Carbon fluxes and environmental interactions during legume development, with a specific focus on Pisum sativum

Grain legumes are major food crops cultivated worldwide for their seeds with high nutritional content. To answer the growing concern about food safety and protein autonomy, legume cultivation must increase in the coming years. In parallel, current agricultural practices are facing environmental challenges, including global temperature increase and more frequent and severe episodes of drought stress. Crop yield directly relies on carbon allocation and is particularly affected by these global changes. We review the current knowledge on source-sink relationships and carbon resource allocation at all developmental stages, from germination to vegetative growth and seed production in grain legumes, focusing on pea (Pisum sativum). We also discuss how these source-sink relationships and carbon fluxes are influenced by biotic and abiotic factors. Major agronomic traits, including seed yield and quality, are particularly impacted by drought, temperatures, salinity, waterlogging, or pathogens and can be improved through the promotion of beneficial soil microorganisms or through optimized plant carbon resource allocation. Altogether, our review highlights the need for a better understanding of the cellular and molecular mechanisms regulating carbon fluxes from source leaves to sink organs, roots, and seeds. These advancements will further improve our understanding of yield stability and stress tolerance and contribute to the selection of climate-resilient crops.