Helical Buckling of Plant Roots 2

Root in gel of intermediate stiffness.

Full details at: http://cohengroup.ccmr.cornell.edu/re...

As global climates change, agriculture and crop breeding programs must increase productivity to meet the demands of growing populations while simultaneously facing decreases in soil quality. For example, desertification of topsoil and compactification of subsurface soil produces mechanical barriers to root growth and challenge the ability of plants to find nutrient resources. To explore how plants respond to these growth conditions, we developed a model system consisting of a 3D layered hydrogel. The hydrogel has two layers: A stiff lower layer and a compliant upper layer. Medicago truncatula plants were then planted in the top gel and their growth over the next 100 hours was monitored. Remarkably, we find that Medicago roots developed a helical morphology just above the gel/gel interface before penetrating into the stiff lower layer.

To study root growth, we developed a 3D time-lapse imaging stage that allows us observe growth dynamics and allow us to quantify root structure. In essence, our apparatus combines a laser sheet, a translating stage, and a digital camera to scan the region of root growth and record a series of images that are reconstructed on a computer. Using this automated system, we were able to directly observe obstructed root growth and the formation of the buckled root morphology. The time-lapse movie shown here illustrates buckling followed by an elastic relaxation of the root-in-gel system that occurs after the root has penetrated into the lower layer.

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