Transport in plants and the structure of specialised plant cells
Plants do not have a heart, blood or a circulation system, but they do need a transport system to move food, water and minerals around.
They use two different systems - Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants. moves water and mineral ions from the roots to the leaves - The tissue in plants that transports the products of photosynthesis, including sugars and amino acids. moves food substances such as sucrose (sugar) and amino acids from leaves to the rest of the plant. This movement of food is called The transport of dissolved material within a plant.. Both of these systems contain cells that make continuous tubes running the full length of the plant from the roots, up the stem and through the leaves. They are like blood vessels for the plant.
Root hair cells
Plants absorb water from the soil by osmosis. They absorb mineral ions by active transport, against the concentration gradient. A specialised cell that increases the surface area of the root epidermis to improve the uptake of water and minerals. are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption. They also contain lots of Structures in the cytoplasm of all cells where aerobic respiration takes place (singular is mitochondrion)., which release energy from A simple sugar used by cells for respiration. during The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration. in order to provide the energy needed for active transport.
The absorbed water is transported through the roots to the rest of the plant where it is used for different purposes:
- it is a reactant used in photosynthesis
- it supports leaves and shoots by keeping the cells rigid
- it cools the leaves by evaporation
- it transports dissolved minerals around the plant
Stomata
Tiny holes in the epidermis (skin) of a leaf. They control gas exchange by opening and closing and are involved in loss of water from leaves. Singular is stoma. are tiny holes found in the underside of leaves. They control water loss and gas exchange by opening and closing. They allow water vapour and oxygen out of the leaf and carbon dioxide into the leaf.
Plants growing in drier conditions tend to have small numbers of tiny stomata and only on their lower leaf surface, to save water loss. Most plants regulate the size of stomata with guard cells. Each stoma is surrounded by a pair of sausage-shaped guard cells. In bright light the guard cells take in water by The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. and become plump and Having turgor - enlarged and swollen with water.. In low light the guard cells lose water and become Lacking turgor. Lacking in stiffness or strength. Soft and floppy., causing the stomata to close. They would normally only close in the dark when no carbon dioxide is needed for photosynthesis. Guard cells are adapted to their function by allowing gas exchange and controlling water loss within the leaf.
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 A plant will wilt if it does not have enough water - it will become soft and floppy..