Toxic metals increase root hair density by reducing epidermal cell length

Abstract Root hair cells, which are instrumental in water and nutrient uptake, grow polarly from the epidermal cell layer of the root. Furthermore, plants growing in challenging climates and complex soil environments acclimatize their root hair phenotypes, either by altering root hair length or density. Toxic metal stress is one of the major environmental stresses faced by plant roots. In this study, we demonstrate that toxic metals, such as chromium and arsenite, increase root hair density as an adaptive response. Using the model plant Arabidopsis thaliana and other crops plants, like Zea mays and Triticum aestivum , we further discovered that increased root hair density is caused by shorter epidermal cell length rather than alteration of epidermal cell fate. This study highlights the adaptive cellular and anatomical features of roots during toxic metal stress in evolutionary diverse plant species.