Pechenik Citation Style Quick Guide
The following are examples based on the 9th edition of A Short Guide to Writing about Biology by Jan A. Pechenik. For further
explanation and for more examples, consult Pechenik’s guide. This information is taken from pages 63 to 67.
Journal names are usually abbreviated. See http://library.caltech.edu/reference/abbreviations/
for title abbreviations.
Source
Literature Cited
Citations in Text
Journal article 1
author
Wykoff, W.R. 2002. Measuring and modeling surface
area of ponderosa pine needles. Can. J. For. Res.
32: 1-8.
(Wykoff, 2002)
Journal article 2
authors
Bassett, T.J., Zueli, K.B. 2000. Environmental
discourses and the Ivorian Savanna. Ann. Assoc.
Am. Geogr. 90(1): 67-95.
(Bassett and Zueli, 2000)
Journal article 3 or
more authors
Field, I.C., Bradshaw, C.J.A., Burton, H.R. Sumner,
M.D., Hindell, M.A. 2005. Resource partitioning
through oceanic segregation of foraging juvenile
southern elephant seals (Mirounga leonina).
Oecologia 142: 127-133.
(Field et al., 2005)
Book 1 author
Wagner, F.H. 1980. Wildlife of the Deserts. H.N.
Abrams, New York, pp. 231.
(Wagner, 1980)
Book Specified
edition 3 or more
authors
Roberts, C., Varty, B., Lucas, V. 2004. Writing for the
Biological Sciences, 10th ed. Addison-Wesley,
Toronto, ON, pp. 73-76.
(Roberts et al., 2004)
Chapter or article in
an Edited Book 2
authors
Evans, S and Smith, J. 2000. Ecotourism in tropical
rainforests: an environmental management option for
threatened resources? In: Forest Tourism and
Recreation: Case Studies in Environmental
Management. (Font, X., Tribe, J., eds.). CABI
Publishing, Wallingford, UK, pp. 127-142.
(Evans, 2000)
Formal Report
available online
Lawrence RA. 1997. A Review of the Medical
benefits and Contraindications to Breastfeeding in
the United States [internet]. Arlington VA: National
Center for Education in Maternal and Child
Health.1997 Oct [cited 2016 Nov 03]. 40 p. Available
from http://ncemch.org/NCEMCH-publications/
BreastfeedingTIB.pdf
(Lawrence, 1997)
Working Paper
available online
Imberman, S., Kugler, A.D., Sacerdote, B. 2009.
Katrina’s children: evidence on the structure of peer
effects from hurricane evacuees (Working Paper No.
15291) [Internet]. Cambridge, MA: National Bureau
of Economic Research. 2009 Aug [cited 2016 Aug
30]. 55 p. Available from http://www.nber.org/
papers/w15291
(Imberman et al., 2009)
Institutional Web
Publication
National Institute of Mental Health. 2001. Teenage
brain: A work in progress [Internet]. [cited 2016 Oct
15]. Available from http://www.nimh.nih.gov/health
/publications/Teenage-brain-a-work-in-progressfactsheet/index.shtml
First Time You Cite Use Full Name:
(Research Institute,
Government, NGO,
non-profit, University)
(National Institute of Mental Health, 2001)
Thereafter Use the Acronym
(NIMH, 2001)
Sample Literature Cited list
Literature Cited
Bassett, T.J., Zueli, K.B. 2000. Environmental discourses and the Ivorian Savanna. Ann. Assoc. Am.
Geogr. 90(1): 67-95.
Cochran, W.W., Mouritsen, H., Wikelski, M. 2004 Apr 16. Migrating songbirds recalibrate their magnetic
compass daily from twilight cues. Science 304: 405-408.
Evans, S and Smith, J. 2000. Ecotourism in tropical rainforests: an environmental management option for
threatened resources? In: Forest Tourism and Recreation: Case Studies in Environmental
Management. (Font, X., Tribe, J., eds.). CABI Publishing, Wallingford, UK, pp. 127-142.
Field, I.C., Bradshaw, C.J.A., Burton, H.R. Sumner, M.D., Hindell, M.A. 2005. Resource partitioning
through oceanic segregation of foraging juvenile southern elephant seals (Mirounga leonina).
