Additional Resources
Lab Report
Investigation on Plant Growth
Hannah Rempel, the Biosciences Librarian at the OSU Valley Library has prepared a
library page in association with your lab report on Investigation of Plant Growth.
http://ica.library.oregonstate.edu/Course_Assignment_Page/846
You can also get to it by going to the library's homepage, looking on the left hand side
bar and clicking on "get help with a class" (third from the bottom), then finding the class
alphabetically.
TAKE THESE PAGES HOME TO COMPLETE YOUR LAB REPORT
INVESTIGATION ON PLANT GROWTH
Background Information
Spacing Plants for Optimal Yield
The distance between plants greatly affects their areal yield (their final biomass per
square meter of field surface). If plants are too close, intense competition for light and
water causes them to grow poorly or die, and areal yield from a field of these crowded
plants will be low. If the plants are too far apart, individual plants will grow well, but
there will be so few plants per square meter that yield will be low. There is an
intermediate distance between plants at which yield per square meter is maximized. The
interplant distance that produces the greatest rate of areal photosynthesis (mg C per m2
per day), and thus the largest areal yield, is influenced by several factors, such as
temperature extremes, light intensities and water availability.
Research Question
How does the interplant distance that maximizes areal yield (yield per square meter of
field surface) change with moist and dry conditions?
Hypothesis You should have already written a hypothesis on an earlier page of this in-lab
assignment. Remember your hypothesis should be a biological explanation for how you
think the optimum interplant distances would change with moist and dry conditions.
Prediction You should have already written a hypothesis on an earlier page of this in-lab
assignment
If the hypothesis is true, then the results of the computer model should give the following
results:
If the hypothesis is not true, then the results of the computer model should give the
following results:
Results and Discussion
You will report the results and write a discussion of your results for your report on your
investigation. The instructions for your report will be provided in the following pages.
To help you interpret your results, review your answers to the following questions when
your lab instructor returns your in-lab assignment.
 Why do plants starve and die at very close interplant distances?
 Why do the leaf area index and soil water depletion change with increasing in
interplant distance?
 For your data what is the leaf area index at which plants are first able to realize
positive net photosynthesis?
 How does net photosynthesis for individual plants change as interplant distance
increases?
 Does individual plant photosynthesis reach a maximum value? Why?
 Which interplant distance gives the greatest net photosynthesis per square meter
for your data? Why does areal net photosynthesis decrease once this optimum
interplant distance is exceeded?
RESOURCES
Glossary
Allocation The assignment of photosynthate to the growth of roots, stem height, stem
thickness, or leaves.
Areal photosynthesis Net photosynthesis per unit area (in Seedling, mg C/m2/day).
Fixed carbon Carbon that has been incorporated into sugar by photosynthesis.
Leaf-area index (LAI) The ratio of total leaf area to underlying soil area. When leaf-area
index exceeds one, leaves must be shading one another. High LAIs mean both severe
shading and serious water loss through transpiration.
Net photosynthesis Carbon fixed by photosynthesis minus carbon consumed by respiration.
Net photosynthesis is positive when photosynthetic production exceeds the requirements of
respiration and negative when respiration outstrips photosynthetic productivity. Net
photosynthesis must be positive for growth to occur. Negative net photosynthesis (due to
shading, water stress, or old leaves) will cause death by starvation.
Net photosynthesis per square meter (m2) Net photosynthesis per plant multiplied by the
number of plants per square meter.
Net photosynthesis per plant A measurement equal to photosynthesis (carbon fixed into
carbon compounds) minus respiration (carbon used up by oxidation). If the result is positive,
the plant has photosynthate (carbon products produced by photosynthesis), to devote to
growth after satisfying its respiratory costs. If it is negative, the plant is starving and not
growing.
Number of plants per square meter (plants/ m2) A measurement computed from the
distance between plants.
Percent of water demand satisfied The percentage of the plant’s water needs that can be
met by the uptake of water from the soil.
Percent of the maximum net photosynthetic rate This rate would be 100% if all leaves
were new, if there was no lack of water, and if there was no shading.
