AS

PLANT HORMONES 2.1

Auxin

  • Definition and Role: Primary plant hormone promoting growth, mainly produced in actively growing tissues (meristematic).

  • Production Sites: Root tips, shoot tips, apical buds, young leaves, developing tissue clumps.

  • Physiological Roles: Regulates overall growth, fruit set/thinning (to increase fruit size), sprout inhibition (e.g., potatoes), and plant architecture/shaping.

  • Light and Growth: Involved in\\\\\\\ phototropic growth; plants seek light for photosynthesis.

Gibberellins

  • Definition: Hormones involved in growth and cell division, named after Gibberella fujikuroi.

  • Main Functions: Stimulates cell division and broadly promotes growth and active growth regions.

  • Flowering Control: Can trigger flowering, reducing reliance on environmental cues (e.g., in grapes and carrots).

Ethylene

  • Production: Produced in most ripening fruits, leading to coordinated ripening (e.g., bananas).

  • Uses: Facilitates uniform/controlled ripening for postharvest handling and distribution.

  • Cautions: Improper or excessive use can reduce produce quality after harvest.

Major Commercial Uses of Plant Hormones

  • Auxin: Fruit thinning, sprout inhibition (potatoes), plant shaping.

  • Gibberellins: Flowering control, growth promotion.

  • Ethylene: Ripening regulation for climacteric fruits.

Real-World Relevance

  • Plant hormones are crucial tools in agriculture for managing fruit set, crop shape, flowering, and postharvest quality.

  • Applications include resource management (fruit size), supply chain optimization (storage, ripening), and shaping plants.

  • Hormones can influence or override environmental signals, impacting farming practices, sustainability, and consumer acceptance.

Terminology Notes

  • "Cytokinesis" refers to the division of the cytoplasm.

  • Gibberellins are named after the fungus Gibberella fujikuroi.

Key Takeaways for Understanding

  • Auxin: Modulates growth, controls fruit set, prevents sprouting, influences plant architecture.

  • Gibberellins: Promotes growth, regulates flowering stages, can reduce environmental cue dependence.

  • Ethylene: Central to ripening; enables controlled ripening but requires careful management to preserve quality.

  • Agricultural Applications: Hormones optimize yield, quality, and efficiency by considering crop species, development, and storage.