Nutrition in Plants and Photosynthesis: Class 7 Study Guide
Plants make their own food. Almost all other life depends on them.
All living things need nutrition, the process of getting and using food. Green plants are autotrophs (self-feeders): they make their own food by photosynthesis. Animals and fungi are heterotrophs that depend on others for food.
In photosynthesis, the green pigment chlorophyll in the leaves captures energy from sunlight. The plant uses carbon dioxide from the air (taken in through tiny pores called stomata) and water from the soil (taken in by the roots) to make glucose (a sugar), releasing oxygen.
Photosynthesis summary
Carried up through the stem.
From the air.
In the leaf.
Food is stored as starch.
Other kinds of plant nutrition
Not all plants make all of their food. Parasites such as the dodder (Amarbel) take food from a host plant. Insectivorous plants such as the pitcher plant trap and digest insects to get extra nitrogen. Saprotrophs such as mushrooms and moulds feed on dead matter. In symbiosis two organisms live together to help each other, as with a fungus and an alga in lichens, or bacteria in the roots of pulses that make nitrogen usable.
| Type | How it gets food | Example |
|---|---|---|
| Autotroph | photosynthesis | mango tree, grass |
| Parasite | from a living host | dodder (Amarbel) |
| Insectivorous | traps insects | pitcher plant |
| Saprotroph | dead matter | mushroom, bread mould |
| Symbiosis | both partners benefit | lichen, root nodules |
Why it matters
Photosynthesis supplies the oxygen we breathe and the food at the base of every food chain. Leaves are broad and thin to capture light. Experiments show that leaves kept in the dark for some days do not form starch (iodine test), while leaves in light do. Protecting forests and growing more plants helps keep a balance of gases in the air.
Worked example and common misconceptions
Example: A plant on a window sill grows toward the light because it needs light for photosynthesis. Common misconceptions: believing plants take their food from the soil (they take water and minerals, but make food from air and water), and thinking plants do not respire (they respire day and night). Test starch in a leaf with iodine solution, with an adult's help.
Check your understanding: model answers
1. Chlorophyll. 2. Dodder (Amarbel). 3. Oxygen.
✨ Key Takeaways
- Green plants make food by photosynthesis.
- They need sunlight, water and carbon dioxide.
- Chlorophyll captures light energy.
- Oxygen is released.
💬 Questions for Discussion & Reflection
- Name the green pigment in leaves.
- Give an example of a parasitic plant.
- What gas is released in photosynthesis?
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