Department of Physics, Cornell University, Ithaca, NY 14853, USA.
Proc Natl Acad Sci U S A. 2012 Oct 16;109(42):16794-9. doi: 10.1073/pnas.1209287109. Epub 2012 Sep 24.
We study the primary root growth of wild-type Medicago truncatula plants in heterogeneous environments using 3D time-lapse imaging. The growth medium is a transparent hydrogel consisting of a stiff lower layer and a compliant upper layer. We find that the roots deform into a helical shape just above the gel layer interface before penetrating into the lower layer. This geometry is interpreted as a combination of growth-induced mechanical buckling modulated by the growth medium and a simultaneous twisting near the root tip. We study the helical morphology as the modulus of the upper gel layer is varied and demonstrate that the size of the deformation varies with gel stiffness as expected by a mathematical model based on the theory of buckled rods. Moreover, we show that plant-to-plant variations can be accounted for by biomechanically plausible values of the model parameters.
我们使用 3D 时程成像研究了异质环境中野生型苜蓿植物主根的生长。生长介质是一种由刚性下层和柔顺上层组成的透明水凝胶。我们发现，根在穿透下层之前就在凝胶层界面上方变形为螺旋形状。这种几何形状被解释为生长介质调制的生长诱导机械屈曲和根尖附近同时扭转的组合。我们研究了上层凝胶层的模量变化时的螺旋形态，并证明变形的大小与凝胶硬度的变化一致，这与基于屈曲杆理论的数学模型的预期相符。此外，我们表明，通过合理的生物力学模型参数值，可以解释植物间的变化。
