IBL2 Biology Summer Work: Plant Biology
Data-based questions: The Renner experiment
Figure 9 shows the results of an experiment
by the German plant physiologist Otto Renner
in 1912. A transpiring woody shoot was placed
in a potometer and the rate of water uptake was
measured. A clamp was attached to the stem to
restrict the flow of water up to the leaves. Later
on, the top of the shoot, with all of its leaves, was
removed. A vacuum pump was then attached to
the top of the shoot.
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and the rate caused by the leaves immediately
before the shoot top was cut off.
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The water in the potometer was at
atmospheric pressure. The vacuum pump
generated a pressure of zero. Discuss what
the results of the experiment showed about
the pressures generated in the xylem by the
leaves of the
shoot.
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stem clamped
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E
0uestions
Describe the effect of clamping the stem on
the rate of water uptake.
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Explain the effect of cutting off the top of the
shoot on the rate of water uptake.
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f;4
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I
P7
+6
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vacuum Pump
2
Calculate the difference between the rate of
water uptake caused by the vacuum pump
/
shoot removed
11-
2
L
time IhrsJ
r
Figure 9 Rebults of the Renner experiment
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Data-based questions: Fungal hgphae and m¡neralion absorption
b) Suggest a reason for the relationship. tll
Figure I0 shows the results of an e>çeriment in
which seedlings of Sitka spruce, Picea sitchens¡s, were
c) Using the data in Figure 10, deduce
grown for ó months in sterilized soil either with
whether the effects of closely related fungi
or without fungi added: C was the control with no
on tree growth are the same.
Í2)
fungi added. The species of fungi added were:
: Laccaria laccata; [.: Laccaria ameythestea;
m: Thelophora terrestni from a tree nursery;
'N : Thelophora terrestr¡s from a fo¡est;
Y : Paxillus involutus;YI: Pisolithus tinctorius.
a) Discuss the effects of the five species of
0.5
I
x
b)
a)
fungi on the growth of the roots and
shoots of the tree seedlings.
Explain the effects of the fungi on the
growth of tree seedlings.
State the reiationship between root
growth and shoot growth in the tree
seedlings.
E
o.¿
Ø
E
E
P
E
E
o.E
0.2
o.r
'E
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Ø
0.0
3
o.r
Ø
0.?
tr
E
? 0.3
E
0.4
Ë
I 0.5 c I il lll v lvvl
r Figure 10 Results of Sitka spruce experiment
IBLZ Biology Summer Work: Plant Biology
I
Data-based questions Fç
I Á The only animals to consume
sap as the main part of their diet are
insects þelonging to a group called the
Hemiptera. The data in this question
comes from research into aPhids.
Aphids ingest larger volumes of phloem
sap than they need, to obtain sufficient
sugar for cell iespiration. This is because
they also need to obtain amino acids and
the concentration of amino acids in phloem
sap is low. Figure I I shows the percentages
of individual amino acids in phloem sap
and the percentages in aphid protein. Nine
of the amino acids cannot be synthesized
in aphid cells and so are called essential
amino acids. The other amino acids can be
synthesized from other amino acids and so
The sugar content of phloem sap is very
high - often greater than I mol dm-r.
(i) Explain how plants increase the
sugar
concentration of phloem sap to such
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high levels.
sugar
high
how
(ii) Explain
concentrations cause a high pressure
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to develop in the Phloem.
Aphids only ingest a small proportion of
the sugar in ptrloem sap.'The remainder
passes out in the faeces, which is a ìiquid
called honeydew. Because of the high sugar
concentrations, phloem sap has a much
higher solute concentration than aphid cells.
Enzymes secreted into the aphid gut reduce
the solute concentration of phloem sap by
converting sugars into oìigosaccharides.
Figure I I shows the relationship between
the sucrose concentrations of phloem sap
ingested by aphids and the oligosaccharide
content of the honeYdew
880
êso
o
U
.9p
9zo
È<
0
0.
