to rhizomes, tubers and seeds to induce early sprouting in them.
5. It is used for thinning of excess flowers and young fruits such as walnuts, cherry, cotton, etc

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By Team Learning Mantras