The kinetic basis of photosynthetic heat tolerance.

Protein denaturation, not lipid membrane breakdown, governs photosynthetic heat tolerance across photosystem II in 177 plant species from 157 families.

• Why it matters: Existing heat-tolerance models often ignore exposure duration or lack causal mechanisms, limiting tests and predictions under new temperature regimes.
• What they did: The authors built a quantitative chemical-kinetics theory of photosynthetic heat inactivation and fit it to photosystem II temperature responses in 177 species, then evaluated protein versus lipid mechanisms.
• The result: The theory predicts an upper acclimatization limit of ~60°C, tied to heat shock protein thermal stability, and this is supported by global data from 826 species.

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