Transpiration
When the plant opens its 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. to let in carbon dioxide, water on the surface of the cells of the The plant tissue in a leaf which has loosely packed cells and air spaces between them to allow gas exchange. and Plant tissue containing closely packed cells in the upper layer of a leaf.The process in which a liquid changes state and turns into a gas. and The movement of molecules from an area of higher concentration to an area of lower concentration. out of the leaf. This process is called The loss of water from leaves by evaporation through the stomata..
Water is drawn from the cells in the Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants. to replace that which has been lost from the leaves.
Xylem
The xylem transports water and minerals from the roots up the plant stem and into the leaves.
In a mature flowering plant or tree, most of the cells that make up the xylem are specialised cells called vessels.
Vessels
- Lose their end walls so the xylem forms a continuous, hollow tube.
- Become strengthened by a chemical called Carbohydrate material lining the xylem vessels providing strength and support.. The cells are no longer alive. Lignin gives strength and support to the plant. We call lignified cells wood.
Transport in the xylem is a physical process. It does not require energy.
Water molecules inside the xylem cells are strongly attracted to each other. There is strong cohesion between the molecules because of Hydrogen bonding is a relatively strong intermolecular attractive force that develops between a hydrogen atom and an electronegative atom. Hydrogen bonding between water molecules involves an attractive force between a hydrogen atom in one water molecule and the oxygen atom in another.. A continuous column of water is therefore pulled up the stem in the transpiration stream by evaporation from the leaves.
As water travels through the xylem in the stem and leaf, it is being replaced by water taken up by the roots.
Transpiration is an unavoidable consequence of A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic. - only about 5% of the water taken up by the plant is used for photosynthesis - but transpiration does have its purposes as it:
- provides the water for photosynthesis
- transports Naturally occurring, inorganic chemical substances. Minerals are necessary for both plant and animal health.
- cools the leaf as water evaporates
- provides water that keeps the cells Enlarged and swollen with water. Having turgor. Description of a plant cell in which the vacuole has swollen due to water gain by osmosis., which supports herbaceous plants
Water uptake and transport across the root
Root hairs are single-celled extensions of Cells of the epidermis, the outer covering layer of an organism. in the root. They grow between soil particles and absorb water and minerals from the soil.
Water enters the root hair cells 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.. This happens because soil water has a higher water potential than the cytoplasm of the root hair cell. Minerals enter by The transport of molecules against their concentration gradient from a region of low concentration to a region of high concentration..
A summary of water uptake, water transport and transpiration:
