3.1.3 Flashcards
Why do we need a transport system in plants?
large SA:V ration
rate of diffusion into plants is too slow
high metabolic rate
What vascular tissues are involved in plants?
xylem and phloem
What is the role of the xylem?
water and soluble minerals move upwards
What is the role of the phloem?
sugars move up/down
Are there pumps in a plants system?
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Where are xylem and phloem found?
vascular bundles
What does the vascular cambium contain?
meristem cells
What is the role of the meristem?
cells undergo differentiation
by mitosis
can differentiate into xylem or phloem
What is transpiration?
evaporation of water from the stomata
What is the transpiration stream?
movement of water up the xylem
How does water enter the leaves in the xylem and pass into the mesophyll?
osmosis
What happens after water enter the leaves in the xylem?
passes into mesophyll by osmosis
How does water vapour form after water passes into the mesophyll by osmosis?
water evapoarates from the surface of the mesophyll
What happens to the water vapour in the spongy mesophyll?
gathers in the air
How does water leave the through the open stomata?
water vapour gathers in air spaces in the spongy mesophyll
once water vapour inside the leaf is higher than outside
What does transpiration involve?
osmosis from xylem to mesophyll
evaporation from surface of mesophyll into air space in the leaf
diffusion out of the stomata
What factors affect transpiration?
temp
humidity
light
air movement
size , position and number of stomata
waxy cuticle
water availability
How does temperature affect transpiration?
the higher the temp,
the more KE the water has
so more evaporation of water vapour through stomata
How does humidity impact transpiration?
the more water vapour surrounding the stomata
less steep diffusion gradient
so less water leaves leaf by evaporation
How does light impact transpiration?
more light
higher rate of photosynthesis
more gas exchange needed
O2 diffuses out of stomata
and CO2 diffuses in
How does air movement impact transpiration?
the more wind/air movement
the less water vapour will surround stomata as it will be blown away
so steeper water vapour gradient and
more water leaves stomata by evap.
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How does having stomata at the top of the leaf impact transpiration?
more likely to lose more water by evaporation
because
more build up of water vapour
How does having bigger stoamata impact transpiration?
more water leaves stomata through transpiration
How does having lots of stomata impact transpiration?
more water leaves stomata by evaporation
How does the presence of a waxy cuticle impact transpiration?
waxy cuticle is waterproof
thicker so les water will leave by evap.
How does water availability impact transpiration?
hydrophytes -> water is readily available so it doesnt matter how much water is lost
xerophytes -> uses different ways to conserve water
How do you use a potometer?
select a healthy plant
cut stem under water at an angle
dry leaves
set up the potometer
introduce an airbubble and set up potometer under H2O
What are the control variables for the potometer experiment?
dry the leaves
use the same/age species of plant
SA of leaves
Why do you have to dry the leaves?
avoid reduction in transpiration of water
due to water not wantin to leave as much if leaves are wet
Why do you cut the stem under water?
avoid any bubbles getting into xylem
Why do you cut the stem at an angle?
to increase SA for xylem to take up water
Why does the potometer not accuratel measure rate of water uptake
some water can be used in turgor pressure
some water used in photosynthesis
What data do you need to calculate water uptake?
SA
length moved
time
What type of transport of molecules is the movement of minerals and salts moving into root hair cells?
active transport
How does water move into the root hair cell?
There is a lower water potential in the root hair cells
due to a higher concetration of solutes
water moves into the root hair cells by osmosis
Why is there a lower water potential in the root hair cells?
higher concetration of solutes
How does water move into the root hair cells?
osmosis
Whata are the 2 pathways that water use?
Symplast
Apoplast
What happens in the apoplast pathway?
Water travels only through cell walls
until it reaches the casparian strip
What does the casparian strip do?
waterproof layer than forces water to move inside of the cell , inside xylem
Where is the casparian strip located?
endodermis
What is the symplastic pathway?>
water travels within cytoplasm
it travels form cell to cell via the plasmodesmata
How does water travel from cell to cell in the symplas pathway?
plasmodesmata
What is the cohesion-adhesion tension theory?
