Rod-like Reinforcements Provide Strength

microscopic cross section of vascular plant with white background blue cells and magenta spots

Biological Strategy

Plants

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Image: Marc Perkins / Flickr / Some rights reserved

Distribute Liquids

Liquids include water, as well as body fluids such as blood, gastric juices, nutrient-laden liquids, and more. To survive, many living systems must move such liquids within themselves or between locations. Because of their properties, liquids tend to disperse unless they are confined in some way. To address this, living systems have strategies to confine fluids for transport, and to overcome barriers such as gravity, friction, and other forces. Some of these same barriers also provide opportunities. Trees and giraffes face the same challenge: how to move fluids (water and blood, respectively) upward against gravity. But their strategies are quite different. The tree moves water using capillary action and evaporation, possibly due to water’s properties of polarity and adhesion. The giraffe’s tight skin provides pressure to assist in blood circulation. and keep blood from pooling in the legs.

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Manage Compression

When a living system is under compression, there is a force pushing on it, like a chair with a person sitting on it. When evenly applied to all sides of a living system, compression results in decreased volume. When applied on two sides, it results in deformation, such as when pushing on two sides of a balloon. This deformation can be temporary or permanent. Because living systems must retain their most efficient form, they must ensure that any deformation is temporary. Managing compression also provides an opportunity to lessen the effects of other forces. Living systems have strategies to help prevent compression or recover from it, while maintaining function. For example, African elephant adults weigh from 4,700 to 6,048 kilograms. Because they must hold all of that weight on their four feet, the tissues of their feet have features that enable compression to absorb and distribute forces.

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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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Vascular bundles in plants provide mechanical strength, serving as rod-like reinforcements.

Image: Louisa Howard, Charles Daghlian, Dartmouth Electron Microscope Facility /

Scanning electron microscope image of a x-setion through Tradescantia virginiana stem. Image shows vascular bundles in a ring, with a central pith.

Image: Louisa Howard, Charles Daghlian, Dartmouth Electron Microscope Facility /

Scanning electron microscope image of x-section through Coleus blumei [coleus] stem. Image shows outer epidermal layer, cortex, vascular bundles in a ring, and a central pith.

“Figure 5: Part of a stem of a robust grass, in cross section. Here mechanical strength of the stem is provided by the vascular bundles set in a matrix of thinner-walled cells, rather like rod reinforcements. Each vascular bundle has an outer sheath of fibres, forming a strong tube in which the two wide vessels can conduct water, and the strand of thin-walled, narrow cells (phloem) can transport sugar solutions with little risk of damage. Just to the inner side of the outer ring of smaller vessels the several layers of narrow cells eventually become thick-walled and provide additional strength in the form of a cylinder to the whole stem.” (Cutler 2005:101)

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