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Specimen lab book: Plant responses
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Study Hack Lab
RP 8 · Biology
Plant responses
Lab book
Name
Specimen
Date
2 November 2026
Course
GCSE Biology
Board and specification
AQA GCSE Biology (8461), 4.5.4.1Apparatus and techniques: AT 1, AT 3, AT 4, AT 7
Run
C29HO
Status
Finished: every stage done
Exam questions
30/30 marks
Aim
Investigate the effect of the direction of light on the growth of mustard seedlings, and the effect of gravity on the growth of bean roots, recording lengths and labelled drawings.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
Exam questions on your data
Simulated data produced by Study Hack Lab from the student's own run (seed 20261004). Every reading, value and mark here is from that run; nothing has been retyped. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
Plants respond to light and gravity by growing unevenly. Auxin, a plant hormone made in the tips of shoots and roots, is spread unevenly when light comes from one side or the plant lies on its side. In a shoot, more auxin on the shaded side makes those cells elongate more, so the shoot bends towards the light. In a root lying on its side, more auxin collects on the lower side and the upper side grows faster, so the root bends down.
Shoots grow towards light (positive phototropism); roots grow towards gravity (positive gravitropism).
Variables
Independent (you change)
Direction of light
Dependent (you measure)
Increase in height of the seedlings, and the direction they grow in mm
Control (you keep the same)
Species and age of the seeds; Number of seedlings in each dish; Volume of water; Temperature; Time
Prediction
Dish A gets light only through a slit on one side. How will its shoots grow?
They will bend towards the slit.Right first time
Your dish A shoots bent towards the slit. Shoots are positively phototropic. Auxin collects on the shaded side of the shoot tip, so cells on that side elongate more and the shoot bends towards the light.
How will the seedlings grown in the dark (dish B) compare with those in light from all round (dish C)?
Taller, thinner and pale yellow.Right first time
Your dish B seedlings grew 32.0 mm on average, dish C’s 22.2 mm. Seedlings in the dark use the food stored in the seed to grow tall quickly, as if searching for light. They make no chlorophyll, so they are pale yellow, and their shoots are thin.
Bean A lies on its side in the dark, its root growing sideways. What will the root do?
Bend downwards.Right first time
Your root A bent downwards. Roots are positively gravitropic. In a root lying on its side, auxin collects on the lower side, where it slows the growth of root cells, so the upper side grows faster and the root bends down.
Risk assessment
Hazard
Harm it could cause
Control you chose
Seeds treated with fungicide
Poisoning if swallowed; skin irritation
Use untreated seed, never eat seeds, and wash your hands after handling them.Right first time
Mould growing on damp cotton wool
Breathing in spores can cause an allergic reaction or an asthma attack
Do not open a mouldy dish: seal it in a bag and put it in the bin.Right first time
Sharp pins
A puncture wound to the fingers
Count the pins out and back, and push them in by the head, away from your fingers.Right first time
Lamps near water
Burns from a hot bulb; an electric shock with wet hands
Use LED lamps, keep the water and syringe away from the lamps and dry your hands before switching them on.Right first time
2 Apparatus
✓Three Petri dishes with cotton wool The seeds germinate and grow on the damp cotton wool.
✓White mustard seeds (untreated), one packet The same species and age of seed in every dish.
✓10 cm³ syringe and a beaker of water (resolution 0.5 cm³) The same volume of water for every dish.
✓Marker pen Labels the dishes and marks the thread.
✓Forceps Thin each dish to the same number of seedlings.
✓Light-proof box with a slit in one side Light reaches dish A from one direction only.
✓Light-proof box with its slit taped over Keeps dish B in the dark.
✓Two LED lamps One shines at the slit; one lights dish C from above.
✓30 cm ruler (resolution 1 mm) Measures shoots and roots.
✓Cotton thread Laid along a curved shoot or root, then measured against the ruler.
✓Two germinated broad bean seedlings Their roots show the effect of gravity.
✓Pins, and two dishes of damp cotton wool Hold each bean in place, kept damp all round.
✓Waterproof ink and a fine brush Marks each root every 2 mm, to show where it grows.
✓Clinostat Turns bean B slowly so gravity acts equally on all sides of its root.
✓Dark cupboard Keeps light from the beans.
3 Method: your choices
Check the dark box is light-tight: DoneDish B must get no light at all. Light getting in through a gap is light from one side, and the seedlings respond to it.
