{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T06:01:57Z","timestamp":1785391317688,"version":"3.55.0"},"reference-count":45,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T00:00:00Z","timestamp":1785369600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Plant Sci."],"abstract":"\n Introduction<\/jats:title>\n \n While CO\n 2<\/jats:sub>\n enrichment studies have provided valuable insights into how plants respond to elevated CO\n 2<\/jats:sub>\n levels expected under future climate conditions (up to ~700 ppm), if and how photosynthesis can adapt to more extreme CO\n 2<\/jats:sub>\n levels in nature remains yet unknown. Here, we investigate changes in photosynthetic metabolism in a C3 plant growing near high CO\n 2<\/jats:sub>\n emission sources in Yellowstone National Park, at levels up to 6000 ppm CO\n 2<\/jats:sub>\n .\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n We analyze chlorophyll variable fluorescence emission kinetics to identify changes in the photosynthetic electron transport chain (PETC) between plants adapted to high CO\n 2<\/jats:sub>\n versus control plants growing at ambient CO\n 2<\/jats:sub>\n . By applying short flashes using the Fast Repetition Rate Fluorometry (FRRF) technique we separate photochemical from non-photochemical quenching events. This enables monitoring electron transport from water oxidation within PSII into the downstream carrier pools (Plastoquinone (PQ), Ferrodoxin, and NADP\n +<\/jats:sup>\n ) of the PETC and into CO\n 2<\/jats:sub>\n carboxylation within the Calvin Benson-Bassham (CBB) cycle.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n We find that plants growing near the extreme CO\n 2<\/jats:sub>\n sources in Yellowstone are much slower to overcome bottlenecks in the PETC and reach lower photochemical Fv\/Fm values indicative of lower photosynthetic efficiency. We observe that these plants require higher CO\n 2<\/jats:sub>\n levels to activate the reactions in the CBB cycle.\n <\/jats:p>\n <\/jats:sec>\n \n Discussion<\/jats:title>\n \n We conclude that plants growing near high CO\n 2<\/jats:sub>\n sources are metabolically poised in Cyclic Electron Flow (CEF) at ambient CO\n 2<\/jats:sub>\n concentrations and switch to Linear Electron Flow (LEF) only in high CO\n 2<\/jats:sub>\n . Second, after a brief period of dark time (3\u20134 minutes), the near-source plants more rapidly restore the PETC bottlenecks, slowing LEF and recovering CEF. This outcome retains electrons in the PQH\n 2<\/jats:sub>\n pool slowing flux into the NADP\n +<\/jats:sup>\n pool through LEF and blocking utilization of CO\n 2<\/jats:sub>\n by reactions in the CBB cycle. We explain this adaptive response as a coping mechanism against acidification at high CO\n 2<\/jats:sub>\n growth conditions, which compromises enzymatic activity and proton motive force generation. We conclude that plants adapt to extreme atmospheric CO\n 2<\/jats:sub>\n by further compromising the inefficient CBB cycle and by rerouting electron flux through the PETC from LEF into CEF to stimulate more proton pumping and ATP production.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fpls.2026.1774168","type":"journal-article","created":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T05:39:41Z","timestamp":1785389981000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Adaptation of plant photosynthetic metabolism to extreme CO2 levels in Yellowstone revealed by in vivo fluorescence dynamics"],"prefix":"10.3389","volume":"17","author":[{"given":"Marie-Claire","family":"ten Veldhuis","sequence":"first","affiliation":[{"name":"Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology","place":["Delft, Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G. Charles","family":"Dismukes","sequence":"additional","affiliation":[{"name":"Waksman Institute of Microbiology, Rutgers University, the State University of New Jersey","place":["Piscataway, NJ, United States"]},{"name":"Department of Chemistry and Chemical Biology, Rutgers University, the State University of New Jersey","place":["Piscataway, NJ, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,30]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"27","DOI":"10.1111\/gcb.15375","article-title":"30 years of free-air carbon dioxide enrichment (FACE): What have we learned about future crop productivity and its potential for adaptation? 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