Cell wall dynamics and biomechanics of root hair morphogenesis

Root hairs are specialized extensions of root epidermal cells that allow plants to explore and attach to the soil. They exhibit polar growth under the influence of isotropic turgor pressure thanks to the anisotropic nature of their cell walls. This unidirectional growth is regulated by myriad subcellular factors such as microtubule and actin dynamics, a tip-focused calcium gradient, and the interplays between gradients of apoplastic and cytosolic pH and reactive oxygen species. All these players also influence cell wall dynamics by forming feedback loops that modulate cell wall assembly and modification, which are essential processes for root hair morphogenesis. In this review we discuss the functions of cell wall polysaccharides and proteins and their impacts on the biomechanics of root hair growth at each developmental stage. We also discuss important open questions and technical advancements in studying root hair mechanobiology. Despite significant progress, many of the spatiotemporal changes that occur in the cell walls of root hairs remain undiscovered. Therefore, we highlight ongoing research and exciting future avenues that will shed light on cell wall dynamics, biomechanics, and mechanobiology of root hair morphogenesis.