B7.1 - Transport in Plants

Question 1

Xylem vessels

Answer 1

transport water and minerals from the roots to the stem and leaves

Question 2

Phloem vessels

Answer 2

transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem

Question 3

Vascular bundles

Answer 3

a strand of conducting vessels in the stem or leaves of a plant, typically with phloem on the outside and xylem on the inside

Question 4

Characteristics of xylem (name 3)

Answer 4

• long, hollow tube
• made of dead cells
• no end walls
• to withstand pressure, strengthened by lignin
• only in upward direction

Question 5

Characteristics of phloem (name 3)

Answer 5

• active transportation
• made up of living cells
• sieve tube cells: no nucleus, perforated end walls, cytoplasm connects cells
• companion cells: provides energy for translocation (lot of mitochondria)

Question 6

Lignin

Answer 6

substance in vascular plants that makes cell walls rigid

Question 7

Source

Answer 7

Where a susbtance is made

Question 8

Sink

Answer 8

Where a susbstance is stored or used

Question 9

What happends to translocation during the winter, the spring and the summer?

Answer 9

• Winter (no leaves): phloem tubes may transport dissolved sucrose and amino acids from the storage organs to other parts of the plant so that respiration can continue
• Spring (growth period): storage organs (eg roots) would be the source and the many growing areas of the plant would be the sinks
• After growth period (summer): 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

Question 10

Active transport

Answer 10

Energy-requiring process that moves material across a cell membrane against a concentration difference

Question 11

Passive transport

Answer 11

The movement of materials through a cell membrane without using energy

Question 12

Cortex cells

Answer 12

The tissue of unspecialised cells between the epidermis and the vascular bundle that transports water and nutrients absorbed by the root epidermis into the bundle and stores substances such as starch, resins, and essential oils

Question 13

Collenchyma

Answer 13

Type of ground tissue cell with a strong, flexible cell wall; helps support larger plants

Question 14

3 steps how water enters the plant

Answer 14

1. From soil to root
2. Into the stem of the leaves
3. Into the leaf

Question 15

How does water enter the plant and move from the soil to the roots?

Answer 15

• enters root hair cells by osmosis
• from the soil through the membrane (from higher water potential to lower water potential)
• diffuses cell to cell until it enters the xylem

Question 16

How does water move through the stem to the leaves?

Answer 16

• in one continuous column due to transpiration pull
• continuous column is due to cohesion between water molecules and adhesion to the wall of the xylem

Question 17

How does water move into the leaf?

Answer 17

• water diffuses out of the xylem to palisade mesophyll cells (for photosynthesis)
• also through the spongy mesophyll
• it evaporates into air spaces and moves out through the stomata

Question 18

Transpiration pull

Answer 18

The force by which column of water is pulled up the xylem as a result of transpiration.

Question 19

Cohesion

Answer 19

Attraction between molecules of the same substance

Question 20

Adhesion

Answer 20

An attraction between molecules of different substances

Question 21

Factors effecting transpiration (4)

Answer 21

• temperature
• humidity
• wind speed
• light intensity

Question 22

Translocation

Answer 22

The transport of sucrose and amino acids in the phloem, from regions of production to regions of storage or use

Question 23

Transpiration

Answer 23

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 24

How does temperature effect the rate of transpiration?

Answer 24

As temperature increases the rate of transpiration increases because water molecules will diffuse from the surface of the leaf faster

Question 25

How does humidity effect the rate of transpiration?

Answer 25

When the atmosphere is humid there will be a decrease in transpiration because there is less of a difference in the water concentration gradient between inside and outside the leaf

Question 26

How does wind effect the rate of transpiration?

Answer 26

The faster the wind speed, the greater the transpiration rate because the movement of air across the surface of leaves causes evaporation of water from the mesophyll cells, and this loss of water must be replaced by water moving up the xylem from the roots

Question 27

Root hair cells

Answer 27

Single-celled extensions of epidermis cells in the root
- water enters by osmosis because soil water has a higher water potential than the cytoplasm of the root hair cell

Question 28

What are the functions of transpiration? (name 3)

Answer 28

• 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 29

How does transpiration keep the leaf cool?

Answer 29

The conversion of water (liquid) into water vapour (gas) as it leaves the cells and enters the airspace requires heat energy. The using up of heat to convert water into water vapour helps to cool the plant down

Question 30

Wilting

Answer 30

• 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
• 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 31

Potometer experiment

Answer 31

1. Cut a shoot underwater to prevent air entering the xylem and place in tube
2. Set up the potometer - beaker with water connected by a capillary tube to test tube with plant shoot; covered by a bung; ruler beneath capillary tube
3. Remove capillary tube to allow a single bubble to form
4. Set up the environmental factor you are investigating
5. Allow the plant to adapt to the new environment for 5 minutes
6. Record the starting location of the air bubble
7. Leave for a set period of time
8. Record the end location of air bubble
9. Change a factor
10. Repeat the experiment
11. The further the bubble travels in the same time period, the faster transpiration is occurring and vice versa

Question 32

Potometer

Answer 32

Apparatus used to measure water uptake in a leaf shoot and so to estimate rate of transpiration

Question 33

How can temperature be investigated using a potometer?

Answer 33

Change the temperature of the room (cold room, warm room)

Question 34

How can humidity be investigated using a potometer?

Answer 34

Potometer experiment but spray water in plastic bag and wrap around plant

Question 35

How can light intensity be investigated using a potometer?

Answer 35

Changing the distance of a light source (e.g. a lamp) from the potometer