Task
Design and conduct a biological investigation on coordination and control in plants. You will be required to keep a journal and then to write a scientific report summarising the results of the investigation.
Instructions
• Select a topic and then develop and refine a research question. Discuss your ideas with your teacher before finalising your experimental investigation.
• Throughout this process you should record in your journal clear links between your chosen topic and the theory associated with the investigation to reveal interrelationships.
• When your topic has been approved, focus your research so to develop a hypothesis and experimental investigation. Consider any safety issues and complete a risk assessment.
•
Trial your proposed method and modify, if necessary, before carrying out your investigation.
•
Consider the types of data that you can collect and collate the results of your investigation in appropriate formats to identify trends and interrelationships.
• Analyse the investigation results with links to theoretical concepts to draw conclusions relating to the question.
• Evaluate the design of the investigation reflecting on the adequacy of the data collected and propose refinements, where needed.
• Although some work will be conducted in groups, each student must submit their own journal and scientific report.
Conditions
•
You have six weeks to research, design, carry out your experiment and complete your report.
•
Complete your investigation with a scientific report. The discussion and conclusion should be 800 –
1000 words.
• Your investigation must be one that can be tested safely. You will be required to submit a risk assessment before commencing the experiment.

www.qcaa.qld.edu.au/downloads/senior/snr_biology_04_syll_standards.pdf
Standard A Standard B
The student communicates their understanding by:
The student communicates their understanding by:
• making links between related ideas and concepts of coordination and control to reveal meaningful interrelationships.
• defining and describing ideas and concepts of coordination and control, and identifying interrelationships.
The student communicates investigative processes by:
The student communicates investigative processes by:
• formulating justified researchable questions
• identifying researchable questions
• designing, modifying and implementing an investigation about coordination and control
• selecting and implementing investigations about coordination and control
• collecting and organising data to identify trends and interrelationships
• collecting and organising data
• interpreting and critically analysing results with links to theoretical concepts to draw conclusions relating to the question about coordination and control
• discussing results and drawing conclusions about coordination and control.
• evaluating the design of the investigation and reflecting on the adequacy of the data collected, and proposing refinements.
Key: Cognition words
Quality or degree words
Note: Colour highlights have been used in the table to emphasise the qualities that discriminate between the standards.
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Comments
Making links between related ideas to reveal meaningful interrelationships.
Formulating justified researchable questions.
The physiological and developmental effect of the hormone auxin on tomato plants
INTRODUCTION (extract)
The natural growth of plants can be altered through the administration of many different, naturally occurring hormones. These plant hormones, or plant growth regulators, are produced in low concentrations and cause physiological or developmental responses. Depending on the hormone, these responses can be either stimulatory or inhibitory (Fauth 2009). Common examples of such a group of hormones are auxins. Auxins are characterised by their ability to produce cell elongation in the stems of plants (Arteca 1996).
Within plants, auxins are produced in the shoot and root tips, young, expanding leaves, and young seeds. Where the auxins are produced is known as the source, and where they are sent to complete their function is known as the target. Although auxins are naturally made inside the plant, there are some synthetically produced auxins which are used in horticulture. Synthetic auxins are commonly used as they have such a variety of sought after effects.
Auxins have many functions within plants which either inhibit or stimulate the growth of the plants. These functions include, but are not limited to the following (Davies 1995):-
• stimulating cell elongation – when cells are new (recently divided) they are small, and densely packed. The hormone auxin causes these new cells to pump H+ ions (acid) into their cell walls, causing the cell to loosen and elongate. This is caused by the higher pH, activating enzymes which break linkages in the wall, allowing the turgidity to elongate the cells.
• the auxin supply from the apical bud suppresses growth of lateral buds – auxin is produced in the apical bud, or the dominant growing tip, and therefore suppresses the growth of lower lateral buds.
• mediating the tropic response in bending because of gravity or light.
