9)Transport in Plants Flashcards
Why do multicellular plants need transport systems
Need important substances to survive
Get rid of waste substances
Have a small SA : Vol ratio
Diffusion to too slow
Move substances from individual cells quickly
What is the 2 types of tissue involved in Transport systems
Xylem
Phloem
What is the role of the xylem
Transport water and mineral ions
What is the role of the phloem
transport sugars up and down the plant
How are xylem vessels adapted for transporting water and minerals
Lonv , tube like
No end walls = uninterupted tube for water
Cells are dead = no cytoplasm
Lignin walls = help support xylem vessels and allow support , prevent collapsing inwards
Pits = water and ions move in and out of the cell.
What structures do phloem tubes have
Phloem fibres , parenchyma , sieve tube elements, companion cells
How do Sieve tube elements allow transport in the phloem
Living cells
End to end create sieve tubes
allow solutes to pass through
no nucleus , thin cytoplasm
How do companion cells allow transport in phloem
lack of nucleus of phloem
Companion cell for every sieve tube element
Carry out function for both structures
Provide enrgy for active transport
What is the symplast pathway
Through living parts of the cell - Cytoplasm
Connect through plasmodesmate
What is the apoplast pathway
goes through non-living parts - cell walls
Absorbent to==so water can diffuse into them.
Move from high hydrostatic preassure to low hydrostatic pressure
From when does the water change path
water gets to the endodermis in the root and reach the casparian strip
How does water move up in the plant
Cohesion and tension.
Water evaporates by transpiration
Creates tension / suction which pulls water
Cohesive as they stick together so it creates a column of water.
Adhesion - attracted to the walls and help water to rise up
What is transpiration
stomata opens to let carbon dioxide in and water out also .
Gas exchange
What are the factors the affect transpiration rate
Light
Temmperature
Humidity
Wind
How does Light affect transpiration
The lighter , the faster the rate
Stomata opens when it is light , when it is dark stomata is closed
How does Temperature affect ranspiration
Higher temp , faster the rate
More energy so eaporate inside the leaf fast , create a steeper water potential .
Make water diffuse out faster
How does humidity affect transpiration rate
Lower humidity , faster transpiration rate
Create a greater water potential gradient
How does wind affect transpiration
Windier , faster rate
Lots of movement blows away water molecules. Increase potential gradient
How are Xerophytic plants adapted to reduce water loss
Sunken pits - sheltered from the wind
Layers of hair - Traps moist air , reduces potential gradient
Rolled leaves - trap moist air , reduce exposed surface area to wind
Thick waxy layer - reduce water loss and is waterproof
Spines - reduces surface area for water loss
How are hydrophilic plants adapted to survive in water
Air spaces - allow plant to float
Large surface area - allow float
Stomata on upper surface - max gas exch
Flexible leaves and stems - prevent damage from water currents
What is translocation
Movement of substances ( assimilates ) around the plant
Energy-required
from source to sink
Describe mass flow hypothesis
Active transport used to actively load solutes into sieve tube
Lowers water potential inside sieve tube , water enters by osmosis
from xylem and companion cells
Creates high pressure inside at source end
Solutes removed at sink
What is active loading
Move substances into the companion cell from surrounding tissues.
Use of co-transporter proteins#
In companion cell - ATP used to actively transport H ions out of celll
Cause a concentration gradient
H bind to co-transporter proteins in companion cell and re-enter cells
Sucrose binds to protein and move into cell
