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A-Level Biology OCR A

Abscission Leaf Falling Describe Role Plant Hormones Loss

Falling light levels reduce auxin, prompting leaves to produce ethene, which initiates enzyme production in the abscission zone, digesting cell walls and leading to leaf fall.

La baisse des niveaux de lumière réduit l'auxine, provoquant la production d'éthylène qui initie la production d'enzymes dans la zone d'abscission, digérant les parois cellulaires et menant à la chute des feuilles.

Front Describe the role of plant hormones in leaf loss in deciduous plants.
Back Abscission & leaf fall:
  • Falling light levels result in falling concentrations of auxin
  • Leaves respond by producing ethene
  • This initiates gene switching in cells of abscission zone, resulting in production of new enzymes
  • They digest and weaken cell walls in outer layer of abscission zone
  • Vascular bundles carrying materials out of leaf are sealed off
  • Abscission occurs

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