Development and Regulation of a Radial Oxygen Loss Barrier to Acclimate to Anaerobic Conditions

Internal aeration is crucial for root growth under waterlogged conditions. Many wetland plants have a structural barrier that impedes oxygen leakage from the basal part of roots called a barrier to radial oxygen loss (ROL). ROL barriers reduce the loss of oxygen transported via the aerenchyma to the root tips, enabling long-distance oxygen transport for cell respiration at the root tip. Because the root tip does not have an ROL barrier, some of the transferred oxygen is released into the waterlogged soil, where it oxidaysizes and detoxifies toxic substances around the root tip. The main component of an ROL barrier is thought to be suberin accumulated at the exodermis. Suberin deposits block the entry of potentially toxic compounds in highly reduced soils. The amount of ROL from the roots depends on the strength of the ROL barrier, the length of the roots, and environmental conditions, which cause spatiotemporal changes in the root system’s oxidization pattern. Here, we summarize recent achievements in understanding how ROL barrier formation is regulated.