How do plant roots overcome physical barriers?

Soil drying and compaction increase mechanical impedance, a common problem in agricultural soils that adversely impacts crop productivity. Plant roots with improved capacity to penetrate hard soil layers can more efficiently explore nutrients and water available in deeper root zones. In this issue, Bello-Bello et al. (2022a) demonstrated that auxin dynamics have a critical role in facilitating root penetration into hard barriers, and mapped a large-effect quantitative trait locus (QTL), ROOT PENETRATION INDEX 3, associated with primary root penetrability in Arabidopsis thaliana. These findings give new insights into the regulatory role of auxin signaling in root penetrability and shed light on related natural genetic variation for this important trait.