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

Edited By Irshad Anwar | Updated on Jul 02, 2025 07:05 PM IST

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.

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Definition of Ethylene
Functions of Ethylene in Plants
Ethylene in Agriculture and Horticulture
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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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Frequently Asked Questions (FAQs)

1. What is ethylene and its function in plants?

Among the hormones participating in the different phases of plant growth and development, ethylene stands out. It is an endogenous, diffusible gaseous hormone controlling fruit ripening, flower senescence, and leaf abscission. Ethylene works by binding to its specific receptors, which changes gene expression that controls these developmental processes.

2. How does ethylene affect fruit ripening?

In fruit-ripening processes, it does this through the advancing of cell wall degradation, rising sugar content in the fruit, and increasing colour pigment biosynthesis. It simply acts as a signalling molecule or activator for the initiation of enzymatic activities involved in fruit softening, flavour development, and aroma production. For instance, this is done on some produce like bananas and tomatoes to promote uniformity in their ripeness and quality by ethylene treatment in controlled environments.

3. What role does ethylene play in leaf abscission?

Ethylene promotes abscission—the shedding of leaves from the plant. It initiates cell wall-degrading genes within the abscission zone, forming the separation layer that cuts off the leaf. This is a resource-saving process in plants, by which they drop damaged/diseased leaves and go through seasonal changes.

4. What role does ethylene play in leaf abscission?

Ethylene is a key promoter of leaf abscission, the process by which plants shed their leaves. It stimulates the formation of an abscission zone at the base of the leaf petiole, where cell wall degrading enzymes weaken the connection between the leaf and the stem. This process is important for plant survival, allowing trees to shed leaves before winter and plants to remove damaged or infected leaves.

5. How is ethylene involved in stress responses in plants?

Ethylene takes part in modulating defence mechanisms in plants against biotic and abiotic stresses. It causes the induction of defensive compounds, enhances resistance to pathogens, and can also switch on stress response genes. For example, it participates in responses to drought and flooding or pathogen attacks, promoting adaptation of plants to unwanted conditions and further growth.

6. What are some commercial uses of ethylene in agriculture?

Ethylene is used commercially to artificially control the process of ripening certain fruits, like bananas, tomatoes, and avocados. This ensures that when they get to consumers, they will be at their best state. Horticulture applies the ethylene inhibitor to prolong the life of cut flowers and prevent senescence. Another application of ethylene in agriculture is controlling fruit dropping and increasing harvest efficiency by allowing farmers to harvest at once.

7. How do plants perceive ethylene?

Plants perceive ethylene through a family of membrane-bound receptor proteins. These receptors are always active in the absence of ethylene, suppressing ethylene responses. When ethylene binds to these receptors, it inactivates them, which paradoxically activates the ethylene signaling pathway. This unique "inverse agonist" mechanism allows plants to respond rapidly to changes in ethylene levels.

8. What is the "ethylene burst" and why is it important?

The "ethylene burst" refers to a sudden, dramatic increase in ethylene production that occurs in response to certain stimuli, such as wounding, pathogen attack, or the onset of fruit ripening. This burst of ethylene acts as a signal, rapidly triggering various physiological responses throughout the plant. It's important because it allows plants to quickly respond to environmental changes or developmental cues, coordinating responses across different tissues.

9. What is the connection between ethylene and plant senescence?

Ethylene is a major promoter of plant senescence, the programmed aging and death of plant tissues. It influences senescence by:

10. What is the "triple response" to ethylene in seedlings?

The triple response is a characteristic set of changes observed in dark-grown (etiolated) seedlings exposed to ethylene. It consists of: 1) inhibition of stem and root elongation, 2) increased radial expansion of the stem (swelling), and 3) horizontal growth of the stem (exaggerated curvature of the apical hook). This response helps seedlings navigate through soil and around obstacles as they grow towards the surface.

11. What is the relationship between ethylene and fruit ripening in climacteric fruits?

In climacteric fruits, ethylene plays a central role in initiating and coordinating the ripening process. As these fruits begin to ripen, they produce a burst of ethylene, which triggers a cascade of biochemical changes including:

12. Why is ethylene often called the "ripening hormone"?

Ethylene is called the "ripening hormone" because it plays a central role in initiating and coordinating the ripening process in many fruits. It triggers a cascade of biochemical changes that lead to fruit softening, color changes, and the development of flavor and aroma compounds. This is why placing a ripe banana near unripe fruit can speed up the ripening process - the ethylene released by the ripe banana triggers ripening in nearby fruits.

13. Can you explain the concept of "climacteric" and "non-climacteric" fruits in relation to ethylene?

Climacteric fruits, such as apples, bananas, and tomatoes, show a sharp increase in respiration and ethylene production during ripening. These fruits can continue to ripen after being picked. Non-climacteric fruits, like strawberries, grapes, and citrus fruits, do not show this respiratory climb and do not continue to ripen significantly after harvest. Understanding this distinction is crucial for post-harvest handling and storage of different fruit types.

