List of top two experiments to demonstrate plant growth:- 1. Measurement of Vertical Growth by Auxanometer 2. Measurement of Vertical Growth by Drum Auxanometers.
Experiment # 1. Measurement of Vertical Growth by Auxanometer (Arc-Indicator):
Materials and Equipments Required:
1. Instrument:
It is a metallic sextant scale (in angular degrees) fitted to a vertical stand by means of arms which meet forming a right angle with each other. At this end they are fixed to an axle fitted with a pulley. The axle holds a pointer which can move up and down the sextant scale when the pulley rotates (Fig. 3.30A).
2. Potted plants
3. Thread with weight
Procedure:
1. Tie a thread to the tip of a potted plant and fix it to the pulley of the arc indicator by a weight.
2. Record the initial reading of the points and allow the plant to grow for a few days. Record the measurement of the pointer at regular intervals, say, 24 hours.
Observations:
As the plant grows in height the pulley rotates by the downward movement of the weight. With the rotation of the axle the pointer moves on the sextant scale and this movement is proportional to the growth in height of the plant.
Result:
By recording the movement of the pointer by angular degrees at particular intervals the growth rate of the plant can be measured:
One angular degree = π/180 = 3.142/180
In linear measurement one angular degree = 3.142/180 × radius of the arc (cm).
Experiment # 2. Measurement of Vertical Growth by Drum Auxanometers:
Materials and Equipments Required:
1. Instrument:
Drum Auxanometer — This is a complex instrument. It consists of a revolving (by a clockwork) drum with a smoked paper pasted on it. The apical region of a growing potted plant is tied with one end of a thread which passes over a pulley holding a weight at the other end.
The pulley is fixed to a vertical stand. Another thread passing over a bigger pulley holds a weight at one end while, to the other end, a pointer is fixed horizontally in such a way that only the sharp end of the pointer just touches the surface of the smoked paper and its course of movement can be traced on the paper.
2. Potted plant.
Procedure:
1. Tie the apex of a potted plant with one end of a thread which passes over a pulley holding a weight at the other end. Adjust the revolving drum in the manner as stated before and turn on the clockwork.
2. Note the pointer reading at regular intervals (both Day and Night) which is done automatically.
Observations:
As the short apex grows in height the hanging weight pulls the pointer upward and, as the drum rotates (once in every hour), the pointer traces its path on the smoked paper.
Results:
The perpendicular distances between tracings on the drum indicate proportional hourly growth. It should be noted that such distances are longer at night compared to day indicating increased growth during the hours of darkness.