Auxanometer

An auxanometer (Gr. auxain, "to grow" + metron, "measure") is an apparatus used to measure the increase or rate of growth of plants.

Arc-auxanometers (shown right) have a wire fixed, with the plant apex on one end and a dead-weight on another. It passes over a pulley that has a pointer attached to it. The the height of the plant increases, the pulley will rotate, and the pointer moves on a circular scale to directly give the magnitude of the plant's growth.

Sensitive auxanometers allow measurement of growth as small as a micrometer, which allows measurement in growth of response to short-term changes in atmospheric composition. Auxanometers are used in the laboratory, the field, and classrooms.