Download RHS R3101 June 2014 Level 3 Past Paper

Including Examiner Comments
R3101
PLANT TAXONOMY, STRUCTURE & FUNCTION
Level 3
Wednesday 25 June 2014
09:30 – 11:00
Written Examination
Candidate Number:
Candidate Name:
Centre Number/Name:
IMPORTANT – Please read carefully before commencing:
i)
The duration of this paper is 90 minutes;
ii)
ALL questions should be attempted;
iii)
EACH question carries 10 marks;
iv)
Write your answers legibly in the spaces provided. It is NOT necessary
that all lined space is used in answering the questions;
v)
Use METRIC measurements only;
vi)
Use black or blue ink only. Pencil may be used for drawings only;
vii)
Where plant names are required, they should include genus, species and
where appropriate, cultivar;
viii)
Where a question requires a specific number of answers; only the first
answers given that meet the question requirement will be accepted,
regardless of the number of answers offered;
ix)
Please note, when the word ‘distinct’ is used within a question, it means
that the items have different characteristics or features.
Ofqual Unit Code H/505/2966
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ANSWER ALL QUESTIONS
MARKS
Q1
Describe FIVE characteristics of angiosperms that allow them to grow and
reproduce on land.
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Q2
a) State what is meant by the term ‘species’ giving ONE NAMED plant example.
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b) Differentiate between subspecies and varietas (variety) giving a NAMED
example for EACH.
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c)
State the reasons for changes in plant nomenclature.
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Q3
Describe, with the aid of diagram(s), the structure AND function of:
i)
ii)
phloem sieve tube elements;
phloem companion cells.
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5
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Q4
a) Describe the following types of inflorescence giving a NAMED example for
EACH:
i)
ii)
iii)
spike;
panicle;
verticillaster.
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b) Compare the structure of a raceme and a cyme.
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9
MARKS
Q5
Explain, using ONE NAMED plant example in EACH case, how specific
names can indicate:
i)
ii)
iii)
iv)
v)
plant origin;
habitat;
colour;
growth habit;
leaf form.
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MARKS
Q6
a) State the environmental factors that could affect the rate of photosynthesis for
EACH of the following:
i)
ii)
light dependent reaction;
light independent reaction.
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b) Explain how levels of carbon dioxide can be manipulated in protected
cultivation to produce an optimum rate of photosynthesis.
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MARKS
Q7
State the role of the following tissues in secondary thickening in a woody
stem:
i)
ii)
vascular cambium;
cork cambium.
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Q8
a) Describe the process of water transport in a plant.
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b) Explain how this process can still occur in conditions of very high humidity.
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MARKS
Q9
Compare aerobic and anaerobic respiration by completing the table below.
Aerobic respiration
Anaerobic respiration
Environmental
requirements
2
Products
2
Energy yield
ATP
2
Location in cell
2
Example of
growing situation
where process
occurs
2
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MARKS
Q10 a) State what is meant by a synthetic plant growth regulator.
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b) Describe the use of TWO NAMED synthetic plant growth regulators.
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©These questions are the property of the Royal Horticultural Society.
They must not be reproduced or sold.
The Royal Horticultural Society, Wisley, Woking, Surrey GU23 6QB.
Charity Registration Number: 222879/SC038262
24
R3101
PLANT TAXONOMY, STRUCTURE & FUNCTION
Level 3
Wednesday 25 June 2014
Candidates Registered
Candidates Entered
Candidates Absent
Candidates Deferred
Candidates Withdrawn
70
50
13
1
6
71.43%
18.57%
1.43%
8.57%
Total Candidates Passed
Passed with Commendation
Passed
Failed
36
19
17
14
72.0%
38.0%
34.0%
28.0%
General comments
Candidates should ensure that they are prepared to answer questions on all aspects of the
syllabus and to attempt all questions.
Diagrams should be large, clear, labelled and preferably drawn in pencil.
Examples of plant names should include genus, species and where appropriate cultivar.
There should be sufficient room in the answer booklet for candidates to complete
drawings/answers on the page without using the marks column.
