Abstract
Sub-surface driveway plants are strong enough to penetrate a macadam surface of thickness 7 – 9 cm. The mechanics of how the Taraxacum officinale accomplishes this feat remain a mystery. Using the Maxwell model for pavement yielding over time, data are presented which may shed some light on this phenomenon. The post-buckling behavior of the plant stalk is quantified. Euler bending and buckling theory enables calculation of the cellular stress field, compared to turgor pressure, indicating impending cell buckling. Post-buckling plastic strain of the plant stem is 19%. At the cell wall, the stress concentration factor is 3-times greater than the applied external field, so the cell’s internal turgor pressure is overwhelmed by imposed external stress. An Impulse Integral is developed for the surface whereby the product of applied FORCE times TIME is CONSTANT, in order to produce a given amount of surface deflection. Taraxacum officinale stems and leaf stalks are strong enough, in buckling mode, to lift and push apart the fractured macadam crater through which they erupt, but not strong enough to initially crack the surface. The purpose of this work is to determine the mechanisms underlying this unusual plant survival phenomenon, backed by quantified data.
Highlights
This paper deals with the interesting topic of how Taraxacum officinale plants manage to grow through apparently impenetrable materials such as asphalt-macadam, Figure 1
It is possible to make some important conclusions about plant and perhaps animal “mechanosensing” at the cellular level, based on the imposed external uni-axial stress field caused by buckling and bending the flower and leaf stems, compared to the cell’s turgor pressure (Baskin & Jensen 2013; Dumais 2013)
The compressive stress due to the external field is magnified 3-times, i.e. there is a “stress concentration factor” of 3.0. This means that the measured axial compressive stress in the celluslose matrix of 23 p.s.i. is augmented to 70 p.s.i. at the cell wall, comparable to the 40 – 80 p.s.i. internal cellular turgor pressure reported by Schopfer (2006) typical for plant cells
Summary
This paper deals with the interesting topic of how Taraxacum officinale plants manage to grow through apparently impenetrable materials such as asphalt-macadam, Figure 1. Commercial products from this plant include latex, and various pharmaceuticals (Kristo et al, 2003). It is possible to make some important conclusions about plant and perhaps animal “mechanosensing” at the cellular level, based on the imposed external uni-axial stress field caused by buckling and bending the flower and leaf stems, compared to the cell’s turgor pressure (Baskin & Jensen 2013; Dumais 2013). The fact that a plant can push through a solid surface suggests impressive biomechanical capabilities worthy of study
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