MIT scientists borrow from fireflies to make glowing plants

The humble house plant could soon start earning its keep by lighting up a room, if new research from MIT pans out. Engineers have hacked watercress plants to make them glow for a few hours at a time, and while it's currently only about as bright as those old stars you might have stuck to your ceiling as a kid, the long-term plan is to develop plants that you could read by to reduce the need for electric lighting.

The idea of a glowing plant is not particularly new. They've been promised by Kickstarter campaigns for years, including the likes of Bioglow and Glowing Plants, but those startups have since gone bust. Although we're not going to pretend that this new project is immune from meeting the same fate, having the backing of MIT scientists gives us a little more hope that the glowing plants might eventually bear fruit.

The work comes from the same "plant nanobionics" team that recently designed explosive-detecting spinach and leaf sensors that can alert farmers at the first sign of thirsty crops. In this case, the researchers wanted to tackle lighting, which accounts for about 20 percent of energy consumption worldwide.

"The vision is to make a plant that will function as a desk lamp – a lamp that you don't have to plug in," says Michael Strano, senior author of the study. "The light is ultimately powered by the energy metabolism of the plant itself."

To make them glow, the scientists embedded specially-designed nanoparticles into the leaves of watercress plants. Three different components were needed for the effect, each one placed inside a carrier nanoparticle.

Fireflies get their glow through the interaction between an enzyme called luciferase and a molecule called luciferin, so both of these were added. Finally, their activity was boosted by a molecule called co-enzyme A. These components were packaged inside nanoparticles and suspended in a solution.

The next step was to soak the plants in that solution and pressurize them, which causes the particles to enter the leaves through tiny pores called stomata. The luciferin and coenzyme A were packaged inside polymer nanoparticles that enter and build up in an inner layer of the leaf, while the luciferase was contained inside much smaller silica nanoparticles, allowing them to enter the plant cells. As the luciferin is released from its particles, it too enters the cells and reacts with the luciferase, creating the glowing effect.

At the moment, the light the plants emit is very dim – about a thousandth of the level required to read by – but the researchers say they can boost the brightness through further work. Already, they've improved the duration of the glow from 45 minutes at the beginning of the project to about three and a half hours currently.

The team says this method can avoid some of the pitfalls that previous attempts fell into, namely trying to genetically engineer plants to express luciferase genes. According to The Atlantic, the Glowing Plant project recently shut up shop after running into some hurdles that they didn't foresee (even if skeptical scientists saw them coming).

Although the new plants currently don't glow any brighter than previous ones did, the MIT researchers say their method is simpler, and can be applied to essentially any type of plant. Ideally, future work would see the soaking method replaced by a spray-on paint, allowing them to apply the glow to trees lining streets.

"Our target is to perform one treatment when the plant is a seedling or a mature plant, and have it last for the lifetime of the plant," says Strano. "Our work very seriously opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes."

Adding a luciferase inhibitor to the mix could also allow the team to eventually create plants that can turn off the glow as well, in response to sunlight or on command, for example.

You can check out the glowing plants in the video below.

The research was published in the journal Nano Letters.

Source: MIT