14. How do plants produce ethylene?

Plants produce ethylene through a biochemical pathway that starts with the amino acid methionine. This pathway involves several enzymatic steps, with the final step catalyzed by the enzyme ACC oxidase, which converts 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. The production of ethylene can be triggered by various factors including developmental cues, environmental stresses, and even other plant hormones.

15. What is the relationship between ethylene and fruit abscission?

Ethylene promotes fruit abscission, which is the shedding of fruits from the plant. It stimulates the formation of an abscission zone at the base of the fruit stem, weakening the connection between the fruit and the plant. This process is important for seed dispersal in many species and can also be a plant's response to stress or overproduction of fruits.

16. How do plants regulate ethylene production?

Plants regulate ethylene production through complex feedback mechanisms. The biosynthesis of ethylene can be induced by various factors including other plant hormones, environmental stresses, and developmental cues. Ethylene can also regulate its own production through both positive and negative feedback loops. Additionally, the sensitivity of plant tissues to ethylene can be modulated, providing another level of control over ethylene responses.

17. What is ethylene and why is it important for plants?

Ethylene is a gaseous plant hormone that plays crucial roles in plant growth, development, and stress responses. It's important because it regulates processes like fruit ripening, leaf senescence, and plant responses to environmental stresses. Unlike other plant hormones, ethylene is unique in its gaseous nature, allowing it to diffuse easily through plant tissues and even affect neighboring plants.

18. How does the simple structure of ethylene contribute to its function?

Ethylene has a very simple structure - it's just two carbon atoms connected by a double bond, with two hydrogen atoms attached to each carbon (C2H4). This simple, small molecule can easily diffuse through cell membranes and move between cells, allowing it to rapidly spread its effects throughout plant tissues. Its gaseous nature at room temperature also enables it to act as a long-distance signaling molecule between plants.

19. How does ethylene affect leaf senescence?

Ethylene promotes leaf senescence, which is the programmed aging and death of leaves. It triggers chlorophyll breakdown, protein degradation, and the remobilization of nutrients from aging leaves to other parts of the plant. This process is important for plant survival, as it allows the plant to recycle nutrients from old leaves and prepare for dormancy or new growth.

20. What role does ethylene play in plant responses to flooding?

When plants are submerged or their roots are waterlogged, ethylene production increases rapidly. This triggers various adaptive responses, including the formation of aerenchyma (air spaces in roots and stems that help oxygen diffusion), the elongation of stems or petioles to reach the water surface, and the initiation of adventitious roots. These responses help plants cope with the low-oxygen conditions associated with flooding.

21. How does ethylene influence plant stem and root growth?

Ethylene generally inhibits stem elongation and promotes radial expansion, leading to shorter, thicker stems. This is part of the plant's response to mechanical stress or wind, known as thigmomorphogenesis. In roots, ethylene can inhibit primary root growth while promoting the formation of lateral roots and root hairs, which can be beneficial for nutrient and water uptake in stressful conditions.

22. How does ethylene interact with other plant hormones?

Ethylene interacts with other plant hormones in complex ways. For example, it can enhance the senescence-promoting effects of abscisic acid (ABA), antagonize the growth-promoting effects of auxins and cytokinins, and work synergistically with jasmonic acid in plant defense responses. These interactions allow for fine-tuned regulation of plant growth and development in response to various internal and external cues.

23. What role does ethylene play in plant defense against pathogens?

Ethylene is an important signaling molecule in plant defense responses. When plants are attacked by pathogens, ethylene production often increases rapidly. This triggers various defense mechanisms, including the production of antimicrobial compounds, the strengthening of cell walls, and the activation of systemic acquired resistance. Ethylene can also promote senescence of infected tissues, which can help contain the spread of pathogens.

24. How is ethylene involved in the shade avoidance response?

In dense plant populations, ethylene accumulates in the lower canopy due to reduced air circulation. This, along with changes in light quality, triggers the shade avoidance response. Ethylene promotes stem elongation, upward leaf movement, and reduced branching, allowing plants to grow taller and compete for light. This response demonstrates how ethylene can mediate plant-plant communication and competition.

25. What is the commercial significance of ethylene in agriculture?

Ethylene has significant commercial applications in agriculture. It's used to artificially ripen fruits post-harvest, synchronize flowering in pineapples, promote rubber production in rubber trees, and induce flowering in bromeliads. Conversely, ethylene inhibitors are used to delay ripening and senescence, extending the shelf life of fruits, vegetables, and cut flowers. Understanding ethylene's effects is crucial for post-harvest management and crop production.

26. What is the connection between ethylene and epinasty?

Epinasty is the downward curving of leaves or other plant parts, often seen in response to stress. Ethylene is a key mediator of this response. When plants are exposed to stressors like flooding or pathogen attack, increased ethylene production can cause the upper sides of leaves to grow faster than the lower sides, resulting in downward curving. This can help plants conserve water or shed excess water in flooded conditions.

