Observation of Geotropism Activity in Gram Seeds

What is Geotropism?

The tropic movement in response to the earth’s gravity is called geotropism or gravitropism.

Plant gravitropism can either be a positive or a negative response.

Unilateral gravity causes curvature in the region of elongation of stem and root. The tip of the stem grows away from the gravity (negative geotropism), and the root tips grow towards it (positive geotropism). Geotropism is also referred to as gravitropism.

Charles Darwin was the first scientist to scientifically prove that roots show positive gravitropism and stems show negative gravitropism.

Explore more: Geotropism

Geotropism Activity in Gram Seeds

Here is an experiment to observe the geotropism activity in gram seeds.

Experiment – No – 1

Aim:

To observe the geotropism activity in gram seeds.

Materials required:

Soaked gram seeds, beaker, water, water spray gun, garden soil, wooden or stone slabs and black paper.

Procedure:

• Collect some good quality seeds of gram or moong.
• Wash and soak the selected seeds in warm water for a day.
• Take a clean and dried plastic beaker of medium size.
• With the help of a sharp-pointed object, make big holes of 2 mm diameter at the bottom of the beaker.
• Now fill the beaker with a 1 cm thick layer of garden soil.
• Spread soaked seeds (moong/gram) over the soil.
• Now gently spray water on the soaked seeds with the help of a water spray gun.
• Place the beaker on two pieces of wooden slabs or stone slabs without disturbing them.
• Make sure that there is enough gap between the table and the bottom of the beaker.
• Cover the lower part of the set-up with black paper.
• Keep spraying water on the soaked seeds regularly.

Observation and Result:

After some days, we can observe small tender roots coming out from the holes of the beaker and growing towards the earth. This experiment demonstrates positive geotropism.

Experiment – No – 2

Aim:

To observe the geotropism activity in gram seeds.

Materials required:

Soaked gram seeds, four Petri dishes, cotton, stand, water, and marker.

Procedure:

• Collect some good quality gram seeds
• Wash and soak the selected seeds in warm water for one day.
• Take clean and dried Petri dishes.
• Spread the cotton in the Petri dishes.
• Now add soaked seeds in between the cotton and close the Petri dishes.
• With the help of a marker, label the Petri dishes as north, south, east and west.
• Fix the labelled Petri dishes on a stand and allow the seeds to grow.

Observation:

After some days, we can observe the changes in the position of the Petri dishes.

The stem and root show curvature. It is found that:

• The stem always moves upwards. Hence, it shows negative geotropism.
• The root always bends downwards. Hence, it shows positive geotropism.

Result

It is considered that the root cap receives the stimulus of gravity.

In case the root tips were removed from the roots of the plant. They would not respond to gravity.

Hence, it is considered that the root cap delivers an inhibitor on the lower side of the roots. Thus, it prevents growth, and the root bends down.

This was a brief introduction to the geotropism activity in gram seeds.

To know more about geotropism, geotropism in roots and shoots, types of tropic movements in plants and important questions on geotropism, keep visiting our website, at BYJU’S Biology.