Plants already aid us in countless ways — feeding and clothing us and providing the very air we breathe. Someday, they may also help us find our way to the bathroom at night.
In a paper published on Wednesday in the journal Matter, researchers at South China Agricultural University describe how they created glow-in-the-dark plants by injecting synthetic materials into the tissues of living succulents. These bionic botanicals can be made to emit light in a variety of colors and can “recharge” with light exposure. But they are not yet quite ready for prime time (or bedtime).
The succulents got their glow-up at the university’s Key Laboratory for Biobased Materials and Energy. Researchers at the lab often explore techno-plant mash-ups, as in a 2018 paper describing the use of carbon nanoparticles to make photosynthesis more efficient. For this project, they wanted to create “a living, light-charged plant lamp,” said Shuting Liu, a lab affiliate and the first author of the paper.
Although glowing plants have lent atmosphere to many sci-fi and fantasy worlds, they have existed in our real one only since the 1980s, when researchers at the University of California, San Diego, spliced a gene from fireflies into tobacco plants. More recently, other groups have created light-up plants, including commercially available glowing petunias. Those were made with the genes of bioluminescent bacteria and fungi.
Rather than borrowing from other species, Ms. Liu and her colleagues decided to work with a human-made material called strontium aluminate, the same stuff in the glow-in-the-dark stars you might attach to your bedroom ceiling. Unlike bioluminescence, which is produced by continuous chemical reactions, strontium aluminate exhibits phosphorescence: It soaks up and stores energy from external light, and then releases it slowly over time.
While strontium aluminate has been incorporated into plants before, Ms. Liu wanted to see if she could achieve a brighter and more lasting glow by using larger particles, each around the size of a human red blood cell. For a while, she said, this meant “continuous trial and error” as she injected different plants. In those like bok choy and pothos, the particles became stuck within the plant tissue, with blotchy results.
Eventually, Ms. Liu turned to a rosette-shaped succulent called Echeveria Mebina. In this plant, she found that “the size of the intercellular channels is just right” to produce a uniform glow. “Within just a few seconds, an entire leaf was shimmering,” she said. “I was struck by how beautiful it looked, almost like glowing emeralds.”
After external light exposure, the plants briefly gleam with an intensity equivalent to that of a candle, and they still emit afterglow for at least two hours. By using different materials to make the particles, the researchers created a buffet of colors, with red, orange and multicolored specimens alongside classic mystery-beaker green.
“The luminescent images are beautiful, and the approach clearly works,” said Scott Lenaghan, the director of the Center for Agricultural Synthetic Biology at the University of Tennessee, who was not involved in the research.
But “the applications for the technology, as it stands, are relatively limited,” he said. Achieving a functional plant lamp with this method would require greatly extending the duration of the luminescence, a significant challenge, he said.
In addition, the technique undercuts the eco-friendly promise of a self-lighting plant. Although plants tweaked in this way could hypothetically be low-energy light sources, they are filled with synthetic materials whose eventual impact is unknown. “What happens to the microparticles once the plant dies?” Dr. Lenaghan asked. “This should be a primary concern for any of these man-made technologies.”
Ms. Liu agrees there is much work to be done, including to reduce environmental impact, and she hopes other researchers will join in. “At this stage, our priority was to establish the proof of concept,” she said.
She is still dreaming of a plant night light, which she pictures as “a small succulent under a glass dome, quietly glowing on its own in the evening,” she said. “I do believe this will become a reality.”
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