Scientific investigation in plants

1. SCIENTIFIC INVESTIGATIONS IN
PLANTS
‘Kuya Placido’ m/
Patrick Go
Guia Rañola
Jordan Santos
Jane Christine Tancio

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?

6. DEVELOPING HYPOTHESES
Hypothesis
 A tentative answer to some question
 An explanation on trial
 An educated guess
 (Campbell, 2004)

7. HYPOTHESIS
 Testable
 Falsifiable

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.

18. DESIGNING EXPERIMENTS TO TEST HYPOTHESIS

19. A. DETERMINING THE VARIABLES

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

26. DEPENDENT VARIABLES
 The number of seeds per pod
 The 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

29. B. CHOOSING OR DESIGNING THE PROCEDURE

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.

35. C. MAKING PREDICTIONS

36. MAKING PREDICTIONS
 Predictions on the phenomenon is formed in question

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.

40. PRESENTING AND ANALYZING
RESULTS

41.  Tables
 Graphs or Figures

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)

45. GRAPHS OR FIGURES
 Provide visual summary of the results

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

65. DISCUSSING AND COMMUNICATING
RESULTS

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.

75. CONCLUSION

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.