AIM
To investigate the effects of varying amounts of the hormone auxin on the development of the physiological features of tomato seedlings, and to determine the differences in growth between seedlings with less auxin, normal amounts of auxin and extra auxin.
HYPOTHESIS
The plants with the higher amounts of auxin (the ones watered with auxin-rich water) will grow the tallest because auxin elongates the cells of the stem of the plant. The seedlings which have had their apex either removed or capped, will not grow as tall but will grow wider, because it is lacking the auxin supply from the apical bud. This means that the growth of the lateral buds will no longer be suppressed; resulting in a shorter plant.
Biology 2004
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Comments
Designing, modifying and implementing investigations.
(See journal also)
Collecting and organising data to identify trends and interrelationships.
METHOD
1. Fill each pot ¾ full with the potting mix. Plant two seedlings for each treatment.
2. Make a hole in the centre of each pot and then place the bean seedlings in the indentation. Cover the roots with potting mix.
3. For Group 2, trim 2cm off the top of each plant.
4. For Group 4, cover the apical bud/s in alfoil.
5. Water the Group 1, 2 and 3 seedlings with 10mL distilled water.
6. Water the Group 4 with 10 mL of 1mg/L auxin solution.
7. Water the Group 5 with 10 mL of 0.5mg/L auxin solution.
8. Measure the size of each seedling and record heights, count each stem and leaf.
9. Water and take measurements of the seedlings each day. Take photographs each day to record the growth of the seedlings.
10. Repeat the experiment to confirm results.
Alfoi
Group 1- Control Group 2- Apical bud removed
Group 3- Apical bud capped
Group 4- Watered with 1mg/L Auxin
Group 5- Watered with 0.5mg/L Auxin
Diagram One. The experimental set-up
RESULTS
Trial One
Graph One – Growth in height over 3 weeks.
The gaps are weekends when the plants weren’t measured.
Group 4 shows the greatest growth, where Group 1 and 2 also show steady growth.
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Table One – total growth in each plant in Trial One.
Group End Height Initial Height
(cm) (cm)
One
Two
Three
Four
Five
9.9
0 (dead)
0
17
10.4
5.8
6.3
5.7
11.1
8.4
Groups 4 and 1 show the greatest growth.
Trial Two
Graph Two – Growth in height over 3 weeks.
Total Growth
(cm)
4.1
- the plant died
- the plant died
5.9
2
Groups 4 and 5 show the greatest growth, all the other groups died.
Table Two – total growth in each plant in Trial Two.
Group End Height Initial Height Total Growth
(cm) (cm) (cm)
One
Two
Three
Four
Five
0 (dead)
0 (dead)
0 (dead)
14.3
13.1
6.3
5.4
7.5
11.6
10.3
- plant died
- plant died
- plant died
2.7
2.8
Groups 4 and 5 show very similar amounts of growth, the other plants died
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Comments
Identifying trends.
Interpreting and critically analysing results (throughout).
Trial Three
Graph Three – Growth in height over 3 weeks.
Groups 4 and 5 displayed the greatest growth and Group 2 showed a steady but small growth.
Table Three – total growth in each plant in Trial Three.
Group End Height
(cm)
Initial Height
(cm)
Total Growth
(cm)
One
Two
Three
Four
Five
0 (dead)
9.1
0 (dead)
11.7
12.1
11.5
8.4
7.1
8.8
8.9
- plant died
0.7
- plant died
2.9
3.2
Groups 4 and 5 showed the greatest growth in this trial.
DISCUSSION
As can be seen in Graphs and Tables 1–3, the amount of auxin available to each plant had an effect on the growth of the plant. The group which is supplied with the highest amount of auxin-1mg/L, (Group 4) had the highest average total growth of the three trials (3.8cm). Group 5, the only other group which showed any consistent growth, and in which all the plants survived, was the other group given extra auxin, 0.5 mg/L IAA, had an average total growth of 2.7cm, over one centimetre less than the average of Group 4.
