Question

How will you measure the rate of growth? Describe an instrument used to measure the increase in height of an angiosperm plant.

Answer 1

Growth is a quantitative phenomenon that can be measured in relation to time. The growth of plants can be measured in terms of: Increase in length or height, Increase in area or volume, Increase in the number of cells.

Complete answer:
The length of a plant or plant organ can be easily measured by an ordinary measuring scale called auxanometer. Auxanometer is a device that measures the rate of growth of shoots of plants and measures accurate and tentative growth of plants. This device also known as an arc-indicator is defined as an apparatus that is used for measuring the growth in plants. The device named auxanometer is the reason behind this, auxin stands for grows and metron stands for the measurement.

To use this device, firstly a thread is tied to the growing tip of a plant and the thread is hung on the pulley of the auxanometer, and the other end of the thread is bound to weight. The pulley is tied with a long needle, which slides over a graduated arc, if the plant grows in length the weight pulls the thread down. This movement of the needle is read on the scale of the arc which indicates the growth.

Additional information:

Limitation of Auxanometer
At a present time, a thread is used to pass on the motion of the growing plant to a record by the device. This construction is always faulty because the change in humidity affects the length of the thread, and so falsifies the records.

Strength Modified Auxanometer
The author has designed a machine that eliminates the thread and its unavoidable errors by substituting for its material which is not affected by humidity and which is very little altered by a change in temperature.
Frost who modified the Auxanometer, in this Frosts used thread, but as the growth was recorded electrically to give an accurate growth rate of the plant. Frosts' model consists essentially of a device which is carried upward as the plant grows.

Note: Angiosperm plants or flowering plants are vascular plants with stem, roots, and leaves. The seeds of angiosperm plants are found inside the flower, and seed develops inside the organ, so the seeds are closed; they are the most abundant plant category found on the earth.