Photosynthate The sugars made by photosynthesis.
Photosynthetic rate The rate of carbon fixation expressed as a percentage of the maximum
rate that would occur under optimum conditions of full sunlight, optimum temperature
(25ºC), abundant water, and all leaves new and unshaded.
Relative humidity The amount of water in the air expressed as a percentage of the
maximum amount of water that air of this temperature could hold. Low relative humidities
greatly increase water loss through transpiration.
Respiration The consumption of sugars and other organic molecules in the process of
metabolism. Every cell in a plant requires photosynthate merely to stay alive. If respiration
requires more photosynthate than photosynthesis can produce, net photosynthesis is negative
and the plant must use its food reserves
Soil water depletion The decrease of soil water (in milligrams per cubic centimeter of soil:
mg/cc) that has occurred due to the uptake of water by plants.
Stomata The microscopic openings on the underside of a leaf through which the leaf
absorbs CO2 from the air and loses water. During water stress, these openings close and
photosynthesis stops.
Transpiration Evaporation of water through the stomata of leaves.
Water demand The percentage of its water needs that a plant is currently satisfying by
water uptake from the soil. A water demand reading of less than 100% indicates water stress.
RESOURCES
Guidelines for Constructing Graphs
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Use graph paper and ruler to plot values accurately.
The independent variable is graphed in the x axis (horizontal axis or abscissa) and
the dependent variable, on the y axis (vertical axis, or ordinate).
The numerical range for each axis should be appropriate for the data being
plotted. Generally, begin both axes of the graph at zero (the extreme left corner).
Then choose your intervals and range to maximize the use of the graph space.
Choose intervals that area logically spaced and therefore will allow easy
interpretation of the graph.
Label the axes to indicate the variable and units of measurement.
Include a legend if colors or shading used to indicate different aspects of the
experiment.
Graphs, diagrams, drawings and photographs are all called Figures and should be
numbered consecutively throughout a lab report or scientific paper.
Each figure is given a caption or title that descries its contents, giving enough
information to allow the figure to be self-contained.
Capitalize only the first word in a figure title and place a periods at the end.
Writing Assignment
Investigation on Plant Growth
Biology 212
Winter 2008
Scientific writing
One of the objectives of the laboratory experience this term is to develop your writing
skills. In science, writing is an important means of communication. A scientific paper
usually includes the following parts: a title (statement of the question or problem), an
abstract (short summary of the paper), an introduction (background and significance of
the research, including any hypotheses and predictions), a materials and methods section
(report of exactly what you did), a results section (presentation of data), a discussion
section (interpretation and discussion of results), and references (books and periodicals
cited in the introduction or discussion sections).
Assignment
Write a lab report on your experiment investigating the effect of moist and dry conditions
on interplant distance that maximizes areal yield (yield per square meter of field surface).
The report should be typed with double-spaced text, 12 pt font and pages numbered with
the following components.
Title
The title should be as short as possible and as long as necessary to communicate to the
reader the question being answered in the paper.
(Additional resource http://www.wisc.edu/writing/Handbook/SciRep_Title.html)
Introduction
This section gives the background and rationale for your research question. In other
words, it places your research in context. This introduction section includes your
research question, hypothesis, and prediction. The background and rationale information
should be no more than 1-1.5 pages. You must give credit for any information that you
gain from other sources and present in your report by citing the reference. Two
references are required only one of which can be a textbook.
(Additional resource http://www.wisc.edu/writing/Handbook/SciRep_Intro.html)
Methods
In this section you can state in 1-2 sentences that you used a computer model Seedling
(BioBytes 3.1, W.H. Freeman and Company) developed by Kosinski, R.J., (1999) to test
your hypothesis. The interplant distance measured at optimal areal yield (dependent
variable) was compared between two environmental conditions, moist and dry
(independent variable).
Results
This section, which is the central section of a scientific paper, has two components: (1) a
figure (graph) summarizing your data and 2) text describing your results (1-2
paragraphs). The graph will show the relationship between moist and dry conditions on
the interplant distance for optimal areal yield. The graph needs to have a complete title.
