- How do plants make food for themselves?
- Why do leaves turn yellow in autumn?
- Why is wind important for plants?
Plants make food from carbon dioxide and water
The gaseous composition of the air remains more or less unchanged. At the same time, we know that breathing and burning constantly consume oxygen and release carbon dioxide into the air. So there must be more oxygen produced somewhere. Let us now find out how the oxygen supply in the air is restored, and why the amount of carbon dioxide in the air remains low.
Like animals, plants need to get food from somewhere. Plants make their own nutrients inside their green leaves. They take water from the soil using their roots, where simple nutrients are dissolved. Plants get carbon dioxide from the air. With green leaves, they catch the sunlight. Using light's energy, water, and carbon dioxide, plants make a special sugar called glucose, and leftover oxygen. This activity of plants is called photosynthesis.
Plants can only photosynthesise when there is enough light, but they breathe constantly. When they breathe, plants use up some of the oxygen they produce, but lots is left over for all other organisms. By using carbon dioxide from the air and producing oxygen, plants keep the composition of air more or less consistent. All green plants and algae produce oxygen.
Bonus: What does "photosynthesis" mean?
The word "photosynthesis" in Greek means assembling something with the help of light. "Photo" should be a familiar word to you - photography means drawing with light.
Think!
- How is plant nutrition different from animal nutrition?
- roots.
- seeds.
- leaves.
- flowers.
Plants get energy from glucose
Glucose is the simplest building block from which other necessary substances are formed in a plant. Glucose provides the energy needed for plant life, and substances produced by plants are consumed by animals such as humans. So, neither we nor other animals can live without the oxygen and nutrients produced by plants.
A green substance called chlorophyll helps plants to absorb light. Chlorophyll means green leaf in Greek. When nature turns green in spring, the plants are ready to catch the light. However, when the leaves turn yellow and red in autumn, this indicates that the chlorophyll is decomposing as the plants prepare for the resting period in winter.
Think!
- What would happen if all the plants disappeared from Earth?
- Houseplants are usually placed near the window. Could they grow in a dark room?
- Oxygen
- Carbon dioxide
- Nitrogen
- Ozone
- Water
- Chlorophyll
- Sunlight
Air movement helps plants to reproduce
For plants not to disappear from the face of the earth, they must produce new plants. Flowering plants reproduce via seeds that develop in their fruits. Fruits and seeds develop from the flowers.
The colourful and bright petals attract our attention to the flower. In the middle of the flower, we discover some parts directly involved in the plant's reproduction. Most flowering plants have both 'female' and 'male' parts, also known as pistillate and staminate parts, either on the same flower or on a different flower of the same plant. Only a small amount of flowering plants will separate which plant has a staminate flower and which has a pistillate flower.
Anthers produce a lot of pollen - the male sex cells needed for the plant to produce seeds. The funnel-shaped upper part of the pistil is called the stigma. For the seeds to develop in the flowers, pollen must get to the stigma. This is called pollination. After pollination, the pistil develops into a fruit with one or more seeds.
Pollen is transmitted by insects or wind. Bees, butterflies, and some other insects fly from flower to flower to get sweet nectar or collect pollen. They also carry plant pollen from flower to flower. The flowers of insect-pollinated plants are usually striking and colourful to attract the insect's attention.
Many plants are pollinated by wind. The flowers of wind-pollinated plants are usually small because they do not have to attract insects with colour and smell, and they produce a lot of pollen. Sometimes this pollen can cause an allergic reaction when someone inhales it.
– the part of the flower that becomes the fruit
– the parts in the middle of the flower in which the pollen is located
– the funnel-shaped upper part of the pistil
– the parts that develop in the fruit of the flowering plant and allow the flowering plant to reproduce
– the process of pollen getting to the stigma
Think!
- What health problems can pollen cause?
Important terms
- photosynthesis – the process by which plants produce nutrients from water and carbon dioxide using light energy, releasing oxygen
- pollen – the male sex cells of plants that are needed for the plant to produce seeds
- pollination – the process of transferring pollen grains from the stamen part of a flower to the pistil part of a flower
I now know that…
Plants use light energy to make a sugar called glucose from water and carbon dioxide. Oxygen is also produced in this process. All green plants and algae produce oxygen. Animals such as humans could not live without the oxygen produced by plants. In plants, there is a green substance called chlorophyll that is needed to capture light. The movement of air helps plants to pollinate.
