Photosynthetic Characteristics of C(3)-C(4) Intermediate Flaveria Species : III. Reduction of Photorespiration by a Limited C(4) Pathway of Photosynthesis in Flaveria ramosissima |
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| Authors: | Rumpho M E Ku M S Cheng S H Edwards G E |
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| Affiliation: | Botany Department, Washington State University, Pullman, Washington 99164-4230. |
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| Abstract: | The initial products of photosynthesis by the C3 species Flaveria cronquistii, the C4 species F. trinervia, and the C3-C4 intermediate species F. ramosissima were determined using a pulse-chase technique with 14CO2-12CO2. The intermediate species F. ramosissima incorporated at least 42% of the total soluble 14C fixed into malate and aspartate after 10 seconds of photosynthesis in 14CO2, as compared with 90% for the C4 species F. trinervia and 5% for the C3 species F. cronquistii. In both F. ramosissima and F. trinervia, turnover of labeled malate and aspartate occurred during a chase period in 12CO2, although the rate of turnover was slower in the intermediate species. Relative to F. cronquistii, F. ramosissima showed a reduced incorporation of radioactivity into serine and glycine during the pulse period. These results indicate that a functional C4 pathway of photosynthesis is operating in F. ramosissima which can account for its reduced level of photorespiration, and that this species is a true biochemical intermediate between C3 and C4 plants. |
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