Revisiting C4 CO2 responsiveness: lessons from millet species in a high-CO2 future
Abstract
C4 photosynthesis is traditionally considered "CO2 -insensitive" because the bundle-sheath CO2 -concentrating mechanism is thought to saturate Rubisco at present atmospheric levels. Recent field and controlled-environment experiments, however, reveal notable growth and yield responses of several C4 cereals, especially millets, when CO2 rises. Millets constitute a phylogenetically diverse group of small-seeded grasses that thrive on marginal, low-input agro-ecosystems, making them ideal models for probing source-sink interactions that are hidden in highly bred maize. This review synthesizes (i) the biochemical and modelling foundations of the classical C4 CO2 -insensitivity concept, (ii) the ecological, genetic and multi-omics attributes of millets that expose C4 plasticity, and (iii) empirical evidence from leaf-to yield-level studies that support a candidate sink-limited frameworkfor C4 responses to elevated CO2 that awaits direct experimental validation. We conclude by highlighting the need for factorial FACE experiments and integrated omics-phenomics approaches to uncover the mechanisms underlying CO2 responses and guide the development of climate-resilient millet ideotypes.
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BibTeX
@misc{hussein2026revisiting,
title = {{Revisiting C4 CO2 responsiveness: lessons from millet species in a high-CO2 future}},
author = {Eelaf Taha Hussein and Vivek Dogra and Rozenn Le Hir},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.17180/xje7-2p88},
url = {https://hal.science/hal-05765475v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Revisiting C4 CO2 responsiveness: lessons from millet species in a high-CO2 future
AU - Eelaf Taha Hussein
AU - Vivek Dogra
AU - Rozenn Le Hir
PY - 2026
DA - 2026/09/26
PB - HAL
DO - 10.17180/xje7-2p88
UR - https://hal.science/hal-05765475v1
AB - C4 photosynthesis is traditionally considered "CO2 -insensitive" because the bundle-sheath CO2 -concentrating mechanism is thought to saturate Rubisco at present atmospheric levels. Recent field and controlled-environment experiments, however, reveal notable growth and yield responses of several C4 cereals, especially millets, when CO2 rises. Millets constitute a phylogenetically diverse group of small-seeded grasses that thrive on marginal, low-input agro-ecosystems, making them ideal models for probing source-sink interactions that are hidden in highly bred maize. This review synthesizes (i) the biochemical and modelling foundations of the classical C4 CO2 -insensitivity concept, (ii) the ecological, genetic and multi-omics attributes of millets that expose C4 plasticity, and (iii) empirical evidence from leaf-to yield-level studies that support a candidate sink-limited frameworkfor C4 responses to elevated CO2 that awaits direct experimental validation. We conclude by highlighting the need for factorial FACE experiments and integrated omics-phenomics approaches to uncover the mechanisms underlying CO2 responses and guide the development of climate-resilient millet ideotypes.
ER -