How do plants make food from sunlight?

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 + light energy → C₆H₁₂O₆ + 6O₂

• CO₂ = carbon dioxide (from air)
• H₂O = water (from soil)
• C₆H₁₂O₆ = glucose (a type of sugar, the plant's food)
• O₂ = oxygen (given out into the air)

Let's understand it simply

Imagine you are making roti in the kitchen. You need flour, water, and heat from the stove. Plants do something similar, but instead of flour, they use carbon dioxide from the air, and instead of a stove, they use sunlight. The green part of the leaf acts like a tiny kitchen. It takes in sunlight, mixes it with water from the soil and carbon dioxide from the air, and cooks up food (sugar) for the plant. Just like you get energy from eating roti, the plant gets energy from this sugar.

How it works

1. The plant's roots absorb water from the soil.
2. The leaves take in carbon dioxide from the air through tiny holes called stomata (like small mouths).
3. The green part of the leaf (chlorophyll) catches sunlight, just like a solar panel on a roof.
4. The leaf uses the sunlight's energy to mix water and carbon dioxide and make glucose (sugar) and oxygen.
5. The plant keeps the glucose for energy and growth, and releases the oxygen back into the air.
6. This whole process is called photosynthesis (photo = light, synthesis = making something).

The story behind it

The word "photosynthesis" comes from Greek: "photo" means light, and "synthesis" means putting together. Scientists started to understand photosynthesis in the 1700s. Jan Ingenhousz, a Dutch scientist, showed in 1779 that plants need sunlight to make oxygen. Before that, people did not know how plants made their food. The discovery helped us understand why plants are so important for life on Earth.

Where you see it in real life

• A potted money plant near a window: It grows better in sunlight because it can make more food.
• A field of wheat in Punjab: The green leaves catch sunlight to make grains for our rotis.
• A mango tree in summer: The tree uses sunlight to make sweet mangoes.
• A kitchen garden at home: Spinach and coriander grow faster in sunny spots because they make more food.
• A sunflower turning towards the sun: It tries to catch as much sunlight as possible for photosynthesis.
• Algae in a village pond: Even tiny green plants in water use sunlight to make food, making the water green.

Why it matters

• All our food starts with plants: Whether you eat dal, rice, or vegetables, the energy in your food comes from plants making food from sunlight.
• Oxygen for breathing: The oxygen we breathe is a gift from plants doing photosynthesis.
• Farming and crops: Farmers depend on sunlight for healthy crops, which feed the whole country.
• Climate and environment: Plants take in carbon dioxide, helping keep the air clean and cool.

Worked example

Let's see how much oxygen a plant can make in a day:

Given: 1 plant can release about 5 ml of oxygen per hour in sunlight
Step 1: Find oxygen released in 12 hours (daytime)
Step 2: 5 ml/hour × 12 hours = 60 ml
Step 3: Answer: The plant releases about 60 ml of oxygen in a day

Common mistakes

• Thinking plants eat soil: Plants use water and minerals from soil, but make food from air (CO₂) and water using sunlight.
• Forgetting the role of sunlight: No sunlight means no photosynthesis, so plants can't make food in the dark.
• Believing only leaves do photosynthesis: Mostly leaves, but green stems can also do it if they have chlorophyll.
• Mixing up oxygen and carbon dioxide: Plants take in carbon dioxide and give out oxygen during photosynthesis.

Remember it

Plants are like tiny chefs: they use sunlight, water, and air to cook up their own food and give us oxygen.