2. INTRODUCTION
Plant Physiology
study of how plant life exists
requires observation, asking questions and proposing
explanations
Scientific Investigations
-way of testing explanation about plant phenomena
- similar to scientific method
Plant Physiologists
- ask questions, make observations, develop explanatory
hypotheses and test those hypotheses
3. ASKING QUESTIONS
Why ask?
Requires well-defined and measurable
phenomenon
Elements must be measurable and controllable
4. ASKING QUESTIONS
Does exposure to ultraviolet radiation cause
increased risk of skin cancer?
Will eating cassava cause poisoning by demons?
Does good nutrition lead to increased intelligence
Why do cacti have spines?
Was the malignant tumor found in the lungs of a 70-
year-old man caused by his 45-year habit of
smoking cigarettes?
Is it true that Plant Physiology students are all
pretty and handsome?
Does overwatering plants cause death of plants?
5. ASKING QUESTIONS
Do plants have feelings too?
Will I get a grade of 1.00 in Plant Physiology?
Are all plants photosynthetic?
8. HYPOTHESIS
Experiments are designed to falsify the hypothesis
by producing evidence to disprove it.
If the evidence that is gathered does support the
hypothesis, the hypothesis is accepted but only on
a trial basis.
It is never accepted as absolute truth because
future investigations may still falsify the hypothesis.
9. HYPOTHESIS
Must be stated in a way that is can be easily
measured and must be constructed in a way that
will help in answering the question
10. B. DEVELOPING HYPOTHESIS
B1. Write a hypothesis for the following questions:
1. Why are there so many trees in the tropical
rainforests of the Philippines?
-> There are many trees due to sufficient sunlight
and abundant rainfall.
11. 2. What is the function of the tendril of ampalaya?
-> The tendril functions as a support for the plant as it
climbs along the substrate.
3. What is the effect of fertilizer on a lettuce patch?
-> Fertilizer improves the growth and the productiveness
on a lettuce patch.
12. 4. How does lahar soil affect plant growth?
-> Lahar soil increases plant growth.
5. Why is organic fertilizer better for plants?
-> Organic fertilizer provides less toxic chemicals than
inorganic fertilizers.
13. DEVELOPING HYPOTHESIS
B2. Which of the following would be useful as a
scientific hypothesis? If yes, give the reason by
stating whether it could possibly be falsified and
what factors are measurable and controllable.
14. 1. Garlic can be used against snake bites.
-> Yes. Garlic has been used through ages and is also
known as remedy for snake bites.
-> The biochemical composition of garlic may be
studied in order to know the efficacy of the remedy on
snake bites.
-> The control variable would be the amount of remedy
to be applied on the affected area of the body.
15. 2. Tetanus is caused by stepping on rusty nails.
-> Yes. It can be falsified by hospital records whether
tetanus is only caused by rusty nails.
3. Parasitic plants are evolutionarily more advanced than
non-parasitic plants.
-> Yes. It can be verified and better understood through
plant systematics.
16. 4. Drinking beer can improve one’s memory.
-> Yes. A standard test can be given to two groups
– one which will be given beer to drink and another
group without beer. This set-up can be used to
support or falsify the hypothesis.
17. 5. Bio 121 students are better gardeners than non-Bio
121 students.
-> No. The definition of “better gardeners” is vague.
Again, the hypothesis is subjective.
20. DETERMINING THE VARIABLES
Scientific experiment
composed of variables, and a procedure to test them.
Defining variables
greatly dependent on the question and hypotheses
formulated at the start of a scientific investigation.
the goal of an experiment is to provide clear evidence
to falsify or support a particular explanation.
21. TYPES OF VARIABLES
Independent Variable
one assumed to cause a particular phenomenon
Dependent Variable
is the effect of the said phenomenon
Controlled Variable
is regulated to determine if the independent variable is
the true cause of a phenomenon
22. METHODOLOGY
Identify the variables in preceding investigation.
Classify whether it is independent, dependent or
controlled variable.
