Sclereid Cells Prevent Soft Tissue Collapse

a cross section of water lily photographed at 40x shows round green cells and a stripe of long, thin green and purple cells

Biological Strategy

Plants

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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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Sclereid cells in vascular plants help prevent the collapse of soft tissues during water stress via thick, lignified walls.

“Sclereids are also cells with thick, lignified walls. They are grouped with fibres under the general term sclerenchyma. They differ from fibres in generally being shorter in relation to their length, but there is some overlap in the range of cells. They may be branched, sinuous or short — often more or less isodiametric. The longer ones commonly feature in the sheaths to veins, particularly near the ends of the finer branches. They can be pit-prop-like when they extend between the upper and lower surfaces of leaves, and appear to help prevent collapse of softer tissues at times of water stress, as in olive leaves and the leaves of many mangrove plants. These plants, and many of the hard-leaved plants found in arid habitats, often have abundant elongated or branched sclereids.” (Cutler 2005:104)

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