{"id":2904,"date":"2026-06-02T09:33:58","date_gmt":"2026-06-02T08:33:58","guid":{"rendered":"https:\/\/research.reading.ac.uk\/lemontree\/?p=2904"},"modified":"2026-06-02T09:33:58","modified_gmt":"2026-06-02T08:33:58","slug":"environmental-controls-on-photosynthetic-efficiency","status":"publish","type":"post","link":"https:\/\/research.reading.ac.uk\/lemontree\/environmental-controls-on-photosynthetic-efficiency\/","title":{"rendered":"Environmental Controls on Photosynthetic Efficiency: New Insights from Global Ecosystem Data"},"content":{"rendered":"

A new study led by LEMONTREE post-doc, David Sandoval, was just published in New Phytologist<\/em><\/a>. It challenges a long-standing assumption used in terrestrial biosphere models that the maximum quantum yield of photosynthesis is effectively constant.<\/p>\n

This study showed that photosynthetic intrinsic (maximum) quantum efficiency follows a predictable bell-shaped response to temperature across ecosystems worldwide, and that this response is strongly shaped by climate.<\/p>\n

Using data from hundreds of eddy-covariance flux tower sites, the team found that plants are most efficient at converting light into carbon uptake within an optimal temperature range, with efficiency declining at both colder and hotter temperatures. Remarkably, this pattern appeared consistent across ecosystems ranging from tropical forests to Arctic tundra.<\/p>\n

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What Is Quantum Yield?<\/h2>\n

The \u201cmaximum quantum yield\u201d of photosynthesis (\u03c6\u2080) is the initial slope of the light response curve of photosynthesis without any other limitations. So, it constraints how efficiently plants convert absorbed light into carbon fixation.<\/p>\n

Because photosynthesis drives the terrestrial carbon sink, \u03c6\u2080 strongly influences how much carbon ecosystems can absorb from the atmosphere. Yet most terrestrial biosphere models still assume \u03c6\u2080 is fixed for each plant functional type, with little or no temperature dependence.<\/p>\n

Experimental studies have increasingly suggested otherwise, but until now there had been no global ecosystem-scale assessment of how \u03c6\u2080 changes with temperature.<\/p>\n

 <\/p>\n

A Global Analysis of Ecosystem Photosynthesis<\/h2>\n

To address this, the team combined half-hourly CO\u2082 flux measurements from eddy-covariance towers with observations of absorbed light from more than 300 globally distributed sites.<\/p>\n

By analysing ecosystem light-response curves and using optimality theory, they inferred ecosystem-level maximum photosynthetic efficiency across a wide range of climates and vegetation types.<\/p>\n

The results showed \u03c6\u2080 consistently followed a bell-shaped temperature response.<\/p>\n

Maximum photosynthetic efficiency increased with temperature up to an optimum point before declining sharply at higher temperatures. Importantly, the overall shape of the curve was not biome-specific. Instead, it shifted gradually with climate conditions:<\/p>\n