Only 1 independent variable is usually chosen
Consider alternative independent variable
23. INVESTIGATION OF THE EFFECT OF SULFUR DIOXIDE ON
SOYBEAN PRODUCTION
Agricultural scientists were concerned about the effect of air
pollution, sulfur dioxide in particular, on soybean production in fields
adjacent to coal-powered power plants. Based on initial
investigations, they proposed the sulfur dioxide in high concentrations
would reduce reproduction in soybeans. They designed an
experiment to test this hypothesis. In this experiment, 48 soybean
plants, just beginning to produce flowers, were divided into two
groups of 6. One group of 6 treated plants were placed in a fumigation
chamber and exposed to 0.6 ppm of sulfur dioxide for 4 hours to
stimulate sulfur dioxide emissions from a power plant. The experiment
was repeated on the remaining three treated groups. The no
treatment plants were placed similarly in groups of 6 in a second
fumigation chamber and simultaneous exposed to filtered air for 4
hours. Following the experiment all plants were returned to the
greenhouse. When the plants matured, the number of bean pods,
number of seeds per pod and the weight of the pods were determined
24. Agricultural scientists were concerned about the effect of air
pollution, sulfur dioxide in particular, on soybean production in
fields adjacent to coal-powered power plants. Based on initial
investigations, they proposed the sulfur dioxide in high
concentrations would reduce reproduction in soybeans. They
designed an experiment to test this hypothesis. In this experiment,
48 soybean plants, just beginning to produce flowers, were divided
into two groups of 6. One group of 6 treated plants were placed in
a fumigation chamber and exposed to 0.6ppm of sulfur dioxide for
4 hours to stimulate sulfur dioxide emissions from a power plant.
The experiment was repeated on the remaining three treated
groups. The no treatment plants were placed similarly in groups of
6 in a second fumigation chamber and simultaneous exposed to
filtered air for 4 hours. Following the experiment all plants were
returned to the greenhouse. When the plants matured, the number
of bean pods, number of seeds per pod and the weight of the pods
were determined for each plant.
25. VARIABLES
Duration of exposure
Selected age of soybeans
Kind of gas exposed
Number of seeds per pod
Weight of the pods
27. INDEPENDENT VARIABLE
Different gases exposed to the set-ups.
It is important to have only one independent variable in
order to have consistency when testing for only one
possible predicted result.
Duration of gas exposure
Age of the soybeans
28. CONTROLLED VARIABLE
Duration of gas exposure
Same age of all soybeans
Same kind of fumigation chamber
30. CHOOSING OR DESIGNING THE PROCEDURE
Once the variables have been decided upon
designing of the procedure takes place.
The procedure should be written in such a way as
to make the experiment repeatable.
Proper designing of procedures is crucial to the
credibility of your work
in order to perform the experiment and obtain the results
consistently for the conclusions to be considered a worthy
contribution to the body of knowledge that is science.
31. Procedure must contain all the steps that have
undertaken in the experimentation, including any
modifications to the original procedure, control
treatments, levels of treatments and number of
replications (Evangelista, 2009)
32. METHODOLOGY
Enumerate the step by step activities of the experiment in
soybean production.
33. Count the
Place one Repeat number of
group in with 3 seeds and
Divide into 4
SO2 other total
groups of 6
chamber groups weight of
for 4 hours pods
Select 48
soybeans Divide into
with 2 groups
approx. of 24
same age
Place one Count the
Divide into Repeat number of
group in
4 groups of with 3 seeds and
filtered air
6 other total weight
chamber
groups of pods
for 4 hours
34. There are two main components of the procedure:
two manipulated variables (SO2 and natural air) and
each component having 4 replicates.
37. EXAMPLE
We can predict that, after the results of the soybean
experiment
if ever the SO2 concentration was doubled, the decrease in
the overall yield could be doubled as well.
One may choose to perform another experiment based on
these predictions, in order to form better conclusions about a
particular phenomenon.
38. Thus predictions are important as they bring us closer to
a better understanding of the natural world (Made
Simple, Inc., n.d.).
39. MAKING PREDICTIONS
If the hypothesis is true, the result would be the
high SO2 concentrations do reduce reproduction of
soybeans.