Wet the cotton wool: Add 5 cm³ to each dish with the syringe, and 2 cm³ to each every dayEvery dish stays damp for the whole investigation, so water is the same for all three.
Choose how dish C gets its light: An LED lamp, 30 cm above dish CAn LED lamp gives out very little heat, so dish C stays at the same temperature as the other two.
Thin the seedlings: Pull out seedlings so every dish has 5, spread outEvery dish has five seedlings, equally spaced: crowding is the same in all three.
Where the beans go: DoneOnly gravity should affect the direction the roots grow. Light from one side would affect it too, so the seedlings are kept so that gravity is the only thing that can change the direction.
Measuring curved shoots and roots: Lay a thread along the shoot, mark the tip on it, then measure the thread against the rulerYou measure the true length of every shoot and root, curved or not (to the nearest mm).
4 Results
42 of 42 readings taken.
Seeds that germinated · 10 white mustard seeds were sown in each dish and left 3 days on the bench.
Dish
Seeds sown
Seeds that germinated
A
10
8
B
10
10
C
10
10
Height of each seedling · Five seedlings in each dish, measured at the start and after 4 days. Curved shoots measured along their length.
Dish
Seedling
Height at the start in mm
Height after 4 days in mm
Increase in height in mm
A
1
5
28
23
A
2
6
9 (anomalous, left out)
3
A
3
4
29
25
A
4
4
26
22
A
5
4
30
26
B
1
6
40
34
B
2
6
42
36
B
3
4
36
32
B
4
3
31
28
B
5
3
33
30
C
1
5
23
18
C
2
5
26
21
C
3
6
35
29
C
4
4
21
17
C
5
5
31
26
Mean increase in height · Any seedling you left out as anomalous is not in its dish’s mean.
Dish
Light
Mean increase in height in mm
A
Light from one side
24.0
B
Dark
32.0
C
Light from all round
22.2
Bean roots (2 days in the dark)
Bean
How it was kept
Root length at the start in mm
Root length after 2 days in mm
Increase in root length in mm
What the root did
A
Still, on its side
37
48
11
Bent downwards
B
On the clinostat
40
50
10
Grown straight on, in the direction it started
Observations
What you looked at
What you saw
Dish A (light from one side) after 2 days
Bending towards the slit
Ink marks on root A after 2 days
The marks near the tip have spread apart; the others are still 2 mm apart
Dish B (dark) beside dish C after 4 days
Dish B’s are taller, thinner and pale yellow, and they grow straight up
0.0 Ringed: the anomaly, left out of your results.
Anomaly: Dish A, seedling 2: height after 4 days, left out of your results. Likely cause: it was knocked over when its dish was topped up with water, and grew along the cotton wool.
5 Graph
Bar chart of the three dishes
6 Analysis
Mean increase in height, dish A
mean = sum of the increases ÷ number of seedlings
Calculate the mean increase in height of the seedlings in dish A (light from one side). Leave out any anomalous seedling. Give your answer to 1 decimal place.
24.0 mmRight first time
Why a bar chart
Why should these results go on a bar chart, not a line graph?
The light conditions are categories (one side, dark, all round), not numbers on a scale.Right first time
How much more did the dark seedlings grow?
percentage difference = (mean in the dark − mean in light from all round) ÷ mean in light from all round × 100
Calculate how much greater, as a percentage, the mean increase in dish B (dark) was than in dish C (light from all round). Give your answer to 2 significant figures.
44 %Right first time
Labelled drawing of a seedling
Labelled drawing, magnification × 2.5Right first time
What height can tell you
What can your height comparison establish about the seedlings?
The results compare elongation. Height alone does not measure how much food the seedlings made.Right first time
7 Conclusion and evaluation
Quantity
Your value
Accepted value
Mean increase in dish A (yours: careful technique; accepted: the same seedlings, careful technique)
24.0 mm
23.8 mm
Mean increase in dish B (yours: careful technique; accepted: the same seedlings, careful technique)
32.0 mm
31.7 mm
Mean increase in dish C (yours: careful technique; accepted: the same seedlings, careful technique)
22.2 mm
22.0 mm
Conclusion
What do your results show? Pick everything that your data support.
