experiment 1 scientific investigations in plants

SCIENTIFIC INVESTIGATIONS IN PLANTS‘Kuya Placido’ \m/

Patrick Go

Guia Rañola

Jordan Santos

Jane Christine Tancio

INTRODUCTION

Plant Physiology study of how plant life exists requires observation, asking questions and

proposing explanationsScientific Investigations -way of testing explanation about plant

phenomena - similar to scientific methodPlant Physiologists - ask questions, make observations, develop

explanatory hypotheses and test those hypotheses

ASKING QUESTIONS

Why ask? Requires well-defined and measurable

phenomenon Elements must be measurable and

controllable

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?

ASKING QUESTIONS

Do plants have feelings too? Will I get a grade of 1.00 in Plant Physiology? Are all plants photosynthetic?

DEVELOPING HYPOTHESES

Hypothesis A tentative answer to some question An explanation on trial An educated guess (Campbell, 2004)

HYPOTHESIS

Testable Falsifiable

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

DESIGNING EXPERIMENTS TO TEST HYPOTHESIS

A. DETERMINING THE VARIABLES

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.

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

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

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 for each plant.

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.

VARIABLES

Duration of exposure Selected age of soybeans Kind of gas exposed Number of seeds per pod Weight of the pods

DEPENDENT VARIABLES

The number of seeds per pod

The weight of the pods

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

CONTROLLED VARIABLE

Duration of gas exposure

Same age of all soybeans

Same kind of fumigation chamber

B. CHOOSING OR DESIGNING THE PROCEDURE

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.

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)

METHODOLOGY

Enumerate the step by step activities of the experiment in soybean production.

Select 48 soybeans with approx. same age

Divide into 2 groups of 24

Divide into 4 groups of 6

Place one group in SO2 chamber for 4 hoursRepeat with 3 other

groupsCount the number of seeds and total weight

of pods

Divide into 4 groups of 6

Place one group in filtered air chamber for 4 hours

Repeat with 3 other groupsCount the

number of seeds and total weight

of pods

There are two main components of the procedure:

two manipulated variables (SO2 and natural air) and each component having 4 replicates.

C. MAKING PREDICTIONS

MAKING PREDICTIONS

Predictions on the phenomenon is formed in question

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.

Thus predictions are important as they bring us closer to a better understanding of the natural world (Made Simple, Inc., n.d.).

MAKING PREDICTIONS

If the hypothesis is true, the result would be the high SO2 concentrations do reduce reproduction of soybeans.

PRESENTING AND ANALYZING RESULTS

Tables

Graphs or Figures

TABLES

Tabulation

A compact and orderly manner of presenting information

Can readily point out trends, comparisons or interrelationships

TABLES

Guiding principles in table construction: Simplicity clean and uncluttered Directness only necessary

information Clarity jive with textual discussion

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)

GRAPHS OR FIGURES

Provide visual summary of the results

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

GRAPHS OR FIGURES

2. Pie chart qualitative shows the breakdown of a group or total

where the number of categories is

not too many

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

GRAPHS OR FIGURES

4. Histogram quantitative continuous graphic representation of the

frequency distribution of

a continuous variable

or measurement including

age groups

GRAPHS OR FIGURES

5. Frequency polygon quantitative same function as histogram

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

GRAPHS OR FIGURES

7. Scatterpoint/scatterplot quantitative shows correlations between two

quantitative variables

(whether directly or inversely related)

GRAPHS OR FIGURES

In making the graph, remember the following:

a. Use graph paper and ruler to plot the values accurately

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

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

GRAPHS OR FIGURES

In making the graph, remember the following:

d. Label the axes to indicate the variable and the units of measurement.

GRAPHS OR FIGURES

In making the graph, remember the following:

e. Choose the type of graph that best represents your data.

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?

TABLE 1. SOYBEAN REPRODUCTION EXPERIMENTPlant No. Control Plant Treatment with SO2

No. of seeds per pod

Ave. weight of seed (g)

No. of seeds per pod

Ave. weight of 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

TABLE 1. SOYBEAN REPRODUCTION EXPERIMENTPlant No. Control Plant Treatment with SO2

No. of seeds per pod

Ave. weight of seed (g)

No. of seeds per pod

Ave. weight of seed (g)

12 5 0.37 3 0.3513 7 0.53 4 0.2214 6 0.42 4 0.3415 5 0.51 4 0.2316 6 0.39 5 0.3517 5 0.48 5 0.1218 5 0.47 5 0.3419 7 0.52 5 0.2220 7 0.50 6 0.3021 6 0.28 2 0.2022 6 0.39 2 0.3023 7 0.21 4 0.2124 7 0.41 3 0.13

TABLE 2. NUMBER OF SEEDS PER PODNo. 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 -

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 -

Figure 1. Comparison on the average number of seeds per pod between plants under control and treatment with SO2

Control Treatment with SO20

1

2

3

4

5

6

7

Treatment

Ave

. se

ed

s p

er

pod

Control Treatment with SO20

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Treatment

Ave

. w

eig

ht

of

se

ed

(in

gra

ms)

Figure 2. Comparison on the average weight of seed between plants in the control and treatment with SO2

DISCUSSING AND COMMUNICATING RESULTS

DISCUSSING AND COMMUNICATING RESULTS

Provide interpretation to the results. State the interpretation’s implications in light

of the hypothesis and its supporting literature.

DISCUSSING AND COMMUNICATING RESULTS

Investigators study the given tables and graphs and determines if the hypothesis is supported or falsified.

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.

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.

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.

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.

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.

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.

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.

CONCLUSION

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.

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.

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.