Transport in Plants Flashcards
What is transpiration?
Transpiration is the movement of water from the roots to the leaves through the xylem and then the loss of water by evaporation
What is transpiration stream?
passage of water and minerals through the roots, stem and leaves of a plant
The loss of water vapour from plant leaves by ——— of water at the surfaces of the ——-cells followed by ——of water vapour through the ——-
The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
Xylem is adapted in many ways
mention 3
- A substance called lignin is deposited in the cell walls which causes the xylem cells to die
- These cells then become hollow (as they lose all their organelles and cytoplasm) and join end-to-end to form a continuous tube for water and mineral ions to travel through from the roots
- Lignin strengthens the plant to help it withstand the pressure of the water movement.
What is lignin and whtat is its function?
Lignin is a woody material present in the cell walls of xylem vessels it provides strength and makes the walls withstand the pressure of the water movement, anlso makes the walls impermeable to water
Movement in xylem only takes place in one direction - from roots to leaves (unlike phloem where movement takes place in different directions)
true or fales
true
in the xylem structure there is no internal cell walls
true or fales
true
choose the correct answer
movement of water
surface of mesophyll to air spaces is by evaporation / diffusion ?
and leaves the stomata by evaporation / diffusion ?
movement of water
surface of mesophyll air spaces is by evaporation
H2O (l) —-> H2O(g)
and leaves the stomata by diffusion
Transpiration has several functions in plants:
list 4
- transporting mineral ions
- providing water to keep cells turgid.
- providing water to leaf cells for photosynthesis
- keeping the leaves cool
How does Transpiration Occur?
evaporation of water from the leaf cell walls into air spaces in spongy mesophyll.
followed by diffusion of water vapour out of the leaf through stomata
How is the Transpiration Stream Created?
- Water molecules are attracted to each other by cohesion - creating a continuous column of water up the plant
- Water moves through the xylem vessels in a continuous transpiration stream from roots to leaves via the stem
- Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the leaves
- As water molecules are held together by cohesive forces (each individual molecule ‘pulls’ on the one below it), so water is pulled up through the plant
- If the rate of transpiration from the leaves increases, water molecules are pulled up the xylem vessels quicker
where does the transpiration stream happens in plants?
xylem
phloem cells are living cells
and xylem has dead cells
true or false
true
what does have a higher water potential?
pure water
solution?
pure water?
define the term osmosis
net diffusion of water molecules accross a partially permeable membrane from from a solution with a high water potential to a solution with a low water potential.
when does the plant cell become flaccid?
if put in dilue solution ?
if put in concentrated solution?
if put in concentrated solution
when does the plant cell become turgid?
if put in dilue solution ?
if put in concentrated solution?
if put in dilue solution
define the term turgid
description of a plant cell with a high internal pressure so that the cytoplasm pushes against the cell wall.
explan what happnes to the plant cell if it’s plasmolysed.
a plant cell that has lost water by osmosis. this is resulting in the cell contents shrinking and the cell membrane and cytoplasm pulling away from the cell wall.
a plant cell was placed in a concentrated sucrose solution. the diagram below shows the appearance of the cell after an hour in the solution
what is the best description of this cell?
- turgid
- flaccid
- plasmolysed
- wilted
plasmolysed
differentiate between the following
evaporation , traspiration
what are the factors affecting the rate of diffusion?
what cause the opening and close of guard cells of stomata during transpiration?
or explain how the guard cell is adapted to its function
differentiate betwwen diffusion and osmosis
explain why xylem transport is unidirectional and phloem transport is bi-directional?
describe the process of plasmolysis
when a cell of a plant is kept in a concentrated solution , the concentrated solution has a lower water potential than the cell contents. it will lose water by osmosis . Eventually the cell contents shrink so much that the membrane and cytoplasm split away from the cell wall and gaps appear between the membrane and cell wall.
label the diagram
left to right
turgid
flaccid
plasmolised
Transpiration can be measured by an instrument called a ———–.
Transpiration can be measured by an instrument called a potometer.
describe how a root hair cell absorbs water
Root hairs are single-celled extensions of epidermis cells in the root
They grow between soil particles and absorb water and minerals from the soil
Water enters the root hair cells by osmosis
This happens because soil water has a higher water potential than the cytoplasm of the root hair cell
in few lines describe how water moves from the soil throug the plant
Root hairs are single-celled extensions of epidermis cells in the root
They grow between soil particles and absorb water and minerals from the soil
Water enters the root hair cells by osmosis
This happens because soil water has a higher water potential than the cytoplasm of the root hair cell.
