Plant roots exhibit nontrivial architecture to optimize absorption of nutrients and water. During my undergraduate study in the Cohen lab, I studied the role of mechanics in plant root gravitropism. By imaging the Medicago truncatula primary root morphology growing on different tilt angles and applying tools from statistical mechanics, I showed that plant roots navigate their environment using a strategy similar to that used by the bacteria E. Coli. Essentially, the plants switch their growth direction more frequently and towards the downhill direction at a rate proportional to the angle between the root tip and the direction of gravity. This ‘grow-and-switch’ mechanism explains the different root patterns such as coiling and waving. These results suggest a method for controlling root architecture to enhance agricultural crop yields. More generally, these results speak to the subtle interplay between root biology and mechanics that produces the amazing morphologies roots create as they grow.
Tan TH, Silverberg JL, Floss DS, Harrison MJ, Henley CL and Cohen I, (2015) “How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula.” Proceedings of the National Academy of Sciences, 112(42), pp.12938-12943. | See also research highlight in Nature Physics 11 (2015) and Cornell Chronicle report.