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Study

The evolution of C4 photosynthesis

Sage, Rowan F.

New Phytologist, 2004

Peer-reviewedsystematic reviewmixed

What they did

A review of why and how the C4 pathway evolved, covering the biochemical problem it solves, the anatomical changes it requires, and its independent appearance across unrelated plant lineages.

Studied in
Poaceae, Angiospermae
Sample size
review of C4 origins across flowering plant lineages

What they found

C4 photosynthesis has evolved independently more than forty-five times. It concentrates carbon dioxide around the fixing enzyme, suppressing photorespiration, and is favoured under high light, high temperature and low atmospheric carbon dioxide — conditions that became widespread in the last 30 million years.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

C4 is a repeatedly-evolved solution to photorespiration, driven by declining atmospheric carbon dioxide and warm open habitats.

How NatureHQ reads it

Photorespiration is the flaw in photosynthesis that most summaries omit. The enzyme that fixes carbon dioxide also reacts with oxygen, wastefully, and does so more as it gets hotter — a legacy of having evolved when there was almost no oxygen about. C4 is a workaround that concentrates carbon dioxide where the enzyme is, and the fact that it has been invented independently more than forty-five times says how much pressure there is to fix the problem. Maize, sugarcane and most tropical grasses use it.

Limitations

  • A review; estimates of independent origins have been revised upward since.
  • The relative weight of atmospheric, climatic and fire drivers is debated.
  • CAM, the other major workaround, is treated only in passing.

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Finding the paper

Published by: Wiley journalsPublished in a Wiley journal.

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NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-10.