Shape of Cells Resists Compression

Biological Strategy

Watercress

Alexandra Ralevski

Image: sternbea / Public Domain - No restrictions

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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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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Tetradecahedral-shaped cells allow for maximal packing space while also resisting compression.

Watercress is a species of aquatic plant native to Asia and Europe. It grows in rivers where it is subject to constant pressure from the flow of water, high flow rates after rain, and impact by any debris caught in the current.

Optimally filling a designated space is one of the major challenges of efficient packing. A space is considered to be optimally packed when a maximum number of objects of a designated shape is able to fill a container, with a minimal amount of space between each object. Different shapes offer varied packing efficiencies, depending on the size of the container being filled. Certain packing problems have optimal solutions for different shapes within a given container. For example, there is an optimal packing solution for same-sized circles in a square container.

One shape that is excellent for packing is a tetradecahedron, which has fourteen faces, eight hexagonal and six square, where all the sides of all the hexagons and all the squares are equal. If soft spheres—like plant cells—are squeezed together in a confined space, they will naturally take on a tetradecahedral shape, because this is the optimal packing configuration. Because the cells in this configuration are packed so tightly together, this packing design is also very compression-resistant.

The cells that are packed into the stems of watercress plants are tetradecahedral-shaped, which allows the stem to absorb damage from impact more effectively, making the stem less prone to breaking in fast flowing water.