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Life Processes in Plants - Do Plants Respire?

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Respiration is the process by which living organisms, including plants, break down glucose to release energy for various cellular activities.

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Unlike photosynthesis, which occurs only in the presence of sunlight, respiration occurs continuously in all living cells of the plant, both day and night.

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In plants, the exchange of gases (Oxygen and Carbon dioxide) takes place through tiny pores called stomata, primarily located on the surface of leaves.

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The roots of plants also respire to generate energy for absorbing water and minerals. They take in air from the air spaces present between the soil particles using root hairs.

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During aerobic respiration, glucose is broken down in the presence of O2O_2 to produce CO2CO_2, H2OH_2O, and energy.

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If a potted plant is overwatered, the air spaces in the soil are occupied by water, preventing the roots from taking in oxygen, which can lead to the death of the plant due to lack of aerobic respiration.

📐Formulae

Glucose+Oxygen→Carbon dioxide+Water+Energy\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon dioxide} + \text{Water} + \text{Energy}

C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

💡Examples

Problem 1:

During the daytime, a plant is performing both photosynthesis and respiration. Explain the net gaseous exchange.

Solution:

During the day, the rate of photosynthesis is higher than the rate of respiration. Therefore, the CO2CO_2 produced during respiration is reused for photosynthesis, and more O2O_2 is released into the atmosphere.

Explanation:

Photosynthesis uses CO2CO_2 and releases O2O_2, while respiration uses O2O_2 and releases CO2CO_2. At day, the consumption of CO2CO_2 for food production exceeds its production via respiration.

Problem 2:

Why is it advised not to sleep under a tree at night?

Solution:

At night, photosynthesis stops due to the absence of sunlight, but respiration continues. This leads to an increase in the concentration of CO2CO_2 and a decrease in O2O_2 around the tree.

Explanation:

Since the tree is only performing respiration at night, it releases CO2CO_2 as a byproduct, which can make the immediate surrounding air less oxygen-rich for humans.

Problem 3:

What happens to the rate of respiration if the soil becomes waterlogged?

Solution:

The rate of aerobic respiration in roots decreases significantly because the water fills the air spaces in the soil, cutting off the supply of O2O_2.

Explanation:

Roots need O2O_2 from soil air spaces. In waterlogged conditions, they may switch to anaerobic respiration or fail to produce enough energy, eventually causing root rot.