The three main structures found in plant cells are:
Cellulose cell wall
Root hair cells
Roots are covered with hairs, which increase the surface area of the root. Root hair cells are long thin hairs found inside the roots of plants. They increase the surface area for the absorption of water and mineral ions into the plant.
Root hair cells have many adaptations:
The cell has root hairs, which increases the area of the root.
A thin cell wall allows water to pass through easily, as it provides a shorter diffusion distance.
Unlike other plant cells, root hair cells do not contain any chloroplasts – Photosynthesis requires light energy from the Sun. As roots are underground, they do not need chloroplasts.
They contain mitochondria for the active transport of mineral ions.
Their permanent vacuole increases the rate of osmosis.
Guard cells are found in plant cells and they control the opening and closing of the stomata on the surface of the leaf. The function of a guard cell is to allow gas exchange and control water loss within the leaf
The guard cells become rigid or flaccid, changing shape depending on the condition of the plant.
Xylem cells are found in the plant stem. Collectively, they form long tubes that are responsible for the transportation of water and dissolved mineral ions, from the roots to the leaves. Substances in the xylem are transported by transpiration.
There are many adaptations in xylem cells, such as:
No end top and bottom walls, which forms a long tube. This allows the water and dissolved minerals to be drawn upwards by transpiration.
The cells have very thick walls, which are lined with a chemical called lignin. This chemical provides a waterproof barrier and it strengthens the tube, which helps to support the plant.
Xylem cells have no internal structures such as a nucleus, a vacuole, cytoplasm or chloroplasts. This makes it easier for water and mineral ions to pass through.
Phloem cells are responsible for the transportation of dissolved sugars and amino acids up and down the plant. They are also found in the stem.
Substances in the phloem are transported by translocation, which is an active process. The phloem is made up of two different types of cells:
Vessel cells – These cells have no nucleus, and each one is joined end-to-end. The end walls of the vessel cells have sieve plates, which allow the dissolved substances to flow through.
Companion cells – Each vessel cell is connected to a companion cell. Since transporting substances in the phloem requires energy, the companion cell provides this energy to the vessel cell.