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; ssaupe@csbsju.edu |
Gravitropism in Dandelion Scapes
Introduction:
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).
Plant Material:
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.
Study Apparatus:
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.
Procedure:
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...
References:
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Last updated:
01/07/2009 � Copyright by SG
Saupe