3 Chestnut blight

By Shelley Casey

Provided by Kenan Fellows Program.

In this lesson, students learn about fungi and Cryphonectria parasitica, the fungus that infects the American chestnut tree. Students will grow common fungi found from spores in the air and show how fungus can affect the function of a tree.

Learning outcomes

Students will be able to describe where fungi can be found and what conditions are optimal for their growth. They will also be able to define the term vascular tissue and tell how the blockage of vascular tissue affects a plant.

Teacher planning

Time required

1 hour with 10 additional minutes for observation on 3 subsequent days

Materials needed

Each pair of students will need:

• biology textbook
• 1 petri dish filled with nutrient agar
• clear tape or Parafilm for closing petri dishes
• 3 50 ml beakers
• red food coloring
• 3 stalks of celery with leaves
• 1 marking utensil
• 1 ruler
• 1 magnifying lens
• 1 scalpel or pair of scissors

Technology resources

If you want students to read the article about the Chestnut blight online, you’ll need computers with internet connectivity.

Student handouts

Pre-activities

Prepare a copy of the lab sheet to give to each student. If you want to print out the article instead of having students read it online, you should do this as well. Gather items listed in the Materials Needed section. If you are not using prepared agar plates, melt nutrient agar and pour into plates. Make sure to replace lids immediately to keep plates sterile. Store the plates upside down until ready to use. Also keep celery refrigerated until ready to use.

Activities

1. Distribute the lab sheet to students.
2. Have students read the Chestnut blight article from forestpathology.org. Then have students use their textbooks to look up information about the general characteristics of fungi. The article and book information are to be used by students to answer questions and define words located under Step 2. This step may be given as a homework assignment to be completed the day prior to the lab.
3. Verbally check with students to be sure that they understand general information about fungi. At a minimum, they should understand:
   • Fungi prefer cool, moist, dark environments.
   • Spores of a fungus are reproductive structures.
   • Mycelium are the “body” of fungi and where extra-cellular digestion and absorption occur.
   • If a fungus lives off of another organism and causes damage, it is considered to be a pathogen.

   Also, make sure that students understand that vascular bundles are the “circulatory system” of plants. Water and minerals are transported through vascular bundles.

4. Group students into pairs and have them gather petri dishes, marking utensils, celery, beakers, tape, ruler, scalpel or scissors, and food coloring. They should begin Step 3 on the lab sheet:
   1. Students will place their initials on the bottom of the petri dish.
   2. Students will remove the lid from the petri dish so that the growth medium is exposed to the air for two minutes. At the end of two minutes, they should replace the lid and tape the sides closed. They should not open the dish on the remaining days. Over the next four days, they will draw what the petri dish looks like on their lab sheets. On the final day of observation, they will observe the dish under a magnifying glass and record their findings.
5. Step 4 can be set up while the petri dishes sit exposed to the open air for two minutes. Students should conduct Step 4 from the lab sheet:
   1. Students will use three 50 mL beakers and place their initials on the outside of each beaker. They should also label the beakers C for control, 1N for one notch, and 3N for three notches.
   2. Next, students will fill each beaker with 40 mL of water and place one drop of red food coloring in each beaker.
   3. Students then will make a fresh cut across the bottom of each celery stalk approximately 1 cm from the end. They will measure the length of each piece of celery in cm and record the information in the chart provided on the lab sheet.
   4. Students should place one stalk in the beaker labeled “C.”
   5. Students will cut a V-shaped notch in the second stalk of celery. Make sure it is at a height that will be above the water line in the beaker. The notch represents the area of the stalk that is damaged by the fungus. They will place this stalk in the beaker labeled “1N.”
   6. Finally, students will cut three V-shaped notches in the last piece of celery at various heights. Again, be sure that the notches are at heights that will be above the water line. They should place this stalk in the beaker labeled “3N.”
   7. Students will record observations in the chart provided on the lab sheets for four days. Each day, they will measure how far the water has moved up the stalk. They will also note if the water seems to be evenly distributed in the stalk.
6. Students will check the progress of the fungus growth in the petri dishes and the movement of water in the celery for three more days. They will need about ten minutes of class time for each for observation and data recording. On the final day, schedule an additional ten minutes for students to write the summary under Step 4 or let students complete the summary for homework.

Assessment

1. Check Step 2 for correct responses to definitions and questions.
2. Step 3 is only to be checked for completion of drawings for each day. If a group does not have fungal growth on their plate, it is acceptable for them to view another group’s fungus. Day 4 should be the most detailed drawing.
3. Step 4 contains a chart that should be assessed. The control should show even movement of water to the entire stalk. The stalk with one notch should show movement to all areas except the area above the notch. The leaf above this area may be slightly withered. The stalk with three notches will have movement of water up to the notches and almost none above this. The leaf of this stalk will be significantly withered.
4. Finally read the summary paragraph for this step to make sure that students understand that significant damage to the vascular tissue of the plant will significantly impair, or even kill, the plant.

Modifications

• Students with learning disabilities or limited English proficiency should be paired with another student to complete Steps 1 and 2. Be available to answer vocabulary-related questions for these students. These groups may need additional time to complete the assignment.
• Students with learning disabilities or limited English proficiency may be allowed to complete the definitions and questions on the computer to help with vocabulary, spelling, and grammar. They may require additional time for completion of this portion.

Critical vocabulary

ascomycete

any of a group of higher fungi (such as yeasts or molds) with septate hyphae and spores formed in asci

ascospore

any of the spores formed by ascomycetes

blight

an organism (such as a fungus) that causes disease

cambium

a thin layer between the xylem and phloem of most vascular plants that gives rise to new cells and is responsible for secondary growth

canker

an area of dying material in a plant

conidia

an asexual spore produced in certain fungi

fungus

any of saprophytic and parasitic spore-producing eukaryotic typically filamentous organisms that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts

mycelium

the mass of interwoven filamentous hyphae that forms especially the vegetative portion of a fungus and is often submerged in another body (such as organic matter or the tissues of a host)

spore

a primitive, usually unicellular, and often environmentally resistant dormant or reproductive body produced by fungi

parasite

an organism who is dependent on something else for existence or support without making a useful or adequate return

pathogen

a specific causative agent of disease

vascular bundle (tissue)

a strand of specialized cells of higher plants consisting mostly of xylem and phloem

• Next: How do we help the American chestnut tree?

References

• Bird, Don et al. A Tree on the Rebound. The American Chestnut Foundation. New York: 1996.

Contents: Restoring the American chestnut

• Next: How do we help the American chestnut tree?
• Previous: Bananas: A modern example of fungus destruction

Learn more

• Charlie Chestnut This interactive website for kids includes a variety of games and activities that educate about the American chestnut tree. Teachers will also find a curriculum manual and lesson plans suggestions about science and the chestnut tree.
• forestpathology.org Forest pathology is the study of tree diseases. This website covers major diseases of trees, their causes (etiology), factors that affect their spread (epidemiology), ecological and economic impacts, and management.

Related topics

• Search LEARN NC for more resources on American chestnut, biology, blight, fungus, and science.

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