|Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University; Biology Department; Collegeville, MN 56321; (320) 363 - 2782; (320) 363 - 3202, fax; email@example.com|
Gravitropism in Dandelion Scapes
In this lab we will study the gravitropic response of the hollow flowering stalk (scape) of dandelion (Taraxacum officinale). The dandelion provides an excellent model system for studying gravitropism (Clifford and Oxlade, 1991).
Cut the dandelion stalks off at the base with a knife or razor blade. The scapes should be maintained in an upright position in water until used. Attempt to collect scapes while the flower is in bud because the gravitropic sensitivity declines once the inflorescence opens. Upon fruiting - formation of the head or "clock" - the scapes become strongly gravitropic. Decapitate the inflorescence.
Insert a few centimeters of the scape into a tube filled with water. Mount the tube on a horizontal surface with tape or place vertically in a test tube rack. Protractors will be available to measure the angles of curvature. Microscopes and slides will also be provided.
Working with a partner, design an experiment to answer a question about gravitropism using the dandelion scapes. Some possible questions are provided below. When designing your experiment, consider: what is your hypothesis? what is your biological rationale for this hypothesis? what data do you need to collect to test this hypothesis? How many samples will you need? what type of tables and/or graphs will you use to summarize your data? How will you analyze your data? Will your data be appropriate to support or refute your hypothesis?
Questions: Consider the following...
01/07/2009 � Copyright by SG