transport in plants
- Created by: aryan26
- Created on: 10-04-19 17:46
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- transport in plants
- xylem tissue
- transports water and mineral ions in solution
- also functions for support
- in a root, the xylem is in the centre surrounded by phloem to provide support for the root
- in the stems xylem and phloem are near the outside to reduce bending
- in a leaf the xylem and phloem make up a network of veins
- adaptations
- 1: they are very long tube like structures formed from vessel elements joined end to end
- 2: there are no end walls so its an uninterrupted tube
- 3: the cells are dead so they contain no cytoplasm
- 4:walls are thickened with lignin which supports them stopping them from collapsing inwards
- deposited in a spiral or rings
- 4:walls are thickened with lignin which supports them stopping them from collapsing inwards
- 5: as a cell gets older the amount of lignin increases
- 6:water and ions move in and out through small pits where there is no lignin
- phloem
- transports solutes mainly sugars like sucrose
- arranged in tubes used for transport
- tissue contains phloem fibres, phloem parenchyma, sieve tube elements and companion cells
- sieve tube elements
- living cells that form the tube for transporting solutes through the plant
- joined end to end to form sieve tubes
- end walls contain holes to let solutes pass
- have no nucleus, thin layer of cytoplasm and few organelles
- cytoplasm in adjacent cells is connected through the holes in sieve plates
- companion cells
- sieve tube elements can't survive alone
- there's a companion cell for every sieve tube element
- carry out living functions for themselves and the sieve cells
- sieve tube elements can't survive alone
- sieve tube elements
- water transport
- water enters through root hair cells and passes through the root cortex to the xylem
- water is drawn into the roots via osmosis
- symplast pathway
- goes through living parts of the cell- the cytoplasm
- cytoplasms of neighbouring cells connect via plasmodesmata (small channels in the cell wall)
- water moves in this pathway via osmosis
- apoplast pathway
- goes through non-living parts- the cell walls
- the walls are very absorbent so water can diffuse through
- the water can carry solutes and move from high hydrostatic pressure to low hydrostatic pressure.
- this is an example of mass flow
- most used as it provides the least resistance
- water enters through root hair cells and passes through the root cortex to the xylem
- xylem tissue
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