Oecologia 142: 127-133.
Alternate Hypothesis: If the pH of the sunflower extract is high (above 7) than less sunflower
seeds will germinate, and root lengths will be shorter.
Null Hypothesis: If pH level is altered than the germination rates and root lengths will not be
affected.
Materials: 14 Petri Dishes, 140 sunflower seeds, 5 fully grown sunflowers, pH tablets, 2 sets of
a Mortar and Pestle, Cheese Cloth, 40 filter paper, 4 jars to hold extracts, 5mL pipette and pipette
tips, light source, and a Caliper.
Techniques: Observing allelopathic effects of pH by measuring root length of germinated seeds
Methods:
To commence the experiment, gather the necessary materials. Obtain 15 sunflower leaves
which will be used to create the sunflower extract. Cut the sunflower leaves into tiny pieces and
place them into a mortar. Add 160 mL of distilled water to the mortar. Use a pestle to grind the
sunflower leaves until the water becomes the color of the leaves. Obtain a clean beaker and place
a piece of cheesecloth over the beaker. Pour the liquid within the mortar over the cheesecloths so
that it filters into the beaker. Label the beaker “sunflower leaf extract” and set it to the side. Grab
a clean mortar and 15 more sunflower leaves. Cut the sunflower leaves into tiny pieces and place
them into the clean mortar. Add 160 mL of distilled water to the mortar, as well as, an acidic pH
tablet. Use a clean pestle to grind the sunflower leaves and the pH tablet until the water is the
color of the leaves. Obtain a clean beaker with a fresh piece of cheesecloth placed over the
beaker. Pour the liquid inside of the mortar over the cheesecloth so that it filters into the beaker.
Label this second beaker “acidic sunflower extract” and set it aside. Obtain a clean mortar and 15
more sunflower leaves and repeat the previous steps, grinding the sunflower leaves in 160 mL of
distilled water. Instead of using an acid pH tablet, however, place a basic pH tablet into the
mortar to be grinded with the sunflower leaves. Then, follow the previous steps to transfer the
liquid within the mortar to a separate clean beaker. Label this third beaker “basic sunflower
extract.”
Obtain 12 clean petri dishes. Spread three pieces of filter paper across the bottom of each
petri dish. Place 10 sunflower seeds within each of the 12 petri dishes. Label three of the 12 petri
dishes “distilled water.” Label another three “sunflower extract w/ distilled water.” Label another
three “acidic sunflower extract” and the last three petri dishes “basic sunflower extract.” Using a
pipette, pour 5 mL of distilled water into the three petri dishes labeled “distilled water.” Then,
using a clean pipette tip, pour 5 mL of the sunflower and water extract into the petri dishes
labeled “sunflower extract w/ distilled water.” Follow these same steps using the acidic
sunflower extract and the basic sunflower extract to place into the petri dishes labeled “acidic
sunflower extract” and basic sunflower extract,” respectively. Once all the 12 petri dishes are
moistened with the correct extracts, place them under a light where they will grow for one week.
Take what is left over of each extract and put them in separate jars that are to be refrigerated. The
remainder of these extracts will be used to water the plants for the rest of the week. The plants
are to be observed each day of the week and watered with the correct extracts when necessary.
Record each day the number of seeds in each petri dish that have germinated and the condition of
each sunflower plant. At the end of one week, measure the root lengths of all of the germinated
sunflower plants.
References:
Bower, D., Morgan, D., Phillips, K., & Roeth, B. (2005, May 20). The Effect of pH on the
Growth of Green Beans. Retrieved from
http://jrscience.wcp.muohio.edu/nsfall05/LabpacketArticles/TheEffectofpHontheGrotwh
o.html
-
We were able to look at how another lab did a similar experiment with green beans. We
saw their thought process and their steps taken. Low pH values could create a nutrient
deficiency in the cells and could cause the plants to die.
