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I am not a biologist but my recollection of high school biology is that photosynthesis is basically carbon dioxide + water + light energy = oxygen + glucose. So

by dbuxton 14y ago

I am not a biologist but my recollection of high school biology is that photosynthesis is basically carbon dioxide + water + light energy = oxygen + glucose. So saying, "About 300 to 500 plants would produce the right amount of oxygen, but it's much harder to estimate the amount of carbon dioxide the plants absorb" is wrong - the quantity of oxygen produced will be exactly proportionate to the amount of carbon dioxide consumed. (There is also an issue of how much oxygen the plants' respiration would consume but let's not get into that). And finally, some plants only "breathe," at night in order to save water - I also remember this (many if not most plants control water loss through transpiration by shutting down their stomata during , but I'm pretty much sure that no plants are able to photosynthesise at night! That would be an interesting species... Overall, seems like some relatively serious misunderstandings of the basic science if even I (not a great GCSE mark in biology...) find myself wringing my hands...

ars 14y ago
> but I'm pretty much sure that no plants are able to photosynthesise at night! That would be an interesting species... There are three types of plants, and instead of explaining them, let me just provide links. The type of plant that breathes at night are the CAM ones. * http://en.wikipedia.org/wiki/C3_carbon_fixation http://en.wikipedia.org/wiki/C3_carbon_fixation - most common, almost all plants are like this * http://en.wikipedia.org/wiki/C4_carbon_fixation http://en.wikipedia.org/wiki/C4_carbon_fixation - very efficient, corn is the most common example * http://en.wikipedia.org/wiki/CAM_photosynthesis http://en.wikipedia.org/wiki/CAM_photosynthesis - night breathing, pineapple is the example
- dbuxton 14y ago
  Very interesting! Although as the other reply points out only some of the photosynthetic reactions take place at night. However I assume (but it's not exactly clear from scanning the article linked) that the actual emission of oxygen is likely also happening at night as this would require stomata to be open, although the actual production of oxygen is one of the light-dependent reactions in the photosynthetic chain. Is this correct?
jonchang 14y ago
> the quantity of oxygen produced will be exactly proportionate to the amount of carbon dioxide consumed Not necessarily. Consider photorespiration -- under certain conditions, some plants will use oxygen instead of carbon dioxide. > I'm pretty much sure that no plants are able to photosynthesise at night Some reactions in photosynthesis are light independent, and many plants (especially ones in hot and arid environments) will perform these reactions at night in order to conserve water.
- gus_massa 14y ago
  The effect of photorespiration is that some of the oxygen is transformed back to carbon dioxide. It reduces the efficiency of the photosynthesis, so you would need more light. But it doesn't change the global amount of oxygen produced form the carbon dioxide.

by dbuxton 14y ago

ars 14y ago

> but I'm pretty much sure that no plants are able to photosynthesise at night! That would be an interesting species... There are three types of plants, and instead of explaining them, let me just provide links. The type of plant that breathes at night are the CAM ones. * http://en.wikipedia.org/wiki/C3_carbon_fixation http://en.wikipedia.org/wiki/C3_carbon_fixation - most common, almost all plants are like this * http://en.wikipedia.org/wiki/C4_carbon_fixation http://en.wikipedia.org/wiki/C4_carbon_fixation - very efficient, corn is the most common example * http://en.wikipedia.org/wiki/CAM_photosynthesis http://en.wikipedia.org/wiki/CAM_photosynthesis - night breathing, pineapple is the example

dbuxton 14y ago
Very interesting! Although as the other reply points out only some of the photosynthetic reactions take place at night. However I assume (but it's not exactly clear from scanning the article linked) that the actual emission of oxygen is likely also happening at night as this would require stomata to be open, although the actual production of oxygen is one of the light-dependent reactions in the photosynthetic chain. Is this correct?

jonchang 14y ago

> the quantity of oxygen produced will be exactly proportionate to the amount of carbon dioxide consumed Not necessarily. Consider photorespiration -- under certain conditions, some plants will use oxygen instead of carbon dioxide. > I'm pretty much sure that no plants are able to photosynthesise at night Some reactions in photosynthesis are light independent, and many plants (especially ones in hot and arid environments) will perform these reactions at night in order to conserve water.

gus_massa 14y ago
The effect of photorespiration is that some of the oxygen is transformed back to carbon dioxide. It reduces the efficiency of the photosynthesis, so you would need more light. But it doesn't change the global amount of oxygen produced form the carbon dioxide.