27. How does ethylene affect root hair development?

Ethylene promotes root hair formation and elongation. It does this by increasing the number of epidermal cells that differentiate into root hair cells and by stimulating the growth of existing root hairs. This response can be particularly beneficial in stressful soil conditions, as increased root hair density improves the plant's ability to absorb water and nutrients.

28. What is the role of ethylene in seed germination?

Ethylene can both promote and inhibit seed germination, depending on the species and environmental conditions. In many species, ethylene promotes germination by weakening the seed coat and endosperm, facilitating radicle emergence. It can also interact with other hormones like abscisic acid (ABA) and gibberellins to regulate the germination process. However, in some species or under certain conditions, high ethylene levels can inhibit germination.

29. How does ethylene influence flower development and senescence?

Ethylene plays a complex role in flower development and senescence. It can promote or inhibit flower initiation depending on the species. In many plants, ethylene triggers flower opening. However, it also promotes flower senescence, causing wilting and abscission of petals. This dual role allows ethylene to coordinate the timing of flower opening and senescence, which is crucial for successful pollination and seed set.

30. How does ethylene affect plant responses to drought stress?

Ethylene plays a complex role in plant responses to drought stress. Initially, drought stress often increases ethylene production, which can promote leaf senescence and abscission, helping the plant conserve water. However, prolonged ethylene exposure can inhibit root growth and reduce water uptake. Some drought-tolerant plants have mechanisms to reduce ethylene sensitivity, allowing them to maintain growth under water-limited conditions.

31. What is the relationship between ethylene and fruit color change during ripening?

Ethylene promotes color changes in many ripening fruits by triggering the degradation of chlorophyll and the synthesis of other pigments like carotenoids and anthocyanins. For example, in tomatoes, ethylene stimulates the conversion of chloroplasts to chromoplasts, resulting in the characteristic red color. This color change is often coordinated with other ripening processes to attract seed dispersers when the fruit is ready to eat.

32. How does ethylene influence plant stem thickness?

Ethylene generally promotes radial expansion of stems while inhibiting longitudinal growth. This results in shorter, thicker stems, which can be beneficial for plant stability. This response is part of the plant's thigmomorphogenic response to mechanical stress or wind. The thicker stems are often stronger and more resistant to bending or breaking, helping plants withstand environmental stresses.

33. How does ethylene affect fruit texture during ripening?

Ethylene promotes fruit softening during ripening by stimulating the activity of cell wall-degrading enzymes like polygalacturonase and cellulase. These enzymes break down cell wall components, leading to softening of the fruit tissue. The degree of softening varies among fruit types and is coordinated with other ripening processes like color change and flavor development.

34. What is the connection between ethylene and plant gravitropism?

Ethylene interacts with auxin to influence plant gravitropic responses. In roots, ethylene can enhance gravitropism by increasing the root's sensitivity to auxin on the lower side of a horizontally oriented root. In shoots, high ethylene levels can interfere with normal gravitropic responses. This interaction allows plants to adjust their growth orientation in response to both gravity and other environmental factors.

35. How does ethylene influence plant responses to pathogen attack?

Ethylene is a key signaling molecule in plant immune responses. Upon pathogen attack, ethylene production often increases rapidly, triggering various defense mechanisms. These can include the production of antimicrobial compounds, the strengthening of cell walls, and the activation of systemic acquired resistance. Ethylene can also promote senescence of infected tissues, which can help contain the spread of pathogens.

36. What is the role of ethylene in fruit dehiscence?

Ethylene promotes fruit dehiscence, the splitting open of fruit to release seeds. It stimulates the formation and activation of separation layers in dehiscent fruits, such as those of many legumes. This process involves the breakdown of cell walls in specific regions of the fruit, allowing it to split open when mature. Ethylene coordinates this process with seed maturation to ensure effective seed dispersal.

37. How does ethylene affect plant responses to flooding stress?

When plants are flooded, ethylene production increases rapidly due to reduced gas diffusion in water. This ethylene accumulation triggers various adaptive responses, including:

38. How does ethylene influence plant responses to mechanical stress?

Ethylene is a key mediator of plant responses to mechanical stress, a phenomenon known as thigmomorphogenesis. When plants experience mechanical stress (like wind or touch), ethylene production increases, leading to:

39. What role does ethylene play in seed dormancy and germination?

Ethylene's role in seed dormancy and germination is complex and can vary among species. In many cases, ethylene can:

40. How does ethylene affect root architecture?

Ethylene significantly influences root architecture by:

41. How does ethylene influence plant responses to herbivory?

Ethylene plays a significant role in plant responses to herbivore attack:

42. What is the role of ethylene in fruit abscission?

Ethylene promotes fruit abscission, the process by which fruits are shed from the plant. It does this by: