Plants Survive Repeated Drying and Rehydration

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Biological Strategy

Lesser clubmoss plants

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Fatigue

When materials that comprise living systems are subjected to repeated loads, they can weaken over time. This is called fatigue and it can lead to cracks and eventually failure. However, fatigue doesn’t occur just anywhere on a material; the cracks usually start in areas subjected to elevated local stresses. Therefore, living systems often employ shapes, materials, and/or smooth transitions to decrease the potential for fatigue. An example of using shape is found in brown algae, an intertidal seaweed. Rather than being bent by the constant flow forces of waves and currents, its shape causes it to be pulled. This reduces stress by roughly 800 times compared to another species that bends with the flow, ultimately reducing structural fatigue.

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Ferns

Class Polypodiopsida (“many footed appearance”): Ferns, horsetails, whisk ferns

Ferns are a class of plants that reproduce without flowers or seeds, but by spores. With over 10,500 known species, ferns are the second most abundant group of vascular plants after angiosperms (flowering plants). Though they can be found in a variety of habitats, ferns prefer moist, humid environments. Ferns first evolved in the Carboniferous Period about 360 million years ago. Today, ferns are grown for food, medicine, ornamental landscaping, and hold importance in culture and folklore. Several species can also remove pollutants from the atmosphere.

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The cells of lesser clubmoss plants prevent deformation during repeated dehydration via small vacuoles filled with mechanical mixtures called colloids.

“Some plants, for example, in the genus Selaginella, can repeatedly dry and rehydrate without structural damage. They avoid critical cell deformations during severe dehydration by using vacuoles of smaller size that are filled with tannin colloids instead of ions. Upon dehydration these colloids undergo minimal volume changes (Walter, 1956). Nature itself points here to the interesting alternative of replacing crystallizing small molecules with larger-sized colloids. ” (Bar-Cohen 2006:476)

Bar-Cohen Y. Biomimetics: biologically inspired technologies. Bar-Cohen Y, editor. Boca Raton, FL: CRC/Taylor & Francis; 2006. 527 p.

Last Updated September 14, 2016

References

Book

Biomimetics: Biologically Inspired Technologies

CRC/Taylor & Francis | 02/11/2005 | Yoseph Bar-Cohen

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