Tropisms and Auxin

Also called

tropism · phototropism · geotropism · gravitropism · hydrotropism · chemotropism · thigmotropism · auxin · plant hormones · plant movements · seedling bends towards light · tendril coils · root grows down shoot grows up · pollen tube · directional growth · अनुवर्तन · प्रकाशानुवर्तन · ऑक्सिन

Topics

• A tropism is a growth movement of a plant part towards or away from a stimulus such as light, gravity or touch.
• Shoots bend towards light (positive phototropism); roots grow away from it.
• Auxin, made at the shoot tip, moves to the shaded side; those cells grow longer, so the shoot curves towards the light.
• Roots grow down towards gravity (positive geotropism) and shoots grow up, away from it.
• A tendril touching a support grows faster on the side away from the support, so it coils round it (thigmotropism).
• A pollen tube grows down the style towards chemicals released by the ovule: this is chemotropism.
• Roots also grow towards water (hydrotropism).
• Tropic movements are slow because they happen by growth; touch-sensitive leaf folding is not growth and is much faster.

About this model

A GLB file of about 363 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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