Topic 8: Transport in Plants Flashcards
Air spaces
Intracellular spaces within the spongy mesophyll layer of the leaf that enable gaseous exchange. The air becomes saturated with water vapour providing a high concentration gradient for its diffusion into the atmosphere.
Cohesion (water movement)
The ‘sticking’ together of water molecules due to attractive forces between them. This enables water molecules to move up the xylem in a continuous stream.
Cortex
The tissue located between the epidermis and the vascular bundles in a plant stem or root. The cells of the cortex often store starch.
Dicotyledons
Plants that produce seeds that contain two cotyledons (embryonic leaves), forming two primary leaves.
Phloem
A transport tissue found in plants that is specialised to transport sugars from the leaves to the rest of the plant in both directions.
Root hair cells
Specialised cells responsible for the uptake of water and minerals from the soil. They have long hair-like extensions known as root hairs, which provide a large surface area for absorption of ions by active transport and water by osmosis.
Sinks (plants)
The regions of a plant that store or remove sugars e.g. roots, buds, fruits.
Sources (plants)
The regions of a plant that produce sugars e.g. leaves, storage organs.
Stomata
Small holes found on the surface of a plant that can be opened or closed by guard cells to control water loss and gas exchange.
Surface area
The total area occupied by the surface of an object. The larger the surface area, the faster the rate of diffusion
Translocation
The movement of sugars (sucrose, amino acids, etc.) up and down a plant, from sources to sinks, via the phloem. Requires energy.
Transpiration
Water loss from plant leaves and shoots via diffusion and evaporation. The rate of transpiration is affected by temperature and humidity.
