physiological role of ethylene

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 Ethylene is a gaseous plant hormone that plays a crucial role in various aspects of plant growth, development, and stress responses. Its physiological roles include:

  • Fruit Ripening: Ethylene is renowned for its role in initiating and accelerating the ripening process in climacteric fruits (e.g., tomatoes, bananas, apples). It stimulates changes in color, texture, aroma, and sugar content.
  • Senescence: It promotes the aging and eventual death of plant tissues, including leaves, flowers, and fruits, leading to their decline.
  • Abscission: Ethylene is a key regulator of abscission, the shedding of leaves, flowers, and fruits from the plant. It promotes the formation of the abscission layer at the base of the plant part.
  • Seed Germination: In some species, ethylene can break seed dormancy and promote germination.
  • Root and Shoot Growth and Development:
    • Triple Response: In developing seedlings, high concentrations of ethylene can induce the "triple response," characterized by inhibited hypocotyl elongation, increased radial swelling, and altered apical hook curvature, especially when growing through soil.
    • It can influence root hair formation and lateral root development.
  • Stress Responses: Ethylene production is often induced by various environmental stresses, such as:
    • Wounding: It plays a role in wound healing and defense responses.
    • Flooding (Hypoxia): It promotes responses to waterlogging, such as accelerated senescence of submerged leaves and the formation of aerenchyma (air channels) in roots.
    • Pathogen Attack: It modulates plant defense mechanisms against pathogens.
  • Flower Development: Ethylene can influence flower senescence, sex determination in some monoecious plants, and the development of specific floral structures.

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