iheartbio.weebly.comiheartbio.weebly.com/.../2htransportplants_2014.docx · web viewunderstand that...

Exexel IG Bio 2h Transport in Plants

Transport in Plants (2h)Learning outcomes (Students will be assessed on their ability to):

2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell

2.50 understand the need for a transport system in multicellular organisms

2.51 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant

2.52 describe the role of xylem in transporting water and mineral salts from the roots to other parts of the plant

2.53 explain how water is absorbed by root hair cells2.54 understand that transpiration is the evaporation of water from the surface of a

plant2.55 explain how the rate of transpiration is affected by changes in humidity, wind

speed, temperature and light intensity2.56 describe experiments to investigate the role of environmental factors in

determining the rate of transpiration from a leafy shoot

N.B. The workbook is strucutured in two parts. The first outlines activities that will help you develop notes that can be used later for revision. The second is a set of summary questions designed to help you test your understanding.

1


Note development

2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell AND 2.50 understand the need for a transport system in multicellular organisms

Watch the click4biology video ‘2.49 Diffusion in unicellular organisms’ and ‘2.50 Transport systems in multicellular organisms’. Which parts of the videos are important for plants? Make some summary notes below.

2


2.51 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant

source: http://click4biology.info/

Complete the table below to outline the steps in the transport of sugars and amino acids in a plant.

Step Notes / outline

1Loading of sucrose and amino acids at

the source

Glucose (monosaccharide) is converted …

Soluble sucrose and amino acids …

2 Companion cell Are actively involved …

3 Mass flow (extension)

High concentration of solutes …

The high pressure near the source …

4 Sieve plate

The cell walls between phloem cells contain …

5 Phloem Pholem cells have a very small …

6 Companion cell Are actively involved in …

7 Unloading at sink / storage

sucrose and amino acids are …

3

http://click4biology.info/


2.53 explain how water is absorbed by root hair cells

Roots branch out in the soil to reach a large area. As a consequence this increases the soil water they come into contact with. On the tips of the smallest roots there are root hair cells, which again increase the surface area of the roots and therefore help to increase the rate of water absorption.

The path of water absorption from root hair cells to xylem vessels

source: http://www.bbc.co.uk/education/guides/zwsdmp3/revision/2

source: http://preuniversity.grkraj.org/

Complete the gap-fill:

Water enters ____________________ ____________________ cells: tiny hairs covering the ends of the

smallest roots. They provide a ____________________ ____________________ ____________________for the

____________________ of water by the process of ____________________ . The uptake of water into the

root hair cell ____________________ the root hair cell and ____________________ it’s water potential.

Therefore ____________________ moves ____________________ the concentration gradient, by

____________________ into the ____________________ ____________________ cell. The process of dilution is

repeated until the ____________________ reaches the ____________________ ____________________ .

n.b. Root hair cells also absorb mineral ions. Mineral ions are often at low concentrations in the soil so uptake is by active transport using the energy from respiration.

4

http://preuniversity.grkraj.org/

http://www.bbc.co.uk/education/guides/zwsdmp3/revision/2


2.52 describe the role of xylem in transporting water and mineral salts from the roots to other parts of the plant

source: http://click4biology.info/ source: http://www.jic.ac.uk/microscopy/Gallery/data/images1/stem_zinnia_leaf_xylem.jpg

The loss of water from the leaves causes water to be pulled-up the xylem from the roots. This continuous flow of water is called the transpiration stream. Complete the statements to show how the transpiration stream is helpful to plants:

Supply water to cells for …

Carries mineral ions …

Supply water to cells to keep …

Heat energy is used to evaporate the water inside the leaf this …

Make brief notes on Xylem cells and how they are adapted to their function (you might find a diagram helpful):

5



2.54 understand that transpiration is the evaporation of water from the surface of a plant

source: http://click4biology.info/

(a) Water is brought to the leaf by the xylem.Water surrounds the cells and is taken in by those cells that need it.

(b) Excess water uses heat energy from the leaf to evaporate.Water vapour collects in air spaces between the spongy mesophyll cells.

