Module 3 - Section 3 - Transport In Plants
- Created by: Nimrahkhan
- Created on: 02-03-16 10:20
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- Transport In Plants
- Xylem and Phloem
- Xylem
- Transports water and mineral ions in solution.
- 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
- Phloem
- Transports sugars in solution up and down plant.
- Sieve tube elements-Living cells are joined 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
- Xylem
- Water entering the Plant
- Osmosis- From high water potential to low water potential inside root hair cell.
- Symplastic Pathway
- Goes through living parts (cytoplasm) of cell. Connects cells through plasmodesmata. Via Osmosis
- 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.
- Moves from high hydrostatic pressure to low hydrostatic pressure.
- Moves through non-living(cell wall) of cells.
- Transpiration
- 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.
- Tension - Pulls more water into leaf when water transpires.
- Cohesion-molecules stick together so whole column of water flows.
- Result of Gas Exchange.
- Plant needs to open stomata to allow in CO2 for photosynthesis but lets out water at the same time.
- Factors Effecting Transpiration Rate
- Wind
- Humidity
- Temperature
- Light Intensity
- Xerophatic Plants
- Adapted to live in dry climates
- Waxy layer on Epidermis, Spines instead of leafs, close stomata in hottest part of days, Sunken pits, Hairs on Epidermis, Roll Leaves
- Hydrophytic Plants
- Adapted to live in aquatic habitats
- Air Spaces, Stomata only present on top of leaves, Flexible leaves and stems
- Translocation
- Movement of dissolved substances (assimilates) to where they're needed in the plant
- Mass Flow Hypothesis
- 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.
- Active transport used to load solutes(sucrose) into sieve tubes
- Sink
- At the end solutes are removed fro phloem to be used. Diffusion.
- Flow
- Pressure gradient from source end to sink end. Pushes solutes along sieve tube toward sink, where they'll be stored or used.
- Source
- Active Loading
- Used at the source to to move substances into companion cells from surrounding tissues, against conc gradient.
- 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
- 2. H+ binds to co-transport protein, and re enters cell via diffusion. sucrose also attaches to protein so moves sucrose into cell too.
- Xylem and Phloem
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