Academic journal article The American Biology Teacher

Mysterious Mycorrhizae? A Field Trip & Classroom Experiment to Demystify the Symbioses Formed between Plants & Fungi

Academic journal article The American Biology Teacher

Mysterious Mycorrhizae? A Field Trip & Classroom Experiment to Demystify the Symbioses Formed between Plants & Fungi

Article excerpt

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Every day humans interact with fungi and their products in foods, medicines, and the environment. Yeasts are used to make bread and beer. Life saving antibiotics like penicillin and cephalosporins are fungal products, as are the enzymes added to detergents to boost their cleaning power. Fungi can cause problems when molds and mildews grow, in our buildings, foods, or cultivated plants. Athlete's toot fungi cause discomfort, while Valley Fever fungus (Coccidioides immitis) and histoplasmosis (Histoplasmosa capsulatum) can cause life-threatening diseases. Despite their many roles in our daily lives, fungi often seem obscure and mysterious and are largely unknown and ignored by the American public.

Biology curricula cover fungi in units on bacteria, protists, and primitive plants, but fungi are more closely related to animals than to bacteria or plants (Wainwright et al., 1993). Like animals, fungi are heterotrophs and cannot create their own food; but, like plants, fungi have cell walls, and are for the most part immobile. Most species of fungi have a filamentous body with indeterminate growth: individual fungi can grow indefinitely until they are enormous and ancient. Students are surprised to learn that the largest and oldest organisms on Earth are fungi, not whales and trees (Smith et al., 1992). Fungi are extremely diverse but much of this biodiversity has yet to be described, as only 5% of an estimated 1.5 million fungal species have names (Hawksworth, 2001). Teachers can help make the fungal kingdom less mysterious and obscure by conducting classroom activities involving fungi. We encourage teachers to read Flannery (2004) and visit some excellent Web sites (Table 1) to gain more background about fungi. Here we describe a series of field and laboratory activities to help teachers introduce students to the symbiotic fungi that are ubiquitous in most roots and soil. The primary objectives of these activities are as follows:

1. Gain an appreciation for the influence of invisible soil organisms on plant growth.

2. Learn about symbioses and their range of outcomes in nature.

3. Conduct an experiment, collect data over several weeks, analyze data, and learn about a method of scientific inquiry that fungal scientists commonly use.

* Learning Goals & Objectives

The purpose of this activity is to introduce students to fungus-root symbioses by comparing plants that are grown with or without mycorrhizal fungi and other soil inhabitants. Mycorrhizal fungi are associations between certain fungi and the roots of most plants. This exercise provides students with experience using the scientific method, spans several class periods requiring periodic monitoring, and takes advantage of the exciting visual connection that students make when watching plants develop over time. The topic, activities, and evaluation follow the stages of Engagement, Exploration, Explanation, Elaboration, and Evaluation of the 5E Learning Cycle Model developed by the BSCS (Bybee et al., 2006). The study of mycorrhizal symbioses fits well within current life science standards, and the classroom experiment promotes the general standards of inquiry-based science learning. Apart from the life science content, the study of mycorrhizae provides opportunities to integrate biological and mathematical problem-solving skills by applying basic mathematics within life science contexts, hone skills in scientific investigations, and develop communication skills to convey scientific concepts.

This activity involves a field trip to a local park to collect natural soil, and an experiment followed by an extended observation period. Each student or group should sow and monitor two plants, one with living soil and one with dead soil. The cumulative data collected by the entire class can be used to determine whether or not plants grow differently when inoculated with soil organisms including mycorrhiral fungi. …

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