Module 3 - Section 3 - Transport in Plants

Why do Plants need Transport Systems?
Small SA:VOL ratio. Have a high metabolic rate. Exchanging substances via diffusion would be too slow, so need a transport system.
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Xylem Use
Transports water and mineral ions in solution.
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Adaptations of Xylem
No end walls and no cytoplasm-So substances can flow uninterrupted. Cell wall contains lignin-Supports cell wall, stopping them collapsing under high pressure.Small pits in walls-Allows minerals in where there's no lignin
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Phloem Use
Transports sugars in solution up and down plant.
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Adaptations of Phloem
Sieve tube elements-Living cells are foined end to end to for. Lots of holes to allow solutes to pass. Have no nucleus, little cytoplasm and few organelles, so rely on companion cell to survive. Companion cell- Carry out living functions for sieve
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How does Water enter Plant?
Osmosis- From high water potential to low water potential inside root hair cell.
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Symplastic Pathway
Goes through living parts(cytoplasm) of cell. Connects cells through plasmodesmata. Via Osmosis
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Apoplastic Pathway
Moves through non-living(cell wall) of cells.Moves from high hydrostatic pressure to low hydrostatic pressure. Water blocked going into Xylem due Casparian *****. So needs to take Symplastic Pathway.
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Transport through Leaves
Transpiration
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Water Movement Up Plant
Transpiration Stream-Cohesion-molecules stick together so whole column of water flows. Tension - Pulls more water into leaf when water transpires. Adhesion-Attract to walls of vessel to help rise.
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Transpiration
Result of Gas Exchange.Plant needs to open stomata to allow in CO2 for photosynthesis but lets out water at the same time.
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Factors Effecting Transpiration Rate
Light Intensity, Temperature, Humidity, Wind
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Xerophatic Plants
Adapted to live in dry climates
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Adaptations of Xerophatic Plants
Waxy layer on Epidermis, Spines instead of leafs, close stomata in hottest part of days, Sunken pits, Hairs on Epidermis, Roll Leaves
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Hydrophytic Plants
Adapted to live in aquatic habitats
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Adaptations Of Hydrophytic Plants
Air Spaces, Stomata only present on top of leaves, Flexible leaves and stems
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Translocation
Movement of dissolved substances (assimilates) to where they're needed in the plant
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Mass Flow Hypothesis
Solutes are transported from source to sink by translocation.
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Source
Active transport used to load solutes(sucrose) into sieve tubes Lowers water potential in sieve tubes, so enters via osmosis into phloem, creates high pressure in sieve tubes at the end source of plants.
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Sink
At the end solutes are removed fro phloem to be used. Diffusion. This increases water potential in sieve tubes, so water leaves tubes via osmosis. Lowers pressure in sieve tubes.
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Flow
Pressure gradient from source end to sink end. Pushes solutes along sieve tube toward sink, where they'll be stored or used.
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Active Loading
Used at the source to to move substances into companion cells from surrounding tissues, against conc gradient.
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Active Loading Process
1. Actively transport H+ ions into surrounding tissue. 2. H+ binds to co-transport protein, and re enters cell via diffusion. sucrose also attaches to protein so moves sucrose into cell too. 3.Sucrose is transported out of companion cell in same way
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Other cards in this set

Card 2

Front

Transports water and mineral ions in solution.

Back

Xylem Use

Card 3

Front

No end walls and no cytoplasm-So substances can flow uninterrupted. Cell wall contains lignin-Supports cell wall, stopping them collapsing under high pressure.Small pits in walls-Allows minerals in where there's no lignin

Back

Preview of the back of card 3

Card 4

Front

Transports sugars in solution up and down plant.

Back

Preview of the back of card 4

Card 5

Front

Sieve tube elements-Living cells are foined end to end to for. Lots of holes to allow solutes to pass. Have no nucleus, little cytoplasm and few organelles, so rely on companion cell to survive. Companion cell- Carry out living functions for sieve

Back

Preview of the back of card 5
View more cards

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