The root cortex of the Poaceae: a diverse, dynamic, and dispensable tissue.

Background: The root cortex in Poaceae is a diverse, dynamic, and dispensable composite layer of tissue. Early in plant growth, the cortex in Poaceae roots primarily consists of parenchyma cells. However, as the root continues to develop, while encountering varying environmental conditions, the cortex undergoes substantial structural and functional changes. These modifications involve either cell wall modifications or programmed cell death, to form tissues including the endodermis, exodermis, sclerenchyma, and aerenchyma, or to result in cortical senescence. The dynamic spatial architecture of these tissues plays a crucial role in storage, microbial interactions, physical protection, biosynthesis of metabolites, and the radial movement of water, nutrients, and gases, and therefore, biotic and abiotic stress tolerance. Scope: Here, we aim to explore cortical tissues in axial roots of Poaceae and how their capacity for plastic responses to environmental cues underscores their role in plant adaptation and climate resilience. We also highlight key research gaps and opportunities to facilitate our understanding of this composite layer of tissue and its role in plant stress response and rhizosphere interactions. Conclusions: Axial root cortical tissues and their capacity for dynamic change are major drivers of adaptation and resilience in the Poaceae. Understanding the function and variability of root cortical tissues has potential to improve plant stress tolerance to a number of abiotic and biotic factors across a range of species and environments. Cortical tissues, and the plasticity thereof, may be useful breeding targets for improved soil resource capture and stress tolerance.