Mechanical coordination of counter-gradient growth maintains organ curvature in the apical hook

How growing tissues convert mechanical forces to stable organ shapes remains a central question in morphogenesis. Curved organ shapes in plants arise from differential growth, yet how curvature is actively maintained while organs continuously grow remains poorly understood. In etiolated seedlings, the apical hook provides a tractable model to dissect this process. Using quantitative imaging, computational modelling, and genetics, we show that antagonistic growth gradients at apical and basal regions are required to sustain hook curvature during growth. Cuticle integrity is a key regulator of these opposing growth programs, linking tissue mechanics to spatial control of cellular elongation. Furthermore, reactive oxygen species (ROS) act downstream of mechanical cues to coordinate growth responses across the tissue. Together, these findings identify a mechanochemical feedback mechanism that maintains organ curvature during continuous growth by stabilizing opposing growth domains. This work provides a mechanistic framework for how developing tissues preserve shape under ongoing growth.