Photosynthesis and stress tolerance: cell walls at the cross-roads

The cell wall (CW) plays a pivotal role in plant responses to abiotic stress and the regulation of photosynthesis. Modifications in CW composition and structure can enhance drought tolerance and other stress responses, but often at the expense of photosynthetic efficiency. This review explores the complex relationship between the CW, photosynthesis, and stress tolerance. We describe how changes in CW composition, such as variations in pectin, hemicellulose, and lignin contents, affect CO2 diffusion and, consequently, mesophyll conductance (gm), but also their known effects driving stress tolerance through mechanisms such as altered cell wall elasticity and water retention, and signalling stress response pathways. New analytical and molecular tools offer an unprecedented set of possibilities to develop biotechnological strategies for sustainable agriculture. We conclude that the CW represents a promising target for crop improvement through genetic engineering and ecophysiological studies, but further research is needed to fully understand the underlying mechanisms and avoid unintended effects on photosynthesis and growth.