Ethylene (plant hormone)

Ethylene (or Ethene) functions as a plant hormone in plants. It stimulates the ripening of fruit, the opening of flowers, and the abscission of leaves. Its biosynthesis starts from methionine with 1-aminocyclopropane-1-carboxylic acid (ACC) as a key intermediate.

Ethylene was discovered when the byproducts of gas burning street lamps were shown to cause plant senescence in a greenhouse.

Location, Characteristics and Occasions for Synthesis Induction

• Directly induced by high levels of Auxin
• Found in germinating seeds
• Induced by root flooding
• Induced by drought
• Synthesized in nodes of stems
• Synthesized in tissues of ripening fruits
• Synthesized in response to shoot environmental, pest, or disease stress
• Synthesized in senescent leaves and flowers
• Rapidly diffuses
• Inhibiting effects of Ethylene on shoot growth (more specifically on stem elongation) reduced in the presence of light. Also Ethylene levels are decreased by light
• Released in mature cells when they do not have enough minerals and water to support both themselves and any dependent cells
• Released by all cells when they are experiencing conditions which would normally cause a mature shoot cell to produce Ethylene

Effects

• Stimulates leaf and flower senescence
• Induces leaf abscission mainly in older versus younger leaves.
• Induces seed germination
• Induces root hair growth – this increases the efficiency of water and mineral absorption
• Stimulates Epinasty – leaf petiole grows out, leaf hangs down and curls into itself
• Stimulates fruit ripening
• Induces the growth of adventitious roots during flooding
• Usually inhibits growth - just shoot growth
• Affects neighboring individuals
• Disease/wounding resistance
• Triple response when applied to seedlings – root ? and shoot growth inhibition and pronounced hypocotyl hook bending
• Inhibits stem swelling ? (Contradictory to the finding below – contradictory sources)
• Stimulates cell broadening (and lateral root growth)
• Interference with Auxin transport (when hormone levels are increasing)
• Directly or indirectly induces Auxin at high levels
• Inhibits the rate of metabolism of cells in the shoot (who are not already at their lowest metabolism rates) in response to an decrease in the levels minerals and/or water

Plant hormones	edit
Auxins - Cytokinins - Ethylene - Gibberellins - Abscisic acid - Brassinosteroids - Jasmonates - Salicylic acid

See also: Ethylene (plant hormone), 1-aminocyclopropane-1-carboxylic acid, Abscisic acid, Auxin, Brassinosteroid, Cell (biology), Cytokinin, Diffuse, Drought