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← 🌱 Biology · usually met in Std 6-12

Photosynthesis

Plants using light to build sugar out of carbon dioxide and water. Almost every meal you have ever eaten traces back to it.

sunlight the leaf carbon dioxide water (from the roots) oxygen, out glucose — stored as starch the plant's body, and your food Leaves are green because chlorophyll uses red and blue light and reflects the green.
Drawn for Star Student.
A green leaf, lit from behind
Md.Farhan Nabil · CC BY-SA 4.0 ↗ · where it came from ↗

In the chloroplasts of green cells, chlorophyll absorbs light and uses that energy to combine carbon dioxide from the air with water from the roots, producing glucose and releasing oxygen. The plant stores the glucose as starch, builds its body from it, and later breaks it down for energy through respiration.

This single process is the base of nearly every food chain on Earth, and the source of nearly all the oxygen in the air. The leaf is built for the job: broad and flat for light, thin for gas diffusion, veined for supply, and dotted underneath with stomata — tiny mouths that open to let carbon dioxide in and inevitably let water vapour out, which is the compromise every land plant lives with.

Worth knowing

  • Leaves look green because chlorophyll absorbs red and blue light well and reflects green — green is the colour a plant does not use.
  • Ocean phytoplankton, not forests, produce a very large share of the world's oxygen.
  • Autumn leaves turn colour when chlorophyll breaks down and the other pigments that were always there become visible.

Want to see it moving? Search YouTube for “Photosynthesis” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.

See also

🌱 Respiration🌱 The cell🌦️ The carbon cycle

🧭 Do not take our word for it

This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.

Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus. Zoological Survey of India ↗India's animal life, surveyed and catalogued since 1916.

Last gone through: 1 October 2026 · How these entries are written

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