Q1
Describe FIVE characteristics of angiosperms that allow them to grow and
reproduce on land.
This question required candidates to identify and describe five structural and
reproductive characteristics of angiosperms in relation to their adaptation to
terrestrial life. Two marks were awarded for each correctly identified
characteristic with a description which indicated successful adaptation for
growth and reproduction on land. Many acceptable answers were given and
credited where specific characteristics of angiosperms, such as production of
flowers for sexual reproduction to protect sex cells/gametes, or to attract
specific pollinators, were linked to their success as terrestrial plants.
Other credited characteristics included efficient water transport by xylem
vessels and tracheids, production of seeds protected by a fruit, variety of seed
/fruit dispersal methods, a range of life cycles and growth habits which enables
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plants to exploit a variety of habitats, structural adaptations to reduce water
loss such as bark.
Marks were not awarded to answers which related to the general
characteristics of plants, such as autotrophic or able to
photosynthesise/respire.
Q2
a) State what is meant by the term ‘species’ giving ONE NAMED plant
example.
b) Differentiate between subspecies and varietas (variety) giving a NAMED
example for EACH.
c) State the reasons for changes in plant nomenclature.
In part a), marks were awarded to candidates who understood the term
‘species’, which is the basic unit of classification consisting of a group of similar
individuals which can interbreed to produce fertile offspring, and were able to
give a correctly named example of a plant species, such as Hedera helix.
Some candidates confused ‘species’ with ‘specific epithet’ the second part of
the binomial, in this example ‘helix’.
The second part of the question asked candidates to differentiate between
subspecies and varietas.
Subspecies is above varietas in the plant classification hierarchy and differs
from the species in a number of characteristics, which have often arisen in a
widely geographically isolated population. An example is Malva sylvestris
subsp. mauritanica. A varietas (variety), differs from species in one or more
characteristics, is ranked lower in hierarchy than subspecies and may evolve
due to a more local geographical isolation, an example being Malva alcea var.
fastigiata.
Marks could not be awarded to candidates who confused the terms variety and
cultivar.
In part c), candidates were asked to state reasons for changes in plant
nomenclature.
The reasons for changes in plant nomenclature and reclassification include:
reclassification due to advances in plant taxonomic research, particularly
advances in DNA profiling, changes following rulings by the International Code
of Nomenclature (ICN) or International Code of Nomenclature for Cultivated
Plants (ICNCP) such as plant family name changes or implementation of the
rule of priority, and changes due to misidentification or misnaming of plant
specimens. Marks were awarded to candidates who stated four of the above
points. Candidates will have been alerted to the fact that four points were
required because of the marks attributed to the question.
Q3
Describe, with the aid of diagram(s), the structure AND function of:
i)
ii)
phloem sieve tube elements;
phloem companion cells.
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Candidates’ answers varied in their detail of knowledge about phloem tissue.
Marks were awarded to candidates who drew large, clear and accurate
diagrams as were candidates who were able to describe aspects of both
structure and function of the cells. Marks were awarded in either the diagram
or the description.
A sieve tube element’s most noticeable structural feature is the sieve plate at
each end of the cell. It has a cellulose cell wall, some cell contents but no
nucleus and is linked by plasmodesmata to the adjacent companion cell. This
has a thin cell wall, nucleus, and cytoplasm containing many mitochondria.
The function of the sieve tube elements is to transport sucrose, organic solutes
and plant hormones from source to sink. The stacked sieve tubes allow
ingress/entry and egress/exit of water from xylem and mass flow. Perforated
sieve plates allow movement of water and solutes from tube to tube. The
functions of the companion cells include aerobic respiration to provide an
energy supply for loading and unloading of sucrose into and out of sieve tube
elements and transport within the sieve tube elements.
Q4
a) Describe the following types of inflorescence giving a NAMED example for
EACH:
i)
ii)
iii)
spike;
panicle;
verticillaster.
b) Compare the structure of a raceme and a cyme.
