Transport in Plants

Question 1

What is transpiration?

Answer 1

Transpiration is the movement of water from the roots to the leaves through the xylem and then the loss of water by evaporation

Question 2

What is transpiration stream?

Answer 2

passage of water and minerals through the roots, stem and leaves of a plant

Question 3

The loss of water vapour from plant leaves by ——— of water at the surfaces of the ——-cells followed by ——of water vapour through the ——-

Answer 3

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

Question 4

Xylem is adapted in many ways

mention 3

Answer 4

• 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.

Question 5

What is lignin and whtat is its function?

Answer 5

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

Question 6

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

Answer 6

true

Question 7

in the xylem structure there is no internal cell walls

true or fales

Answer 7

true

Question 8

choose the correct answer

movement of water

surface of mesophyll to air spaces is by evaporation / diffusion ?

and leaves the stomata by evaporation / diffusion ?

Answer 8

movement of water

surface of mesophyll air spaces is by evaporation

H2O _(l) —-> H2O_(g)

and leaves the stomata by diffusion

Question 9

Transpiration has several functions in plants:

list 4

Answer 9

1. transporting mineral ions
2. providing water to keep cells turgid.
3. providing water to leaf cells for photosynthesis
4. keeping the leaves cool

Question 10

How does Transpiration Occur?

Answer 10

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

Question 11

How is the Transpiration Stream Created?

Answer 11

• 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

Question 12

where does the transpiration stream happens in plants?

Answer 12

xylem

Question 13

phloem cells are living cells

and xylem has dead cells

true or false

Answer 13

true

Question 14

what does have a higher water potential?

pure water

solution?

Answer 14

pure water?

Question 15

define the term osmosis

Answer 15

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.

Question 16

when does the plant cell become flaccid?

if put in dilue solution ?

if put in concentrated solution?

Answer 16

if put in concentrated solution

Question 17

when does the plant cell become turgid?

if put in dilue solution ?

if put in concentrated solution?

Answer 17

if put in dilue solution

Question 18

define the term turgid

Answer 18

description of a plant cell with a high internal pressure so that the cytoplasm pushes against the cell wall.

Question 19

explan what happnes to the plant cell if it’s plasmolysed.

Answer 19

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.

Question 20

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

Answer 20

plasmolysed

Question 21

differentiate between the following

evaporation , traspiration

Question 22

what are the factors affecting the rate of diffusion?

Answer 22

Question 23

what cause the opening and close of guard cells of stomata during transpiration?

or explain how the guard cell is adapted to its function

Answer 23

Question 24

differentiate betwwen diffusion and osmosis

Answer 24

Question 25

explain why xylem transport is unidirectional and phloem transport is bi-directional?

Answer 25

Question 26

describe the process of plasmolysis

Answer 26

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.

Question 27

label the diagram

Answer 27

left to right turgid flaccid plasmolised

Question 28

Transpiration can be measured by an instrument called a **_-----------_**.

Answer 28

Transpiration can be measured by an instrument called a **_potometer_**.

Question 29

describe how a root hair cell absorbs water

Answer 29

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

Question 30

in few lines describe how water moves from the soil throug the plant

Answer 30

**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

Question 31

where does evaporation take place in the leaf?

Answer 31

Evaporation takes place from the **surfaces of spongy mesophyll cells**

Question 32

label the diagram cross section through the stem of a plant

Answer 32

Question 33

label the diagram cross section through the root of a plant

Question 34

How does light intensity affect the rate of transpiration?

Answer 34

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.

Question 35

How does the temperature affect the rate of transpiration?

Answer 35

high temperature increase the rate of transpiration by increasing the rate of evaporation of water frmo the mesophyll cells.

Question 36

What is a potometer?

Answer 36

apparatus used to estimate transpiration rate. Measures water uptake by a plant .

Question 37

What are the adaptations of a xylem cell?

Answer 37

## Footnote 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

Question 38

What are the adaptations of a phloem cell?

Answer 38

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

Question 39

in Investigating transpiration rates using a potometer ## Footnote 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?

Answer 39

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

Question 40

specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next.

Answer 40

Sieve tubes

Question 41

specialised cells lying next to a sieve tube in the phloem and controlling its activities.

Answer 41

Companion cells

Question 42

Explain why the transpiration rate increases when the temperature increases.

Answer 42

1. Molecules have more kinetic energy 2. Faster diffusion of water/more evaporation of water (as temperature increases in leaf)

Question 43

what is the difference between weight potometer and volume potometer?

Answer 43

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

Question 44

label the following diagram of a structure of the phloem

Answer 44

Question 45

mention 3 differences between xylem and phloem

Answer 45

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)

Question 46

in potometer the student measured the rate of water uptake three times. Suggest how the reservoir allows repeat measurements to be made

Answer 46

Returns bubble to start

Question 47

Explain how the leaf reduces water loss. can you label the part responsible for this function on the diagram?

Answer 47

stomata can close

Question 48

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.

Answer 48

higher temperature causes higher rate of evaporation/transpiration.

Question 49

xylem and phloem grouped together in a stem or root

Answer 49

vascular bundle

Question 50

explain how a guard cell is adapted to its function

Answer 50

* 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

Question 51

explain how a root hair cell is adapted to its function

Answer 51

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 l**ow water potential** This causes water to move into the root hair cell by osmosis

Question 52

explain how a xylem vessel is adapted to its function

Answer 52

* **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

Question 53

explain how phloem is adapted to its funciton

Answer 53

* 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

Question 54

label the diagram

Answer 54

A = stomata B = guard cell C = epidermis cell

Question 55

label the diagram

Answer 55

A = upper epidermis B = palaside mesophyll C = stomata

Question 56

Name the process by which gases move in or out of a leaf.

Answer 56

Gas exchange

Question 57

label the vascular bundle

Answer 57