Seedlings in the dark grew taller than those in light from all round. A root on its side bends down; turned on a clinostat, it grows straight on. Shoots lit from one side grow (bend) towards the light.Right first time
Shoots are positively phototropic: auxin collects on the shaded side, cells there elongate more, and the shoot bends towards the light. In the dark, seedlings use the food in the seed to grow tall fast. Roots are positively gravitropic; turning slowly on a clinostat, gravity acts equally on all sides, so the root grows straight on. The shaded side grows faster, not the lit side, and the clinostat does not remove gravity.
Sources of error
Measuring bent shoots with a ruler held upright: systematic or random?
SystematicRight first time
A bent shoot reaches less high than its length, so dish A’s heights and increase are too small.
One dish drying out (water added by eye): systematic or random?
SystematicRight first time
The seedlings in the dry dish stop growing, so that dish’s mean increase is too small.
A warm lamp over dish C: systematic or random?
SystematicRight first time
Dish C is warmer, so its seedlings grow faster: temperature has changed as well as light.
Light leaking into the dark box: systematic or random?
SystematicRight first time
Dish B’s seedlings get light from one side and lean towards it, so dish B is not a fair dark control.
Different numbers of seedlings in each dish: systematic or random?
SystematicRight first time
Crowded seedlings compete for light and grow taller, so the dishes are not a fair comparison.
Differences between seedlings: systematic or random?
RandomRight first time
Seeds germinate at different times and grow at different rates, so seedlings in one dish differ by up to a third.
Only five seedlings in each dish: systematic or random?
RandomRight first time
A mean of five is still affected by one unusual seedling, and one anomaly leaves only four.
Reading a small, curved shoot to the nearest millimetre: systematic or random?
RandomRight first time
Each height can be up to 1 mm out, which is a large fraction of a 5 mm seedling at the start.
Beans left in the light: systematic or random?
SystematicRight first time
Light from one side also changes the direction roots grow, so the clinostat root does not grow straight.
Improvement
Which change would most improve your results?
Measure more seedlings in each dish (or repeat the investigation) and use the mean.Right first time
Repeatable or reproducible
Suppose you measured the five seedlings in dish A a second time and got the same heights both times. That would show your measurements are…
RepeatableRight first time
Repeatable: the same person, method and equipment give similar results.
Another group used cress seedlings and a different box, and also found the shoots bent towards the slit and the dark seedlings grew tallest. This shows the results are…
ReproducibleRight first time
Reproducible: a different person, method or equipment gives similar results.
8 Make safe and clear up
Switch off the lamps and the clinostat
Put the seedlings, beans and cotton wool in the bin (seal any mouldy dish in a bag first)
Count the pins back into their box
Wash the Petri dishes, put the ruler, thread and boxes back, and wash your hands
9 Exam questions on your data
On your own readings, self-marked against the mark scheme, with error carried forward where it applies. Total 30/30.
01.1[1 mark]
A student investigated the effect of light on mustard seedlings. Dish A was in a box with a slit facing a lamp (light from one side), dish B in the same box with the slit taped over (dark), and dish C in the open under a lamp (light from all round). The student measured the height of five seedlings in each dish at the start and after 4 days.
Your dish A shoots bent about 53° towards the slit.
Name the response of the shoots in dish A to light from one side.
Your answer
Positive phototropism
1/1 self-marked
Phototropism (allow positive phototropism) (do not accept negative phototropism; do not accept phototrophic)
Self-marked: 1 of 1 mark. This is your own judgement against the mark scheme.
Model answer: (Positive) phototropism.
01.2[2 marks]
Look again at the investigation in Question 01.1.
Give two variables the student should control.
Your answer
The volume of water added to each dish, and the temperature.
2/2 self-marked
Volume (amount) of water
Temperature
Species or type of seed (the same packet)
Age of the seedlings
Number of seedlings in each dish
Cotton wool (soil, dish) the same
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Any two of: the volume of water; the temperature; the type (species) of seed; the age of the seedlings; the number of seedlings in each dish. (Not light: light is what is being tested. “Time” is ignored here: the 4 days are given.)
01.3[2 marks]
The shoots in dish A bent towards the slit. The shoots in dish B (dark) and dish C (light from all round) did not bend.
Dishes B and C are controls. Explain what dish B shows and what dish C shows.
Your answer
Dish B shows that the bending is caused by light. Dish C shows that the bending is caused by light coming from one direction.
