How much do plants respire?

Asked March 1, 2013, 5:56 AM EST

http://www.cmg.colostate.edu/gardennotes/141.html

Hi, at what rate do plants photosynthesize, and respire... what is the net change in CO2/O2 levels? Thanks

Outside United States plants science photosynthesis horticulture

4 Responses

Your question is not a simple one and I have to say that it depends. Net photosynthesis varies from species to species. Many grasses are what we call C4 plants, which means that the first sugar manufactured by the plant has four carbons and are typically grasses. The first sugar of a C3 plants, broadleaves, have three carbons. C4 plants have a greater net photosynthesis rate ranging from 30-80 mg carbon dioxide per square decameter leaf surface per hour. C4 plants range from 15 to 45 mg carbon dioxide per square decameter of leaf surface per hour. Plants endiginous to the forest floor can be as low as 4 mg carbon dioxide per square decameter of leaf surface per hour.

Net photosynthesis is best described as the accumulation of carbon in the form of carbon dioxide by a plant at a rate greater than the respiration rate, which is the burning of sugar as an energy source releasing carbon dioxide.

Depending upon the temperature, respiration rates range from about 0.5 to 4 mg carbon dioxide per square decameter leaf surface per hour. Warmer temperatures result in greater respiration rates.

Plants respire 24/7 and photosynthesis occurs only during daylight hours.

Great, thanks for a speedy reply.

So, there might well be some plants, in warmer climates (perhaps tropical rainforests with low light too) that Produce more CO2 than they 'Destroy' (for lack of a better word...)?

Oh, and I do mean Alive Plants....

Cheers, Arjay.

Plants that respire at rates great enough to have a negative net carbon gain die.