Thermotropism


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Thermotropism

 

in plants, the bending of growing parts, such as the stems or root tips, in response to a heat stimulus. Thermotropism may be observed by placing rootlets in moist sawdust between two vessels—one filled with cold water and one with warm water. Up to a certain temperature the rootlets bend in the direction of the warmer vessel (positive thermotropism); above that temperature they bend toward the cooler vessel (negative thermotropism).