Thigmotropism
/ˌθɪɡmoʊˈtroʊpɪzəm/
Definition
Thigmotropism is a directional growth response to touch or physical contact. In plants, it occurs when contact with a support or obstacle changes growth on one side of an organ, causing it to bend toward or away from the stimulus. It is most clearly seen in climbing plants, where tendrils or twining stems wrap around supports. Unlike a simple touch response, thigmotropism involves sustained, growth-based movement rather than a quick temporary motion.
Biological Role
- Climbing support: In vines and other climbers, contact-guided growth helps shoots or tendrils find and wrap around nearby supports, improving access to light without investing as much in thick, self-supporting stems.
- Uneven growth response: Touch triggers growth changes on opposite sides of the responding organ. That unequal growth bends the organ toward or around the object it contacts.
- Common in tendrils: The response is especially visible in tendrils of plants such as peas and many cucurbits, where repeated contact can produce a tight coil that anchors the plant more securely.
- Practical observation in gardens: Gardeners often see this when climbers are placed near trellises, strings, or wires. Gentle guidance works better than force, because the plant responds after contact rather than being tied into every turn.
Related Terms
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