Where is high hydrostatic pressure according to cohesion -tension theory?
roots
Where is low hydrostatic pressure according to cohesion-tension theoru?
leaves
What happens as a result of water evaporating formm the smtata according to cohesipon-tension theory?
tension is created in the xylem
What gradient does water move up thezylem along in cohesion tension theory?
Hydrostatic pressure
How does water move up xylem along hydrostatic pressure gradient?
cohesion
adhesion
capillary action
mass flow
What are xerophytes?
plants adapted to reduce water loss
Why do xerophytes have rolled leaves?
reduced surface area for evaporation
How does having rolled leaves help reduce water loss?
they trap a layer of water vapour
What does trapping a layer of water vapour do?
creates a water vapour potential gradient outside the stomata
reducing the water vapour potential gradient
What does reducing the water vapour potential gradient do for the leaf?
reduces evaporation of water from the leaf
How is having hairy leaves an adaptation of xerophytes?
traps a layer of water vapour
What does trapping a layer of water vapur arounf a ;eaf help reduce water loss?
creates a higher water vapour potentil outside the stomata
reducing thr water potential gradient
How does reducing the water potential gradient help reduce water loss?
reduces evaporation of the leaf
How does sunken stomata help reduce water loss?
traps a layer of water vapour
What does trapping a layer of water vapour do to help reduce water loss?
creates a higher water vapour potential outside the stomat
reducing the water vapour potential gradeint
How does having needle-like leaves help reduce water loss?
reduces the SA of the leaf
so there is less evaporation of water vapour
How does having a dense spongy mesophyll layer help to reduce water loss
smaller surface area for evaporation
How will stoamata be in xerophytes?
less stomata
closed in day’
found on lower surface of leaf What will the waxy cuticle be llike?thicker waxy cuticle
waterproof
prevents water leaving through evaporation
What does having a dep root system help reduce water loss?
long deep roots take up water
high solute conc in root hair cells
What does plant tissue with air spaces in it allow?
buoyancy
What are hydrophytes?
plants that live in areas of high water concentration
What is beneficial about hydrophytes having large leaves?
large SA
to inc rate of photosynthesis
How is having long roots that grow out of water a beneficial characteristic for plants?
aids with gas exchange
inc rate of photosynthesis
Why do hydrophytes have so many stomata?
to aid with gas exchange
Where are stomata found in hydriohytes?
upper surface of leaf
What is the waxy cuticle thickness in a hydrophyte?
thin
How long are the root systems in hydrophytes?
short
Why are the root systems short in hydrophytes?
so they are not damaged by current
water is readily available
What is the source?
where sugars are made or released from starch
What are examples of sources?
leafs
roots
What is a sink?
where sugars are used in respiration
or converted for storage
so low in concentration
What happens in active loading?
H+ in the companion cells
are actively transported out into
surrounding tissue
What happens as a result of H+ being pumped out of companion cells?
H+ conc increases and H+ reenter companion cells
How do H+ move back into the companion cell?
cotransporter protein by facilitated diffusion
What type of cotransporter protein would be used?
sucrose or amino acid
What diffuses through the plasmodesmata and into the sieve tube elements
sucrose
What does sucrose diffuse through to get to the sieve tube elements?
plasmodesmata
What is the mass flow hypothesis?
sucrose lowers W.P of sieve tube elements
so water moves into sieve tube elements from xylem by osmosis
What impact does sucrose have on the water potential of sieve tube elements?
lowers W.P
What happens as a result of the low water potential in the sieve tube element?
water moves into the sieve tube element from xylem by osmosis
How does water move into the sieve tube element?
osmosis
What does the osmosis into the sieve tube element cause?
inc in hydrostatic pressure inside sieve tube lements at source
How does sucrose leave the sieve tube lements?
diffusion
What happens to the W.P after surcrose leaves the S.T.E?
inc
What happens in the sieve tube elments when W.P inc?
water leaves by osmosis
How does water leave the S.T.E?
OSMOSIS
How do assimilates move from source to sink?
down the hydrostatic pressure gradient by mass flow
What does the phloem do?
transports assimilates from source to sink
examples of assimilates?
sucrose or amino acids
Outline translocation?
Hydrogen ions in companion cells are actively transported into the surrounding tissue
H+ move back into the companion cell wiht a sucrose
