How do plants make their own food?

In one line

The rule

Photosynthesis is the process by which green plants use sunlight to make food from carbon dioxide and water, releasing oxygen as a byproduct.

The formula is: 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂ Where:

• CO₂ = carbon dioxide (from air)
• H₂O = water (from soil)
• C₆H₁₂O₆ = glucose (food for the plant)
• O₂ = oxygen (released into air)

Let's understand it simply

Imagine you are making roti in the kitchen. You need flour, water, and heat. Plants also have a kitchen inside their leaves. This kitchen is called a chloroplast (the green part of the leaf). The plant takes water from the soil (like you fetch water from the tap), carbon dioxide from the air (like you breathe in), and sunlight (like the heat from your stove). Using these, the plant cooks its own food, which is a kind of sugar called glucose. Oxygen is like the steam from your cooker – it is released into the air.

How it works

1. The plant absorbs water from the soil through its roots.
2. The leaves take in carbon dioxide from the air through tiny holes called stomata (like small windows).
3. The green pigment chlorophyll in the leaves traps sunlight.
4. Inside the leaf, the energy from sunlight helps combine water and carbon dioxide to make glucose (food).
5. Oxygen is produced as a waste and goes out through the stomata.
6. The plant uses the glucose for energy and growth, and stores extra as starch (like rice or potato stores energy).

The story behind it

The word "photosynthesis" comes from Greek: "photo" means light, and "synthesis" means putting together. The process was first studied in the late 1700s. Scientists like Jan Ingenhousz (from the Netherlands) discovered that plants need sunlight to make oxygen. Later, Joseph Priestley (England) showed that plants clean the air. These discoveries helped us understand that plants are the base of all food chains, making food from sunlight.

Where you see it in real life

• A potted tulsi plant on your balcony: It grows well in sunlight, but looks weak in the dark. This is because it needs sunlight for photosynthesis.
• A banyan tree in the park: Its big leaves catch more sunlight, making more food for the huge tree.
• Rice fields during monsoon: The green paddy uses rainwater and sunlight to grow fast.
• Algae in a village pond: The green layer on water is algae, making food by photosynthesis.
• Coriander leaves in your kitchen garden: They grow bushy in sunlight, but become pale and thin if kept inside.
• A closed classroom with a plant: The plant may survive for a while, but without sunlight, it cannot make food and will die.

Why it matters

• All food starts with plants: Even if you eat chicken or fish, those animals eat plants or plant-eating animals.
• Oxygen for breathing: Plants release oxygen, which we and animals need to live.
• Basis of food chains and food webs: Plants are the first step (producers) in every food chain.
• Climate and environment: Plants absorb carbon dioxide, helping to keep the air clean and cool.

Worked example

Let's say a plant is kept in sunlight with enough water and air. What will happen?

Given: Sunlight, water, carbon dioxide available
Step 1: Plant absorbs water from soil
Step 2: Leaves take in carbon dioxide from air
Step 3: Chlorophyll traps sunlight energy
Step 4: Photosynthesis happens: 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂
Step 5: Plant makes glucose (food) and releases oxygen
Answer: The plant grows and gives out oxygen

Common mistakes

• Thinking plants "eat" soil: Plants take water and minerals from soil, but make food from air and water using sunlight.
• Forgetting the role of sunlight: Without sunlight, photosynthesis cannot happen, even if water and air are present.
• Mixing up oxygen and carbon dioxide: Plants take in carbon dioxide and give out oxygen during photosynthesis (not the other way around).
• Believing only leaves do photosynthesis: Mostly leaves, but green stems and some fruits can also do it if they have chlorophyll.

Remember it

Plants are nature’s cooks: they use sunlight, water, and air to make food and give us oxygen.