Plants

Plants are living things that make their own food using sunlight, water and carbon dioxide. Every blade of grass, every flower, every shrub and every giant tree is doing the same trick: turning sunlight into stored chemical energy through a process called photosynthesis. Plants form the foundation of almost every food chain on Earth and produce most of the oxygen in our atmosphere. There are around 390,000 known plant species, ranging from a duckweed less than a millimetre wide up to coast redwood trees over 100 metres tall.

  • Known plant speciesapprox. 390,000Mostly flowering plants
  • Tallest treeHyperionA coast redwood, 116 m tall
  • Oldest individual treeapprox. 4,800 yearsMethuselah, a bristlecone pine
  • SmallestWolffiaLess than 1 mm long, the smallest flowering plant
  • First land plantsapprox. 470 million years agoSimple moss-like growth
  • Oxygen made by plantsapprox. 50%Phytoplankton in the ocean make the other half

Photosynthesis: making food from light

The key trick that plants do (and no animal can) is photosynthesis. Inside the green parts of plants are tiny structures called chloroplasts that contain a green pigment called chlorophyll. Chlorophyll absorbs sunlight and uses its energy to combine carbon dioxide (from the air) and water (from the soil) into glucose (a sugar) and oxygen. The simplified word equation is:

carbon dioxide + water + sunlight → glucose + oxygen

The glucose feeds the plant. The oxygen is released into the air, which is where almost all the oxygen we breathe comes from. Without photosynthesis, almost nothing else on Earth could live.

The main parts of a plant

  • Roots: hold the plant in the ground and suck up water and nutrients from the soil.
  • Stem (or trunk): holds the plant up, and carries water from the roots and food from the leaves around the plant.
  • Leaves: the green factories where photosynthesis happens.
  • Flowers: the reproductive parts, used to make seeds. Often coloured and scented to attract pollinators like bees.
  • Fruits and seeds: the next generation, often wrapped in tasty fruit to encourage animals to spread them.

Why plants matter

Plants do far more than just sit there looking green. They produce almost all the oxygen we breathe, they capture carbon dioxide and slow climate change, they hold soil together and stop erosion, they regulate rainfall and the water cycle, they shelter wildlife, and they provide almost all of our food (either directly, or by feeding the animals we eat). Almost every medicine in modern pharmacies was first discovered in a plant.

Fact The world's tallest tree, a coast redwood called Hyperion, stands 116 metres tall in northern California, taller than the Statue of Liberty (with pedestal). Its exact location is kept secret to protect it from tourists. Hyperion is over 600 years old and still growing.

Pick a topic below to explore plants in more depth.

What Is a Plant?A living thing that makes its own food from sunlight. Plants are the base of nearly every food chain on Earth.
PhotosynthesisThe trick plants use to turn sunlight, water, and carbon dioxide into sugar (their food) and oxygen (our breath).
Parts of a PlantRoots, stem, leaves, flowers, fruit, and seeds. Each part has a different job in keeping the plant alive and helping it spread.
Plant Life CycleFrom seed to seedling to flowering plant to seed again. Some plants do this in months, others take centuries.
TreesThe biggest, oldest, and tallest living things on Earth. Trees can live for thousands of years and grow over 100 metres tall.
Flowering PlantsPlants that make flowers and fruit to spread their seeds. Most of the plants you see every day are flowering plants.
PollinationHow plants move pollen from flower to flower to make seeds. Bees, butterflies, bats, and wind all help.
Carnivorous PlantsPlants that catch and eat insects. The Venus flytrap, the sundew, and the pitcher plant all hunt for their dinner.