2/2 self-marked
Dish B (dark) shows that the response (bending) is caused by light (do not accept control variable)
Dish C (light from all round) shows that the response is caused by light from one side (the direction of the light)
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Dish B shows that the bending is caused by light (with no light, the shoots do not bend). Dish C shows that it is caused by light coming from one side: with light from all round, the shoots grow straight.
01.4[2 marks]
After a few days, mould can grow on damp cotton wool.
Give one harm the mould could cause andone way to reduce the risk.
Your answer
Breathing in the spores could cause an allergic reaction. Do not open a mouldy dish: seal it in a bag and put it in the bin.
2/2 self-marked
Harm: an allergic reaction / asthma / breathing in spores / an infection
Control: do not open a mouldy dish / keep the lid on / seal it in a bag and bin it / wash your hands
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Breathing in mould spores could cause an allergic reaction or an asthma attack. Do not open a mouldy dish: seal it in a bag and put it in the bin.
01.5[1 mark]
After 4 days the shoots in dish A were curved.
Describe how the student should measure the length of a curved shoot.
Your answer
Lay a thread along the shoot, mark where the tip is, then measure the thread against a ruler.
1/1 self-marked
Lay a thread (string) along the shoot, then measure the thread with a ruler / straighten the shoot against a ruler / use a flexible ruler or tape (“with a ruler” alone is not enough)
Self-marked: 1 of 1 mark. This is your own judgement against the mark scheme.
Model answer: Lay a piece of thread along the curved shoot from the cotton wool to the tip, mark the thread at the tip, then straighten the thread against a ruler and read the length.
02.1[1 mark]
Table 1 shows your results for the five seedlings in dish A (light from one side).
Which seedling gave an anomalous result?
Select one row.
Table 1
Seedling
Height at the start in mm
Height after 4 days in mm
Increase in height in mm
1
5
28
23
2
6
9
3
3
4
29
25
4
4
26
22
5
4
30
26
Your answer
seedling 2
1/1
Seedling 2: it grew far less than the other four
Full marks. Your answer meets all the points for this question. Seedling 2 grew only 3 mm; the others grew much more.
Model answer: Seedling 2. Its increase in height, 3 mm, is far smaller than the other four.
02.2[2 marks]
Look again at Table 1.
Calculate the mean increase in height of the seedlings.
Do not use the anomalous result. Give your answer to 1 decimal place.
Your answer
24.0
Working: mean = (23 + 25 + 22 + 26) ÷ 4
= 96 ÷ 4
= 24.0 mm
2/2
(23 + 25 + 22 + 26) ÷ 4 (the anomaly left out)
24.0 (mm)
Full marks. Your answer meets all the points for this question.
Model answer: mean = (23 + 25 + 22 + 26) ÷ 4
= 96 ÷ 4
= 24.0 mm
02.3[1 mark]
The seedlings in Table 1 grew for 4 days.
Use your answer to Question 02.2 to calculate the mean growth rate of these seedlings in mm per day.
Your answer
6.00
Working: rate = 24.0 ÷ 4
= 6.00 mm per day
1/1
24.0 ÷ 4 = 6.00 (mm per day); allow error carried forward from 02.2
Full marks. Clear and precise.
Model answer: rate = 24.0 ÷ 4
= 6.00 mm per day
02.4[1 mark]
The student measured 5 seedlings in each dish, not just one.
Give one reason for measuring five seedlings in each dish.
Your answer
Seedlings vary, so you can calculate a mean.
1/1 self-marked
To calculate a mean / seedlings vary (biological variation) / to identify anomalies / to reduce the effect of random error (ignore “to make it accurate”)
Self-marked: 1 of 1 mark. This is your own judgement against the mark scheme.
Model answer: Seedlings vary, so measuring five lets you calculate a mean (and spot an anomalous seedling).
03.1[3 marks]
Your dish A shoots bent about 53° towards the slit.
Explain, in terms of auxin, why the shoots in dish A bent towards the slit.
Your answer
More auxin collects on the shaded side of the shoot. The cells on the shaded side elongate more, so the shoot bends towards the light.
3/3 self-marked
More auxin on the shaded side (away from the light) / auxin moves to the shaded side / unequal distribution of auxin (do not accept more auxin on the light side)
Cells on the shaded side elongate (grow) more / faster (do not accept the lit side grows more)
So the shoot bends (grows) towards the light (unequal growth)
Self-marked: 3 of 3 marks. This is your own judgement against the mark scheme.
