A species of begonia living on the floor of tropical rainforests has blue leaves because of a trick of quantum mechanics that allows the plant to extract a greater amount of energy from dim light and prevents it from dying out, according to a new University of Bristol study.
In fact, as Dr. Heather Whitney and her colleagues explained in Monday’s edition of the journal Nature Plants, the Malaysian species Begonia pavonina uses a type of nanotechnology known as photonics to create special structures in their leaves that allow them to effectively harvest energy in low-light conditions, but which causes their leaves to turn a shiny cobalt color.
These blue leaves, Popular Mechanics and Gizmodo said, enable the begonias to wring a greater amount of energy from the slight amount of red-green light that travels through the forest canopy and makes it to the floor of the rainforest. The new research shows that the coloring of the plants is essential for their survival and is not simply for appearance sake, the authors noted.
“It’s actually quite brilliant,” Whitney told Popular Mechanics on Monday. “Plants have to cope with every obstacle that’s thrown at them without running away. Here we see evidence of a plant that’s actually evolved to physically manipulate the little light it receives. It’s quite amazing, and was an absolutely surprising discovery.”
Findings could be used to improve solar cells, increase crop yields
The Bristol team’s research solves a longstanding mystery surrounding these blue leaves, which some experts has hypothesized may have been an adaptation to scare off potential predators or a way to prevent the plant from being exposed to more light than it could handle. In fact, the study authors found that exposing the plants to more light caused the blue color to slowly fade.
“We discovered under the microscope, individual chloroplasts in these leaves reflected blue light brightly, almost like a mirror,” Matt Jacobs, a doctoral student at the Bristol School of Biological Sciences and the first author of the study, explained in a press release. “Looking in more detail by using a technique known as electron microscopy, we found a striking difference between the ‘blue’ chloroplasts found in the begonias… and those found in other plants.”
These chloroplasts, which Jacobs said are also called iridoplasts because of their blue coloration, were found to possess a photonic crystal structure comprised of uniform layers that were only a few hundred nanometers thick, or approximately 1,000th the width of a human hair. The Bristol team, known that these structures were small enough to interfere with blue light waves, began to explore for a possible link between the chloroplasts and the blue color of the begonia leaves.
They found that the structures appeared to be similar to artificial constructs often used to make lasers and other light-controlling photonic devices, and sure enough, performing the exact same optical measurements used on those components provided a great deal of insight into the natural structures found in the plants. They found that the crystal structures reflect blue light and absorb green light, useful since the trees that make up the forest canopy above them tend to absorb blue light and leave nothing but green light for the plant life on the rainforest floor.
In short, the begonias essentially evolved to become green light scavengers, and while that part of the mystery is solved, the researchers noted that there are still many questions left to answer. For instance, could this same design be used by scientists to modify crops and increase yields, or to improve electronic devices? And just how common is this adaptation in nature?
Whitney told Gizmodo that she believes that this trait could be “more common than currently thought. Several of the Begonia species that we know have these photonic irioplasts do not look visibly iridescent – and we know that a wide range of other plants produce similar structures, but haven’t been investigated yet.” She also noted that the research could help improve “solar energy capture” and “could serve as inspiration for future work” in that field.
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Image credit: University of Bristol
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