Fig. 7.

Gravitropism versus phototropism. In A–E, a fixed light source is located to the right, at the point (4,1), while gravity points vertically downward. For each parameter set, the tropic response is simulated for the same total time and with equivalent axial growth. The evolving plant shape, deformed under self-weight, is shown in increasing time from yellow to blue, with the unstressed shape appearing as a dashed line. The moment at the base for the four cases is plotted against time in E. F depicts the setup for a plant escaping from the shade under a rigid obstacle. The phototropic signal points either horizontally, if the tip is under the shade, or vertically, if the tip is out of the shaded region. (G) A sample simulation showing a successful escape. Further simulation details and parameters are provided in SI Appendix, section 8.