Model answer: Auxin collects on the shaded side of the shoot, away from the slit. The cells on the shaded side elongate (grow) more than those on the lit side. This uneven growth makes the shoot bend towards the light.
03.2[2 marks]
The student pinned two bean seedlings on damp cotton wool with their roots horizontal. Dish A stood still. Dish B was fixed to a clinostat, which turned it slowly.
Explain why dish B on the clinostat is a control.
Your answer
Gravity acts equally on all sides of the root, so its effect is cancelled out. This is compared with dish A to show the bending is caused by gravity.
2/2 self-marked
Gravity acts equally on all sides of the root / the effect of gravity is cancelled out (do not accept there is no gravity; ignore cancels out gravity)
So it can be compared with dish A / it shows the bending in A is caused by gravity (do not accept control variable)
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Turning slowly makes gravity act equally on all sides of the root, so the effect of gravity cancels out. Comparing it with dish A shows that the bending in A is caused by gravity.
03.3[1 mark]
Both bean dishes were kept in a dark cupboard for 2 days.
Give one reason why the bean dishes were kept in the dark.
Your answer
So that light does not affect the direction the roots grow.
1/1 self-marked
So that light does not affect the direction of growth / so only gravity affects the roots (ignore as a control variable)
Self-marked: 1 of 1 mark. This is your own judgement against the mark scheme.
Model answer: So that light does not affect the direction the roots grow: only gravity affects it.
03.4[1 mark]
Bean A’s root was marked with ink every 2 mm. The dish stood still on its edge, the root horizontal, in the dark for 2 days.
Figure 1
Which drawing in Figure 1 shows root A after 2 days?
Tick (✓) one box.
Drawing A
✓ Drawing B (your choice)
Drawing C
Drawing D
Your answer
Drawing B
1/1
Drawing B
Full marks. Clear and precise.
Model answer: Drawing B: the root has bent down, and only the marks near the tip, in the bend, have spread apart. Further back they are still 2 mm apart.
03.5[2 marks]
Root A bent downwards.
Explain, in terms of auxin, why root A bent downwards.
Your answer
More auxin collects on the lower side of the root, so the upper side grows faster and the root bends down.
2/2 self-marked
More auxin on the lower side / unequal distribution of auxin (do not accept more auxin on the upper side)
The upper side grows faster (elongates more) than the lower side (allow auxin slows growth on the lower side)
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Auxin is unevenly spread: more collects on the lower side of the root. In roots this slows growth, so the upper side grows (elongates) faster and the root bends downwards.
04[2 marks]
Another student put dish C on a windowsill above a radiator. Dishes A and B were on a bench across the room.
Explain how this would affect their result for dish C, and suggest one improvement.
Your answer
Dish C would be warmer so its seedlings would grow faster, so its increase is too big. Keep all three dishes away from the radiator at the same temperature.
2/2 self-marked
Dish C would be warmer, so its seedlings grow faster (its increase too big; temperature not controlled)
Move dish C away from the radiator / keep all three at the same temperature / same place / heat shield
Self-marked: 2 of 2 marks. This is your own judgement against the mark scheme.
Model answer: Dish C would be warmer, so its seedlings would grow faster and its increase would be too big: temperature would change as well as the direction of light. Keep all three dishes in the same place, away from the radiator, at the same temperature.
05[6 marks]
A student wants to investigate the effect of the direction of light on the growth of seedlings.
The student has: pots of seedlings, a cardboard box with a slit in one side, a lamp, a ruler, some thread and a measuring cylinder.
Plan an investigation to find the effect of the direction of light on the growth of seedlings.
Your answer
1. Use two groups of seedlings of the same species and age, with the same number of seedlings (for example 10) in each pot.
2. Measure and record the height of each seedling with a ruler.
3. Put one pot in a box with a slit in one side, facing a lamp, so the light comes from one direction.
4. Put the other pot in the dark (or in light from all round) as a control.
5. Keep the temperature and the volume of water the same for both, and leave them for the same time (3 days).
6. Measure the height of each seedling again, laying a thread along any curved shoot and measuring the thread with the ruler.
7. Record which way the shoots bend, and calculate the mean increase in height for each pot.
6/6 self-marked
Seedlings of the same species and age; the same number in each pot
Measure the height of the seedlings at the start
Put one pot in a box with a slit / hole so light comes from one direction
A control pot in the dark, or in light from all round (or on a clinostat)
Keep the temperature, volume of water and soil the same
Leave them for a suitable time (hours to days), the same for both
Measure the height again at the end
Measure a curved shoot with a thread (or straighten it) against the ruler
Record the direction the shoots grow (bend), or measure the angle with a protractor
Calculate the mean increase in height for each pot
Self-marked: Level 3, 6 of 6 marks. You ticked 10 of 10 indicative points. This is your own judgement against the mark scheme.
