Two-Phase Composite Tissues Handle Tension

Biological Strategy

Dutchman's pipe

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Manage Tension

When a living system is under tension, it means there is a force pulling on it, like a person pulling on a rope tied to a horse. When applied to a living system, unless the system is completely rigid, the result is that it gets stretched. If stretching exceeds the strength of the living system’s material, it can damage it. Living systems manage tension using materials that are flexible and stretchable enough to survive most tension that occurs in their environment. The ocean’s intertidal zone offers a good example. The waves and incoming and outgoing tides put tension on soft-bodied organisms. Mussels resist tension with flexible threads that hold them onto rocks; in contrast, large algae have stretchy fronds.

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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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Plant tissues resist pulling forces using layers of tiny cellulose fibers embedded in a mix of flexible and strong materials.

Introduction

Dutchman’s pipe (Aristolochia macrophylla) is a deciduous vine native to the eastern United States. It thrives in moist, well-drained soils and often climbs trees and fences in forests and gardens. Known for its large, heart-shaped leaves and unique pipe-shaped flowers, the dutchman’s pipe has developed remarkable structural adaptations that allow it to withstand various mechanical stresses in its environment.

The Strategy

The dutchman’s pipe exhibits a fascinating example of mechanical in its tissues. As a climbing vine, it must endure significant mechanical forces such as bending, twisting, and pulling, especially as it wraps around structures to gain height. The key to its mechanical resilience lies in the specialized structure and composition of its plant tissues, which extend beyond the typical simple elasticity observed in many plants.

The plant tissues of the dutchman’s pipe are composed of a network of fibers embedded in a matrix of hemicellulose and lignin. Cellulose fibers provide strength to resist pulling forces, much like steel rods in reinforced concrete, while hemicellulose and lignin act as the glue that holds everything together, offering compressive strength and flexibility. This combination allows the plant to bend without breaking, a property essential for climbing vines that need to wrap around various supports.

When subjected to mechanical stress, the cellulose fibers in the dutchman’s pipe can realign and slide past one another, allowing the plant to deform without breaking. This deformation means the plant can absorb and dissipate energy, making it more resilient to environmental forces such as wind or the weight of the vine itself. The study by Köhler and Spatz (2002) delves into these mechanical properties, showing that plant tissues like those in the dutchman’s pipe exhibit behavior beyond simple elasticity, including plasticity (the ability to bend without breaking) and viscoelasticity (the ability to slowly return to their original shape). These properties enable the vine to endure and adapt to dynamic and unpredictable mechanical stresses in its habitat.

The Potential

Understanding the micromechanics of the dutchman’s pipe can inspire innovative designs in various fields. For instance, engineers can develop flexible and resilient materials for construction that mimic the plant’s ability to bend without breaking. Such materials could be used in buildings or structures in earthquake-prone areas, where the ability to absorb and dissipate energy is crucial.

Additionally, the composite nature of the plant tissues—combining strength and flexibility—can inform the creation of advanced materials for sports equipment, protective gear, and even biomedical devices like flexible prosthetics. These materials would be lightweight yet durable, providing both strength and flexibility.

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Last Updated June 19, 2024

References

“The first portion of the biphasic stress-strain curve, exhibiting a high modulus of elasticity and little viscoelasticity, is due to elastic extension. The second portion is explained by yielding of the matrix and slippage of the microfibrils past each other. This leads to a decreased modulus of elasticity and a much higher viscoelasticity. The extension during the first phase causes the microfibrillar angle to decrease…In our case, the cellulose microfibrils may have the ability to align more in the direction of the applied strain and in turn take up increasingly more load.” (Kohler and Spatz 2002:38,40)

Journal article

Micromechanics of plant tissues beyond the linear-elastic range.

Planta | May 2002 | Kohler, L.; Spatz, H.C.

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