Plants respire too

All living beings respire. Do plants respire like we do? Activity 10.8 finds out, as a teacher demonstration.

Soak some moong seeds overnight. Put a layer of wet cotton in a conical flask and place the soaked seeds on it. Close the flask with a cork with two holes, fit two tubes through them, and leave it in the dark for 24 hours.

Take two test tubes of lime water. Cork one, dip a glass tube into it, and connect it to the flask with a rubber pipe. Leave the other test tube as it is, for comparison.

The lime water connected to the flask turns milky; the other does not.

Lime water turns milky with carbon dioxide. Air has only a tiny amount of carbon dioxide, so the extra must have come from the seeds, as they respired.

In respiration, glucose is broken down with oxygen, giving carbon dioxide, water and energy:

• Glucose + Oxygen → Carbon dioxide + Water + Energy

This is exactly the same as respiration in animals. Notice that it is photosynthesis turned around.

Plants use the energy from respiration to grow and develop. And every part of a plant respires — green or not, leaves, stems, roots and seeds — all the time, day and night. Photosynthesis happens only in green parts, and only in light.

So plants have their own ways to make, move and use food to get energy.