Science and Environment

What are rounded bumps and why are they important to plants?

Do you know what plants need to grow besides soil, water, and sunlight?

The essential element required for the survival of plants is nitrogen (N). Plants and animals could not live without nitrogen. It is an important part of many cells and processes such as amino acids, proteins, and even our DNA. It is also needed to make chlorophyll in plants, which plants use in photosynthesis to make their food and energy. The problem is, although the Earth’s atmosphere is made up of 78% nitrogen, the form of nitrogen found in the atmosphere cannot be used by plants.

How do plants get their nitrogen?

Either through nitrogen deposits in the soil, or through a friendly relationship with nitrogen-fixing bacteria.


Figure 1. Description of nitrogen cycle (

Let us learn through this simple and easy science experiment:

a) What are the nitrogen-fixing bacteria?

b) Why are they so important for some plants survival?

Materials needed:


clover seeds/plants

quart liter plastic bucket

tap water

paper towels

magnifying lens/simple microscope

Ready to start??


Step 1. Take out the clover plants from their roots using a trowel.


Step 2. Dip the roots of the clover plants in a bucket of water in order to remove the dirt from the roots.

Step 3. Using a paper towel blot the plants to absorb any excess water.



Step 4. Observe the roots using a magnifying lens. You can also observe the nodules under a microscope by cutting a section of the root and placing it on a microscope slide.

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What do you observe?


These tiny potatoes like structures are called as nodules. The nodules are separate and appear at different places along the roots and most of them are clumped together.

What are the functions of these nodules on roots?


Nitrogen gas makes up 78% of the earth’s atmosphere, but plants cannot use this form of nitrogen.

Then how plants take up the nitrogen for their growth and survival???

a) Here comes the role of bacteria called nitrogen-fixing bacteria that change nitrogen gas into nitrogen compounds that plants can use. Some nitrogen-fixing bacteria live in the soil, while others live on the roots of the plants as clover.

b) The bacteria enter the root hairs of the plant, and as they multiply a nodule forms. The bacteria and clover help each other.

c) The bacteria “fix” nitrogen gas so that the plant can use it, and the plant provides food for the bacteria. This process is known as symbiosis: when two organisms living together, are mutually benefitted.

Science Fair Ideas: You can observe the content of the nodules through a microscope by cutting the nodule into halves and displaying the photographs.



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