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One, Two, Three....TMV

Susan Plati



Type of Entry:

  • project

Type of Activity:

  • hands-on activity
  • inquiry lab
  • authentic assessment
  • group/cooperative learning

Target Audience:

  • Biology

Notes to Teacher:

This particular project is inexpensive, safe, fosters student inquiry, and gives good results that students can discuss in their final assessment--a poster session that models a "Science Congress" The project lends itself to cooperative group work. Groups design their own experiments to determine how the mode of application of the virus extract affects the various plants that students have grown from seed. All cigarettes reportedly have TMV in their tobacco...and this, too, could be a question for testing--i.e....Do different brands of cigarettes contain different amounts of TMV? Because TMV is a plant virus, there is no worry about students getting infected. However, it probably would be a good idea to do this experiment away from any other classroom plants that you have. Plants that have been successfully used include, tomatoes, sunflowers, beans, peas, marigolds, geraniums (done from cuttings). Infection can be either systemic (i.e.. spreads through entire plant through the vascular system) or localized (only affects the portion of the plant that has been inoculated).

Use accepted safety guidelines while working, and disposing of, any potentially, infectious or hazardous materials.

Required of students:

Background reading about viruses, infection, disease, plant growth and development, plant physiology. Actually this project can be used as a vehicle to teach each of the above content areas. In fact, this is the way that I use it. Students keep a notebook of their experimental protocol, data, further questions, and library research.

Preparation time needed one class period to assemble materials and mix up buffer

Class time needed:

About 5 periods in all:

  • one class period for planting seeds and discussing experimental design

  • one class period for group design of protocols and inoculation of the plants with the virus (This occurs about 3-4 weeks after seeds have grown)

  • portions of several class periods during the two weeks following the inoculation to record data and have groups discuss significance of data

  • one class period for groups to plan their poster and presentation for the Science Congress

  • class period for the Science Congress


Abstract

This is a six-eight week research project in which student teams investigate the nature of infection of various plants by Tobacco Mosaic Virus. Each group works with a different species of plant and all groups infect their plants with TMV that they have isolated from cigarettes. The actual experiment varies from team to team because each group formulates the specific question that it wishes to answer and then designs its own protocol for the experiment that will help them answer this question. Teacher guidance helps to ascertain that only one variable is being tested, that appropriate controls are included, and that the sample size is large enough for meaningful results. Students decide what data will be required, how to record these data, and how the final data will be analyzed. Upon completion of the experiments, the students participate in a poster session--"The Science Congress of Plant Pathologists", an exhibition that occurs during class. Other students and faculty are invited to view the posters. Results of the experiments are shared and discussed with classmates and visitors.

In order for the students to design an effective experiment that will yield information about the mode of action of Tobacco Mosaic Virus, they must do library (or internet) research about plant physiology and virology. In this way they learn much about plant structure and function and gain this knowledge by reading and through discussion with each other (prodded by teacher guide questions), rather than by listening to teacher dominated lectures. Because they grow their experimental plants from seed, they also learn about plant growth and development. The final poster session gives each group an opportunity to describe its experiment, defend its hypothesis, and look for patterns in the results of all the teams as they compare and contrast the various TMV infections.

This activity is one that I designed last year for my Medicine and Society class following a discussion with colleagues at Education Development Center in Newton, MA, where I served (part time) as a consultant on the Insights in Biology Project. I was especially interested in having the students use a model of a disease to learn more about the way in which disease develops and spreads. I wanted to use an organism that would be safe and easily obtainable. Thus the Tobacco Mosaic Virus Long Term Project was developed, successfully completed, and has been repeated this year in both the Medicine and Society course and the first year biology course that I teach.


Background

What question does this activity help students to answer? How does Tobacco Mosaic Virus isolated from commercially purchased cigarettes infect a variety of common garden plants?


Project

Materials needed (for each lab group)

  • tobacco (two pinches from one cigarette) Specify the brand of cigarette that you use for this part of the experiment mortar and pestle

  • 10 ml 0.1 M dibasic potassium phosphate buffer

  • 2 test tubes or small beakers

  • cotton swabs

  • 10 paper cups for planting seeds

  • emery board

  • potting soil

  • 30-40 seeds of one species

Activity One, Two ,Three...TMV

A long term research project that uses a plant disease to model infection, teach plant physiology, and develop an understanding of experimental techniques.