This demonstrates that plants which have access to higher amounts of auxin grow taller in a shorter time as a result of the elongating effect of this particular hormone. These findings were in line with the information from Cartage 2008 who says that cells in plants are elongated when supplied with higher amounts of auxin, therefore higher concentrations of auxin results in greater plant growth.
Figure Five.
Some of the plants displayed a scorched like appearance. This is the Control group at the start of week three.
The leaves appear scorched on this plant.
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Comments
Links to theoretical concepts.
Identifying trends and interrelationships.
Interpreting and critically analysing results (throughout).
Modifying an investigation.
Link to theoretical concepts.
Evaluating the design of the investigation and reflecting on the adequacy of the data collected and proposing refinements.
Tables 1–3 show the plants in Group 2 and 3 (cut or capped by alfoil) died or showed very little growth. They could not produce auxin which is produced in the plant tip and were prevented from photosynthesising, which stopped them from being able to produce energy to live off, and died as a result.
The tomato seedling in Trial 3, Group 2 which had its uppermost leaf cut off survived as it could continue photosynthesis. However, it showed very little growth (0.7cm) as it was unable to produce auxins to elongate the cells of the plant. Although only one result was obtained over the three trials, this modification of only cutting the very top leaf off shows that a reduced amount of auxin leads to a shorter plant.
The ‘cut’ group had the smallest growth recorded. The control group showed the next lowest average growth then 0.5mg/L group and finally the 1mg/L showed the most growth. This order of growth (smallest to largest) is proportional to the amount of auxin available to each seedling.
Although the withering and dying of the plants in groups 2 and 3 was a result of a lack of photosynthesis, the two seedlings that died from the control group are both anomalies. It was noticed at the start of the second week that they had developed a scorched appearance possibly as a result of the sun burning them through the glass windows they were situated next to.
The plants were then put under artificial lighting so they would no longer be burnt. For the plants in Groups 4 and 5 this seemed to solve the problem.
However, for the other three groups the plants still remained burnt-looking.
Control trial two was brown all over.
As the plants overall didn’t benefit from the artificial light, the light was not the factor which was destroying the plants. It was hypothesised that the acidity of the soil was not at an optimum level so an acidity test was undertaken.
The soil had a pH 5-6, which leads to an excess absorption of boron and a deficient absorption of phosphorous. An excess of boron resulted in necrosis occurring, and plant leaves yellowing and developing a scorched appearance.
Necrosis is death of plant tissue in spots. This is a possible cause for the death of control trials 2 and 3. The yellowing and scorched appearance on the leaves can be seen in Figure Five.
It does not explain all the anomalies as all the plants were planted in the same soil and some of the seedlings did recover under the artificial lighting.
The experiment did return the expected results, however the accuracy of data collection was low. If the experiment was to be repeated these would all have to be modified to ensure better results:
• the plants should be as close as possible to the same height at the start of the experiment
• the dilution of the auxin solution could have been performed with a more accurate measuring instrument
• the soil pH should have been between 6 and 7 as that is the range where the absorption of elements is at an optimum for most elements
• the seedlings should have been kept in one place and an artificial light should be used for the duration of the experiment
• the plastic ruler used for measuring was too wide to fit in the pot, so the zero could not line up with the base of the plant. Measurements were very subjective as the plants did not come to a point.
• only the very top leaf or stem should be cut off or capped in groups 2 and 3
• a larger sample size.
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Comments
Drawing conclusions.
Making links between related ideas to reveal meaningful interrelationships.
Designing investigations.
For farmers growing produce it is important to know whether, and to what level the use of synthetic auxins will help their produce grow. The experiment shows that higher levels of auxin results in taller plants. As these results show a substantial difference in a short period of time, this experiment could be the deciding factor as to whether or not the expense of indole-acetic acid is beneficial.
CONCLUSION
The findings indicate that the amount of auxin available to a plant affects the height. The hypothesis was supported by the findings as the plants with the highest availability of auxin were the plants which showed the most vertical growth, and the seedlings with less auxin result in shorter plants. This is because auxin elongates the cell, resulting in a taller plant.