Model answer: 1. Use two groups of seedlings of the same species and age, with the same number of seedlings (for example 10) in each pot.
2. Measure and record the height of each seedling with a ruler.
3. Put one pot in a box with a slit in one side, facing a lamp, so the light comes from one direction.
4. Put the other pot in the dark (or in light from all round) as a control.
5. Keep the temperature and the volume of water the same for both, and leave them for the same time (3 days).
6. Measure the height of each seedling again, laying a thread along any curved shoot and measuring the thread with the ruler.
7. Record which way the shoots bend, and calculate the mean increase in height for each pot.
Unseen data: the same skills, new apparatus
01[3 marks]
A student grew six maize seedlings in pots on a windowsill for 7 days and measured the increase in height of each shoot. One seedling’s tip was damaged on the first day.
Increase in height
Seedling
Increase in height in mm
1
52
2
9
3
51
4
55
5
51
6
52
Calculate the mean increase in height, leaving out the anomalous result. Give your answer to 1 decimal place.
Your answer
52.2
Working: 52 + 51 + 55 + 51 + 52 = 261
261 / 5
3/3
Leaves out 9 mm: total of the other five = 261 mm.
÷ 5.
The mean, in mm, to 1 decimal place.
Full marks. Clear and precise.
Model answer: 9 mm is anomalous: far less than the others, because the damaged tip made little auxin.
Mean = 261 ÷ 5 = 52.2 mm.
02[2 marks]
Scientists grew three groups of oat seedlings with light coming from the right only. Group 1 was left as it was. Group 2 had a foil cap over the tip of each shoot. Group 3 had the tip of each shoot cut off.
Results after 2 days
Group
Treatment
What the shoots did
1
none
grew and bent towards the right
2
foil cap over the tip
grew straight up
3
tip cut off
grew very little and did not bend
Which TWO statements explain these results? Tick (✓) two boxes.
✓ In group 1, auxin collected on the shaded side, so the cells there elongated more and the shoot bent towards the light. (your choice)
✓ The tip detects the light and makes the auxin: with a cap it cannot detect where the light comes from, and with no tip there is almost no auxin, so the shoot hardly grows. (your choice)
In group 1, the cells on the lit side grew faster and pulled the shoot towards the light.
The foil cap stopped group 2 photosynthesising, so its shoots could not bend.
Group 3 did not grow because without a tip it could not detect gravity.
Your answer
In group 1, auxin collected on the shaded side, so the cells there elongated more and the shoot bent towards the light.; The tip detects the light and makes the auxin: with a cap it cannot detect where the light comes from, and with no tip there is almost no auxin, so the shoot hardly grows.
2/2
In group 1, auxin collected on the shaded side, so the cells there elongated more and the shoot bent towards the light.
The tip detects the light and makes the auxin: with a cap it cannot detect where the light comes from, and with no tip there is almost no auxin, so the shoot hardly grows.
Full marks. Clear and precise.
Model answer: Auxin is made in the tip. Light from one side makes it collect on the shaded side, where the cells elongate more, so the shoot bends towards the light (positive phototropism). Covered, the tip cannot detect the direction of light, so auxin spreads evenly and the shoot grows straight up; cut off, there is no tip to make auxin, so the shoot hardly grows and does not bend.
03[2 marks]
A student grew cress seedlings in two trays for 5 days: one in full sun and one in the shade of a hedge. They measured the increase in height of ten seedlings in each tray.
Mean increase in height
Tray
Mean increase in height in mm
Full sun
22.1
Shade
27.3
Calculate how much greater, as a percentage, the mean increase in the shade was than in full sun. Give your answer to 2 significant figures.
Your answer
24
Working: 27.3 - 22.1 = 5.2
5.2 / 22.1 * 100
2/2
(27.3 − 22.1) ÷ 22.1.
× 100, to 2 significant figures.
Full marks. Clear and precise.
Model answer: Difference = 27.3 − 22.1 = 5.2 mm.
Percentage = 5.2 ÷ 22.1 × 100 = 24 %.