(c) Water vapour exits the leaf by the stomata

2.55 explain how the rate of transpiration is affected by changes in humidity, wind speed, temperature and light intensity

Complete the gap-fill to summarise how transpiration is affected by different environmental factors:

The rate of transpiration is depends on ____________________ ____________________, i.e. for

transpiration to be ____________________ the concentration of ____________________ ____________________

inside the leaf needs to be much higher than the ____________________ of water vapour

____________________ the leaf.

If the ____________________ is high that means the concentration of

____________________ vapour in the air is high. This ____________________ the

difference in the ____________________ of water vapour between the inside and outside of

the leaf, therefore the higher the ____________________ the ____________________ the

rate of transpiration.

6



As transpiration continues water vapour ____________________ the leaf. This leads to an

____________________ in the concentration of water vapour outside the ____________________ .

____________________moves the air with a high concentration of water vapour ____________________

from the leaf ____________________ it with air that has a ____________________ ____________________ of

water vapour, therefore as the ____________________ speed ____________________the rate of

transpiration increases.

As ____________________ increases energy available to the water for ____________________ increases,

therefore the higher the temperature the ____________________ the concentration of water vapour

inside the ____________________ . This ____________________ the concentration gradient of water

vapour between the inside and outside of the leaf, which in turn leads to an ____________________

in the rate of transpiration.

The greater the ____________________ of light the faster the rate of ____________________.

Photosynthesis requires water therefore the ____________________ are opened to

____________________the rate of transpiration.

7


2.56 describe experiments to investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot

A bubble potometer can be used to illustrate the effects of light, wind, temperature and air humidity.

Potometers come in a variety of designs, but all follow the same basic principles and usually consist of:

A length of capillary tube A bubble is introduced to the capillary. As water is taken up by the plant, the bubble moves. The distance the bubble travels in a given time is determined by the rate of water uptake by the plant.

A reservoir. By turning the tap on the reservoir, the position of the bubble can be set at the start of the experiment. Some designs of potometer use a syringe instead of a funnel with a tap.

A tube for holding the shoot. In the diagram the shoot is held in place by inserting a rubber bung in the tube. The hole in the bung through which the shoot passes must be thoroughly greased with petroleum jelly to keep it airtight.

The rate of transpiration can be calculated using the formula below:

Rate of transpiration (cm/s) = Distance moved by the air bubble (cm)Time taken (s)

CORMS is Edexcel’s preferred way of structuring an experimental design:

C - CHANGE: what is your IV?O - ORGANISM: what organisms will be involved and what similarities do they need to have e.g. same sex, age, health, etc?R - REPEAT: ALWAYS REPEAT (this improves RELIABILITY)M1 - MEASURE: what is your DV and how will you measure it?M2 - More detail on your DVS1 - What needs to be kept the SAME, i.e. your CVs?S2 - You need to identify and control at least two CVs, but the more can identify, the better

8


Using the CORMS criteria write out a method to illustrate how transpiration is affected by wind.

For each of remaining environmental factors outline how you would change the method to measure the effect of each:

Humidity

Light

Temperature

9


Summary questions:

1. Both the adults and larvae of whitefly suck the sap of plants. After feeding, both produce honeydew, a sugary waste, in their faeces. This food source and damp air conditions encourage the growth of black mould on leaf surfaces. The diagram shows a leaf from a tomato plant which has been attacked by whitefly. Suggest why whitefly are found around the veins on the leaf. (1)

2. An aphid feeds by piercing the phloem tissue of a plant leaf with its mouthparts. After the mouthparts were removed, a fluid, rich in carbohydrate, continued to flow from the cut phloem.

a. Name the carbohydrate present in the fluid. (1)

b. Apart from being transported through the plant, name two other ways in which the glucose made in photosynthesis may be used by a plant. (2)

3. The diagram shows the movement of water in a plant.

a. What would happen to the plant on a bright breezy day if it lost more water than it could absorb? (1)

b. What other substances does the plant take in with the water it absorbs? (1)

c. Through which type of cell is the water carried in the plant? (1)

10


4. The diagram shows the end of a root.

a. Name X. (1)

b. Explain how X help in the absorption of water from soil. (2)

5. The diagram shows a root hair cell in soil. The soil particles are surrounded by a thin layer of water, which contains dissolved minerals.

a. Use the diagram to explain the process of osmosis in this root hair cell. (3)

b. Explain how the root hair cell takes up nitrate ions from the soil. (2)

c. Gardeners dig soil to let more air into it. This increases the uptake of nitrate ions.Explain why. (2)

6. The diagram shows the movement of water into a plant root.

a. Water enters the root hair cells by osmosis. Explain why this happens. (1)

