Abstract
Plant species that fix CO 2 by the C 4 cycle have higher rates of CO 2 uptake than species using the C 3 photosynthetic carbon reduction cycle. Greater CO 2 fixation capacity has been associated with reduced photorespiration, specialized leaf anatomy, and biochemical pathways that differ in C 3 and C 4 plants. The higher photosynthesis rate of C 4 species also results in more dry matter production per unit of water transpired. This paper reviews published reports of productivity and N content of some C 4 and C 3 species. It hypothesizes that C 4 plants have a greater N use efficiency (biomass production per unit of N in the plant) than do C 3 plants. This difference presumably results from the relatively smaller investment of N in the photosynthetic carboxylation enzymes of C 4 plants than of C 3 plants. Some adaptive and evolutionary implications of such a hypothesis as well as limitations of supporting data are discussed.
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Claims 4
Claim · model-written summary
C4 species have higher CO2 uptake than C3 species.
Verbatim
e0“Plant species that fix CO 2 by the C 4 cycle have higher rates of CO 2 uptake than species using the C 3 photosynthetic carbon reduction cycle.”
Claim · model-written summary
C4 species produce more dry matter per unit water transpired.
Verbatim
e0“The higher photosynthesis rate of C 4 species also results in more dry matter production per unit of water transpired.”
Claim · model-written summary
The paper hypothesizes greater nitrogen use efficiency in C4 than C3 plants.
Verbatim
e0“It hypothesizes that C 4 plants have a greater N use efficiency (biomass production per unit of N in the plant) than do C 3 plants.”
Claim · model-written summary
The proposed efficiency difference is attributed to smaller nitrogen investment in C4 carboxylation enzymes.
Verbatim
e0“This difference presumably results from the relatively smaller investment of N in the photosynthetic carboxylation enzymes of C 4 plants than of C 3 plants.”