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 growth hormone, produced at the tips of shoots and roots, that stimulates cell elongation, maintains apical dominance and controls tropisms.
- tropism
- A directional growth response of a plant towards or away from a directional stimulus such as light or gravity.
- electron transport chain
- A series of protein complexes in the inner mitochondrial (or thylakoid) membrane that pass electrons along a chain of redox reactions, pumping protons across the membrane to generate a proton gradient.
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 AQA A-level Biology topics