G. Bio. Labs

Anne Heise aheise at ORCHARD.WASHTENAW.CC.MI.US
Sat Feb 1 09:48:33 EST 1997


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





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