Reconsidering photorespiration through the eyes of guard cells

Sustainable agriculture, climate change, and a growing global population require resilient crops that deliver more with fewer resources. Leaf gas exchange is an important physiological crossroads, where CO₂ uptake and water loss must be balanced, especially under hotter, drier, and more variable extreme environmental conditions. We argue that an overlooked leverage point lies at the interface between photorespiration and stomatal regulation. Although each process is well described in isolation, how photorespiration can shape guard cell opening remains unresolved. We describe the impact of photorespiration on stomatal opening, discuss whether this involves photorespiration in mesophyll cells, guard cells, or both cell types, propose potential underlying mechanisms, and highlight photorespiration-stomata interactions as a target to improve plant water-use efficiency and resilience without compromising yield.