Evidence map›Paper›PMID 32409834›Full record

ArticleJournal of experimental botany2020

Why is C4 photosynthesis so rare in trees?

Sophie N R Young, Lawren Sack, Margaret J Sporck-Koehler, Marjorie R Lundgren

Open access · hybridAbstract read
In one paragraph

Article in Journal of experimental botany, 2020. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 8 papers.

0numbers the graph read from it
0cells of the map it votes in
8citing papers in PubMed
0.8field-weighted citation impact, top 29% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

8 citing papers in PubMed, 17 citations in OpenAlex.

  1. Centennial-scale atmospheric COThe New phytologist · 2025
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4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

4 authors at 3 institutions in 2 countries.

Sophie N R YoungLancaster Environment Centre, Lancaster University, Lancaster, UK.
Lawren SackDepartment of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA, USA.
Margaret J Sporck-KoehlerDepartment of Botany, University of Hawaii at Manoa, Honolulu, HI, USA.
Marjorie R LundgrenLancaster Environment Centre, Lancaster University, Lancaster, UK.
Lancaster University · GBUniversity of California, Los Angeles · USUniversity of Hawaiʻi at Mānoa · US

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

Since C4 photosynthesis was first discovered >50 years ago, researchers have sought to understand how this complex trait evolved from the ancestral C3 photosynthetic machinery on >60 occasions. Despite its repeated emergence across the plant kingdom, C4 photosynthesis is notably rare in trees, with true C4 trees only existing in Euphorbia. Here we consider aspects of the C4 trait that could limit but not preclude the evolution of a C4 tree, including reduced quantum yield, increased energetic demand, reduced adaptive plasticity, evolutionary constraints, and a new theory that the passive symplastic phloem loading mechanism observed in trees, combined with difficulties in maintaining sugar and water transport over a long pathlength, could make C4 photosynthesis largely incompatible with the tree lifeform. We conclude that the transition to a tree habit within C4 lineages as well as the emergence of C4 photosynthesis within pre-existing trees would both face a series of challenges that together explain the global rarity of C4 photosynthesis in trees. The C4 trees in Euphorbia are therefore exceptional in how they have circumvented every potential barrier to the rare C4 tree lifeform.

Indexed as

PhotosynthesisTreesBiological EvolutionCarbon CyclePhenotypePlantsC4 photosynthesisChamaesycedisjunct veinsEuphorbiaEuphorbiaceaephloem loadingquantum yieldsymplastictrees

Identifiers

PMID32409834
PMCPMC7410182
OpenAlexW3024192418

What OpenQuestion holds

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LicenceCC BY
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Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.