BRAINCAKETropisms
Tropisms are directional growth responses to stimuli. Examples are phototropism in response to light and geotropism in response to gravity. If plants are exposed to light on one side only, shoots will grow towards the light (positively phototropic) and roots will grow away from the light source (negatively phototropic). If roots emerge from the soil due to heavy rain etc., they will rapidly return to the soil.
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Key terms in this lesson
- Auxin
- A plant hormone, produced mainly at shoot and root tips, that stimulates cell elongation and controls tropisms and apical dominance.
- Geotropism
- Growth of a plant shoot or root in response to the direction of gravity.
- Electron transport chain
- A series of protein complexes and electron carriers in the inner mitochondrial (or thylakoid) membrane that pass electrons along in redox reactions, releasing energy used to pump protons across the membrane.
More in Plant Responses
- Stomatal Control
- Chemical Defences
- Pheromones
- Response to Touch
- Growing inthe Dark
- Geotropism
- Fruit Ripening
- Rooting Powder
All 19 lessons in Plant Responses · All OCR A-level Biology topics