The gravitropic set-point angle (GSA) defines the orientation of roots relative to gravity and is a central determinant of root system architecture (RSA). By shaping soil exploration patterns, GSA influences plant anchorage, water and nutrient uptake, stress resilience, and rhizosphere interactions. While dicots and monocots differ fundamentally in RSA, recent studies described that core regulators of GSA, including gravity sensing, auxin transport, and hormonal crosstalk are conserved. Arabidopsis thaliana has served as a model plant to uncover the molecular basis of GSA. Integrating discoveries from multiple model and crop systems now provides a systems-level view of how plants regulate root distribution. Beyond hormonal networks, GSA integrates mechanical cues, cytoskeletal dynamics, calcium and pH gradients, and environmental inputs, providing plants with remarkable developmental plasticity. This review compares conserved and lineage-specific mechanisms across plant groups. Finally, we outline molecular targets of GSA as breeding traits to optimize RSA for resource efficiency and climate-resilient agriculture.
Choudhary et al. (Thu,) studied this question.