Nastic movement
/ˈnæstɪk ˈmuvmənt/
Definition
Nastic movement describes a plant movement triggered by a stimulus such as touch, light, temperature, or day-night change, but not directed by the stimulus’s source. It is a biological concept that differs from tropisms, where growth follows a stimulus direction. In plants, nastic movement usually results from changes in cell water pressure or growth rates in specialized tissues, as seen when Mimosa pudica leaflets fold after touch or flowers open and close with light.
Biological Role
- Rapid responses without growth: Unlike tropic responses, these movements usually come from changes in cell water pressure rather than new tissue growth, so they can happen quickly and often reverse.
- Protection and resource balance: Leaf folding or closing can reduce water loss, limit damage from touch or heavy rain, and help some species protect pollen or other delicate tissues.
- Common examples in plants: Well-known cases include Mimosa pudica folding after touch and many legumes raising or lowering leaves between day and night through a structure called the pulvinus, a swollen joint at the leaf base.
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