Coordination of cortex modifications in time, space, and under stress.

In roots, cell-type-specific differentiation enables specialized responses to environmental stress. The cortex, located between the vasculature and epidermis, is a key site for stress-responsive modifications. The distinct specializations of the cortex are controlled by developmental, positional and environmental signals. Cortex layers are developmentally and transcriptionally diverse, with capacities of forming protective barriers such as endodermis and exodermis and other cell-type modifications such as multiseriate cortical sclerenchyma and aerenchyma to aid in edaphic stress tolerance. Additionally, the cortex is essential in forming nitrogen-fixing nodules and arbuscules, and therefore symbiotic interactions. These modifications enhance stress resilience by regulating the two-way fluxes of water, solutes and nutrients between the soil and the plant, increasing mechanical strength or facilitating biotic interactions. Understanding how cortex modifications coexist, synergize to influence plant fitness, or compensate for each other remains a challenge. Future research should focus on their combined effects across root types to reveal trade-offs and optimize stress protection.