In order to survive a leaf needs to carry out photosynthesis effectively. This means the leaf needs a way to:
Transport water and glucose around the plant
Exchange carbon dioxide and oxygen
Absorb light energy efficiently
Lets look at the first point. Transporting water and glucose around the plant.
This may seem simple, but plants don’t have muscles like you and me, nor do they have a pump to push the fluid through.
However what they do have, is a Xylem and Phloem which sit in the spongy layer of the leaf.
The xylem and phloem stretch from the roots all the way to the top of the plant.
The xylem is responsible for the movement of water through the plant. Since the concentration of water is so much more at the root, the water moves up the xylem to the leafs where the water potential is lower.
This movement of water is called transpiration.
The phloem transports carbohydrates and amino acids, from the leafs to the roots and stem of the plants. This movement of nutrients is called translocation.
The movement in both these tubes is one way. The xylem allows water to flow up, while the phloem also nutrients to flow down into the stem and roots.
Water is absorbed through the roots, and then transported throughout the plant via the xylem.
If we look at a root, we notice small hair cells. These grow outwards into the soil, increasing the roots surface area. This means the can absorb water quicker and more efficiently.
In the air around us there is carbon dioxide, oxygen, nitrogen and a few other gases.
Plants will capture the Carbon dioxide from the air through diffusion. The gas enters the plant through the stomata.
If its a hot day, the plant is at risk of dehydration. So the guard cell may close the stomata or decrease its size so the plant doesn't loose too much water.
Try some questions bellow
1. Explain the role of the Stomata and guard cells, 2 marks
2. What is the purpose of the waxy layer covering the leaf?
3. What layer is responsible for photosynthesis?
4. Draw the bellow into your book and fill in the blank squares bellow
5. What is the name of the structure which carries water through the plant?
6. What is the name of the structure which carries food through the plant?
7. List 3 adaptations of the plant for photosynthesis (3 marks)
Copy in the sentence bellow and fill in the blanks
8. Water is absorbed through the ________ and transported up the _________ towards the leaves, so it can be used in ___________ to create __________.