BIBLIOGRAPHY
Arteca, R. (1996). Plant Growth Substances: Principles and Applications.
New York: Chapman & Hall.
Davies, P. J. (1995). Plant Hormones: Physiology, Biochemistry and Molecular
Biology. Dordrecht: Kluwer
Fauth, P 2009, Hartwick, viewed 31 January 2010, http://users.hartwick.edu/fauthp/HORTHormone.ppt
Mendipweb, Plant-hormones Info 2009, viewed 31 January 2010 http://www.plant-hormones.info/auxins.htm
Cartage 2008, Plant regulation and response, viewed 12 March 2010 http://www.cartage.org.lb
Graig, P 2008, Mid Wales-Trees, viewed 12 March 2010 www.midwales-trees.co.uk
EXTRACTS FROM JOURNAL
Hypothesis: The plants with the higher amounts of auxin (the ones watered with auxin-rich water) will grow the tallest because auxin elongates the cells of the stem of the plant, whereas the seedlings which have had their apex either removed or capped, will not grow as tall but will grow wider because they are lacking auxin from the apical. This means that the growth of the lateral buds will no longer be suppressed, resulting in a shorter plant.
Materials:
•
•
•
•
•
•
•
•
• bean seedlings (tomatoes instead) soil (potting mix) auxin solution of two different concentrations, 1mg/L and 0.5mg/L scissors (scalpel) alfoil pots ruler water measuring cylinder
Method
1. Plant seedlings in the same amount of soil, two seedlings for each trial (6 in total). The control group will be named Group 1, the group with the apical bud will be named Group 2, and the group being watered with auxins will be named
Group 3.
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Comments
Modifying investigations.
2. For Group 2, trim their tops off. How much?
3. Water the Group 1 and 2 seedlings with x mL distilled water.
4. Water Group 3 seedlings with x mLs of the auxin solution.
5. Measure the size of each seedling and record heights, widths and internodal heights.
6. Water and take measurements of the seedlings each day. Take photographs each day to record the growth of the seedlings.
7. Repeat and modify the experiment to confirm results.
Changes may need to be made later on.
[…]
Modification
As it appeared that the plants were turning brown (or burning) so they were moved under artificial light to stop this from happening. The plants now have
24 hour light so can photosynthesise all the time but without the heat to burn them.
Although at first it didn’t seem to make a difference – the plants did eventually revive and start growing under the artificial light.
[…]
Acidity test
Because the plants were dying I did an acidity test on the soil that they are planted in, the auxin solutions and the distilled water.
[…]
From the research it seems that either an excess of boron or deficiency of phosphorous are causing this as these symptoms are the same as what appears in the plants being grown. This would be a pH of around 6 because that is where a lot (:. Excess) of boron is absorbed and where not much (:.
Deficient) amount of phosphorus is absorbed.
[…]
If the pH is around 8, then either of these problems could be behind this. Most likely the boron excess.
[…]
Conclusion
Because the pH of the soil was 5-6 the problems seen in the plants could be caused by either an excess of boron being absorbed or a deficiency of phosphorous. It can be assumed it was more likely to be the boron because the symptoms were more evident.
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Comments
Describing ideas and concepts and identifying interrelationships.
Identifying researchable questions.
Selecting and implementing an investigation.
Ethylene and Fruit Ripening Experiment
Introduction:
The aim of this experiment was to test if the hormone ethylene, produced in banana’s, would affect the ripening rate of certain fruits. Ethylene is unlike other plant hormones as it is a gaseous hormone. Ethylene is used for fruit ripening at a fruits last maturing stages. The ethylene slowly reaches to 0.1 to
1.0ppm while the fruits ripening, and once it’s ready to mature, the ethylene has reached it’s right amount of ppm to expose it’s gas and start the maturing process. What is being tested is if allowing the ethylene from the ripening fruit and extended ethylene from an already ripened banana will ripen the fruits faster.
