Long Term Plant Experiment - Lab Report
DUE TUESDAY, MAY29th
A very important aspect of laboratory work is being able to communicate your results effectively. The lab report
is divided into several sections in order to organize the contents and make it easy for the reader to follow and to
find information.
Title
Should be one simple sentence that describes the purpose of the lab. For example, if you are investigating how
quickly a plant will grow in response to sunlight in a sunny window, your title might be "The effect of sunlight
on plant growth." Your reader should be able to tell what the experiment was about just by reading the title.
Introduction
This section provides the reader with any background information or concepts she/he might need in order to
understand what you have done in the experiment. The Introduction defines the subject of the report. It defines
the nature and scope of the area to be investigated, as well as the motivation behind the experiment. In the
introduction to our plant experiment above, you might explain what photosynthesis is and why it is dependant
on sunlight. Remember, you are trying to give some basic background, not a PhD in plant biochemistry.
Background material should be used only if it is relevant to the experiment being performed. Major topics
which you wish to discuss later (i.e., in the Discussion) should be introduced here. Conclude the Introduction
with a brief statement as to the purpose of the experiment. After reading this section a person should have a
good idea of what was done experimentally by you and why.
Hypothesis
Your hypothesis should be stated in the positive and using the "If . . . then" format. For example, "If a plant is
placed in direct sunlight, then it will grow more quickly." Do not state negative hypotheses such as "If a plant is
removed from the sunlight, then it will not grow as quickly." The hypothesis should actually be tested in the
experiment. For example, you would not use "If a plant is well-watered and placed in direct sunlight, then it will
grow more quickly" as your hypothesis if you do not plan to test the effects of watering on the growth of the
plant.
Materials and Methods
You may be more familiar with calling this section a "Procedure" but many scientific journals refer to it as
"Materials and Methods." The Materials & Methods section contains the technical information and methods
used to obtain the results; it tells the reader what you did. This section should contain enough detail to allow
another scientist to repeat your experiment, but should not be overwhelming. Do not use lists of equipment or a
numbered list of steps that you followed. Rather, present the materials and methods as if it were a story.
Mention the equipment or apparatus used as you describe the steps you followed in completing the experiment.
Procedures are presented in chronological order for each part (avoid mixing experimental procedures even if
this was what was done in the lab) and subdivided using paragraphs and headings. Include items such as growth
conditions, organisms, and the chemicals used in the experiment. Experiments described in a scientific paper
must be reproducible. For this reason, the quality of the Materials & Methods section is judged by the reader's
ability to repeat the experiment (and obtain similar data). If a colleague cannot repeat your experiment using
only this section it is probably poorly written. This section is always written in past passive tense, as are all
sections. This means that there are no references to the first person, or pronouns. For example, you would not
state "I/we/Jack/Jill looked at the cells using a microscope", but would state, "The cells were examined using a
compound light microscope." Or, in our plant experiment above, you might write "A geranium plant was placed
in a sunny window and the temperature was recorded using an alcohol thermometer. The number of hours of
exposure to sunlight was measured using a timer and recorded on a daily basis." Notice that you have explained
a few of the steps and indicated the equipment necessary at the same time.
Results
This is where all your data belongs. Both quantitative (measured values) and qualitative (observed
characteristics) are included. You might use tables, charts or graphs. Remember that you must show your raw
data (i.e., what you actually observed or recorded) as well as the results of any calculations. Imagine that you
are answering the questions "What did you find?" or "what did you see or measure?" The results section should
summarize the data and observations from your experiments without discussing their implications. Organize
the data into figures (graphs, drawings, etc.) and tables, each with a descriptive title and a separate number, so
they can be referred to in the text of your Discussion section. Remember, each table or figure should be selfexplanatory; the reader should be able to understand each without referring to the written text . Keep titles
simple and to the point.
Note: There are no labels "Drawing" or "Graph" used in formal reports. Only use Figure (for drawings,
diagrams, flow-charts, graphs, etc.) or Table (for tabulated data).
All results must be fully described. Presentation of data (figures or tables) without adequate description, in
words, is inadequate and incorrect. Present only what was actually observed/obtained in the experiment and not
what theoretically or by inference should have occurred. If calculations are included present an example.
The most common error is to begin discussion of the results (ie., discussing their implications) in this section.
For example, consider these sentences:
1. A cell, 50 pm in diameter, was observed.
2. A cell, identified as B. bunnyus based on its size of 50 pm, was observed.
The first sentence belongs in the Results section as it describes an observation (cell size). The second sentence
belongs in the Discussion section as it describes an observation (cell size) and interprets this information
(identifies the cell).
Discussion
The discussion is perhaps the most important part of your lab report. This is where you provide an interpretation
or explanation of your results. It is not enough to only report your findings (results), you must also discuss what
they mean and why they are important. Discuss what you are able to learn from your results. In this section the
author (you) is expected to analyze and interpret the experimental data relative to the objectives described in the
Introduction. If the experiment appears to have gone well and you find results that you were expecting (i.e.,
agree with generally accepted values), you need to interpret those results. This means that you explain for the
reader what your results mean. If you find some unexpected results, you face the difficulty of explaining those
results. In other words, you must provide a possible explanation as to why you did not find what you had
expected to find. Don't worry if your results seem strange - discuss the results you got. Remember, a great deal
of science comes from finding the unexpected. be sure to validate or disregard your hypothesis.
Discuss the topic concisely and succinctly, with direct reference to your experimental results. Attempt to
present the principles, relationships and generalizations shown by the results but do not repeat the results more
than absolutely necessary. Attempt to explain the theoretical basis for your results (e.g., reaction mechanisms
for stains, or role of sunlight in photosynthesis) where possible. Compare your results with the literature on the
subject (textbooks, journal articles, etc.). If questions are provided for the lab, they are meant to be a guide to
build your discussion around. Do no limit your Discussion to only answering the questions.
A good discussion section should do each of the following:
1.
Discuss the results, that is, present relationships, principles and generalizations.
2.
Point out exceptions and lack of correlations; define unsettled points.
3.
State how the results relate to the existing knowledge. All experimental results must be
addressed, whether they agree or disagree with the literature.
4.
State the significance and implications of the data. What do the results mean?
Conclusion
This is a short, one or two sentence conclusion. This should sum up the experiment, what was found and
whether the hypothesis was validated or rejected.