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PHOTOSYNTHESIS & RESPIRATION      TreeSign.jpg (15262 bytes)

"Air Plants", Project Learning Tree Pre K-8 Guide, Seventh Edition, page 85, Activity #28


Plants play a part in every breath we take.  Use this activity to help your students understand how photosynthesis works and how humans depend on this process.


The purpose of photosynthesis is to produce sugars (plant food).  The energy stored from photosynthesis is also what animals rely upon.  Oxygen is a by-product that gets too much of the "limelight".   The amount of oxygen produced by plants is tiny compared with atmospheric quantities of oxygen, so, some argue the role of plants in our oxygen supply is not significant.  The oceans produce far more oxygen than trees, another good comparative observation.  Additionally, plant respiration uses oxygen, similar to animal respiration.  Older trees and older forests may actually be net users of oxygen, not net producers.  It is important to place emphasis on the major role of photosynthesis . . . sugar production, not oxygen production.  A direct relationship between oxygen production of just trees and the air we breathe is difficult to establish.

Teacher Guide Link   Also see PLT "Sunlight & Shades of Green"

Note Many of the activities on this website reference Project Learning Tree (PLT) activities.  PLT has copyrights on these activities but has granted permission to provide outlines to render a general ideas of what each activity covers.  There are two PLT activity books, one for Pre K-8 and another for high school (recent revisions).  There are also a number of special modules available through PLT in 2004.  For more information about PLT, visit the national website at and the Michigan PLT website at

MSUElogo.tif (16254 bytes) This website was developed and created by Michigan State University Extension for the teachers of the State of Michigan. 

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