The leaf is a plant organ adapted to carry out photosynthesis. The table describes some of its adaptations:
|Thin||Provides a short distance for carbon dioxide to move by diffusion into the leaf|
|Contains chlorophyll||Absorbs light|
|Stomata||Allows carbon dioxide to move by diffusion into the leaf|
|Guard cells||To open and close the stomata depending on the conditions|
|Network of tubes (xylem and phloem)||To transport water (xylem) and food (phloem)|
A leaf usually has a large surface area, so that it can absorb a lot of light. Its top surface is protected from water loss, disease and weather damage by a waxy layer.
The upper part of the leaf is where the light falls, and it contains a type of cell called a palisade cell. This is adapted to absorb a lot of light. It has lots of chloroplasts and is shaped like a tall box.
Plants get the carbon dioxide they need from the air through their leaves. It moves by diffusion through small holes in the underside of the leaf called stomata. Guard cells control the size of the stomata so that the leaf does not lose too much water in hot, windy or dry conditions.
The lower part of the leaf is a spongy layer with loose-fitting cells. These let carbon dioxide reach the other cells in the leaf, and also let the oxygen produced in photosynthesis leave the leaf easily.
The water needed for photosynthesis is absorbed through the roots and transported through tubes to the leaf.
The roots have a type of cell called a root hair cell. These project out from the root into the soil, and have a big surface area and thin walls. This lets water pass into them easily.
Note that root cells do not contain chloroplasts, as they are normally in the dark and cannot carry out photosynthesis.