Question

Explain the procedure you have adopted in your school to prove that heat is liberated during respiration. What result we will get, if you perform this experiment with dry seeds.

Answer 1

Hint: A thermo flask along with a thermometer is used to prove that heat is liberated during respiration. As the germinating gram seeds in the thermo flask respire, the temperature in the thermometer rises indicating release of heat energy.

Complete answer:
Respiration involves utilization of glucose produced during photosynthesis and oxygen taken in through stomata to produce energy for plant growth. To prove that heat is liberated during respiration, thermo flasks with a thermometer, germinating gram seeds and boiled gram seeds are used. Some germinating seeds are placed in the thermo flask and the opening of the flask is tightly closed with a cork to prevent contamination of the seed and inlet of air. A thermometer is then introduced into the flask through the cork in such a manner that its bulb rests along the germinating seeds.

A similar setup is done for boiled gram seeds which acts as a control to the experiment. The mercury reading is then noted for both the thermo flask. During respiration, glucose is broken down into simpler molecules with the evolution of energy in the form of heat. The rise of mercury level in the thermometer denotes the rise in temperature. Such a rise in temperature is noticed in the setup with the germinating gram seeds as they are respiring while the boiled gram seeds don’t show such rapid rise in temperature. This proves that some amount of heat energy is released during respiration.

When this experiment is performed with dry seeds, no results are obtained as dry seeds show minimal respiration. The thermometer reading doesn’t change rapidly as in case of germinating gram seeds.

Note: During dry state, seeds cannot produce their own food. Hence, in order to stay alive, they depend on stored energy reserves as well as undergo cellular respiration. However, throughout dormancy, seeds respire at a low rate.