transport in plants Flashcards
what does dicotyledeneous
2 seed leaves
where are places in plants in which gas exchange can occur
stomotas
root hair cells
what do xylem transport
water and mineral ions
what do phloem transport
sugars and amino acids
what is the transpiration stream
the movement of water up a plant
what is transpiration
the evaporation of water
what process allows water to move from cell to cell
osmosis
draw a root hair cell
how does water move into the root hair cells
facilitated diffusion and active transport
what is an apoplastic pathway
water moves from cell to cell through the cellulose cell wall
why is the apoplastic pathway the more effective and quicker way
the cellulose cell wall is fully permeable for water can diffuse easily
what is a symplastic pathway
water moves from cell to cell through the cytoplasm (plasmodesmata)
why is the apoplastic pathway blocked
the water molecules have reached the endodermis of the root which is waterproof so water molecules cannot get through so divert onto the symplastic pathway
draw a stem
give 3 adaptations of xylem cells
lignified cell walls (provides strength)
no end plates (mass flow of water)
made up of dead cells (doesn’t impede the mass flow of water)
what is the movement of water up a stem called
mass flow
give 3 mechanisms which make water flow up the stem
root pressure
cohesion
adhesion
how does water pressure make water flow up the stem
as water continuously enters the root it will create a small amount of pressure
how does cohesion make water flow up the stem
water is polar and makes hydrogen bonds, it forms bonds with other water molecules and pull it up the stem
how does adhesion make water flow up the stem
hydrogen bonds between water molecules and sides of xylem walls
what is capillary action
water molecules stick to each other and can rise up narrow tubes
what does capillary action do
increases as the diameter of the tube decreases
is water transport passive or active
passive
where does water enter into from the xylem vessels
mesophyll cells
what is the process of water evaporation
diffusion
what is transpiration
water evaporating out of a leaf
give 5 examples of adaptations which minimise the water vapour lost
waxy cuticle
stomota found underneath the leaf
stomata closed at night
deciduous plants lose their leaves in the winter as there is less water available
how is stomatas being underneath the leaf an efficient way of minimising the water lost
it reduces evaporation as the leaf is not in direct sunlight from the sun
give 2 reasons why it is important that plants don’t lose too much water by transpiration
so the plant doesn’t wilt and stays turgid so the stem is stable
water is needed for photosynthesis
describe the route of water into the root
soil
root hair cell
epidermis
cortex
endodermis
pericycle
xylem
explain how the total lack of cell contents makes the xylem efficient at transporting water
the water can flow up the column uninterrupted without meeting resistance
explain how the xylem having no end walls in individual xylem element makes it efficient at transporting water
no end walls means that the water can flow continuously without meeting resistance
explain how the xylem having a diameter of between 0.01mm and 0.2mm makes it efficient at transporting water
smaller the diameter
increase in adhesion
increase in capillary action
increase in hydrostatic force
explain how the xylem having lignified walls makes it efficient at transporting water
very strong- withstand the mass flow and won’t collapse
waterproof- water won’t leak out
explain how the xylem having pits makes it efficient at transporting water
allows water to move into cells
if there any blockages, water can move to other vessels
what is translocation
the transport of organic solutes across a plant
give 3 examples of assimilates (transported in the phloem)
amino acids
hormones
sugars
what is phloem tissue made up of
sieve tube elements which make a continuous column
companion cells which help them to function
what organelles do the sieve tube elements lack
nucleus
vacuole
little cytoplasm
what is a sieve plate
where to sieves meet
what are the pores called in phloem
sieve pores
why do the companion cells use active processes
to actively load sugars into the sieve tubes
how can scientists collect sap from the phloem
aphids
is the transport in phloem active or passive
active
what is a source
any part of a plant that loads organic solutes into the phloem
what is a sink
any part of the plant that takes organic solutes out of the phloem
what is the difference in the direction between phloem and xylem
phloem- up and down
xylem- up only
describe the general mechanism for mass flow of phloem sap
sucrose is actively loaded into the sieve tube elements and reduces the water potential
water follows by osmosis
sap moves down the sieve tube by hydrostatic pressure
sucrose is removed from the sieve tubes, which increases the water potential in the sieve tube
water is removed and this reduces hydrostatic pressure
give an example of a source
leaf
give an example of a sink
growing tip
what cells carry out photosynthesis
mesophyll cells
what is the cell membrane phloem called
plasmodesmata
describe the steps of sucrose being ‘loaded’ into the phloem
H+ ions are actively pumped out of the companion cells using ATP (active transport)
this creates a high concentration of H+ ions so will need facilitated diffusion to move back into the companion cells involving a protein carrier (which will only work if sucrose is present)
sucrose concentration is too high in the companion cell and then diffuses across the plasmodesmata
what is the process that moves sucrose for a higher concentration to a lower concentration
facilitated diffusion
what are the 2 uses of sucrose in a cell
can be hydrolysed into glucose and fructose
can be used as energy storage (e.g. starch)
how do we know that phloem uses an active process
companion cells have mitochondria
what are terresterial plants
plants that live on land
what are the 2 things that plants which live on land must be adapted for
loss of water
replacing water lost
what are xerophytes
plants that live in dry conditions
how do sunken stomatas minimise water loss
reduces air movement
increases humidity (creates a water vapour potential gradient)
how does a reduced number of stomatas minimise water loss
less gas exchange occurs
less water lost via transpiration
how does a reduced number of leaves minimise water loss
reduced surface area
minimises water loss as there is a reduction in transpiration
how does a plant having curled leaves minimise water loss
all the stomatas are within a micro-environment which increases humidity which reduces water loss
what root adaptations are present in xerophytes
long roots
cover a large surface area to reach optimum water available
how does a plant having needles as leaves minimise water loss
reduces surface area
give an example of a xerophyte
cacti
what plants grow on sand dunes
maram grass
give 3 reasons why sand dunes are harsh environments
sand does not hold water
usually windy conditions
salty sand usually lowers water potential around the root
give 3 ways that maram grass is adapted to its harsh conditions
curl leaves in windy weather
hairs on epidermis
thick waxy layer on epidermis
give 3 ways that cacti are adapted to its harsh conditions
thick waxy layer on epidermis
spines instead of leaves
cacti close stomata in the day as it is the highest rate of transpiration
what are hydrophytes
plants that live in water
if plants float, why is it important that their leaves are on the surface of the water (3 ways)
in order to reach sunlight for photosynthesis
oxygen for respiration
CO2 for photosynthesis
why do hydrophytes have thin waxy cuticles
water loss by transpiration is not a need
why do hydrophytes have stomata found on the upper side of the leaf
gas exchange
why do hydrophytes have reduced supporting tissues
no need for it as the water creates support for them
why do hydrophytes have air sacs
in order for the plant to float
what is aerenchyma
packing tissue that forms in leaves
it has many air spaces
what is the function of aerenchyma
makes stems and leaves more boyant
forming a low resistance internal pathway for the movement of substances such as oxygen
what are hyathodes and why are they useful in hydrophytes
they release droplets off water which can be evaporated
this stops the transpiration stream being blocked
