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 |
Stomatal
Morphology
Background
Information:
The structure of the stomatal apparatus varies from species
to species. In general, guard cells
are either bean-shaped (eudicot type) or barbell-shaped (grass type).
Guard cells may or may not be accompanied by subsidiary cells.
Questions:
What is the structure of the stomatal apparatus of plants
such as wandering Jew (Tradescantia),
Broad bean (Vicia faba), RCBr (Brassica
rapa) and maize (Zea mays)?
Hypotheses: Since RCBr and Broad bean are eudicots they will
have bean-shaped guard cells. Maize,
a monocot, will have barbell-shaped guard cells.
Protocol:
Obtain
a Broad bean leaf and make an epidermal peel
from the lower (abaxial) surface.
Mount
the strip in a drop of water on a microscope slide and cover with a cover
glass. Examine at 400x. Do not
use the oil immersion lens.
Sketch the stomatal apparatus. Be sure to record the
magnification of the object and calculate the plate
magnification (= drawing size / actual size; same units).
Be sure to give your diagram a caption and label stomata, guard cells, subsidiary cells and epidermal cells.
Obtain a leaf of a plant from the greenhouse and prepare an epidermal peel. Use the digital camera to prepare an image from this species. Record the actual size of the guard cell or stomata.
Data: Sketch of the stomatal apparatus of broad bean and digital image of a species of your choice. Label these Fig's 1 & 2).
Analysis/Conclusions:
What
organelles do you observe in the epidermal cells? Guard cells?
What
similarities do you observe between the stomatal apertures of the species?
Differences?
Did
they appear as you expected? Explain.
How
good (free of mesophyll) are your epidermal strips?
What
organelles do you observe in the guard cells?
other epidermal cells?
Which
species was easiest to peel? Offer
an explanation.
Do any of the species you observed have distinct subsidiary cells? Which ones? What do they look like?
Further Experiments:
What percent of the epidermal cells are guard cells?
On average, how many epidermal cells are between a stoma and its nearest neighbor?
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Last updated:
01/07/2009 � Copyright by SG
Saupe