Dietarg sucrose concentration (mol]
10
Describe the relationship between the
sucrose concentration of phloem sap
ingestedby aphids and the percentage of
oligosacdrarides þ the honeydew t3l
(ii)
Suggest reasons for aPhids
secreting enzyrnes to reduce the
solute concentration of the fluid
the
o
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o
È
o
=a
õ
z
v
o
*ã1
o Non-essential
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'6
amino acids
o
o
o Essential
,-
å0 /
amíno acids
Amino acid %¡n
sap
À Figure 11
(i)
Evaluate phloem sap as a source of
amino acids for
(ii)
aPhids'
Suggest reasons for the differences
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in
organisms contain bacteria called Buchnera,
Ë+o
(i)
c
Ë10
cells have been discovered
@ inSpecialized
aphids called bacteriocytes' These
E
À Figure
Ø
amino acid content between Phloem
sap an{ aphid protein.
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100
0.00
are non-essentia-1.
gut.
in
Í21
which synthesize essential amino acids
from aspartic acid and sucrose. Aspartic
acid is a non-essential amino acid that is
found in much higher concentrations in
phloem sap than any other amino acid.
When aphids reproduce, theY Pass on
Buchnerabacteria to their offspring.
(i) E>iplain how antibiotics could be used
to obtain evidence for the role of
Buchnera in aPhids.
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question,
this
in
data
(ii) Using the
discuss the reasons for few animals
using phloem sap as the main Part
of their diet.
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lB12 Biology Summer Work: Plant Biology
ö;,;ï;;; ;;;;li;;;;
R;;ì;;;irve ia¡.rring
Source leaves were supplied
(
whether the source
ture leaf.
t2)
with a pulse of
radioactively-labelled carbon and the time taken
for the radioactive carbon to be found in sink
leaves was measured by radiophotography. The
photosynthetic rate was varied, primarily, by
altering the concentration of unlabelled carbon
dioxide. The experiment was carried out at three
different intensities of light (green squares are
20,000Iux; orange diamonds are 40,000lux;
purple circles are 80,000Ìux).
5.
I
E
E
o
ß
Suggest whether this is a correlation or a
cause and effect relationship.
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Determine the ratio of translocation to net
photosynthesis at two different points on the
distribution
sugar beet plant
The
a
Ê
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qu
1-
o,
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Data-based
ta
o¡
between light
@ (i) Deduce theandrelationship
translocation.
graph.
a
a
U
[l]
I
a
I
o
o
o
o
a
c
(ii)
-,1-
E
Outline the relationshiP between
photoslmthesis rate and translocation rate.
intensity
a
.=
a
aa
a
oa
)¡l
r
2 0
2
1,
net photosi¡nthesis rate [pg
C
dm-2 min-t)
Figure 13
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ng(Z1qoyLW
"
I week after raCO, was supplied for 4 hours to
a single source leaf (labelled with an arrow in
figure 14). The degree of radioactive labelling is
indicated by the intensity of shading of the leaves'
Leaves are numbered according to their age; the
youngest, newly emerged leaf is designated l.
@
Üsing fi.gure I4A describe the location of the
sink leaves receiving the most photosynthate
in relation to thd source
leaf.
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the hypothesis that leaves directly
@ Evaluate
above and below the source leaf are most
likely to receive photosynthate and that
pruning causes a rerouting of translocation
pathways to include lateral leaves.
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The purpose of the e>rperiment was to determine
the position of sink leaves in relation to the position
of source leaves. The hypothesis was that leaves
directly above and below the source leaf are most
likely to receive photosynthate (the products
of photosynthesis) and that pruning causes a
rerouting of translocation pathways to indude
lateral leaves. Figure I4A shows the distribution of
photosynthate in an intact plant. Figure l4B shows
the pattern afler several leaves have been removed.
In flgure I4A, identify the two leaves that
received the most photosynthate.
Í21
Al
Bl
t4coz
l4coz
9
6
5
4
4
7
I
2
A Figure 14
I
I
tt
"tr' 6
1t
I
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I
lBI2 Biology Summer Work: Plant Biology
The acid growth hypothesis of auxin effect is
that auxin stimulates the action of a proton (H+)
pump. The pump moves protons out of the cell,
leading to an increase in the acidity of the cell
wall. This leads to the activation of the protein
called expansin. E>çansin plays a role in breaking
and reforming the connections between cellulose
fibres and the polysaccharides that cross-link the
pH
length
I
CL
160
É,
L 20
o
o
oo
5.0
80
t
010
o
o
40
AA
20 30
0
40
50
60
time IminJ
^
Suggest the effect of the application of IAA
on the pH of the solution surrounding the
coleoptiles.
