Plant Structures
Plants need a number of substances in order to grow. These substances
include carbon dioxide, water and sunlight.
Plants get carbon dioxide from the atmosphere. The plant absorbs carbon
dioxide through the leaves, where it can get to the cells where it is needed.
The leaves also take in sunlight through the upper surface, where it can also
enter cells within the leaf.
Plants get water into their cells in a number of ways. Plants can absorb water
through their roots, where the water travels up the stem and is transported
around the plant. Plants also take in water vapour from the atmosphere into
the leaves, where it can be used in photosynthesis.
Plants and Soil
Lots of people think that plants get their food from the soil. In fact, plants
produce their own food through a chemical reaction called photosynthesis. If
you think about it, plants couldn’t get all their food from the soil. Think about
the number of plants in the world – in forests, rain forests, grassland etc. If
they were all taking food out of the soil, very quickly there wouldn’t be enough
soil left!
Plants do take in water from the soil. This water gets into the soil when it rains
or through lakes, rivers and the sea.
Plants also take in mineral ions from the soil which they need to be healthy,
just like humans need vitamins and minerals. However, this is not their food.
Plants use glucose as their food source, which they make through
photosynthesis.
Photosynthesis
Green plants do not absorb all their food from the soil, and they do not eat it
like we do. Plants make or synthesise their food in a reaction called
photosynthesis. This uses the raw materials carbon dioxide from the air and
water from the soil to make glucose. This reaction happens within the plant
cells. Oxygen gas is given off as a by-product.
Plant cell:
Photosynthesis needs energy, and this comes from sunlight. Plant cells have
chloroplasts which contain a green pigment called chlorophyll. This absorbs
sunlight energy and drives photosynthesis.
Word Equation:
carbon dioxide + water  glucose + oxygen