transport in plants

Question 1

What two types of transport vessels do plants have?

Answer 1

Xylem vessels

Phloem vessels

Question 2

What is the function of xylem vessels?

Answer 2

Transport water and minerals ions and support the plant.

Question 3

What is the function of phloem vessels?

Answer 3

Transport sucrose and amino acids.

Question 4

How are the transport vessels in a plant arranged?

Answer 4

These vessels are arranged throughout the root, stem and leaves in groups called vascular bundles

Question 5

What are root hairs?

Answer 5

Root hairs are single-celled extensions of epidermis cells in the root

Question 6

What is the function of root hairs?

Answer 6

The function of root hairs is to absorb water and mineral ions from the soil.

Question 7

By what process does water enter the root hair cells?

Answer 7

Water enters the root hair cells by osmosis

Question 8

How does water move by osmosis into the root hair cells?

Answer 8

This happens because soil water has a higher water potential than the cytoplasm of the root hair cell

Question 9

What adaptation does the root hair cell have and how does this help?

Answer 9

The root hair increases the surface area of the cells significantly
This large surface area is important as it increases the rate of the absorption of water by osmosis and mineral ions by active transport

Question 10

What is the path by which water travels from root hair cell to the leaf?

Answer 10

root hair cell → root cortex cells → xylem → leaf mesophyll cells

Question 11

How can the pathway of water in a plant be investigated?

Answer 11

The pathway can be investigated by placing a plant (like celery) into a beaker of water that has had a stain added to it (food colouring will work well)

Question 12

What can you see after a few hours? (investigating pathway of water)

Answer 12

After a few hours, you can see the leaves of the celery turning the same colour as the dyed water, proving that water is being taken up by the celery

Question 13

Why does water have to keep travelling to the leaf?

Answer 13

Water travels up xylem from the roots into the leaves of the plant to replace the water that has been lost due to transpiration

Question 14

Transpiration definition

Answer 14

Transpiration is defined as the loss of water vapor from plant leaves.

Question 15

How does transpiration happen?

Answer 15

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 16

What substance helps with the adaptation of xylem vessels and what does it do?

Answer 16

A substance called lignin is deposited in the cell walls which causes the xylem cells to die

Question 17

Does the movement in the xylem take place in many directions?

Answer 17

NO

-Movement in xylem only takes place in one direction – from roots to leaves

Question 18

Does movement in the phloem take place in many directions?

Answer 18

YES

movement takes place in different directions

Question 19

What are the main ways in which transpiration helps plants? (

Answer 19

-transporting mineral ions
-providing water to keep cells turgid in order to support the structure of the plant
-providing water to leaf cells for photosynthesis
-keeping the leaves cool

Question 20

What are the three adaptations of the xylem?

Answer 20

Cells are joined end to end with no cross walls to form a long continuous tube.
Cells are dead, without cell contents, to allow free passage of water.
Outer walls are thickened with a substance called lignin, strengthening the tubes, which help support the plant.

Question 21

What are the two adaptations of phloem vessels?

Answer 21

The cells are joined end to end and contain holes in the end cell walls (called sieve plates) which allow easy flow of substances from one cell to the next.
Phloem tubes are made of living cells.

Question 22

What is the effect of temperature on transpiration rates?

Answer 22

The higher the temperature, the greater the kinetic energy of water molecules. This means that water evaporates faster from the surface of the mesophyll cells, and the water vapour diffuses out of the leaf into the air more quickly.

Question 23

what is the effect of humidity on transpiration rates?
Humidity means the moisture content of the air.

Answer 23

The higher the humidity of the air outside the leaf the lower the transpiration rate because water usually diffuses down a concentration gradient, but if the air outside is already saturated with water, there is more likely to be a net movement of water into the leaf (providing the stomata are open) rather than out.

Question 24

Evaporation takes place from the surfaces of spongy mesophyll cells. How do the interconnecting air spaces between these cells increase the rate of evaporation?

Answer 24

The many interconnecting air spaces between these spongy mesophyll cells and the stomata create a large surface area meaning evaporation can happen rapidly when stomata are open.

Question 25

What are water molecules attracted to each other by and what does this create?

Answer 25

Water molecules are attracted to each other by cohesion – creating a continuous column of water up the plant

Question 26

How does transpiration help the transpiration stream?

Answer 26

Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the leaves

Question 27

How is water pulled through the plant?

Answer 27

a transpiration pull that draws up a column of water molecules, held together by forces of attraction between water molecules

Question 28

Define transpirational pull.

Answer 28

Transpiration pull is the force that aids in drawing water upwards from roots to leaves.

Question 29

Difference between what process is carried out by the xylem and phloem

Answer 29

X - transpiration stream

P - translocation

Question 30

What is the effect of wind speed on transpiration rates?

Answer 30

The faster the wind speed, the faster the water is moved away from the plant, creating a steeper gradient and increasing the transpiration rate.

Question 31

What is wilting and what is the effect of this?

Answer 31

This is when all the cells of the plant are not full of water, so the strength of the cell walls cannot support the plant and it starts to collapse.

Question 32

How and why does wilting occur?

Answer 32

If more water evaporates from the leaves of a plant than is available in the soil to move into the root by osmosis, then wilting will occur.

Question 33

What is translocation?

Answer 33

This is the movement of sucrose and amino acids in the phloem from sources to sinks.

Question 34

What are the sources (where its made) of translocation?

Answer 34

Sources as the parts of plants that release sucrose or amino acids.

Question 35

What are the sinks of translocation?

Answer 35

Sinks as the part of plants that use or store sucrose or amino acids.

Question 36

Despite the fact that translocation can take place in many directions, what is the one way in which this process has to take place?

Answer 36

dissolved food is always transported from source (where it’s made) to sink (where it’s stored or used):

Question 37

What is the direction of translocation during winter?

Answer 37

During winter, when many plants have no leaves, the phloem tubes may transport dissolved sucrose and amino acids from the storage organs to other parts of the plant so that respiration can continue

Question 38

What is the direction of translocation during a growth period?

Answer 38

During a growth period (eg during the spring), the storage organs (eg roots) would be the source and the many growing areas of the plant would be the sinks

Question 39

What is the direction of translocation after the plant has grown?

Answer 39

After the plant has grown (usually during the summer), the leaves are photosynthesising and producing large quantities of sugars; so they become the source and the roots become the sinks – storing sucrose as starch until it is needed again