Daily Heat Stress Induces Donor-Side Limitation of PSI Via Downregulation of the Cyt b(6)f Complex.

Daily exposure of Arabidopsis thaliana to 38°C for 4 h throughout growth reduces Cytochrome b6f complex content by 30–40%, limiting PSI electron flow.

• Why it matters: Prolonged heat waves threaten photosynthesis, but how sustained heat affects the primary photosynthetic reactions is still unclear.
• What they did: Plants were grown under daily 38°C for 4 h, and photosynthetic performance was assessed alongside changes in PSII stability and Cytochrome b6f complex abundance.
• The result: PSII-LHCII stayed relatively intact, while downstream acceptors became more oxidized and PSI over-reduction was prevented when carbon assimilation was inhibited.

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