Are the plants colour sensitive?
Prior to working out the details of the project Nelly grasped it
with the help of this diagram. Can they distinguish a colour and
grow towards that? The results of this experiment may even help
NASA who are trying to grow plants in space vehicles bound to
It is a well known fact that the plants grow towards light. This
sensitivity is exhibited in many ways. The sunflowers follow the
sun from dawn to dusk. For what purpose? No body seems to know.
Lotus flowers open in the morning and close as the sun sets. The
compound leaves of the legume family close at night. It is
generally believed that this is an adaptation to reduce the loss
of water. But even when there is a plentiful supply of water
they continue this exercise.
Plants need light for the vital function of ‘photosynthesis’.
(Making of food by combining carbon dioxide and water using
light energy) This can be performed only by the green matter
called Chlorophyll. These are generally the leaves and the young
shoots. What about the other growing parts that lack
chlorophyll, such as the roots? Do they grow towards
light(Positive) or away from light (Negative) or remain
Lights have colours. Sunlight is supposed to be white. (not at
sun rise or sun set) The human eye is capable of differentiating
six to seven colours. [ROY Grows Blue Violets…
Red,Orange,Yellow,Green,Blue and Violet] Some animals are
believed to see ultra violet and infra red too. How many colours
can the plants detect? What are these colours? What experiments
can we devise and carry out in order to solve this problem? Lack
of which colour will make some leaves fold?
To find the Favourite colour of seedlings.
When baby shoots and the roots are coming out of the seeds they
are called seedlings. Ali wanted to find out which colour will
attract the baby shoots and the roots. He took a light proof
circular box and fixed three LEDs on the sides. LEDs have been
chosen as they need very low current. They were connected to a
battery as shown here. The blue circle shows the negative wire
while the positive is shown by the red circle. Three seedlings,
may be mustard, green gram or any other were placed in the
centre. They could be horizontally placed on moist paper. The
box has to be covered from above. Lights have to be switched on
only after the roots and shoots have come out.
To find the colour that will accelerate plant growth.
Ali and Nelly planned this experiment using the stored up Wesak
lanterns (buckets). These are weather resistant and allow only
certain colours to pass through. By placing the cover over a few
stones it is possible to allow some ventilation. It was a long
term experiment that had to be done in the garden.
They selected a few plants of the same kind and size in their
garden. Two plants are shown in the diagram.
Each one is covered with water proof coloured paper.
The first plant receives only red light while the other one gets
only blue light. The wire which is used to hang the lantern is
cut in the middle and used to tie the lantern to pegs in the
ground. Some stones or sticks may be kept at the base to permit
ventilation. It is very important to attend to the needs of the
plants. The soil must supply air, water and the mineral salts.
All plants must receive the same amount of sunlight. They must
be protected from insects etc.
The number of similar experiments that could be done will depend
only on your ingenuity. If you do these experiments, and
maintain reports your teachers will help you to prepare them for
publication in the school magazine, or you may even send them to