Sripad, G., Prakash, V., & Narasing, M. S. (1982, June). Extractability of polyphenols of
sunflower seed in various solvents[Scholarly project].
https://link.springer.com/article/10.1007/BF02702723#citeasv
-
We were able to see that there is a chemical called chlorogenic acid in sunflower seed
that helps to regulate pH values. This chemical can be extracted from the sunflower seed
with the assistance of another chemical.
Perry, L. (2003). PH for the Garden. Retrieved from http://pss.uvm.edu/ppp/pubs/oh34.htm
-
From this article the author posted several different pH of the soil of surrounding plants.
This can be used to compare natural soil type.
Raya-Díaz, S., Quesada-Moraga, E., Barrón, V., Campillo, M., & Sánchez-Rodríguez, A.
l02saroa@uco. e. (2017). Redefining the dose of the entomopathogenic fungus
Metarhizium brunneum (Ascomycota, Hypocreales) to increase Fe bioavailability and
promote plant growth in calcareous and sandy soils. Plant & Soil, 418(1/2), 387–404.
https://doi.org/10.1007/s11104-017-3303-0
-
They added different doses of EF and tested the affects on sunflower growth but also
found that it affected the pH levels in the sunflower.
Lasa, B., Frechilla, S., Aleu, M., González-Moro, B., Lamsfus, C., & Aparicio-Tejo, P. M.
(2000). Effects of low and high levels of magnesium on the response of sunflower plants
grown with ammonium and nitrate(1-2 ed., Vol. 225, Rep.). Retrieved from
https://link.springer.com/article/10.1023/A:1026568329860
-
This focuses on the effect of different levels of magnesium on plants. This will help us
compare the effects of other chemicals that affect pH level in sunflowers.
https://pubs.acs.org/doi/abs/10.1021/jf049612j
-
A study on how heat and pH work hand and hand to affect growth on the sunflower.
https://homeguides.sfgate.com/ph-affect-plants-49986.html
-
How pH levels normally affect plants. It can affect the plants ability to absorb nutrients.
http://plantsinmotion.bio.indiana.edu/plantmotion/earlygrowth/germination/sunflower/sun.html
-
Video on seed germination (maybe for presentation)
Allopathic Effects of pH on Roots’ Length
Abstract
According to research, the pH level of the surrounding environment of a plant
is considered to have a significant effect on the root length, especially in legumes
(Butnariu & Negrea, 2015). Most studies indicate that acidic soil usually inhibits the
range of the roots of a plant. This research is among the several studies that are
conducted to determine the allopathic effect of pH on the length of the roots of
germinated seeds. The study is performed to determine whether the pH can promote
or inhibit the size of roots. In this case, an extract from the petals of sunflower is used
where two of the solutions are labeled ‘acidic extract' and ‘alkaline extract.' On the
acidic extract, an acid is added while on an alkaline extract, an alkaline it put. The
seeds of a leguminous plant known as lettuce are used in the experiment to determine
the length of its roots under acidic extract, alkaline extract and in distilled water
which is considered to be neutral. The length of the roots will be determined by the
consideration of the seedlings in the distilled water. If the range of roots of the
seedlings in either the alkaline extract or the acidic extract will be smaller than the
roots of the seedlings on the distilled water, it will be concluded that pH level used
inhibits the length of roots. However, if the roots-length will be high compared to the
roots in the distilled water, it will imply that the pH level enhances the size of roots.
Keywords: pH, legumes, acidity, alkalinity, extract, allopathic
Introduction
PH refers to the acidity or alkalinity of a substance. The pH level ranges from
one to fourteen. As the pH of seven represents the neutral pH level such as that of
water, the pH above seven represents an alkaline substance while the pH below seven
represents the acidity of a surface. This aspect is considered to have a significant
effect on the growth of plants especially the roots. Some plants as believed to have
allopathic effects in which they limit the growth of other plants since they release the
chemicals that are not favorable for plants growth (Bhadoria, 2011). This effect is
mostly observed among tall trees that inhibit the growth of other plants below them.
The chemical that is released is considered to be retained on the leaves in most cases.