Cite your figure in the text portion of your report. Do not interpret your results in this
section. Review pages 14-18 in your lab manual for tips on presenting and analyzing
results. Use the guidelines in the handout attached to your in-lab assignment to prepare
your graphs.
Discussion
(Additional resource: http://www.wisc.edu/writing/Handbook/SciRep_Disc.html).
In this section, you will analyze and interpret the results of your experiment. Use the
following guidelines from your lab manual Appendix A: “Simply restating the results is
not interpretation. The Discussion must provide a context for understanding the
significance of the results. Explain why you observed these results and how these results
contribute to our knowledge. Your results will support or confirm your hypothesis or
will negate, refute or contradict your hypothesis but the word “prove” is not appropriate
in scientific writing. If you results do not support your hypothesis, you must still state
why you think this occurred. Support your ideas from other work (book, lectures or
outside reading of scientific literature). State your conclusions in this section.
“Complete your Introduction and Results sections before you begin writing the
Discussion. The figures and tables in the Results section will be particularly important as
you begin to think about your discussion. The graphs allow you to visualize the effects
that the independent variables had on the dependent variables in your experiment.
Studying these data will be one of the first steps in interpreting your results. As you
study the information in the introduction section and your data in the Results section,
write down relationships and integrate these relationships into a rough draft of your
discussion.
“The following steps may be helpful as you begin to outline your discussion and before
you write the narrative:
 Restate your question, hypothesis, and prediction.
 Write down the specific data, including results of statistical tests.
 State whether your results did or did not confirm your prediction and support or
negate your hypothesis.
 Write down what you know about the biology involved in your experiment. How
do your results fit in with what you know? What is the significance of your
results?
 How do your results support or conflict with previous work? Include references
to this work.
 Clearly state your conclusions.
 You are now ready to write the narrative for the Discussion. Integrate all of the
above information into several simple, clear, concise paragraphs. Discuss the
results; do no simply restate the data. Refer to other work to support your ideas”.
References You must give credit to any information that you gain from other sources
and that you present in your report. At least two references are required only one of
which can be a textbook. See resources below for guidelines on citing references.
References need to be listed in alphabetical order by author’s last name.
No references from the Internet will be accepted for this assignment unless from an online peer reviewed scientific journal.
 How to decide what information must be referenced
http://www.wisc.edu/writing/Handbook/QPA_plagiarism.html
 How to write a successful summary without plagiarizing
http://www.wisc.edu/writing/Handbook/QuotingSources.html
http://www.wisc.edu/writing/Handbook/QuotingSources.html
 How to cite references
http://www.wisc.edu/writing/Handbook/DocCBE_NameYear_Intext.html
http://www.wisc.edu/writing/Handbook/DocCBE_NameYear_RefList.html
Additional Resources
 General information on writing a scientific report: Appendix A Scientific Writing in
your lab manual.
 Evaluation form included with this assignment sheet.
 Be sure to talk with your Lab Instructor if you have any questions.
Due Date
Your Lab Instructor will assign the due date. The grade on late reports will decrease 5%
per day.
Evaluation
Your lab report will be evaluated on the content and the effectiveness of your
communication, including text and figures. See the attached page for a sample evaluation
form.
Writing Assignment
Evaluation of Report on Plant Growth Investigation
Biology 212
Winter 2008
CONTENT
Title
Introduction
Background and rationale
Research question
Hypothesis
Prediction
Methods
Description of experimental design
Procedures
Results
Table or figure (graph)
Text describing results
Discussion
COMMUNICATION
Writing
Grammar, spelling, punctuation,
capitalization
Sentence construction
Paragraph structure: sentences in
logical order supporting one main
idea in each paragraph
Organization of paragraphs
Conciseness and clarity of writing
References
Required number
Listed in Reference section
Cited in text
Figure (graph)
Each title tells a complete story
Organization of report
Headings and subheadings included
Double-space text
Pages Numbered
COMMENTS