Transpiration

• The stem, root and leaves form an organ system that transports substances into, around and out of a plant.
• The need for transport in plants is highlighted by transpiration.
• Transpiration is the loss of water from leaves by evaporation through the stomata.
• Factors affecting transpiration include environmental factors such as temperature and humidity.
• Transpiration can be investigated using potometers, which measure water uptake.
• The distribution of stomata and guard cells can be investigated as part of transpiration research.
• When the plant opens its stomata to let in carbon dioxide, water on the surface of the cells of the spongy mesophyll close spongy mesophyll.
• The plant tissue in a leaf which has loosely packed cells and air spaces between them to allow gas exchange is called the spongy mesophyll.
• The plant tissue containing closely packed cells in the upper layer of a leaf is called the palisade mesophyll.
• Evaporation is the process in which a liquid changes state and turns into a gas.
• Diffusion is the process where particles spread out from a region of higher concentration to a region of lower concentration.
• Water is drawn from the cells in the xylem to replace that which has been lost from the leaves.
• Water molecules inside the xylem cells are strongly attracted to each other due to strong cohesion between the molecules because of hydrogen bonding.
• 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.
• As water travels through the xylem in the stem and leaf, it is being replaced by water taken up by the roots.
• Non-communicable diseases are also part of animal organisation.
• Soil water moves into the root hair cell by osmosis and across the root cortex to the xylem.
• Minerals are necessary for both plant and animal health.
• Only five per cent of the water taken up by the plant is used for photosynthesis, but it does have its purposes: it provides the water for photosynthesis and transports mineral ions.
• Water enters the root hair cells by osmosis because soil water has a higher water potential than the cytoplasm of the root hair cell.
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• A continuous column of water is pulled up the stem in the transpiration stream by evaporation from the leaves.
• Minerals enter by active transport.
• Animal organisation also includes digestion.
• Factors affecting transpiration include the need for transport in plants.
• Sample exam questions for organisation include topics such as Biology, Bitesize revision podcasts, and Personalise your Bitesize.
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• Algae subsumed within plants and some bacteria are also photosynthetic.
• Water uptake and transport across the root occur through root hairs, which are single-celled extensions of epidermal cells.
• Animal organisation includes gaseous exchange systems.
• Transpiration is an unavoidable consequence of photosynthesis.
• Animal organisation also includes transport systems.