Root Hair Development and Adaptation to Abiotic Stress.

Root hairs tie the root system to the soil substrate, facilitate water and nutrient absorption, and enable the interaction with microbes in the soil. Root hair development can be classified into three main development types (I-III). Root hair development type III has been extensively studied, mainly represented using the model plant Arabidopsis thaliana . Transcription factors, plant hormones, and proteins are involved at different root hair developmental stages. The mechanisms underlying development in types I and II have been examined using other representative plant species but have not been studied as intensively. Many key developmental genes in types I and II are highly homologous with those in type III, exhibiting conservation of related mechanisms. Root hairs are also involved in the regulation of plant response to abiotic stress by altering developmental patterns. Abiotic stress, regulatory genes, and plant hormones jointly regulate root hair development and growth; however, few studies have focused on how root hair recognizes abiotic stress signals. This review examines the molecular mechanisms of root hair development and adaptations under stress, and prospective future developments in root hair research are also discussed.