Based on that knowledge, most experiments conducted to test allopathic effects of pH,
applies to the sunflower extract since it is considered to be favorable for such
experiments for its pH lies between the slight acidity of 6.0 to slight alkalinity of 7.5
(Bubna & Ferrarese-Filho, 2011). Due to its pH level, the extract from the sunflower
petals can be manipulated into acidity or alkalinity without significant reaction. In the
experiment regarding the allopathic effects of pH in root length of germinated seed,
an extract from sunflower petals was used where three types of extracts were used.
One was acidic, the other was alkaline, and the third was neutral since the distilled
water was used. The reason behind the use of the three solutions was to determine
whether there is any effect of the acidity to the growth of roots, particularly in
legumes such as lettuce seed. The research has explained every step from the
extraction of the solutions to the determination of the root sizes after the experiment.
Methods Draft
Creating the Extract
A total of 60 sunflower petals were used to create a sunflower extract. The
sunflower petals were placed into a mortar. Two hundred mL of distilled water was
poured into the mortar. A pestle was used to grind the sunflower leaves until the
water changed its color to the same tint of the leaves. A clean
beaker was obtained, and a piece of cheesecloth was placed over the beaker. The
extract was poured from the mortar into the cheesecloth, so it was filtered into the
beaker. This beaker was then labeled “sunflower leaf extract” and set aside. The
process was then repeated two more times. One of the two new beakers was
then labeled “acidic sunflower extract” and an acidic capsule was opened and poured
into the beaker and was mixed until it was dissolved. The final pH of the solution
was 3. Then it was set aside. The second of the two was then labeled “basic sunflower
extract” and a basic pH capsule was opened and poured into the beaker and was
mixed until it was dissolved. The final pH of the basic solution was 11.
Setting Up the Petri Dishes
Twelve clean petri dishes were obtained. Three pieces of filter paper were
spread across the bottom of each petri dish. Twenty-eight lettuce seeds were
placed within each of the 12 petri dishes. Three of the 12 petri
dishes were labeled “distilled water.” Another three were labeled “sunflower
extract.” Three more were labeled “acidic sunflower extract” and the last three petri
dishes were labeled “basic sunflower extract.”
Moistening the Petri Dishes
Using a clean pipette each time, 5 mL of each extract was placed into
the corresponding petri dishes. Each dish was moistened until the filter paper looked
damp and all seeds seemed to be covered with their assigned extracts.
Setting up for weekly Observation
Once all the 12 petri dishes were moistened with the correct extracts, they
were then place under a LED light in a controlled room where they were left to grow
for one week. Four jars with lids were then labeled “distilled water,” “sunflower
extract,” “acidic sunflower extract,” and “basic sunflower extract.” The excess
extracts were then poured into their corresponding jars and put away in a refrigerator
for preservation. They were preserved for future watering through the week.
Data Analysis
The lettuce seeds were observed each day of the week and watered with the
correct extracts when necessary. Each day the number of seeds germinated in each
dish was recorded along with the condition of each plant. At the conclusion of the
week, the root lengths of all germinated seeds were measured and recorded. The lab
was repeated one more week for more data. A chi-squared test was then preformed for
the number of germinated seeds. Along with that the averages for each root length
were taken for each day and plotted on a ling graph.
Results
The following data displayed in Figures 1 and 2, as well as Tables 1 and 2,
demonstrate trends in the rate of germination, as well as, root lengths of seeds within
the varied solutions. Figure 1 presents the data for the overall rate of germination of
seeds for each solution for the first trial. The total average of germinated seeds for
each solution was used to obtain a Chi-squared value, which was calculated as 2.35.
Since there were four samples, the degree of freedom was three, meaning that the Chi-
squared value, 2.35, was compared to the value 7.81. Since the Chi-squared value was
not larger than 7.81, the null hypothesis, that all the samples would have the same
germination rate, failed to be rejected.
Number of Germinated Seeds
Figure 1: Number of Germinated Seeds Per Day
(Trial #1)
30
25
20
15
10
5
0
0
1
2
3
4
5
6
7
Day
# seeds (acidic)
# seeds (basic)
# seeds (sunflower)
# seeds (water)
Figure 1: The trend in germination rate for each solution is that the seeds in the acidic
extract and
basic extract germinate at a slower rate than the seeds in the sunflower extract and
distilled water.