Osmosis causes water to pass into the root hair cells, through the root cortex and into the xylem vessels.
Once the water gets into the xylem, it is carried up to the leaves where it enters mesophyll cells
So the pathway is:
root hair cell → root cortex cells → xylem → leaf mesophyll cells.
Water travels up xylem from the roots into the leaves of the plant to replace the water that has been lost due to transpiration
Transpiration is defined as the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
Water moves through the xylem vessels in a continuous transpiration stream from roots to leaves via the stem
Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the leaves
As water molecules are held together by cohesive forces (each individual molecule ‘pulls’ on the one below it), so water is pulled up through the plant
If the rate of transpiration from the leaves increases, water molecules are pulled up the xylem vessels quicker
where does evaporation take place in the leaf?
Evaporation takes place from the surfaces of spongy mesophyll cells
label the diagram
cross section through the stem of a plant
label the diagram
cross section through the root of a plant
How does light intensity affect the rate of transpiration?
Brighter the light, greater the transpiration rate. Stomata close cause it’s dark. They don’t need to be open to let co2 in. Very little water can escape.
How does the temperature affect the rate of transpiration?
high temperature increase the rate of transpiration by increasing the rate of evaporation of water frmo the mesophyll cells.
What is a potometer?
apparatus used to estimate transpiration rate. Measures water uptake by a plant .
What are the adaptations of a xylem cell?
No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
Cells are essentially dead, no nucleus, no cytoplasm, to allow free passage of water
Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
What are the adaptations of a phloem cell?
Made of living cells that are supported by companion cells
Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through
in Investigating transpiration rates using a potometer
In this investigation, there are several different variations of the method depending on which environmental factor you are testing. However, if testing the effect of light intensity, y
what is the IV?
what is the CV?
what is the DV
how can you make results reliable?
what is the IV? the intensity of the light
what is the CV? temperature / wind speed / humidity
what is the DV? distance travelled by the bubble
to make it reliable repeat the investigation several times
specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next.
Sieve tubes
specialised cells lying next to a sieve tube in the phloem and controlling its activities.
Companion cells
Explain why the transpiration rate increases when the temperature increases.
- Molecules have more kinetic energy
- Faster diffusion of water/more evaporation of water (as temperature increases in leaf)
what is the difference between weight potometer and volume potometer?
weight potometer measures the los of mass from a potted plant or leafy shoot
volume potometer to find the rate of uptake of water by leafy shoot
label the following diagram of a structure of the phloem
mention 3 differences between xylem and phloem
xylem transport water and minirals
phloem transports sugars
xylem transports up only from roots to leaves
phloem transports up and down from leaves to parts of the plant
xylem has no end walls between cells
phloem has cell ends with perforations ( sieve plates)
in potometer the student measured the rate of water uptake three times. Suggest how the reservoir allows repeat measurements to be made
Returns bubble to start
Explain how the leaf reduces water loss.
can you label the part responsible for this function on the diagram?
stomata can close
Between 8am and midday the rate of flow of water continues to rise although the total area of the stomatal openings remain constant. Explain why the rate of flow of water rises.
higher temperature causes higher rate of evaporation/transpiration.
xylem and phloem grouped together in a stem or root
vascular bundle
explain how a guard cell is adapted to its function
- huard cells surrounds the stomata and have banana like shape
- the inner wall close to stomata is thicker than the outer wall
in the light
water enters the guard cells by osmosis –> becomes turgid –> open stomata
in the dark
the guard cell lose water –> becomes flaccid –> close stomata
explain how a root hair cell is adapted to its function
They grow between soil particles and absorb water and minerals from the soil
Root hairs increase the surface area this increases the rate of the absorption of mineral ions by active transport
The high proportion of dissolved minerals and sugars in the cytoplasm gives it a low water potential
This causes water to move into the root hair cell by osmosis
explain how a xylem vessel is adapted to its function
- No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
- Cells are essentially dead, without organelles or cytoplasm, to allow free passage of water
- Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
explain how phloem is adapted to its funciton
- Made of living cells that are supported by companion cells
- Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through
label the diagram
A = stomata
B = guard cell
C = epidermis cell
label the diagram
A = upper epidermis
B = palaside mesophyll
C = stomata
Name the process by which gases move in or out of a leaf.
Gas exchange
label the vascular bundle
