Autumn Red Maple Leaves
An exercise on observations, hypotheses, and testing predictions.

Plant Physiology 455 - Jonathan Monroe
Department of Biology, James Madison University
 
 

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Introduction

Just like stretching before engaging in physical activity, this is a exercise for loosening up your brain.  Walking in the George Washington National Forest in the fall of 2002 I began looking at red maple (Acer rubrum) leaves and noticed the amazing patterns of reds, yellows and browns.  The browns were mostly dead spots probably caused by pathogen infections.  The yellows were carotinoid pigments revealed after the green chlorophylls were broken down and the reds were anthocyanins synthesized during senescence.  The more I looked the more I could see and that led me to think about cause and effect.  What caused the patterns I was seeing?  Below are eight sets of 4 pictures of those leaves.

What to do

Working in pairs look carefully at one set of leaves (i.e. the A set or the B set...) writing down all that you see.  Don't bother drawing images or printing them because they will still be here to refer back to.  After making a long list of observations, look for patterns.  Once you start to see patterns, write hypotheses to explain your observations, and then make predictions based on your hypotheses.  Once you have a set of predictions, test them by looking at the next set of leaves.  Do your predictions hold up?  Do you need to modify any of them?

Assignment

Turn in a description (2-5 pages) of your observations, hypotheses, predictions, and the outcome of your "tests".  Keep in mind that there isn't a right answer to this assignment.  Wrong predictions are worth just as much as ones that seem to hold up under scrutiny.  Most importantly - have fun!

1/6/03 Copyright (C) 2003, Jonathan Monroe, monroejd@jmu.edu. All rights reserved.
URL: http://csm.jmu.edu/biology/courses/bio455_555/acerleaf/acerleaf.html