Root morphogenetic responses to waterlogging stress in plants: from structural reconfiguration to molecular...

Climate change is increasing the frequency of extreme rainfall events, making waterlogging a major constraint on crop production. Waterlogging imposes a composite stress on plants by causing rhizosphere hypoxia and promoting the accumulation of toxic reduced compounds. Root morphological plasticity is a central adaptive strategy under these conditions. It relies on the coordinated deployment of four linked modules: adventitious root (AR) formation, aerenchyma development, barrier formation to radial oxygen loss (ROL), and root system architecture (RSA) remodeling. These responses are initiated by ERF-VII-dependent hypoxia sensing and further shaped by ethylene-auxin interactions, ROS/Ca²⁺ signaling, gaseous regulators such as NO and H₂S, and the capacity for metabolic reprogramming and carbon reallocation. Differences among species and genotypes likely reflect variation in signaling sensitivity, regulatory-network organization, and metabolic efficiency. In this review, we integrate current knowledge across three levels: root morphological modules, their regulatory networks, and rhizosphere constraints. We highlight key leverage points for improving waterlogging tolerance and propose a mechanistic framework to support both crop breeding and field management under increasingly flood-prone conditions.