9700 · 7.1
Structure of transport tissues
Just like humans need blood vessels, plants need specialised tissues to move vital substances around. These are the xylem, which carries water and minerals from roots to leaves, and the phloem, which transports sugars (food) from leaves to where they're needed.
Need to know
What you need to know
- epidermis – the outermost layer; made up of a single layer of parenchyma cells and its outer wall is covered with a cuticle - cuticle prevents infection of the plant by bacteria or fungi - also aids in reducing water loss.
- cortex – divided into three regions: - hypodermis provides mechanical support - middle cortex is involved in photosynthesis - inner cortex helps in gaseous exchange and stores food materials.
- endodermis – the innermost layer of the cortex, consists of a single layer of cells that contain starch grains.
- pith – large, central, parenchymatous zone with intracellular spaces; helps in storage of food materials Structure of leaves (dicot) Transverse section Image: https://www.brainkart.com/.
- upper epidermis – the outermost layer made up of a single layer of parenchyma cells without intracellular spaces; outer walls have cuticles, stomata are less in number.
- lower epidermis – single layer of parenchymatous cells with a thin cuticle - contains numerous stomata - chloroplasts are only present in guard cells - helps in exchange of gases - loss of water vapour is facilitated through this chamber.
- transports water and mineral ions via mass flow (passive).
- unidirectional movement (from roots à rest of the plant).
Explanation
Plant's Plumbing System
- Visualise xylem as continuous, hollow tubes.
- Understand why lignin is crucial for xylem function.
- Recall the key components of phloem: sieve tubes and companion cells.
- Link each structural feature to its specific role in transport.