Write a note an ethylene.

Explanation

Almost all plant tissues produce ethylene gas in mintue quantities.
Discovery:
1. In 1924, Denny found that ethylene stimulates the repening of lemons.
2. Cocken et al., identified ethylene as a natural plant hormone.
Occurrence: Maximum synthesis occurs during climacteric ripening of fruits and tissues undergoing senescence.
Precursor: It is a derivative of amino acid methionin, linolenic acid and fumaric acid.
Physiological Effects: 1. Ethylene stimulates respiration and ripening in fruits.
2. It stimulates radial growth in stem and root and inhibits linear growth.
3. It breaks the dormancy of buds, seeds and storage organs.
4. It stimulates formation of abscission zone n leaves, flowers and fruits. This makes the leaves to shed prematurely.
5. Inhibition of stem elongation (shortening the internode).
6. In low cocentration, ethylene helps in root initiation.
7. Growth of lateral roots and root hairs. This increases the absorption surface of the plant roots.
The growth of fruits is stimulated by ethylene is some plants. It is more marked in climacteric fruits.
9. Ethylene causes epinasty.
Agricultural role:
1. Ethylene normally reduces flowering in plants except in pine apple and mange.
2. It increses the number of female flowers and decreases the number of male flowers.
3. Ethylene spray in cucumber crop produces female flowers and increases the yield.