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Discovery, Occurrence, Transport, Physiological Effects, Agricultural role - Ethylene (Gaseous Phytohormone) - Natural Plant Growth Regulators (PGRs) | 11th Botany : Chapter 15 : Plant Growth and Development

Chapter: 11th Botany : Chapter 15 : Plant Growth and Development

Ethylene (Gaseous Phytohormone) - Natural Plant Growth Regulators (PGRs)

Almost all plant tissues produce ethylene gas in minute quantities.

Ethylene (Gaseous Phytohormone)

Almost all plant tissues produce ethylene gas in minute quantities.

 

1. Discovery

 

In 1924, Denny found that ethylene stimulates the ripening of lemons. In 1934, R. Gane found that ripe bananas contain abundant ethylene. In 1935, Cocken et al., identified ethylene as a natural plant hormone.

 

2. Occurrence

 

Maximum synthesis occurs during climacteric ripening of fruits (see Box info) and tissues undergoing senescence. It is formed in almost all plant parts like roots, leaves, flowers, fruits and seeds.

 

3. Transport in plants

 

Ethylene can easily diffuse inside the plant through intercellular spaces.

 

4. Precursor

It is a derivative of amino acid methionine, linolenic acid and fumaric acid.

 

5. Bioassay (Gas Chromatography)

Ethylene can be measured by gas chromatography. This technique helps in the detection of exact amount of ethylene from different plant tissues like lemon and orange.

 

6. Physiological Effects


·            Ethylene stimulates respiration and ripening in fruits.

 

·            It stimulates radial growth in stem and root and inhibits linear growth.

 

·            It breaks the dormancy of buds, seeds and storage organs.

 

·            It stimulates formation of abscission zone in leaves, flowers and fruits. This makes the leaves to shed prematurely.

 

·            Inhibition of stem elongation (shortening the internode).

 

·            In low concentration, ethylene helps in root initiation.

 

·            Growth of lateral roots and root hairs. This increases the absorption surface of the plant roots.

 

·            The growth of fruits is stimulated by ethylene in some plants. It is more marked in climacteric fruits.

 

·            Ethylene causes epinasty.

 

7. Agricultural role

 

·            Ethylene normally reduces flowering in plants except in Pine apple and Mango­.

 

·            It increases the number of female flowers and decreases the number of male flowers.

 

·            Ethylene spray in cucumber crop produces female flowers and increases the yield.

 


Climacteric fruits: In most of the plants, there is sharp rise in respiration rate near the end of the development of fruit, called climacteric rise. Such fruits are called climacteric fruits. The ripening on demand can be induced in these fruits by exposing them to normal air containing about 1 ppm of ethylene. A liquid called ethephon is being used in fruit ripening as it continuously releases ethylene.

Example: Tomato, Apples, Banana, Mango.

Non climacteric fruits: All fruits cannot be ripened by exposure to ethylene. Such fruits are called non-climacteric fruits and are insensitive to ethylene.

Example: Grapes, Watermelon, Orange.



 

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11th Botany : Chapter 15 : Plant Growth and Development : Ethylene (Gaseous Phytohormone) - Natural Plant Growth Regulators (PGRs) | Discovery, Occurrence, Transport, Physiological Effects, Agricultural role

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11th Botany : Chapter 15 : Plant Growth and Development


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