|Plant Taxonomy (BIOL308) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; firstname.lastname@example.org; http://www.employees.csbsju.edu/ssaupe/|
I. Eudicot Seed -
no endosperm. In these species, the endosperm is reabsorbed during seed
development and stored in the embyro (typically in the cotyledons). Thus,
in the mature seed there is little endosperm but the embryo is usually
Obtain a soaked lima, kidney bean or other bean seed. Locate the hilum and micropyle. Squeeze the seed slightly and observe a drop of water from the micropyle region. Remove the seed coat. Now, pull apart the two halves (cotyledons) of the seed. What is the function of the cotyledons? What is inside the cotyledons? Locate the remainder of the embryo. Look for the hypocotyl and radicle on the end. Locate the epicotyl (plumule).
Can you identify the: pericarp, seed coat, embryo (cotyledons, epicotyl or plumule, hypocotyl). Which part(s) do you eat? If this is a fruit, why does it grow underground?
II. Eudicot seed -
with endosperm. In these species, the embryo is surrounded by a "sea of
endosperm." The cotyledons in these species are usually thin (little
nutrient storage) and often organs that help funnel endosperm nutrients to the
Study the seed provided.
III. Monocot Grain
Study a corn grain. Observe the pericarp. On the front side, look for the U-shaped depression indicating the position of the embryo. Just above the depression is a slight projection, the silk scar. What part of the plant is the silk? The sharp end of the grain is the peduncle, where it was attached to the ear. Then, cut through the grain to expose the embryo. Note the endosperm tissue. Note the single large cotyledon and the embryo.
08/20/2007 / � Copyright by SG