Download public exam_nutrition and gas exchange in plants_R1

ECF Saint Too Canaan College
Biology public exam exercise
Nutrition and gas exchange in plants
Name: ___________________
Class: ______ (
)
Date: _____________________
CE 2000_I_Q.1(b)
1. The diagram below shows part of a section of a leaf:
(a) Name tissues A and B.
(2 marks)
(b) Regions 1 and 2 have the same area. Work out the ratio of the density of chloroplasts in
region 1 to that in region 2.
(2 marks)
(c) With reference to your answer to (b), what would be the significance of this pattern of
chloroplast distribution in the leaf? Explain your answer.
(4 marks)
Bio_public exam exercise_nutrition and gas exchange in plants
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CE 2002_I_Q.2(b)
2. The photomicrographs below show part of the transverse section of the leaf blade of a terrestrial
dicotyledonous plant and that of a moss:
(a) (i)
(ii)
Name structure A.
(1 mark)
Explain one way in which A contributes to the function of cell B under bright
sunlight.
(2 marks)
(b) The moss above is often covered with a thin film of water.
obtains oxygen from the atmosphere at night.
Describe how the moss leaf
(3 marks)
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CE 2005_I_Q.9
3. Mary examined the epidermis of the leaf of a land plant under the microscope. The
photomicrographs below show the appearance of the upper and lower epidermis under different
magnifications:
(a) Using the information provided in photomicrograph 2, calculate the stomatal density (i.e.
number of stomata per unit area) of the lower epidermis. (Take  
(2 marks)
(b) Compare the stomatal density of the upper and lower epidermis of the leaf. Explain the
significance of this pattern of stomatal distribution to the plant when it is under direct
sunlight.
(3 marks)
(c) Name structures P and Q.
P:
Q:
(2 marks)
(d) Under certain conditions, the stomata of the leaves may become closed during daytime.
Explain how this would affect the rate of photosynthesis of the plant.
(2 marks)
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DSE_PP(CS Bio)_B_Q.7
4.
In some plant species, leaves that develop in shady places (shade leaves) are structurally and
metabolically different from leaves that grow in sunny places (sun leaves).
(a) The photomicrograph below shows the cross section of a leaf taken from a plant species
grown in a shady place:
(i)
With reference to two features observable in the photomicrograph, describe how the
leaf is adapted to allow the palisade mesophyll cells to obtain the gas required for
photosynthesis.
(ii)
(2 marks)
The sun leaves of this plant species have a thicker cuticle than its shade leaves. Why
is it important for the sun leaves to have a thicker cuticle?
(2 marks)
(b) The graph below shows the net carbon dioxide uptake of two plants of species P in
different light intensities. One plant is grown in a sunny place and the other is grown in a
shady place.
(i)
What is the implication of having a positive net uptake of carbon dioxide for a plant?
(1 mark)
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4.
(b) (ii)
From the graph, compare the compensation points of the leaves of species P grown
in a sunny place and in a shady place. Hence, explain how this plant species can
adapt to living in shady places.
(2 marks)
(iii) The following photographs show two potted plants, Q and R:
Using hydrogencarbonate indicator solution, design an experiment to compare the
compensation points of these two potted plants. Illustrate the set-up used with a
labeled diagram.
(5 marks)
Diagram of the set-up:
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ECF Saint Too Canaan College
Biology public exam exercise – Nutrition and gas exchange in plants answer
1.
(a)
Tissue A is *palisade mesophyll
Tissue B is *spongy mesophyll
1
1
(b)
Number of chloroplasts in region 1 is 20; while that in region 2 is 12
Ratio of chloroplast density in region 1 to that is region 2 is 5:3
1
1
(c)
This allows the leaf to carry out photosynthesis at a higher rate
because tissue A has a higher density of chloroplasts
and it is located in the upper layer of the leaf
so its cells are under direct illumination / can receive more sunlight than the cells of
1
1
1
1
tissue B.
(7)
2.
(a) (i)
(ii)
*stoma
1
It allows carbon dioxide to enter the leaf
for photosynthesis in cell B
1
1
(b) Atmospheric oxygen dissolves into the water film on the moss leaf
and then diffuse in
through the entire surface of the leaf.
3.
(a)
(b)
(c)
1
1
1
(6)
Stomatal density of lower epidermis =
5
3.14  (0.25) 2
mm  2
1
= 25.48 mm– 2
1
The upper epidermis has a lower stomatal density than the lower epidermis / the
upper epidermis has no stomata while the lower epidermis has stomata.
1
This helps to reduce water loss / the rate of transpiration of the leaf
because the temperature at the upper epidermis is higher when the plant is under
direct sunlight.
1
1
P: *chloroplast
Q: *cell wall
1
1
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3.
(d)
The closure of the stomata limits the diffusion / intake of carbon dioxide into the
leaf.
1
Thus the rate of photosynthesis of the plant is reduced.
1
(9)
4.
(a) (i)
Any two of the following:
 The presence of stomata allows carbon dioxide to diffuse rapidly from the
atmosphere into the leaf. (1)
 The large spaces among the spongy mesophyll cells allow the carbon dioxide
to diffuse freely to the palisade mesophyll cells for photosynthesis. (1)
 The leaf is thin, which reduces the distance over which carbon dioxide has to
2
diffuse from the lower part of the leaf to the palisade mesophyll cells for
photosynthesis. (1)
(ii)
Being always exposed to a high light intensity, the sunny leaves have a higher
1
evaporation rate.
The thick cuticle prevents the sun leaves from excessive loss of water through the
cuticle.
1
(b) (i)
A positive net uptake of carbon dioxide implies that the photosynthetic rate of the
plant exceeds its rate of respiration / implies a net production of food in a plant.
1
(ii)
When grown in a shady place, the leaves of species P have a lower compensation
point than those grown in a sunny place.
This ensures that the plant can still attain positive growth in an environment with
low light intensity.
1
A workable set-up illustrated with a labeled diagram.
Keep the controlled variables (environmental conditions, e.g. temperature)
identical for both set-ups.
Subject the set-ups to very low light intensity for a fixed period of time (e.g. 30
2
1
(iii)
minutes) and note the colour of the indicator. Repeat this step with increasing
light intensity (i.e. by reducing the distance between the light source and the plant
OR adjusting the dimmer-control to increase the brightness of the light bulb).
Determine the light intensity at which the indicator in each set-up remains red.
Compare these light intensities.
1
1
1
(12)
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