Chlorophyll a Fluorescence Kinetics Reveal That Ozone Stress Redistributes Electron Transport Limitations Between PSII and PSI in Wheat.

Acute exposure to 100 ppb tropospheric ozone in wheat redistributes electron-transport limitations between PSII and PSI in a cultivar-specific way, not as a uniform PSII decline.

• Why it matters: Ozone reduces crop productivity, but the specific photosynthetic sites where electron transport is altered are unclear, limiting mechanistic phenotyping and screening for tolerance.
• What they did: Chlorophyll a fluorescence induction kinetics were analyzed in wheat cultivars PAN 3434 and PAN 3161 after controlled 100 ppb O3 exposure, using charcoal-filtered air as a low-ozone reference.
• The result: PAN 3434 showed suppression of J-I and I-P phases with reduced plastoquinone pool reduction and PSI acceptor-side capacity plus declines in active PSII reaction centers and electron-transport probabilities, linked to cultivar-specific yield reductions. PAN 3161 showed smaller changes consistent with partial preservation of reaction center and intersystem electron transport, also associated with yield reductions.

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