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Name:  Anne
Status: educator
Grade: K-3
Location: MD
Country: N/A
Date: 7/28/2005


Question:
I understand plants need oxygen to produce sugar and energy...but I'm still confused about whether plants produce more CO2 or oxygen.


Replies:
Cellular respiration (process that uses oxygen to break sugar into energy for life functions) and photosynthesis (green plants converting sunlight energy into sugars using water and carbon dioxide) are distinct and separate processes. Animals only use cellular respiration. Plants do not have muscles and the other functions necessary in animals functioning that require a high levels of oxygen. Plants also CAN NOT take the energy directly for their energy needs from photosynthesis. Photosynthesis produces a far greater amount of oxygen and sugars, etc. then the small amount the plant requires to produce its energy needs. OK - but only during the day when the sun light is available! During the night, the plant actually uses oxygen it has left over from the daylight photosynthesis or takes the oxygen from the air surrounding the plant to meet its energy needs. This is not nearly the amount of oxygen an animal needs over the same period of time. To answer your question, during the day the plant produces far more oxygen from photosynthesis than it produces carbon dioxide from cellular respiration. It is a waste gas and if not expelled from the plant, can cause serious harm. Since plants do not utilize large amounts of oxygen over a twenty-four hour period (ideal conditions, winter is another issue), oxygen wins. It is a good thing too, for ALL the oxygen in the atmosphere is the result of plants producing far more oxygen than they need!!! Take a deep breath! I hope this helps.

Steve Sample



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