42. TABLES
Tabulation
A compact and orderly manner of presenting
information
Can readily point out trends, comparisons or
interrelationships
43. TABLES
Guiding principles in table construction:
Simplicity clean and uncluttered
Directness only necessary information
Clarity jive with textual discussion
44. TABLES
Essential parts of a table:
Table number
Title
Column headings
Row headings or stubs
Body with data
Footnotes (if applicable)
Sources of data (if applicable)
46. GRAPHS OR FIGURES
1. Bar graph
qualitative or
quantitative discrete
for comparisons of absolute or relative
counts, rates or proportions between
categories of a qualitative or
a quantitative discrete variable
47. GRAPHS OR FIGURES
2. Pie chart
qualitative
shows the breakdown of a group or total
where the number of categories is
not too many
48. GRAPHS OR FIGURES
3. Component bar diagram
qualitative
same as pie chart except that it can
be used to compare the breakdown
of categories of more than one group
49. GRAPHS OR FIGURES
4. Histogram
quantitative continuous
graphic representation of the
frequency distribution of
a continuous variable
or measurement including
age groups
50. GRAPHS OR FIGURES
5. Frequency polygon
quantitative
same function as histogram
51. GRAPHS OR FIGURES
6. Line diagram
time series
shows trend data or changes with
time or age (x-axis) with respect
to some other variable
52. GRAPHS OR FIGURES
7. Scatterpoint/scatterplot
quantitative
shows correlations between two
quantitative variables
(whether directly or inversely related)
53. GRAPHS OR FIGURES
In making the graph, remember the following:
a. Use graph paper and ruler to plot the values
accurately
54. GRAPHS OR FIGURES
In making the graph, remember the following:
b. The independent variable is graphed on the x axis
and the dependent variable on the y axis
55. GRAPHS OR FIGURES
In making the graph, remember the following:
c. The numerical range for each axis should be
appropriate for the data being plotted
56. GRAPHS OR FIGURES
In making the graph, remember the following:
d. Label the axes to indicate the variable and the
units of measurement.
57. GRAPHS OR FIGURES
In making the graph, remember the following:
e. Choose the type of graph that best represents your
data.
58. QUESTIONS
1. Given the following data from the soybean
experiment, how do you arrange the following
data (in the manual) from the experiment in a
table?
2. What kind of graph are you going to construct?
59. TABLE 1. SOYBEAN REPRODUCTION EXPERIMENT
Plant No. Control Plant Treatment with SO2
No. of seeds Ave. weight of No. of seeds Ave. weight of
per pod seed (g) per pod seed (g)
1 5 0.42 2 0.21
2 6 0.37 4 0.33
3 4 0.41 4 0.23
4 5 0.36 3 0.35
5 5 0.48 3 0.25
6 6 0.33 3 0.34
7 7 0.44 1 0.21
8 6 0.23 4 0.32
9 5 0.51 5 0.21
10 7 0.47 3 0.38
11 4 0.46 4 0.27
60. TABLE 1. SOYBEAN REPRODUCTION EXPERIMENT
Plant No. Control Plant Treatment with SO2
No. of seeds Ave. weight of No. of seeds Ave. weight of
per pod seed (g) per pod seed (g)
12 5 0.37 3 0.35
13 7 0.53 4 0.22
14 6 0.42 4 0.34
15 5 0.51 4 0.23
16 6 0.39 5 0.35
17 5 0.48 5 0.12
18 5 0.47 5 0.34
19 7 0.52 5 0.22
20 7 0.50 6 0.30
21 6 0.28 2 0.20
22 6 0.39 2 0.30
23 7 0.21 4 0.21
24 7 0.41 3 0.13
61. TABLE 2. NUMBER OF SEEDS PER POD
No. of Plants
No. of seeds per pod Control Treatment
1 - 1
2 - 3
3 - 6
4 2 8
5 8 5
6 7 1
7 7 -
62. TABLE 3. AVERAGE WEIGHT OF SEEDS IN DIFFERENT RANGES OF
WEIGHTS
No. of Plants
Weight (g) Control Treatment
0.10 - 0.14 - 2
0.15 – 0.19 - 0
0.20 – 0.24 2 9
0.25 – 0.29 1 2
0.30 – 0.34 1 7
0.35 – 0.39 5 4
0.40 – 0.44 5 -
0.45 – 0.49 5 -
0.50 – 0.54 5 -
63. 7
6
Ave. seeds per pod 5
4
3
2
1
0
Control Treatment with SO2
Treatment
Figure 1. Comparison on the average number of seeds per
pod between plants under control and treatment with SO2
64. 0.45
0.4
Ave. weight of seed (in grams)
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Control Treatment with SO2
Treatment
Figure 2. Comparison on the average weight of seed between
plants in the control and treatment with SO2
66. DISCUSSING AND COMMUNICATING RESULTS
Provide interpretation to the results.
State the interpretation’s implications in light of the
hypothesis and its supporting literature.
67. DISCUSSING AND COMMUNICATING RESULTS
Investigators study the given tables and graphs and
determines if the hypothesis is supported or
falsified.
68. DISCUSSING AND COMMUNICATING RESULTS
IF FALSIFIED: Investigators must suggest other
possible alternate hypotheses.
