thermonastic

Thermonasty is a type of nastic movement in plants that is a response to a change in temperature. Nastic movements are plant movements that occur in response to a stimulus, but unlike tropisms, they are not dependent on the direction of the stimulus. In the case of thermonasty, the movement is triggered by a temperature change, and the direction of the movement is not determined by the direction of the heat or cold.

A common example of thermonasty is the opening and closing of flower petals. For instance, the petals of the tulip (Tulipa) will open when the temperature rises and close when the temperature falls. This movement is due to differential growth rates in the cells on opposite sides of the petal. When the temperature increases, cells on one side may elongate faster than those on the other, causing the petal to open. Conversely, a drop in temperature can lead to differential cell elongation in the opposite direction, causing the petal to close.

Another example is seen in the leaves of certain plants. The leaves of the dandelion (Taraxacum officinale), for example, will spread open in warmer temperatures and fold together in cooler temperatures. This thermonastic response can help the plant to regulate its temperature, either by exposing more surface area to sunlight for warmth or by reducing surface area to conserve heat. The specific mechanisms can vary between species, but they generally involve changes in turgor pressure within specialized cells or differential cell elongation.