Hypothesis: Ripening of unripe fruits is unaffected by storing it with a banana.
Prediction: The fruits won’t change their ripening rate after being exposed to more ethylene.
Procedure:
1. Label bags clearly from 1-3
2. Put fruit in bags.
−
Bag One-1 Banana, 1 Pear
−
Bag Two-1 Banana, 1 Pear
−
Bag Three-1 Pear
3. Fold the tops of the bags down twice so that it’s not fully concealed but not much air is entering or escaping.
4. Place all bags in a constant room temperature area (independent variable)
5. Check all bags every day for 5 days and record results accordingly e.g. photos, tables, etc.
6. After the 5 days are complete, cut the pears in half and put cover one half in
Iodine and leave the other to compare how much starch is in the pears. The lighter the colour goes, the riper the pear is. The darker the colour stays, the more likeliness that the pear is still unripe.
Results:
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Comments
Collecting and organising data.
Selecting, modifying and implementing an investigation (B standard)
Discussing results.
Identifying interrelationships.
Discussion:
Before the experiment was tested with pears, it was tested with mandarins.
By the end of the five days of the experiment, the mandarins were brown and mouldy. No one in the group could figure out why this happened as none of it was in our background research. So we looked into why this may have happened. We found that ethylene is a base, like the pear. And on the pH scale, mandarins aren’t on the same level as ethylene as they are acidic.
So mixing the ethylene with the acidic mandarins wouldn’t have any affect as mandarins are form 7 on the pH scale, meaning it’s neutral. And the acidic fruits, like mandarins, release glycol ethylene, not normal ethylene. So the ethylene was stronger in the bananas and the proteins were all wrong so the two fruits just reacted against each other, and that’s why it went all mouldy.
We decided to conduct the experiment again but with a different fruit. So further research was made to see what fruits were essential for the ethylene test. We chose to use pears as they are easier to notice when it’s ripening as the colour goes from dark green to light yellow/green. And the fruit goes from hard to soft and appetizing.
From the results above and in the journal, you can evidently see in the photos and tables provided that there were some unsuspected results. The prediction of this experiment was that ethylene would not contribute to the ripening rate of pears. The results prove otherwise.
From day one to day three of the experiment, the pears in bags one and two were clearly lighter than the pear in bag three. By day five, the pears in bags one and two were softer than the pear in bag three and also had brown bruises on them as they started to spoil. This links us back to the background research. It verifies that the research was legitimate and appropriate when saying that adding a fruit already with the high amount of ethylene needed to start the ripening process, fastens the process.
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Comments
Discussing results.
Drawing conclusions.
You can see in the table and photos, that day five of the ripening, we have named ‘Iodine Day.’ At the end of the experiment, we cut the pears in half and covered the flat surface of one half in iodine and left the other one to compare colour. The iodine started off as a dark colour from the pears in bags 1 and 2 but then slowly turned lighter; meaning the pears were ripe. The pear from bag
3 was also lighter but was not overripe like the other two pears. This was concluded that the bananas were left in the bags for too long, leaving the pears to spoil. So linking back, we were proven wrong when predicting that ethylene had nothing to do with ripening fruits faster than their normal ripening rate.
Conclusion:
In conclusion, testing if ethylene ripens fruit faster than it ripens by itself is a limited experiment. The fact that we didn’t know that there were limited fruits for this experiment proves that we didn’t do enough background research.
This has been noted for future experiments. Our results and data proved that ethylene can ripen specific fruits if given the right ppm level. Therefore our prediction and hypothesis were proven wrong. Ethylene can help fasten the ripening rate of fruits such as pears. It contributes to the ppm level needed to start the ripening process, but earlier. And that’s why the pears from bags 1 and 2 were overly ripe by the pear from bag 3 was ripe.
Bibliography http://www.plant-hormones.info/ethylene.htm http://www.catalyticgenerators.com/whatisethylene.html http://www.biology-online.org/11/10_growth_and_plant_hormones.htm
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