IF SUPPORTED: Investigators must suggest other
experiments and studies that will strengthen the
current hypothesis.
69. DISCUSSING AND COMMUNICATING RESULTS
The results must be communicated to other
scientists.
May be in the form of a laboratory class
presentation or during scientific gatherings.
70. DISCUSSING AND COMMUNICATING RESULTS
Most important: The study is to be presented in the
form of a scientific paper or a journal after
subjecting it to review by different scientists in the
same field of study.
71. DISCUSSING AND COMMUNICATING RESULTS
E1. Using your graphs and tables, analyze your
results and discuss your conclusions with your
group.
-> 1. According to the graph of the number of seeds
per pod, there is higher number of results in the
controlled set-up, while the number of seeds with
SO2 treatment has lower yield. As to the weight of
the seeds, higher values were gathered in the
control as well as lower values were gathered in the
set-up with SO2 treatment. It is therefore concluded
that SO2 decreased the productivity and
development of the seed.
72. DISCUSSING AND COMMUNICATING RESULTS
E2. Critique your experiment. What weaknesses do
you see in the experiment? Suggest improvements.
-> 2. The number of replicates is somehow too
much, but still it gave a meaningful result. The
results somewhat gave overlapping information and
lacks some data. The range of the measurements
is somehow inconsistent.
73. DISCUSSING AND COMMUNICATING RESULTS
E3. Write a summary statement for your
experiment. Use your results to support or falsify
your hypothesis.
-> When the plants were treated with SO2, the
number of seeds per pod decreased as well as the
average weights of the plants. These results
supported the hypothesis which states that SO2 in
high concentrations would reduce reproduction in
soybeans.
74. DISCUSSING AND COMMUNICATING RESULTS
E4. Suggest additional and modified hypotheses
that might be tested.
-> High concentrations of SO2 sometimes do not
decrease the reproduction in soybeans; high
concentrations of SO2 decrease usually the
reproduction in soybeans.
76. CONCLUSION
The essential feature of science that makes it difficult from
other ways of understanding the natural world is the
scientific method.
The scientific method provides a step by step process of
finding explanations behind the different phenomena
observed in the natural world.
It begins by asking a question that is well defined and
testable.
Also, its elements are measurable and controllable.
77. CONCLUSION
After forming a scientific question, one can develop a
hypothesis which is a possible explanation to answer the
scientific question.
For a hypothesis to be scientifically useful, it must be
testable and falsifiable.
In order to test the hypothesis, a scientific experiment must
be designed.
Its components are determining variables, designing
procedure and making predictions.
78. CONCLUSION
Results from the experiment must be summarized
and presented in tables or figures.
Also, these must be interpreted, discussed and
communicated to other scientists.
Hence, this step by step procedure makes certain
that the knowledge obtained cannot be fabricated
because a lot of processes must be undertaken
before conclusion can be done.
Notes de l'éditeur
Thus, as much as possible, you should only have one independent variable in your experiment. Additional independent variables will require more complicated procedures and data analysis, however, if one is willing to put more effort in getting conclusive results, are not prohibited. In fact, any of the controlled variables have the potential to be independent variables. Multiple independent variables, could also give data on combination effects of these variables. For example, while magnitude and length of exposure both might have separate effects on the yield of the soybean plants, they could also produce different results when their treatments are applied together. However, as stated, analysis of effects becomes complicated, requiring greater effort in part of the performers of the experiment (Palmer, M., n.d.). Some of the variables of the sample experiment on soybeans and SO2 have already been stated earlier.
1. duration of exposure; selected age of soybeans; kind of gas exposed 2. the number of seeds per pod; the weight of the pods (both after exposure to gases) 3. The different gases exposed to the set-ups. It is important to have only one independent variable in order to have consistency when testing for only one possible predicted result. 4. duration of gas exposure; age of the soybeans 5. duration of gas exposure; same age of all soybeans; same kind of fumigation chamber
Proper designing of procedures is crucial to the credibility of your workas other scientists should be able to perform your experiment and obtain your results consistently for your conclusions to be considered a worthy contribution to the body of knowledge that is science.
Count the number of seeds and total weight of podsCount the number of seeds and total weight of podsRepeat with 3 other groupsRepeat with 3 other groupsPlace one group in filtered air chamber for 4 hoursPlace one group in SO2 chamber for 4 hoursDivide into 4 groups of 6Divide into 4 groups of 6Divide into 2 groups of 24Select 48 soybeans with approx. same age