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Coordination in plants

source of light. This occurs when a stationary plant receives light from one side. For
example, light streaming in a window from one direction will often cause the stems of
plants to bend toward the light source after a few days (Figure 1.1).

Investigation of tropisms in plants
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Experiment 1.1

Investigating the effect of light on plant seedling
Aim: Investigating phototropism in shoots
Materials
Two potted bean plant seedlings, two cardboard boxes, clinostat and source of light
Procedure
1. Select two potted bean seedling which are at the similar stage of growth. Place
one bean seedling in a cardboard box labelled “A” with window cut on one side
of the cardboard that allows light to pass through and reach the bean seedling
from only one direction.
2. Place the second potted bean seedling in another cardboard labelled “B” which
also has a window cut on one side, but the second bean seedling should be placed
on a slowly rotating clinostat that allows the potted bean seedling to rotate so that
light can reach all sides of the seedling.
3. After seven days, remove the two potted plants from the cardboard boxes and
observe them carefully. See Figure 1.1.

Cardboard box
“A” “B”

A hole in the box
allows light entry
Seedling

Clinostat

Bench
(a) Experimental set (b) Control set

Figure 1.1: Experiment set up to investigate phototropism in shoots
Observation
(a) Note down what you have observed.
(b) Describe your observations.

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