What is "thermotropism"

Thermotropism \Ther*mot"ro*pism\, n. [Thermo- + Gr. ? to turn.] (Bot.) The phenomenon of turning towards a source of warmth, seen in the growing parts of some plants.

n. (context botany English) thermotropic movement of a plant or plant part in response to changes in temperature.

Thermotropism or thermotropic movement is the movement of a plant or part of a plant in response to a change in temperature. A common example is the curling of Rhododendron leaves in response to cold temperatures. Mimosa pudica also show thermotropism by the collapsing of leaf petioles leading to the folding of leaflets, when temperature drops.

The term "thermotropism" was originated by French botanist Philippe Van Tieghem in his 1884 textbook Traité de botanique. Van Tieghem stated that a plant irradiated with an optimum growth temperature on one side laterally, and a much higher or lower temperature on the opposite side, would exhibit faster growth on the side exposed to optimum temperature.

The precise physiological mechanism enabling plant thermotropism is not yet understood. It has been noted that one of the earliest physiological responses by plants to cooling is an influx of calcium ions from the cell walls into the cytosol, which increases calcium ion concentration in the intracellular space. This calcium influx is dependent upon mechanical changes in the actin cytoskeleton that alter the fluidity of the cell membrane, which allows calcium ion channels to open. From this information, a hypothesis has formed that the plant cell plasma membrane is an important site of plant temperature perception.