Photo means light and synthesis means put together.

Photosynthesis is how plants use light and water to make sugar. Sugar is created in the green parts of a plant and every animal on Earth depends on it. Without plants we would have no food to eat or oxygen to breathe. Here is a picture to show how it happens.


Plants absorb a common gas called carbon dioxide, pull water up through their roots and use light to make sugar. Plants use the sugar to grow. Plants give off oxygen as a by-product. The green parts of the plant makes the sugar and oxygen.


Carbon dioxide + water + sunlight = sugar + oxygen



  • Put a bean plant into a dark room or cupboard. Water it as often as the other plants, watch what happens over a few weeks.
  • Put a plant into a partitioned box. Observe how it bends and twists to get to the light.
  • Keep some plants in natural light.
  • Compare all three plants.

Consider the vines in a rain forest. Why do these cling to trees and grow upwards?

Why might we choose the sunniest place in the garden to grow vegetables and fruit?