Many candidates were able to answer part a) of the question well. Some used
diagrams to help describe the structure of each inflorescence. Where named
plant examples are asked for candidates should give the full binomial name.
A Spike is an inflorescence with a group of flowers sessile on the peduncle,
without individual flower stalks. A NAMED example is Acanthus spinosus.
A Panicle is a branched raceme. (A flower spike where flowers have stalks of
equal length). Each branch has a smaller raceme of flowers. The terminal bud
of each branch continues to grow, producing more side shoots and more
flowers. A NAMED example is Lagerstroemia indica.
A Verticillaster is a whorled inflorescence, where the flowers are borne in rings
at intervals up the stem. The tip continues to grow, producing more whorls.
A NAMED example is Phlomis russeliana. Fewer candidates were able to
achieve full marks describing this inflorescence.
Marks were not awarded to candidates who stated that Digitalis purpurea has
a spike inflorescence which is wrong as each flower has a short pedicel rather
than being sessile on the axis of the inflorescence.
In part b), candidates found it difficult to distinguish between a raceme and a
cyme. A raceme has the oldest (stalked) flower at the base, and growth of the
main inflorescence stalk (peduncle) is not stopped by flower production.
Growth is monopodial or indeterminate.
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A cyme has the oldest flower at the top of inflorescence stalk and all
succeeding flowers are formed on succeeding side branches. Growth is
sympodial or determinate. Marks were awarded for accurate comparisons and
diagrams were helpful, although not asked for, if they showed the structure of
the inflorescence and positioning of flowers.
Q5
Explain, using ONE NAMED plant example in EACH case, how specific names
can indicate:
i)
ii)
iii)
iv)
v)
plant origin;
habitat;
colour;
growth habit;
leaf form.
This question was answered well by most candidates. Full marks were
awarded for examples like v) Leaf form:, if the named plant was Acer
palmatum, ‘palmatum’ meaning palmate or shaped like palm leaves with five or
more veins arising from a point.
Marks were not awarded if candidates confused habitat with growth habit,
stating the wrong genus with appropriate specific epithet, giving the wrong
interpretation of a stated specific epithet, giving an example of a cultivar name
rather than specific epithet and not interpreting their choice of specific epithet.
Q6
a) State the environmental factors that could affect the rate of photosynthesis
for EACH of the following:
i)
ii)
light dependent reaction;
light independent reaction.
b) Explain how levels of carbon dioxide can be manipulated in protected
cultivation to produce an optimum rate of photosynthesis.
Marks were awarded to candidates who mentioned that the light dependent
reaction could be affected by light intensity, duration and quality. Candidates
were credited who mentioned the appropriate wavelengths of light for PAR.
Marks were awarded for mentioning that water is also required for the light
dependent reaction and for the uptake of nutrients such as N, Mg, and Fe
which are essential for chlorophyll production.
Marks were awarded for the factors affecting the light independent reaction
that are temperature and atmospheric levels of carbon dioxide (CO2), which
can also be affected by levels of water availability. If leaves are water stressed,
stomata will close reducing the diffusion of carbon dioxide gas into the leaf.
Marks were not awarded when candidates did not distinguish between the light
dependent and light independent reactions.
Valid answers in part b) covered technical details for method of supply and
monitoring of levels of carbon dioxide (CO2) in protected production.
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Marks were awarded for identifying optimum levels of CO2, methods of
supplementing with piped CO2, or by burning propane, kerosene or paraffin, or
by utilising exhaust gases from adjacent industry, monitoring CO2 levels with
sensors, and ventilating on very bright, warm days to allow more gas exchange
with the atmosphere.
Q7
State the role of the following tissues in secondary thickening in a woody stem:
i)
ii)
vascular cambium;
cork cambium.
Some candidates were able to show the role of vascular cambium and cork
cambium in secondary thickening. Other candidates showed limited knowledge
of the different roles of both tissues.
