Geotropism
/ˌdʒiˈɑtrəˌpɪzəm/
Definition
Geotropism describes a plant growth response to gravity, a biological concept in which direction of growth changes according to gravitational pull. Roots usually show positive geotropism by growing downward, while shoots show negative geotropism by growing upward. Unlike movement caused by touch or light, this is driven by gravity sensing in plant tissues and helps orient roots for anchorage and water uptake and shoots toward the surface.
Biological Role
- Root anchorage and water access: In most plants, this response directs primary roots downward, helping seedlings anchor quickly and reach deeper moisture and mineral-rich soil layers.
- Shoot orientation after germination: Stems usually grow in the opposite direction, which lifts leaves toward light and keeps new growth positioned for photosynthesis after a seed sprouts or a pot is tipped.
- Hormone-driven bending: The growth change is controlled largely by auxin, a plant hormone. Uneven auxin distribution causes cells on one side of a root or stem to elongate differently, producing curvature.
- Propagation and transplanting clues: Cuttings, bulbs, and germinating seeds often reorient themselves after being moved. This helps explain why upside-down placement can slow establishment even when the plant later corrects its direction.
Related Terms
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Stem
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Phototropism
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Hydrotropism
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Thigmotropism
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Radicle
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