7.1

Question 1

State the functions of xylem and phloem

Answer 1

Xylem vessels transport water and ions.

Phloem tubes transports sucrose and amino acids

Question 2

Identify the position of xylem and phloem as seen in sections of roots, stems and leaves, limited to non-woody dicotyledonous plants

Answer 2

see photo and diagrams from notebook or from quizlet

Question 3

Identify root hair cells, as seen under the light
microscope, and state their functions

Answer 3

see the diagrams in quizlet (you know what they look like!)

functions:
- single-celled extensions of epidermis cells in the root
- They grow between soil particles
- absorb water and minerals from soil
- Water enters the root hair cells by osmosis

Question 4

State the pathway taken by water through root, stem and leaf as root hair cell, root cortex cells, xylem and mesophyll cells

Answer 4

• Water moves through a root hair by osmosis. It then travels by osmosis through the cortex, from cell to cell, until eventually it reaches the xylem vessels in the middle of the root.
• These transport it all the way up through stem and into mesophyll cells in leaves.

Question 5

Investigate, using a suitable stain, the pathway of water through the above-ground parts of a plant

Answer 5

• 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).
• 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.
• If a cross section of the celery is cut, only certain areas of the stalk is stained with the dye, showing that the water is being carried in specific vessels through the stem - these are the xylem vessels.

Question 6

Water is transported from ____ to ____ through ___.

Answer 6

Water is transported from roots to leaves through xylem vessels.

Question 7

Define transpiration

Answer 7

A 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 8

Explain that the large surface area of root hairs increases the rate of the absorption of water by osmosis and ions by active transport

Answer 8

• 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 9

Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by cohesion

Answer 9

• Water moves through the xylem vessels in a continuous transpiration stream from roots to leaves via the stem.
• As the water moves into a root hair, across to xylem vessels, up to leaves and then out into air, it is moving down a water potential gradient.
• This produces a transpiration pull from above, drawing a column of water molecules held together by cohesion up the plant.

Question 10

Explain the effects of variation of temperature and humidity on transpiration rate

Answer 10

Temperature - transpiration increases as the temperature increases. On a hot day, water will evaporate more quickly from leaves of plant.
Humidity - transpiration decreases as humidity increases. This is because there is not much of a diffusion gradient for water between air spaces inside leaf, and wet air outside it.

Question 11

Define translocation (both definitions)

Answer 11

Translocation is the movement of sucrose and amino acids in the phloem, from regions of production, to regions of storage,
OR
Translocation is the movement of sucrose and amino acids in the phloem, from source to sink

Question 12

factors that can affect the rate of transpiration?

Answer 12

temperature being higher, air being dry, it being windier

Question 13

describe the route of water as it moves through a plant

Answer 13

enters through the root hair cells, moves through root cortical cells to the xylem up the stem into the leaves

Question 14

which process is used in a root to absorb:

1. water
2. mineral ions from soil water

Answer 14

1. osmosis
2. active transport

Question 15

why is the transportation rate faster when:

1. temp is higher
2. humidity of air is higher

Answer 15

1. when temp is higher particles move faster so water molecules will diffuse out of the leaf more quickly
2. when air humidity is high there is a high concentration of water in the air so more water particles will move from the air into the leaf - meaning rate of diffusion will be slower

Question 16

what is cohesion

Answer 16

Water molecules sticking together

Question 17

what is Adhesive

Answer 17

Water molecules attached to the xylem cell wall