200
5.5
45
When a shoot first emerges, it has a protective
sheath called a coleoptile. Oat coleoptiles were
bathed in a solution containing IAA. The pH of
the solution surrounding the coleoptiles was
determined (see figure 5).
;{
?40
60
cellulose. As the cell wall becomes weak, turgor
pressure from within the cell pushes the wall
outward, causing elongation.
F gure 5
X
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nstimate the time where the change in length
of the coleoptiles was the greatest.
Ill
O.rtiin. the relationship between pH and
{
change in
length.
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In a further experiment, coleoptiles were
immersed in a pH 3 solution at time zero. The
first arrow in figure ó indicates the point where
the coleoptiles were transferred to a pH 7
solution. The second arrow indicates the point at
which IAA was added.
elongat¡on unpeeled segments in auxin
1.00
auxtn
c
.o
control
c
G
o0
.9
P
E
Io
o
coo¡,
t
1001020
40
0.50
+KCN
o
AA
60
80
KCN added
at arrow
tnuous
0
100
030609030
time (minl
L Fgu re 6
Compare the effect of pH 3 on elongation
with the effect of pH 7 on elongation.
State the effect of the addition of IAA on
elongation.
To test the hypothesis that active,transport
plays a role in mechanism of action of auxin, a
respiratory inhibitor (potassium cyanide, KCN)
was applied continuously to one treatment group,
and to a second treatment group at the arrow A
time IminJ
A Figure
7
third treatment group (the control) did not have
I(CN applied.
@
State the effect of the addition of KCN on
elongation.
on the data, to what extent is there
@ Based
support for the conclusion that auxin
stimulates the active transport of protons out
of the shoot and that these protons promote
elongation.
lBI2 Biology Summer Work: Plant Biology
;;ï;;;;; ;; ;;ii ;;;; ili
ü ìi;;;
;;
;
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both
by humans and livestock. AÏter germination,
soybean plants grow a series of sections of stem,
with nodes between them. Leaves are produced
at the nodes. The stem sections are called
Soybeans are rich in protein and are eaten
internodes. Flowers are produced at each node
Compare the growth of the soybean plants
sown on the different dates.
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a)
b)
a)
b)
Deduce when the soybeans started to
flower.
Deduce with reasons, the factor that
triggers flowering in soybeans.
Explain the advantage, in terms of
soybean yields, of sowing the crop as
earþ as possible.
Suggest two possible disadvantages of
sowing soybeans earlier than the dates
used in the trial.
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i
and pods containing beans develop from them.
When they stail to flower, soybean plants stop
growing more nodes and internodes.
Fisu¡e 4 shows the mean numbers of nodes of
rolpean plants sown on different dates in Nebraska.
2?
r
-20
Êre
3rs
o
+
+
+
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Ø
+
812
Ero
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17-Ju n
rll
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Figure 4
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181,2
Biology Summer Work: Plant Biology
flgure l3 show the results of
into the rafe at which water
is able to diffuse though the waxy cuticle of
plants, which is called the water permeance of
the cuticle. Figure I3a shows the relationsìrip
between temperature and water permeance
of four species of plant. Figure I3b shows the
relationship between the thickness of cuticular
wax and water permeance. The results of the
experiment show how important it is to test
hypotheses, even when it may seem that this is
not necessar-y.
20
o Hedera
€ts
É Pvrus
.
@
o
Liriodendron
äro
o
E
o
o
F
Es
o
Ê
v
v
(Helianthus spp.) anther sheds its pollen before
the stigma is mature enough to receive it.
Early in the morning the anther is exposed by
elongation of the fllaments. The anthers open
at this time to release their pollen (anthesis).
The stigma appears above the anthers by late
afternoon, and by the following morning it is
fully receptive.
To see how the filament (F) and the style
(S) are affected by light, their lengths were
measured at time intervals starting l2 hours
before anthesis (-12). Some plants were grown
in continuous white ligbt &2a) and some
plants grown under cycles of ló hours white
light followed by 8 hours dark (Ll6lD8). The
results are shovrn in the graph.
v Camellia
¡
In order to prevent transfer of pollen from
an anther of one plant to the stigma of the
same plant (self-pollination), the sunflower
a
_-1
L24
0
35
40 45
Ia]
s0
dark
dark
55
116/D8
temperature /"C
11
I
10
Ø 5
E
o
õ
3
o
c,
o
ca
o
E
o
q
tbl
Ê
E
4
d
c
o
o
^
3
^
â.