Introduction:

In this long term experiment you will work in a team to investigate the nature of infection of various plants by Tobacco Mosaic Virus. We will be using this plant disease as a model to learn more about the way in which disease develops and spreads. We are using an organism that is safe to humans and easily obtainable. Each student group will work with a different species of plant and all groups will infect their plants with TMV that they have isolated from cigarettes. The actual experiment that you do will vary from team to team because each group formulates the specific question that it wishes to answer and then designs its own protocol for the experiment that will help you to answer this question. It is important that you design an experiment in which only one variable is being tested, that appropriate controls are included, and that the sample size is large enough for meaningful results. You also will ultimately decide what data will be required, how to record these data, and how the final data will be analyzed. Upon completion of the experiments, you will participate in a poster session-- "The Science Congress of Plant Pathologists". This is an exhibition that occurs during class to which other students and faculty are invited to view your posters in which the results of your experiments are shared and discussed with classmates and visitors.

First Lab Session: Choosing and planting your seeds

Before the project can be undertaken, you must grow your experimental organisms. Each group will be given seeds from a different plant. You will plant your seeds in paper cups of potting soil. Each cup should be filled almost to the top with potting soil. three seeds should be planted in each cup and the soil watered to good planting consistency (you don't want mud!). Rule of thumb is to plant seeds twice as deep as the longest seed dimension. Gently press the soil down on top of each group of seeds. Each group should plant at least 10 cups of 3 seeds each. After the seeds have grown, you will thin the seedlings leaving one seedling per cup. Planting 10 cups will give you an experimental sample size of 10 plants. You may wish to have a larger group of plants on which to experiment. This will be a group decision. When all seeds are planted place the cups in clear plastic bags--2-3 cups per bag. This will provide "greenhouse" conditions, keeping the soil damp, and the temperature warmer, thus helping your seeds to germinate more quickly. Place the completed watered pots of seeds in clear plastic bags under the lights in the classroom.

Observations: You should monitor the growth of your seeds even before your actual experiment begins. Thus, set up a chart in which you record such information as date of planting, date of first sprouting, numbers of seeds sprouted, diagrams of early plant growth, date of cotyledon appearance, date of first true leaves appearance, and any other information that might be significant.

Preliminary Research: Find out as much as you can about the particular plant that you are growing. Is it a monocot or a dicot? Does it need much or little water. What is its maximum size. Is it considered, "disease resistant". You may wish to read about plant growth and development in your textbook. (Ultimately such reading will be assigned anyway, so this will give you a head start)

Second Lab Session: Designing your experiment and inoculating your plants

Procedure:

  1. Design a procedure that will help you answer the question, How are Plants Infected with

    1. Tobacco Mosaic Virus?

      To do this you will have to consider the following questions:

      • How and where you will inoculate the plants in your experimental group?

      • How will you set up your control group?

      • How many plants will be in each group?

      • How do you think the virus will enter the plant?

      • Can the virus move from one part of the plant to another?

      • What are the needs of the plants to assure that they will have good conditions for growth?

      • How can you prevent contamination of your controls by your experimental plants?
      Some parts of the protocol are briefly outlined in steps 3-7 below.

  2. Write the protocol for your experiment in your lab book. Do this by setting up your procedure in numbered steps. You may use diagrams if it will help you.

  3. Prepare the solution for inoculation of your plants as follows:

    1. Place 2 pinches of tobacco from a cigarette into the mortar. Add 5 ml of buffer and grind the mixture with the pestle until it is a fine slurry. Place the slurry in a test tube or small stoppered or covered vial until it is ready for use. Label with pertinent information including the names of the people in your group.

    2. Prepare your control solution and place it in an appropriate labeled covered container.

  4. Using the emery board, gently abrade (scrape) the surface of some of the leaves or all of your plants (experimentals and controls). Be careful: DO NOT SCRAPE THE LEAF TOO HARD OR YOU WILL DESTROY THE PLANT. Note the position of the leaves on each plant and where they have been abraded by making a sketch in your lab book and labeling appropriately.

  5. Using a cotton swab, treat the abraded leaves of your control plants with the control solution. Set these plants in the designated area for your controls. Make sure you indicate on your sketch where the solution has been applied.

