in Low Light (LL) plants 3.5:1 in high light acclimated (HL-ACC) plants 2.3:1 unitless
||Thale cress Arabidopsis thaliana
||Ma F, Jazmin LJ, Young JD, Allen DK. Isotopically nonstationary 13C flux analysis of changes in Arabidopsis thaliana leaf metabolism due to high light acclimation. Proc Natl Acad Sci U S A. 2014 Nov 25 111(47):16967-72. doi: 10.1073/pnas.1319485111. abstract and p.16970 left column 4th paragraphPubMed ID25368168
||Abstract: "[Investigators] performed in vivo isotopic labeling of Arabidopsis thaliana rosettes with (13)CO2 and estimated fluxes throughout leaf photosynthetic metabolism by INST-MFA [Isotopically nonstationary metabolic flux analysis]. Plants grown at 200 µmol m^(-2)s^(-1) light were compared with plants acclimated for 9 d at an irradiance of 500 µmol⋅m^(-2)⋅s^(-1)."
||Abstract: "Despite a doubling in the carboxylation rate, the photorespiratory flux increased from 17 to 28% of net CO2 assimilation with high-light acclimation (Vc/Vo: 3.5:1 vs. 2.3:1, respectively)." P.16970 left column 4th paragraph: "Absolute fluxes (µmol metabolite/gFW/hr) obtained from the best-fit models were subsequently normalized by the net assimilation rate to enable direct comparisons of carbon partitioning between LL and HL-ACC conditions (Fig. 3). Both the carboxylation and oxygenation activities of RuBisCO were established through the modeling process, resulting in a ratio of Vc/Vo that dropped from 3.5:1 in LL plants to 2.3:1 in HL-ACC plants. The change in this ratio reflected an absolute increase in photorespiratory flux from 19 to 60 µmol CO2 released/gFW/hr, whereas carboxylation changed from 135 to 278 µmol CO2 fixed/gFW/hr. As a result, photorespiratory fluxes were 17 and 28% of net assimilation, respectively. The additional carbon lost to photorespiration in the HL-ACC condition was offset primarily by decreases in the relative flux to starch accumulation (from 33 to 24% of net assimilation)."