2
Ð
Ø
L
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Discuss the consequences for plants of the
effect of temperature on cuticular water
permeance.
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Using the data in figure l3b, state the
thickness of cuticular wax with:
3.0 ÈI
g
2.5 0
permeance.
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Evaluate the hypothesis that the water
permeance of the cuticle is positively
correlated with its thickness, using the data
in figure
l3b.
Ill
5
c
1.5
ø1,
Jou rno I of Exper i mentol Boto ng, [ 2000 ],
5
1,
Filaments of the plants grown in continuous
white light increased in length by 0.25 mm
in the 28 hours after anthesis. Calculate
how much the filaments of the plants
grown in alternating white light and dark
increased during the same period.
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b) Compare the increase in the lengh of the
(i) the highest water peilneance
d)
7
pages 1403-1412
a)
d
¡.s
Source; Lobello et
Using the data in figure I3a, describe the
relationship between temperature and
(ä) the lowest wateÍ
E
t¡me efter stârt of anthesis/hours
13 Factors
-E
4.0 >
5
water peflneance.
c)
4,5
I
thicknessofcuticularwax/p,m
affectingwater
permeance of waxg cuticle
b)
5.0
ILza)
+ F [116/08]
--+-F (L24J
2.O
01?34s6
Ä Figure
a)
9
-+s
[116/D8J
5
À
0
5,5
+S
6
style in the plants grown in continuous
white light with those grown in alternating
white light and dark.
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The table compares the percentage of ovules
that have been fertilized and developed
into seeds in sunflower plants grown under
IBLZ Biology Summer Work: Plant Biology
continuous white light with those grown
under alternating light and dark. The numbers
represent the mean i one standard deviation.
The graph below shows the sodium ion
concentration in plant parts of sweet
pepper grown in l5 mM sodium chloride for
three weeks.
Percentage of
L¡ght treatments
30
fertilized ovules
Continuous white light [124J
Alternating light and dark
t1..40
s8.26
28
t7.76
+
26
t24
d
í. z¿
4.06
(116/D8J
c)
€zo
c
Explain the differences in the percentages of
ovules fertilized using the data in the graph
about the growth of filaments and styles. [3]
d)
Explain how standard deviation (SD)
shown in this table can be used to help in
comparing the effect of light treatm€nts on
the fertilization of ovules.
t3ì
To analyse the effect of growth regulators on
filament elongation, further experiments were
performed in the dark, white light and red light.
The flowers were treated with auxin or with
gibberellic âcid and compared to a control with
no growth regulator. The results are shown in
the bar chart below.
6
E
I
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3u
C
C
3
c
c
lO
4
o
c
o
3
gE
Ø
4
2
0
r00t
f)
stem
exposed to varging sodium concentrations" , Journol of Experimentol
Botang 1L November 1998], vol.49, íssue 328, pp. 1863-1868, by
permission of 0xford Universitg Press
a) (i)
State the concentration of sodium ions
in
fruits.
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(ii)
b)
L
e)
fruit
leaves
plant part
Source: M Blom-Zandstra et. ol, 'Sodjum fluxes in sweet pepper
control tr auxin tr gibberellic acid
?
0
10
õob
É.
ú
c
1.2
.e
5
r
18
õ
PIO
cont nuous dark
continuous while
light
continuous red
líght
Identify, with reasons, which factors
promote and which factors inhibit the
elongation of filaments.
Explain the disadvantages to a plant of
self-pollination.
c)
d) Scientists
Sweet pepper (Capsicum annuum) is an
important widespread agricultural crop.
Scientists studied the transport and distribution
of sodium in sweet pepper by growing plants in
sodium chloride solutions.
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tll
[]
also found that the concentrations
of sodium ion in cells of the stem and in
xylem sap were the same. Explain why this
led the scientists to believe there was no
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Calculate the percentage increase in
sodium ion concentration between
root and stem.
Suggest why a high sodium ion
concentration in the cells of the stem
is important in providing support to this
type of plant.
State one possible use of sodium in plants.
e)
active transport between xylem and stem. [2]
Suggest one possible method of
Jranspofi of sodium ions between xylem
and stem.
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