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

What Is 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. 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.

Chemical Structure of Ethylene

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.

Functions of Ethylene in Plants

There are various functions of ethylene-

Role in Fruit Ripening

Ethylene regulates the conversion of starches and acids into sugars, causing the fruit to become softer, sweeter, and colorful.

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

Ethylene promotes the shedding of leaves, flowers, and fruits by stimulating cell wall-degrading enzymes in the abscission zone (base of petiole).

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 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 in plants cope with biotic and abiotic 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 breaks seed dormancy, allowing it to germinate by stimulating the action of the enzymes responsible for the breakdown of the seed coat.

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

• Fruit Ripening Chambers: Ethylene in ripening chambers promotes uniform ripening of fruits as bananas, tomatoes, and avocados. This makes all of them ripe simultaneously and improves the market quality.

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

• 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 – 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 are the chemicals used to inhibit ethylene action:

1-Methylcyclopropene 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.

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

• 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.

• It is an important ethylene inhibitor in the flower industry, guaranteeing the outlook and extending the life of cut flowers.

Agricultural Benefits of Ethylene Regulation

The agriculture benefits of ethylene regulation:

Ethylene NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Functions of Ethylene in Plants

• Ethylene in agriculture

Practice Questions for NEET

Q1. Name the only plant growth hormone regulator.

1. ABA

2. Cytokinin

3. Auxin

4. Ethylene

Correct answer: 4) Ethylene

Explanation:

The only gaseous plant growth regulator is ethylene, which is produced by the majority of plant organs, including ripening fruits and ageing tissues. It is a doubly covalently bonded unsaturated hydrocarbon with carbon atoms both nearby and between it.

Hence, the correct option is 4) Ethylene.

Q2. Who of the following scientists observed that ethylene can alter the tropic responses of the roots?

1. Crocker et. al

2. H.H. Cousins

3. Went

4. Neljubow

Correct answer: 4) Neljubow

Explanation:

Dimitry Neljubow, a scientist, noted that ethylene is an important growth regulator as it changes the tropic responses of the roots. During his research, he proved that ethylene causes a triple response in the seedlings of peas, which includes horizontal growth, inhibition of elongation, and radial swelling. This led to the research of ethylene on the behaviour of roots along with patterns of growth, making it an essential plant hormone involved in regulating most developmental processes among plants.

Hence, the correct answer is Option (4) Neljubow.

Q3. A ripe mango, kept with unripe mangoes causes their ripening. This is due to the release of a gaseous plant hormone

1. AUxin

2. Gibberllin

3. Cytokinin

4. Ethylene

Correct answer: 4) Ethylene

Explanation:

Ethylene is the only gaseous natural plant growth regulator and is responsible mostly for the ripening process in fruits. It hastens the transition of starches to sugars, softens fruit texture, and amplifies flavour and aroma. Furthermore, ethylene affects flowering, leaf senescence, and responses of plants to environmental stresses. Being produced in a regulated fashion by higher plants, it is significant for growth and development regulation, making it significant in agricultural and horticultural practices.

Hence the correct answer is option 4) Ethylene.

Also Read:

• MCQs on Ethylene

• Auxin Bioassay

• Plant Growth Regulators

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