To grow in paddy fields, roots of rice plants form aerenchyma and radial O2 loss (ROL) barrier (i.e. a barrier that reduces oxygen leakage from basal part of root) to facilitate internal aeration. The ROL barrier not only completely blocks radial O2 diffusion but also works as a barrier to radial water loss in basal parts of the roots. 
In rice roots, aerenchyma constitutively forms even under aerobic conditions and is induced under oxygen-deficient conditions. The former and latter are respectively designated as “constitutive” and “inducible” aerenchyma formations. Recently, we demonstrated that AUX/IAA proteins-mediated auxin signaling was involved in constitutive aerenchyma formation in rice roots (Yamauchi et al., PNAS 2019). We also found that production of reactive oxygen species (ROS) and calcium signaling were essential for inducible aerenchyma formation in rice roots (Yamauchi et al., Plant Cell 2017; Li et al., Plant Physiol. 2024).

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