Transport in Plants Flashcards
Transport System
Xylem transports water and minerals through transpiration
Phloem transports sugars to all parts of plants through translocation
The Vascular Bundle
The Vascular Bundle
Vascular Bundle in Roots
- Xylem and Phloem enable transport of substances and provide structural support
- Xylem vessels arranged in X-Shape in centre of vascular bundle
- Enables plant to withstand mechanical forces (pulling)
- X-Shape arrangement of xylem vessels is surrounded by endodermis, which is a outer layer of cells which supply xylem vessels with water
- There are inner layers of meristem cells known as the pericycle
Vascular Bundle in Stems
- Xylem located on the inside of non-wooded plants to provide support and flexibility to stem
- Phloem is found on the outside of the vascular bundle
- Layer of cambium between xylem and phloem, this is meristem cells involved in production of new xylem and phloem tissue
Vascular Bundle in Leaf
- Vascular Bundle form midrib and veins of leaf
- Have network of veins starting at midrib and spreading outwards which are involved in transport and support
Xylem and Phloem
Xylem
- transport water and minerals, provide structural support
- long cylinders made of dead tissue with open ends to form continuous column
- Contain pits which enable lateral movement
- Thickened with lignin in spiral pattern to allow flexibility to remain
- Water can only flow upwards
Phloem
- Made of living cells
- Involved in translocation, movement of nutrients to storage organs and growing parts of the plant
- consist of sieve tube elements and companion cells
- sieve tube elements form tube to transport sugars (sucrose) in sap, can be upwards or downwards
- Cytoplasm of sieve tube elements and companion cells is linked through structures known as plasmodesmata, which are gaps between cell walls which allow communication and flow of substances such as minerals between cells
- Companion cells are involved in ATP production for active processes such as loading sucrose into sieve tubes
Transpiration
Transpiration
- Transpiration, plants absorb water through roots, moves up plant and is released into the atmosphere as water vapour through pores in leave, carbon dioxide enters while water and oxygen exit through stomata
- Transpiration stream, movement of water up the stem, enables photosynthesis and growth, supplies plant with vital minerals, enables control over temperature via evaporation of water
- Water moves from xylem to mesophyll cells via osmosis, water evaporates from surface of mesophyll cells, water diffuses down a water vapour potential gradient out of the stomata
- rate of transpiration can be measured using a potometer, vapour lost is replaced by water in capillary tube, measure movement of air bubble to determine rate of transpiration
Factors affecting rate of transpiration
Factors affecting rate of transpiration
- number of leaves
- number and size of stomata
- presence of waxy cuticle layer
- amount of light present
- temperature
- humidity
- air movement
- water availability