Marks were awarded for answers including statements like vascular cambium
is a secondary, lateral meristem, which develops from intra and interfasicular
cambium to form a ring of meristematic tissue. As the cambium cells divide
they produce secondary xylem tissue to inside of the cambium, and secondary
phloem tissue to the outside. Other products are parenchyma for the medullary
rays and sclerenchyma. The variation in lumen diameter of the secondary
xylem from spring to autumn creates annual rings. The activity of the vascular
cambium increases the girth of the stem and also enables greater transport
capacity in a woody plant. Six valid points gained full marks for this section.
The cork cambium is also a secondary meristem and arises in the outer cortex
parenchyma outside the secondary phloem. The meristematic cells (phellogen)
divide to produce suberised cork cells (phellem), a protective outer layer to
stem, and parenchyma secondary cortex (phelloderm). The activity of the cork
cambium also increases the girth of the stem.
Candidates who stated terms such as ‘phelloderm’ or labelled layers in their
diagrams similarly with no explanation were not given full marks. Four valid
points gained full marks for this section.
Q8
a) Describe the process of water transport in a plant.
b) Explain how this process can still occur in conditions of very high humidity.
Many candidates achieved high marks on this question. Some candidates
used diagrams, although these were not asked for, to illustrate their answers.
In part a), marks were awarded to candidates able to describe the movement
of water from the growing medium into the root or root hairs by diffusion into
the apoplast pathway or osmosis into the symplast pathway. This root pressure
ensured that the flow of water continued across the cortex to the endodermis
and then took the symplast pathway because the apoplast route was blocked
by the suberised Casparian strip. Water then moved into the xylem vessels in
the stele. The main force moving water up the plant in the xylem is
transpiration pull, aided by capillary rise and the forces of cohesion between
water molecules and adhesion to the walls of the xylem vessels.
Water is distributed through the vascular system to the leaves where it
evaporates into the air spaces and diffuses into the atmosphere mainly through
stomata.
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Water follows a water potential gradient from the soil, through the plant to the
atmosphere.
In part b), many candidates understood that transpiration would be slower in
conditions of high humidity surrounding the leaves and aerial parts of the plant.
Root pressure would continue to force water into the xylem and excess water
could be lost by guttation of water droplets from hydathodes on the leaves.
Marks were awarded for answers reflecting any two of the above points.
Q9
Compare aerobic and anaerobic respiration by completing the table below.
The majority of candidates showed detailed knowledge of the processes of
aerobic and anaerobic respiration and were able to complete the table. An
outline of correct answers is given below.
Aerobic respiration
Anaerobic respiration
Oxygen
Low/no oxygen
Water
Carbon dioxide
Ethanol
Carbon dioxide
Energy yield ATP
38 ATP
2 ATP
Location in cell
Cytoplasm
Mitochondria
Cytoplasm
Example of growing
situation where process
occurs
Well aerated growing
medium
Water logged or
compacted growing media
Environmental
requirements
Products
Q10
a) State what is meant by a synthetic plant growth regulator.
b) Describe the use of TWO NAMED synthetic plant growth regulators.
This question asked candidates to define what a synthetic plant growth
regulator was and to describe the use of two named synthetic plant growth
regulators.
In part a), many candidates were awarded marks by being able to state that a
synthetic plant growth regulator is a manufactured chemical applied to the
plant in order to produce specific growth responses or to mimic or inhibit
endogenous plant growth regulators.
In part b), it was expected that candidates would choose two synthetic PGRs
from the syllabus list and describe their mode of action, their purpose in terms
of horticultural process, and application method with possible details of
formulation and timing for maximum marks.
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An example of a full answer for one synthetic plant growth regulator would be:
Paclobutrazol, which inhibits gibberellin production, is used in bedding plant
production to produce uniform, compact, sturdy plants, and increase flowering.
Details of its application could include that it is applied as a spray from when
plants have made new growth, two weeks after pricking out, and repeated as
necessary.
Some candidates were able to give the technical details required for their
chosen named synthetic plant growth regulators but many were not.
©These questions are the property of the Royal Horticultural Society.
They must not be reproduced or sold.
The Royal Horticultural Society, Wisley, Woking, Surrey GU23 6QB.
Charity Registration Number: 222879/SC038262
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