What Happens:

      In this exercise, students will investigate the effects of ecological factors on the growth of rapid-cycling brassica (Brassica rapa L.: RCB's; Wisconsin fast plants) seedlings in the field. Wisconsin Fast Plants belong to the Mustard family (Brassicaceae) and have been genetically bred to complete their life cycle in approximately 1 month. The students are asked to formulate a hypothesis and design an appropriate experiment to test their hypothesis. Possible variables that could be measured include growth (height, number of leaves, leaf area) or reproduction (number of flowers) with respect to treatments such as light, wind, herbivory, chemical or organic fertilizer, insecticides, or growth regulators (i.e., gibberellic acid spray, auxin paste). We also supply dwarf RCB's that lack genes for gibberellic acid production. These plants offer an additional test plant for the students to use.

      Students spend two, 2-hour lab sessions on this project following a 20-30 minute introduction to the topic. During the introductory session (normally at the end of the preceding lab), the experiment is discussed and the students are encouraged to consider factors that affect seeding growth. Students should work in pairs and each group should formulate a hypothesis before the first field trip (lab 1). During the first field trip, the students should make observations about their study site, then design and implement their experiment (i.e., collect "before" data). During the second field trip, the students will collect response "after" data, which will be analyzed and used to write a scientific paper.

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Lab Objectives:

     At the conclusion of this lab, students will be able to...

1. ask scientific questions, develop hypotheses, employ and understand the scientific method,


2. use critical thinking skills,


3. develop their writing skills to present a written report,


4. use their collaborative skills to work together on a group project,


5. appreciate the value of native ecosystems for ecological research,


6. appreciate difficulties in designing a good, controlled experiment in a natural setting.

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Equipment/ Logistics Required:

* access to a suitable field site (local)
* 7 day old dwarf and wild type Brassica seedlings (12 per pair of students)
* guards (wind, insect, and herbivory)
* meters (soil, air, and light)
* measuring equipment (vegetation pins, metric rulers, graduated cylinders, rain gage)
* gibberellic acid (10 ppm) in a spray bottle
* auxin paste, control paste, and sterile swabs for application
* Miracle Gro fertilizer (½ , normal, double, and triple recommended concentrations)
* pH buffers in plastic dropping bottles (pH of 2, 5, 7, 10, and 12)
* salt water in plastic dropping bottles (5%, 10%, and 15% concentrations)
* sugar water in plastic dropping bottles (5%, 10%, and 15% concentrations)

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Summary of What is Due:

     From this lab, students should submit the following:

1. Hypothesis and experimental design before performing experiment,


2. Individually written, original scientific paper based on data collected by the pair of students, due the week following final data collection. Maximum length is 7 pages and the minimum length is 5 pages (not including tables and figures). Each paper must include at least 1 table and 1 figure,


3. Five minute in-class presentation to be given the week following data collection.

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Keyword Descriptors:

Principal Ecological Question Addressed:     How do biotic and abiotic factors affect the growth of seedling plants?

Ecological Topic Keywords:     plant ecology, Brassica, abiotic factors, biotic factors, seedling growth.

Science Methodological Skills Developed:     experimental design, scientific writing, hypothesis testing, implementation of the scientific method, identify biotic and abiotic interactions affecting seedling growth.

Pedagogical Methods Used:     cognitive skills, hands-on experience, problem-based learning