Ans.

An auxanometer is an apparatus for measuring increase or rate of growth in plants. In case of an arc-auxanometer, there is a wire fixed with the plant apex on one end and a dead-weight on the other. It passes over a pulley which has a pointer attached to it. When the plant’s height increases, the pulley rotates and the pointer moves on a circular scale to directly give the magnitude of growth. The “rate of growth” is a derived measurement obtained by dividing the length of growth measured by the auxanometer, by the time said measurement took.

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