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Plants and algae, surprisingly similar, yet uniquely different

Both land plants and marine microalgae play crucial roles in their respective ecosystems, although they differ significantly in size and efficiency. Both are essential for oxygen production and for transforming electromagnetic radiation into usable energy. However, they both face a common challenge: the phenomenon of self-shading. This phenomenon limits their efficiency and has implications beyond the biological realm, including renewable energy technology like solar cells.

Photosynthesis is a vital process that allows the transformation of solar energy into stored chemical energy and ultimately into food for various forms of life. Although this process is essential for the survival of complex organisms like humans, it is limited by several factors, one of which is self-shading.

In terrestrial plants, the morphology of leaves, whether large or small, is heavily influenced by the amount of light available in their immediate environment. For instance, in regions where sunlight is abundant, plants tend to develop larger leaves to maximize the surface area for capturing photons. However, this natural design advantage comes with a drawback—self-shading. As the outer leaves grow larger and more expansive to capture sunlight, they inevitably create a canopy that shades the inner, lower leaves. This overshadowing reduces the overall efficiency of the photosynthetic process, which is essentially the conversion of captured photons into usable chemical energy stored in the form of carbohydrates.

Similarly, marine microalgae residing in water columns also face the conundrum of self-shading. The cells located closer to the water surface are in a prime position to intercept the majority of incoming sunlight, rich in the photons necessary for photosynthesis. However, this effectively hampers the light penetration to the cells situated deeper in the water column. These deeper-lying cells are thereby deprived of adequate light, diminishing the collective photosynthetic efficiency of the microalgal community. In fact, it's commonly observed that in aquatic environments densely populated by algae, light penetration seldom exceeds a depth of 2 cm. This poses a significant limitation on the energy conversion process within these communities.

A Successful Strategy to Reduce Self-Shading by Marine Corals

Symbiotic microalgae in marine corals have solved the problem of self-shading through symbiosis with the coral (polyp). Corals receive nutrients and carbon for building their calcareous skeletons, while microalgae gain a protected habitat and an enhancement in light capture. This latter aspect is achieved through "scattering," or the dispersal of light that occurs through the calcareous structure of the coral (Enriquez, 2005; Teran, 2010). This phenomenon improves the efficiency of photosynthesis in microalgae, making this ecosystem especially resilient and productive, as evidenced by the Great Barrier Reef in Australia.


The phenomenon of self-shading poses challenges for both plants and microalgae and has significant implications in the field of renewable energies. However, nature provides us with an exceptional example of how to overcome this obstacle: the symbiosis between corals and microalgae. This phenomenon could inspire technological innovations in areas like the development of more efficient solar cells, once again showing that careful observation of the natural world could offer solutions to our most pressing problems.

Emiliano Terán


  • Terán, E., Méndez, E. R., Enríquez, S., & Iglesias-Prieto, R. (2010). Multiple light scattering and absorption in reef-building corals. Applied optics, 49(27), 5032-5042.

  • Enríquez, S., Méndez, E. R., & ‐Prieto, R. I. (2005). Multiple scattering on coral skeletons enhances light absorption by symbiotic algae. Limnology and Oceanography, 50(4), 1025-1032.


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