Figure 2 displays the data for the overall rate of germination of seeds for each
solution for the second trial. The total average of germinated seeds for each solution
was used to obtain the Chi-squared value for trial two. The Chi-Squared value was
calculated as 7.97. Since there were four samples, the degree of freedom was three,
meaning that the Chi-squared value, 7.97, was compared to the value 7.81. Since the
Chi-squared value was larger than 7.81, the null hypothesis, that all the samples
would have the same germination rate, was rejected.
Number of Germinated Seeds
Figure 2: Number of Germinated Seeds Per Day
(Trial #2)
30
25
20
15
10
5
0
0
1
2
3
4
5
6
7
Day
# seeds (acidic)
# seeds (basic)
# seeds (sunflower)
# seeds (water)
Figure 2: The trend in germination rate for each solution is that the seeds in the acidic
extract and
basic extract germinate at a slower rate than the seeds in the sunflower extract and
distilled water.
The following two tables, Table 1 and Table 2, depict the data for the average
root length of each germinated individual for each trial. Both tables show that average
root length for individuals within the acidic and basic extracts differ significantly
compared to the average root length of individuals in the sunflower extract and
distilled water. Thus, the null hypothesis, that the root length of each individual does
not vary within each was solution, was rejected, as it is evident that the root length of
individuals within each extract vary significantly.
Table 1: Average Root Length Of Each Germinated Individual For Each
Solution (Trial 1)
Solution
Average Root Length (mm)
Acidic Sunflower Extract
0
Basic Sunflower Extract
0.77
Sunflower Extract
35.78
Distilled Water
29.43
Table 2: Average Root Length Of Each Germinated Individual For Each
Solution (Trial 2)
Solution
Average Root Length (mm)
Acidic Sunflower Extract
0
Basic Sunflower Extract
0.58
Sunflower Extract
31.40
Distilled Water
37.16
References
Bhadoria, P. B. S. (2011). Allelopathy: a natural way towards weed
management. American Journal of Experimental Agriculture, 1(1), 7.
Bubna, G. A. & Ferrarese-Filho, O. (2011). Exogenous caffeic acid inhibits the
growth and enhances the lignification of the roots of soybean (Glycine
max). Journal of plant physiology, 168(14), 1627-1633.
Butnariu, M. & Negrea, P. (2015). Allelopathic effects of Pteridium aquilinum
alcoholic extract on seed germination and seedling growth of Poa
pratensis. Allelopathy journal, 35(2).
The Discussion Section
When starting the discussion consider the research question
first. You posed the research question, explained your
methods for answering it, and provided the results; now
answer the question. The discussion is the place for interpreting
the results. Use the statistical results to make conclusions
regarding the research question. In other words, if
the hypothesis is statistically confirmed by the results,
what does that mean?
The discussion is usually the easiest section to write,
and there is no “magic formula.” From my standpoint, if
you are having trouble with the discussion, you can use the
simple construct in Table 2. The most common mistake in
the discussion section is overstating the findings. For instance,
if you found that high-frequency ventilation improved
oxygenation, you cannot infer that other outcomes
(eg, mortality) are also improved. If a new bronchodilator
reduces airway resistance faster than the old one, you cannot
infer that patients will come off the ventilator faster.
That type of unjustified inference appears to indicate that
the authors knew what they wanted the results to be prior
to the study and that they set out to prove that the new
treatment is better, not to find out whether the new treatment
is better. Such bias is apparent in phrases such as
“We have demonstrated that. . . . ”
The reader should easily follow the research question
through the methods, results, discussion, and to the conclusion.
As a good test, read your hypothesis and conclusion
out loud. If you do not see an obvious logical connection
between the two, there is a problem.
The preponderance of references should be cited in the
discussion section. A few historical references may be helpful
for perspective. Most of the references should be recent
and aid in the interpretation of your results. If a report you
cited disagrees with your findings, clearly explain why.
The discussion section is your chance to review the
current knowledge and explain how your study’s findings
add to the body of knowledge. You can provide opinion as
long as you identify it as such.
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