Functions of Ethylene: Definition, Structure, Sources, Production, Uses, & Facts

Definition of Ethylene

Ethylene is a simple hydrocarbon gas, C₂H₄, which is an important plant hormone helping to regulate some of the physiological processes, such as fruit ripening and abscission of leaves. Chemically, it has a small molecule that contains only a double bond between two atoms of carbon; thus, it will turn out to be the simplest alkene. Probably one of the most important gases in plant biology, ethylene was discovered early in the 20th century because of its effect on hastening fruit ripening. It is for this very reason that techniques for manipulating fruit ripening have since been developed to help increase agricultural yields.

Functions of Ethylene in Plants

There are various functions of ethylene-

Role in Fruit Ripening

Mechanism of action in ripening

It is surmised that ethylene does so by binding to receptors in the fruit, setting off a series of reactions that ultimately alter cell-wall structure and metabolism, leading to the softening and sweetening of the fruit.

Examples of fruits affected by ethylene

Some common examples include bananas, apples, tomatoes, and avocados.

Regulation of Leaf Abscission

Process of leaf shedding

Abscission is a process of shedding leaves from the plant. Ethylene promotes it through the degradation of the cell wall in the abscission zone—a region where the petiole joins the stem.

Ethylene’s role in promoting abscission

Due to increased ethylene production, cell wall degrading enzymes are activated, which allows leaves to fall.

Flower Senescence

Ethylene's involvement in ageing and wilting of flowers

Ethylene acts to promote senescence in flowers, resulting in ageing and eventual wilting.

Examples of ethylene-sensitive flowers

It is known that some flowers, such as orchids, carnations, and petunias, are sensitive to ethylene.

Stress Responses

Ethylene’s role in response to biotic and abiotic stress

Ethylene in plants coping with stress regulates various physiological responses to such stresses.

Examples of stress responses

The stress responses include those against attack from pathogens, drought, and mechanical damage.

Seed Germination and Root Growth

Ethylene’s effect on seed dormancy and germination

Ethylene breaks seed dormancy, allowing it to germinate by stimulating the action of the enzymes responsible for the breakdown of the seed coat.

Influence on root growth and root hair development

Ethylene promotes an increase in the growth of roots and root hair and promotes increased uptake of water and nutrients from the soil.

Ethylene in Agriculture and Horticulture

Various uses are explained below-

Commercial Uses

Ethylene in fruit ripening chambers

Ethylene in ripening chambers promotes uniform ripening of such varied fruits as bananas, tomatoes, and avocados. This controlled application makes all of them ripe simultaneously and improves the market quality. Hence, wastage is reduced and presents better market quality.

The fruit should be treated with ethylene gas under specific temperature and humidity conditions for the natural process of ripening to take place.

Applications in horticulture

Flower Preservation: Inhibitors of ethylene respiration prolong the life of cut flowers by preventing senescence and wilting. This aspect assumes great significance for ethylene-sensitive flowers such as carnations and orchids.

Stress Management: Ethylene induces stress responses in plants to strengthen defences against any undesirable incidents of drought, flood, and pathogen attacks

Case study: Use of ethylene in commercial tomato ripening

Use of Ethylene in Commercial Tomato Ripening

Process: Green harvested tomatoes are then gassed with ethylene gas in a ripening chamber to develop uniform colour and texture before the produce reaches consumers.

Benefits: This process allows tomatoes to naturally ripen off the vine and extends the period of in-transit time without spoilage, thus providing the consumer with a consistently ripe product. Ethylene Inhibitors

Ethylene Inhibitors

Chemicals used to inhibit ethylene action

1-Methylcyclopropene: This is one of the most common ethylene inhibitors, which acts by binding to ethylene receptors in plant tissues and preventing ethylene from inducing a response for ripening and senescence.

Applications: 1-MCP has very broad applications in extending the shelf life of fruits, vegetables, and flowers during storage and transport by delaying the onset of their ripening and senescence processes.

Applications and benefits in agriculture

Extended Shelf Life: 1-MCP, by inhibiting the action of ethylene, helps in maintaining the quality of produce during storage and transport. This in turn reduces losses of yield after harvesting.

Quality Preservation: It is an important Ethylene inhibitor in the flower industry, guaranteeing the outlook and extending the life of cut flowers.

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