The twining habit has evolved countless times among plants and clearly provides an easily derived strategy for reaching the canopy with little investment in structural tissues. However, the form of the twining helix shows a consistency in radius of curvature across different support sizes that defies easy explanation and calls obvious hypotheses for the twining mechanism into question. With Alex Guth, I have been working to determine how the growth response of the vine stem, circumnutation (a periodic bending of growing plant axes), and vine mechanical properties might interact to allow twining.

Our approach is based on the observation that both circumnutation and a relatively low torsional modulus (relative to bending modulus) are characteristics shared among plants. Because the final form of the twining helix is achieved outside the growing region of the stem, we suspect that mechanical deformation of the stem by the forces generated through circumnutation plays a role in morphogenesis.