BIOL 202 LAB 4: Seeds & Germination

Lab Overview:

Seed plants (also known as the Spermatophyta, or spermatophytes), are those plants that produce seeds. The living seed plants consist of the gymnosperms (or Gymnospermae—the naked seed plants) and the angiosperms (or Angiospermae—the fruiting or flowering plants). Gymnosperms include the familiar conifers (cone-bearing trees and shrubs) as well as the less familiar ginkgo, cycads, and gnetophytes (Ephedra, Gnetum, and Welwitschia). Angiosperms include most other plants, which are widely distributed, diverse, and represent many species. Extinct "seed ferns" (Pteridospermatophyta), i.e., plants resembling ferns but which produced seeds, also are known from the fossil record.

The purpose of this lab is to study various environmental factors that influence seed germination where our focus will be on common species, i.e., Phaseolus vulgaris (bean) andZea mays(maize or corn). Sample variables to be explored aretemperature, moisture level (saturated vs. damp), seed (or fruit) orientation (vertical vs. horizontal), and photoperiod (24-hour darkness vs. 24-hour light, which are artificial photoperiods). Natural photoperiod (natural sunlight) may be another variable to consider.

Students may take different approaches in this lab, and will be responsible for developing their own experimental hypotheses.

This lab may extend to two or three weeks in duration.

Materials—Seeds & Seed-like Fruits (for both Lummi & Swinomish):

  • Camas seeds (for camas stratification)
  • 'Carl's Glass Gems' (or simply, Glass Gem) corn kernels (caryopses)
  • Pinto bean seeds
  • Seeds (others to be determined)

Materials—Equipment & Supplies (for both Lummi & Swinomish):

  • Microscopes, dissecting
  • Microscopes, compound
  • Petri dishes
  • Paper towels(*circles for germination studies)
  • Water, tap
  • 10 ml graduated cylinder or other vessel to add water to Petri dishes
  • Light source (lamp or sunny windowsill)
  • Cardboard boxes (with lids and of sufficient size to provide dark environment for seeds, or other dark conditions)
  • Tape, labelling (for Petri dishes)
  • Pen, for labelling
  • Refrigerator* (*or incubator)
  • Vermiculite (for camas stratification and for seed orientation)
  • Thermometers (minimally 2)
  • Metric rulers
  • Data sheets
  • Optional: Potting soil and pots (or paper cups, to study extended growth and development of seedlings)
  • Optional: Digital scale (for weighing seeds to determine imbibition rates)

Assignment:

  • Lab Report #4, to address the following points:
  • Observation, sketching, and labeling of seeds
  • Hypothesis (or hypotheses), to be developed
  • Experimental design and setup
  • All other elements of a standard lab report, e.g.:
  • Title Page: Include title that reflects the variables being tested
  • Introduction: Research on the environmental variables that affect the rate of seed germination and on the type of plant used in the experiment. Be sure to cite your sources. Please use aminimum of two sources.
  • Materials & Methods: Be sure to describe the procedures followed by your group and the materials used to do so.
  • Results (Data): Your data section should include the following (1) complete data table showing the average root and stem growth measured by each group for the duration of the experiment. (2) Line graph showing the average root length for each group, (3) line graph showing the average stem length for each group, (3) line graph showing the average overall length for each group.
  • Discussion: Summarize the data presented. Be sure to address the following in your discussion as well:
  • Did any of the variables tested show significant differences in the rate of root growth?
  • Did any of the variables tested show significant differences in the rate of stem growth?
  • Did any of the variables show significant differences in overall growth?
  • Which variable does the data suggest is the most important for seed germination (all seed germination depends on a variety of environmental conditions, but which does our data suggest might play a key role?).
  • Can you think of any sources of error in our data? Was there anything about our experimental design that might have skewed the data?
  • Conclusion: Draw a logical conclusion to this lab.
  • References & Citations: Include your sources used in your references section and using in-text citations.

Procedure:

  1. Divide the class into groups. Each group will test a different variable (two conditions).
  2. Place five (5)pinto beans or corn kernels on damp/wet paper towels in each of two Petri dishes. Place each dish in one of the test conditions.
  3. Groups will collect data each day for approximately two to three weeks. Groups should measure the stem and root growth for each bean seedor corn kernel each day and calculate an average (mean) length of root and average length of stem each day. Keep a data collection record (a data collection sheets will be provided).
  4. At the end of the two-week period, data collected by each group will be displayed for the class. Each student is to write a lab report comparing the variables tested by the class.
  5. If you wish, enter your data into the VasserStats t-test webpage to determine if your results for any given variable indicate a statistically significant difference (and please note that you will use a one-tailed test here, as growth should be expected in one direction only). And please be sure to submit a copy of your t-test results with your lab report.

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