Fluorophores Enhance Photosynthesis

close up a green pine tree with purple tones on the branches in the sunlight

Biological Strategy

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Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Transform Radiant Energy (Light)

The sun is the ultimate source of energy for many living systems. The sun emits radiant energy, which is carried by light and other electromagnetic radiation as streams of photons. When radiant energy reaches a living system, two events can happen. The radiant energy can convert to heat, or living systems can convert it to chemical energy. The latter conversion is not simple, but is a multi-step process starting when living systems such as algae, some bacteria, and plants capture photons. For example, a potato plant captures photons then converts the light energy into chemical energy through photosynthesis, storing the chemical energy underground as carbohydrates. The carbohydrates in turn feed other living systems.

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Capture, Absorb, or Filter Energy

Energy is naturally available in many forms, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities, and have developed strategies appropriate to one or more of those forms. For example, some plants maximize their surface area available for capturing radiant energy from the sun while others have strategies to focus scattered light onto photosynthesizing areas.

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Conifers and Others (Pines, Spruce, Gingko)

Clade Gymnosperms (“naked seeds“): Conifers, cycads, Gingko, gnetophytes

There are approximately 1,000 known species of Gymnosperms. These include well known needle-bearing plants like pines, firs, and spruce, as well as some with broad leaves like the Gingko and the gnetophytes. Instead of flowers, gymnosperms produce unenclosed (“naked”)seeds exposed on the surface of cone scales. Economically, conifers make up 45 percent of the world’s lumber production. The first gymnosperms evolved over 390 million years ago in the Paleozoic Era and dominated landscapes for a quarter of a billion years before the evolution and diversification of flowering plants.

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The cuticular wax of the dwarf mountain pine enhances photosynthesis by using fluorophores that convert UV light into blue light that can be used for photosynthesis, even under low-light conditions.

Introduction

The dwarf mountain pine (Pinus mugo), native to the high elevations of the Alps, thrives in an environment exposed to high levels of UV radiation. Due to their long-lived foliage, these pines are more susceptible to UV damage, requiring an effective protective . Unlike many plants which produce seed seasonally, the mountain pine produces seed all-year round. The production and development of these seeds requires significant amounts of energy from .

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Pinus mugo Terra

The Strategy

Plants normally absorb light in the visible spectrum, and scatter or filter UV light because it can be damaging to multiple plant processes. However, the leaves of the dwarf mountain pine contain a waxy cuticle loaded with fluorophores––small, organic molecules that can absorb ultraviolet light and convert it into visible blue light.

When a fluorophore absorbs a photon of light, it gets excited from its ground state to a higher-energy excited state. After a brief period, it returns to a lower-energy state, releasing the excess energy as a photon of light with a longer wavelength.

This conversion protects the plant and even enhances photosynthesis, giving the trees an ecological advantage, particularly in low-light conditions.

The Potential

Humans could learn from this natural strategy to develop technological innovations for protection against harmful radiation. The UV protective cuticular layer could be mimicked to provide a UV protective coating, transforming the harmful part of radiation into usable energy. This concept could be applied to make solar cells more efficient by adding a fluorescent coating that converts an unexploited high-energy fraction into useful radiation.

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Last Updated August 31, 2023

References

Journal article

UV protective coatings: A botanical approach

UV protective coatings: A botanical approach. Progress in Organic Coatings. 58(2-3): 166–171. | Jacobs JF, Koper GJM, Ursem WNJ.

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