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Plants producing Oxygen at Night

Carsten Richter carsten.richter at rz.hu-berlin.de
Wed Oct 25 03:04:48 EST 2000


I also do not know of a plant which releases oxygen at night. But I think
that the production or consumption of oxygen by plants is without any
practical relevance to the quality of the air in a bedroom.
Lets do some calculations (assuming a gastight room :-) ):

A typical rate of photosynthesis of a C3-plant under good environmental
conditions is 30 mg CO2 * dm-2 * h-1,
that means this plant consumes per dm2 leaf area 30 mg CO2 in every hour. 30
mg CO2 are about 15.2 ml (44 g/mol, 22.4 liter/mol).
On the other hand the plant produces 15.2 ml oxygen ( assuming a
photosynthetic quotient of 1).
Lets say we have many plants in our room with a total leaf area of 10 m2,
and the room has a volume of 60 m3 (4m wide, 5m broad, 3m high).
Then the plants are producing 15.3 liter oxygen in every hour, or  182.4
liter during a 12 hour light period.
The normal oxygen concentration is 21%. That means our room of 60m3 (60,000
liter) contains 12600 liter of oxygen at the beginning of the light period.
12 hours later the room contains 12782.4 liter of oxygen or 21.3%.
That means even in a gastight room, the oxygen production of a lot of plants
is without practical relevance.

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