Describe an experiment to measure the growth of a plant.

Explanation

1. The increase in the lentht of the stem tip can easily be measured by an arc auxanometer which consists of a small pulley to the axis of which is attached a long pointer sliding over a graduated arc.
2. A thread one end of which is tied to the stem tip and another end to a weight passes over the pulley tightly.

3. As soon as the stem tip increases in lenght, the pulley moves and the pointer slide over the graduated arc.
4. The reading is taken. The actual increase in the lenght of the stem is then calculated by knowing the lenght of the pointer and the radius of the pulley. If the radius of the pulley is 4 inches and the lenght of pointer 20 inches the actual growth is measured as follows:
Actual growth in lenght
`=("Distance traavelled by the pointer"xx"radius of the pulley")/("Lenght of the pointer")`
For example, actual growth in lenght
`=(10xx4"inches")/(20"inches")=2"inches"`.