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Name: Amir
Status: student
Grade: 9-12
Location: Outside U.S.
Country: Pakistan
Date: Winter 2012-2013

We all know that plants carry out respiration all the time. When stomata close at night, how can oxygen enter the leaves for respiration to happen? Similarly how would the extra Carbondioxide come out?

Most C3 and C4 pathway- plants take in carbon dioxide for photosynthesis during the day and release oxygen during the day, but the stomates also stay open during respiration while taking in oxygen and releasing carbon dioxide at night. Stomates close to conserve water.

However, CAM plants (such as cacti) open stomates at night and close them during the day - they have a different photosynthesis pathway.

Anthony R. Brach, Ph.D. Harvard University Herbaria c/o Missouri Botanical Garden

Dear Amir,

The more appropriate questions to ask are how much oxygen is needed for plant respiration and why does the carbon dioxide need to “come out”?

J. Tokuhisa Ph.D.

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