Here's a cheap, simple lab.
What is the trade-off if a plant could either make a few well-endowed
seeds or
more smaller ones? Students grow bean seeds with both cotyledons, one
cotyledon, or practically no cotyledons. You soak bean seeds overnight
so the seed coat can be slipped off. A whole cotyledon is easily
removed, or students might cut off half of each cotyledon w/ a knife.
For the no-cotyledon treatment, you carefully remove (w/ a knife) as much
of both cotyledons as you can. Plant, monitor. Allow maybe 6 weeks for
the plants to grow. I ask
students to decide what variables they will measure, so they can decide
for themselves how the plants are affected. (e.g, germination time, #
leaves, color of leaves, time to flower, etc.)
Since the seeds w/o as much stored energy usually do from worse to much
worse, you can use the results to talk about r and K strategies. It's
also fairly clean in terms of controls, and it's also intuitive.
Anne Heise
Washtenaw Community College
Ann Arbor MI
