Ripening of fruits by Ethylene Phytohormone

• Ethylene is  only phytohormone  which stimulates transverse or isodiametric growth  but retard the longitudinal growth.

• It is synthesised  from amino acid methionine in plants. 

• H. H. Cousins confirm the  release of volatile substance from ripened  orange that enhanced  the ripening of the stored unripened banana.

• Richard gane found that the substance causing ripening was ethylene. However, it was recognised as a plant hormone by crocker. 

• It is found in almost all parts of the plant in minimum amount but maximum production occurs during ripening  of the fruit and in tissue undergoes senescence. 

• The triple response of etiolate pea plants and gas chromatographic assay  are used as bioassays.

• Ethylene is the first discovered  plant growth regulator, found in gaseous form.

• It is synthesised by those tissues that  undergo  senescence and ripening fruits

• Richard Gane was pioneered  to demonstrate  that plants synthesise ethylene.

• In addition to this ethylene was the first gaseous growth regulator that  was to be identified in any living organism.

• The biosynthesis of ethylene  with biological activity was a  positive approach that withdrew the attention various biologist  that a gas could be a plant hormone. 

• In plants Ethylene causes the  horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings.

• Ethylene promotes senescence and abscission of plant organs, fruit ripening, enhances the respiration rate during ripening of the fruits.

• Ethylene breaks seed and bud dormancy. Ethylene gas is a major plant hormone that influences diverse processes in plant growth, development and stress responses throughout the plant life cycle.

👌👌Remember - The  enhancement of the rate of respiration is called respiratory climactic.

• Ethylene is different from non-gaseous hormones. The Ethylene moves within the plant by diffusion and it is synthesised at or near its site of action.

• Ethylene can diffuse across the  membranes and there is no requirement for carrier proteins to deliver ethylene to target cells. 

Use of Ethylene in Agriculture 

• Ethylene initiates germination in peanut seeds, sprouting of potato tubers, promotes rapid internode/petiole elongation in deep water rice plants.

• Ethylene also promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.

• The most widely used compound as source of ethylene is ethephon, which hastens fruit ripening and accelerates abscission in flowers and fruits and promotes female flowers in cucumbers.