# C2 Resilient Photosynthesis: A Practical Option for Long-Term Stable Carbon Sinks?

## TL;DR

C2 photosynthesis could help plants maintain carbon absorption under climate stress by efficiently recycling CO2 without extra energy.

## Contribution

The paper reviews the potential of C2 photosynthesis as a resilient carbon sink strategy and identifies key research gaps.

## Key findings

- C2 photosynthesis recycles CO2 during photorespiration without extra ATP use, improving carbon uptake under stress.
- C2 plants show greater resilience compared to C3 and C4 plants in fluctuating climate conditions.
- Research gaps include understanding molecular mechanisms and identifying more C2 species.

## Abstract

C2 photosynthesis enhances net CO2 assimilation by capturing, concentrating, and reassimilating CO2 released during photorespiration, all while minimizing the additional energy expenditure. This process significantly improves carbon uptake, particularly under stress conditions. This review provides an overview of the diversity, distribution, evolution, and environmental resilience of C2 plants, highlighting their potential to stabilize carbon assimilation in the face of climate variability. It also addresses critical research gaps, including the identification of additional C2 species and the need for a deeper understanding of their molecular and ecological mechanisms. The review advocates for a more focused research effort to fully exploit the potential of C2 photosynthesis in enhancing climate resilience.

In recent years, extreme climate events such as high temperatures and droughts have become increasingly frequent and intense, posing significant threats to the carbon sink stability of C3, C4, and CAM plants. As a result, identifying photosynthetic strategies that balance adaptability with resilience has emerged as a critical focus in carbon sink research. C2 photosynthesis offers a promising solution by recycling photorespiratory CO2 through the glycine shuttle between mesophyll cells (MCs) and bundle sheath cells (BSCs), thereby optimizing carbon concentration and recovery without additional ATP expenditure, thus minimizing carbon loss. This review provides a comprehensive analysis of the diversity, distribution, evolutionary status, and regulatory mechanisms of C2 photosynthesis, emphasizing its physiological and ecological resilience in carbon sequestration. In comparison to C3 and C4 pathways, C2 photosynthesis demonstrates distinct carbon sink resilience, positioning it as a vital strategy for addressing both current and future global climate challenges. The review also highlights existing gaps in C2 research, particularly in species identification, molecular mechanisms, and ecological studies, and recommends prioritizing these areas to fully harness its potential for enhancing climate resilience.