Convex Surface Geometry Resists Adhesion

a pile of yellow zucchini stacked vertically at a farmers market

Biological Strategy

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Protect From Dirt/solids

When dirt and other small solids adhere to living systems, they can slow them down, create blockages, reduce their ability to carry out vital functions, or cause surface wear and tear. Due to electrostatic forces, it’s easy for dirt and other solids to adhere to surfaces, so living systems must overcome those forces. An earthworm, for example, uses a small electric current to keep soil particles from adhering to its body as it moves through the soil. This enables it to move more efficiently by reducing drag.

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Plants

Phylum Plantae (“plants”): Angiosperms, gymnosperms, green algae, and more

Plants have evolved by using special structures within their cells to harness energy directly from sunlight. There are currently over 350,000 known species of plants which include angiosperms (flowering trees and plants), gymnosperms (conifers, Gingkos, and others), ferns, hornworts, liverworts, mosses, and green algae. While most get energy through the process of photosynthesis, some are partially carnivores, feeding on the bodies of insects, and others are plant parasites, feeding entirely off of other plants. Plants reproduce through fruits, seeds, spores, and even asexually. They evolved around 500 million years ago and can now be found on every continent worldwide.

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Plant leaves resist adhesion of water and dirt due to convex geometry on their surface.

Image: Wildfeuer / Wikimedia Commons /

Image: Lmbuga / Wikimedia Commons /

“Non-smoothness is a common natural phenomenon in [the] biological world, which has been formed during the long evolutionary process of living creatures as a stable, self-adaptive system. The non-smooth surfaces of plants, resulting from long interaction between self-growing mechanism and external environment, exert several important functions, such as water repellency, anti-adhesion, and self-cleaning.” (Ren et al. 2007:33)

Last Updated September 14, 2016

References

Journal article

Non-Smooth Morphologies of Typical Plant Leaf Surfaces and Their Anti-Adhesion Effects

Ren, Lu-quan; Wang, Shu-jie; Tian, Xi-mei; Han, Zhi-wu; Yan, Lin-na; Qiu, Zhao-mei

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