Improving photosynthetic efficiency in fluctuating light to enhance yield of C₃ and C₄ crops

Abstract

Photosynthetic adaptations to light fluctuations do not occur instantaneously, leading to reduced carbon gain and lower productivity in agricultural crops. Enhancing the rapidity of photosynthetic responses to these fluctuations could potentially increase carbon assimilation by 13-32%, indicating a substantial opportunity for yield improvement of major crops. Most crops can be categorized into C₃ or C₄ crops by their photosynthetic pathways. This review provides a comparative overview of the photosynthetic responses of both C₃ and C₄ crops to light fluctuations, highlighting the unique and shared challenges for these two photosynthetic pathways. In C₃ crops, fast adjustments in non-photochemical quenching, stomatal and mesophyll conductance, and Rubisco activation are essential for optimizing photosynthesis under variable light conditions. In contrast, C₄ crops, including maize, sorghum, and sugarcane, benefit from their carbon concentration mechanism under high light conditions but face challenges in coordinating the C₄ and Calvin-Benson-Bassham cycles. Strategies to enhance the activation of pyruvate phosphate dikinase and Rubisco, as well as to improve electron transport capacity and flexibility, could markedly boost the photosynthetic efficiency and productivity. Through a detailed understanding of the distinct mechanisms involved in C₃ and C₄ photosynthesis, this review underscores the need for tailored strategies to optimize the photosynthetic efficiency specific to each crop type. Exploring and leveraging these differences is crucial for propelling agricultural productivity forward.

Keywords

C₃ photosynthesis / C₄ photosynthesis / Photosynthetic induction / PPDK regulatory protein / Rubisco activase / Stomatal conductance

Abbreviations

BSC: bundle sheath cells

CAM: crassulacean acid metabolism

CBB: Calvin-Benson-Bassham

Cyt b₆f: cytochrome b₆f

FBPase: fructose-1,6-bisphosphatase

GAPDH: glyceraldehyde-3-phosphate dehydrogenase

g_bs: bundle sheath conductance

g_m: mesophyll conductance

g_s: stomatal conductance

Mal: malate

MC: mesophyll cells

M&E: mutase and enolase

NADP-ME: NADP-malic enzyme

NPQ: non-photochemical quenching

NTRC: NADPH-thioredoxin reductase C

OAA: oxaloacetate

PDRP: pyruvate phosphate dikinase regulatory protein

PEP: phosphoenolpyruvate

PEPC: phosphoenolpyruvate carboxylase

PGA: 3-phosphoglycerate

PPDK: pyruvate phosphate dikinase

PRK: phosphoribulose kinase

Pyr: pyruvate

Rca: Rubisco activase

Rubisco: ribulose-1,5-bisphosphate carboxylase/oxygenase

SBPase: sedoheptulose-bisphosphatase

TDL: tunable diode laser

WUE: water ues efficiency

Availability of data and materials

Not applicable.

Authors’ contributions

Y.W.: conception, data curation, investigation, visualization, writing original draft, reviewing, and editing.

Declaration of competing interest

I declare that I have no competing interests.

Acknowledgements

Not applicable.

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