Flux of carbon into photorespiration as a proportion of the flux into photosynthesis at various [CO2]

Range at [CO2]=235µmol/mol 30%: at [CO2]=270µmol/mol 26.1%: at [CO2]=380µmol/mol 18.3% %
Organism Plants
Reference Zhu XG, de Sturler E, Long SP. Optimizing the distribution of resources between enzymes of carbon metabolism can dramatically increase photosynthetic rate: a numerical simulation using an evolutionary algorithm. Plant Physiol. 2007 Oct145(2):513-26. p.522 left column bottom paragraphPubMed ID17720759
Method p.514 right column 2nd paragraph:"The aim of this study was to demonstrate the application of dynamic photosynthesis models in engineering higher light-saturated photosynthetic rates. Another aim was to determine whether total protein, expressed as protein-nitrogen, is partitioned optimally with respect to maximizing light-saturated photosynthetic rate for a typical C3 leaf and, if not, what reallocation would maximize light-saturated photosynthesis."
Comments p.522 left column bottom paragraph:"(4) Atmospheric [CO2] has risen from approximately 270 μmol mol^−1 in 1850 to 384 μmol mol^−1 today. Yet, [investigators’] current C3 plants evolved over the past 25 million years in a [CO2] of 235 μmol mol^−1 (Barnola et al., 2003). Because CO2 competitively inhibits RuBP oxygenation at Rubisco, the flux of carbon into photorespiration as a proportion of the flux into photosynthesis gradually decreases with increase in [CO2]. Calculations using this model showed that the proportions of flux into photorespiration are 30%, 26.1%, and 18.3% for atmospheric [CO2] of 235, 270, and 380 μmol mol^−1, respectively. Therefore, the flux into the photorespiratory pathway was decreased about one-third with increase of atmospheric [CO2] from 270 to 380 μmol mol^−1 since the industrial revolution. Thus, they may be poorly adapted to the increase that has occurred in the brief period of 150 years on an evolutionary time scale. Consistent with this, the optimized enzyme distributions under a higher ci, i.e. 490 μmol mol^−1, showed the lower concentration of photorespiratory enzymes needed to deal with the decreased flux of carbon into this pathway with rising [CO2] (Fig. 5B)."
Entered by Uri M
ID 111952