  6. Using another cotton swab, apply the tobacco slurry to the abraded leaves of the experimental plant, indicating the placement of the slurry in the diagram. Set these plants in the designated area for your experimental plants.

  7. Place the plants in a well lit area for a week to 10 days. Observe your plants and record your observations every day. Make notes daily on the condition of all the leaves. Set up a chart to record your data to describe the condition of leaves quantitatively. Develop a scale by which to compare the leaves, or make drawings of your observations. Analyze what happens to each leaf you infected and what happens to the entire plant.

CAUTION; IF YOU HANDLE PLANT LEAVES BE SURE TO WASH YOUR HANDS BETWEEN TOUCHING DIFFERENT PLANTS.


Method of Assessment/Evaluation

(Poster Session--student directions follow)

The Science Congress Poster Session of Virologists investigating Tobacco Mosaic Infections of Plants

Scientists periodically come together in meetings to share some of the questions and answers that are the result of research they are undertaking. The Science Congress Poster Session will give you an opportunity to share with your classmates the questions that your project has answered and the new questions that have been raised. It will also give you a chance to really think about your project and to apply the knowledge that you gain from talking with your classmates about your project.

  1. The poster that your group designs will present information about your experiment and the results that you obtained. You will have one class session to design your poster. The poster must contain the following information:

    1. Project title

    2. Names of members of your research group

    3. Questions that you hoped to be able to answer (These are questions that you should have written in your lab book at the beginning of your study)

    4. Clearly summarized procedure

    5. Data clearly presented including graphs where appropriate. Data must include at least one diagram and is more likely to include a series of diagrams depicting changes that you observed.

    6. Summary of your conclusions (Which of the questions listed in c were you able to answer?)

    7. Most significant information that you want to share with other groups

    8. nanswered questions, new questions, and suggestions for further study (at least three)

  2. Since all of this information must fit on the poster board you are given, your group needs to plan its presentation carefully. You may choose to write some of the information outside of class and attach it to the poster, or write directly onto the poster. Any graphs that you make should be done on graph paper (or on the computer) and be attached to the poster. It is critical that all information is legible and well organized.

Presentation of your Poster at the Science Congress Poster Session

  1. During the poster session, you and the other members of your group will take time standing by your poster and answering questions you may get from the other groups and visitors to the class. Half of your group members should remain by the poster while the other half visits each of the other groups. Your poster must never be left unattended.

  2. Half way through the session you should switch roles with your group members in order to enable each person to visit all of the other groups. As you visit each of the other groups you should ask questions that will help you to learn about the other projects, and apply some of what the other groups have learned to your own project. For example, perhaps another group asked questions of their data that differed from yours. And perhaps if you asked these questions of your data, you might gain a new perspective from which to analyze the information that your project yielded.

  3. You will also have the opportunity to evaluate each of the other projects conducted by the other groups and, in turn, your group will be evaluated when other groups visit your poster. Therefore, it is important that every person in your group understand the study that you performed, be able to explain the results clearly, and know background information on all parts of your project in case questions come up about materials used, diagrams that you've included, graphs of results, questions answered and further questions asked. A copy of the form that will be used for project evaluation is found at the end of these directions.

  4. When all members of your research team have visited all the other teams in the class share your information with the other members of your group.

Analysis

Your group will participate in the Science Congress concluding session that will be led by your teacher. In this discussion you will have an opportunity to add to the information that you presented on your poster as the class comes to some general conclusions about Tobacco Mosaic Virus infections of plants and suggests a list of questions that warrant further study.

Poster Session Evaluation

Tobacco Mosaic Virus Experiment

Scientific team (group members)
________________________________

Title of Experiment____________________________________________

Rate the following statements with 1 being the lowest and 5 being the highest.

1. The poster was clearly written and easy to understand.

1     2     3     4     5

2. The scientist was able to explain my questions in a clear manner.

1     2     3     4     5

3. The scientist demonstrated significant knowledge of the particular organism studied and the way in which the group undertook the study.

1     2     3     4     5

4. The study performed showed good scientific method and technique (careful procedure, accurate data collection, appropriate graphs, logical conclusions)

1     2     3     4     5

5. The suggestions for further research make sense in light of the results obtained by this group.

1     2     3     4     5

6. Any other comments not covered by the above statements?

  
  
  


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