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Specialised Plant Cells

Xylem

The basic function of the xylem is to transport water and nutrients from the roots up to the leaves. 

Xylem vessels are dead cells that have no cytoplasm or cell contents. This means that there is more space water containing mineral ions to move through.

They have holes in their walls called pits in them to allow for water and mineral ions to move out. 

The walls are strengthened by lignin ridge, which makes them very strong and prevents them from collapsing. Also, they do not have end walls which form a long tube that water can flow through easily.

Phloem

The phloem moves food substances sucrose (sugar) and amino acids from leaves to the rest of the plant around a plant that the plant has produced by photosynthesis to where they are needed for processes such as:

  • Storage organs such as bulb or tuber

  • Growing parts of the plants for immediate use

  • Developing seeds

The movement of food around a plant is called translocation.

Root hair cell 

Plants absorb water from the soil by the process of osmosis. They absorb mineral ions by the process of active transport against a concentration gradient. Root hair cells have adapted to have a large surface area which allows for maximum absorption of water and mineral ions.

As well as this, root hair cells also contain lots of mitochondria, which release energy from glucose during respiration in order to provide the energy needed for active transport. 

Stomata

Stomata are tiny holes in the underside of the leaf which allow for gas exchange and control water loss. They allow water vapor and oxygen out of the leaf and carbon dioxide into the leaf. Plants growing in dry locations adapt to have a small number of tiny stomata on the lower leaf surface only which helps lower the amount of water loss.

Plants regulate the size of the stomata opening with guard cells. Each stomata is surrounded with banana shaped guard cells which become turgid when the plant is in a bright location and are flaccid in the dark. This helps maintain water loss and gas exchange.

The size of the stomatal opening is used by the plant to control the rate of transpiration and therefore limit the levels of water loss from the leaf. This helps to stop the plant from wilting.