BRAINCAKEPlant Hormones
- Auxins produced at the tops of roots and shoots cause cell elongation, prevent leaf abscission, maintain apical dominance, control tropisms and stimulate the release of ethene for fruit ripening.
- Gibberellins cause stem elongation, the breaking of dormancy and the use of food stores during germination and pollen tube growth during fertilisation.
- Ethene causes fruit ripening and leaf fall.
- ABA (abscisic acid) maintains dormancy, stimulates antifreeze production and stomatal closing in response to abiotic stress.
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Key terms in this lesson
- Hormone
- A chemical messenger, secreted directly into the blood by an endocrine gland, that travels to target cells and alters their activity.
- Tropism
- A directional growth response of a plant towards or away from a directional stimulus, such as light or gravity.
- Apical dominance
- The suppression of the growth of lateral (side) buds by auxin produced in the apical (tip) bud.
- Abscission
- The shedding of leaves, or fruit, from a plant, brought about by enzymes that digest cell walls in the abscission zone.
More in Plant Responses
- Plant Growth Responses
- Seed Germination
- Apical Dominance
- Gibberellins: Synergy and Antagonism.
- Leaf Loss
- Flowering and Day-Length
- Preventing Freezing
- Stomatal Control
All 19 lessons in Plant Responses · All OCR A-level Biology topics