11


b. Why does the root have so many root hair cells? (1)

c. Name cell W, which transports water to the other parts of the plant. (1)

7. Diagrams A and B represent two root hair cells. A is from a root in very dry soil and B is from the same root after water has been added to the soil.

a. (a) Give two ways cell B differs in structure from cell A. (2)

b. What has entered cell B? (1)

c. Name the process which has occurred in cell B. (1)

d. What cell structure limits this process? (1)

12


8. Some students were interested in how leaves lose water. They set up an experiment using four green leaves. Some of the leaf surfaces were covered with a waterproof jelly. Each leaf was treated differently, as shown in the diagram. The leaves were then fixed to a piece of string and left to hang in a warm laboratory for one week. The students recorded their observations.

a. Suggest two factors that the students must control make this experiment a fair test. (2)

b. The students found that leaves A and C showed no change after one week, but leaf B had become dry and curled up. Explain these results. (3)

c. Suggest how leaf D will look after one week. Explain your answer. (2)

d. Suggest one change that could be made to the conditions in the laboratory to slow down the changes in leaf D. (1)

13


9. The diagram shows the movement of water into, through and out of a plant. Complete the following sentences. (3)

Water enters a plant through special cells called

____________________ ____________________ cells.

Water is drawn up the stem through dead hollow cells

called ____________________.

Most water passes out of the plant through tiny holes

called ____________________.

10. The diagram shows the passage of water from a cell in a leaf to the outside air.

a. State the process by which water passes through stomata. (1)

b. Give two functions of water in the cells of a leaf. (2)

11. Plants lose water through their leaves. The environment where the plant is growing determines how quickly the water is lost.

a. Give TWO environmental conditions that affect the rate of water loss. (2)

b. Name the part of the leaf that the water escapes through. (1)Stomata/between the guard cells;

14


12. An experiment was carried out to see which surface of a leaf loses most water. Three leaves were differently treated with petroleum jelly. The results are shown below:

Time (mins) Loss of mass (mg)Leaf A Leaf B Leaf C

Leaf not treated Lower surface of leaf covered with petroleum

jelly

Upper surface of leaf covered with petroleum

jelly0 0 0 0

60 19 11 18120 44 25 41

a. Which leaf is the control? (1)

b. Through which surface is most water lost? (1)

c. Explain why most water is lost through this surface. (1)

d. Suggest why leaf A loses more water than leaf C. (1)

13. The graph below shows the amount of water lost each day by a potted plant left near an open window.

a. Using these results, state TWO weather conditions that were likely on day 6. (2)

b. What is the name given to the loss of water through leaves? (1)

15


14. The graph shows the water loss from a plant during a hot windy day.

a. Explain how the plant loses water. (2)

b. Explain why the plant might wilt two hours after the start of the experiment on a hot windy day. (4)

16


c. Draw a line on the graph to show the water loss from the same plant on a hot humid day. (1)

15. The diagram below shows a simple potometer.

a. What does this apparatus measure? (1)

b. When setting up a potometer suggest why the plant stem is cut under water. (1)

c. State would happen to the rate of transpiration if the leafy shoot was enclosed in a polythene bag and explain why. (3)

d. How might the result differ if the experiment was repeated with a shoot with fewer leaves? (1)

17


e. Students often think that a potometer measures water loss. Suggest ONE reason why water loss is not always the same as water uptake. (1)

16. Mary set up a potometer to investigate the transpiration rate in a shoot. In her notebook, Mary wrote the following method:

Sprinkle 10cm³ of water around the leaves of the shoot. Leave the shoot for 5 minutes. Measure the distance moved by the air bubble in the

capillary tube at the end of the next 3 minutes.

a. What factor, affecting the rate of transpiration, was Mary investigating? (1)

b. Why was the shoot sprinkled with water and then left for 5 minutes before any measurement was taken? (1)

c. In which direction Mary would expect the bubble to move. (1)

17. Potometers were placed in three different greenhouses with the conditions shown in the table.

Greenhouse Temperature Humidity VentilationA Warm High StillB Warm Low WindyC Cold High Still

a. In which greenhouse will the movement of the air bubble, in the apparatus, be greatest? (1)

b. What other environmental condition, in the greenhouse, must be kept constant during the investigation? (1)

18

iheartbio.weebly.comiheartbio.weebly.com/.../2htransportplants_2014.docx · web viewunderstand that...

Documents