Internal stress controls tendril writhing dynamics in climbing plants
2026-07-13
We present experimental results on the writhing dynamics of cucumber plant tendrils subjected to an axial traction force. At low forces, the tendrils’ curvature saturates exponentially in time at a limiting value. At forces higher than the critical threshold, the tendril fails to coil but develops an intrinsic coiling-prone stress, corresponding to an intrinsic residual curvature, visible if the load is released. Growth-field assessments indicate that curvature arises from differential growth. To understand these experiments we develop an autotropic morphoelastic growth model with a bi-strip geometry, in which one strip undergoes mechanosensitive growth. In the absence of an external load, curvature generation is solely limited by internal stresses. To link the actual curvature to a finite external force, the tendril is approximated as a Kirchhoff rod. The resulting model reproduces the two observed regimes: below the critical axial force, the tendril coils, and above this force, the tendril remains straight but still exhibits intrinsic curvature.