If workspaces illuminated by glowing plants could become a reality, going by the first steps taken by a group of engineers from the Massachusetts Institute of Technology (MIT), it would slash energy consumption worldwide. It is estimated that lighting accounts for about 20% of worldwide energy consumption. By embedding specialised nanoparticles into the leaves of a watercress plant, the researchers induced the plants to give off dim light for 3.5 hours. 
The vision is to make a plant that will function as a desk lamp, is ultimately powered by the energy metabolism of the plant itself, according to Michael Strano, the Carbon P Dubbs Professor of Chemical Engineering at MIT and the senior author of the study funded by the US Department of Energy and published in the journal Nano Letters.
This technology could also be used to provide low-intensity indoor lighting, or to transform trees into self-powered streetlights. Plant nanobionics, a new research area pioneered by Strano’s lab, aims to give plants novel features by embedding them with different types of nanoparticles. The researchers have previously designed plants that can detect explosives and communicate that information to a smartphone, as well as plants that can monitor drought conditions.
To create their glowing plants, the MIT team turned to luciferase, the enzyme that gives fireflies their glow. Luciferase acts on a molecule called luciferin, causing it to emit light. Another molecule called co-enzyme A helps the process along by removing a reaction byproduct that can inhibit luciferase activity. The MIT team packaged each of these three components into a different type of nanoparticle carrier. The nanoparticles, which are all made of materials that the US Food and Drug Administration classifies as “generally regarded as safe,” help each component get to the right part of the plant. They also prevent the components from reaching concentrations that could be toxic to the plants.
The researchers used silica nanoparticles to carry luciferase, and they used slightly larger particles of the polymers PLGA and chitosan to carry luciferin and coenzyme A, respectively. To get the particles into plant leaves, the researchers first suspended the particles in a solution. Plants were immersed in the solution and then exposed to high pressure, allowing the particles to enter the leaves through tiny pores called stomata. Particles releasing luciferin and coenzyme A were designed to accumulate in the extracellular space of the mesophyll, an inner layer of the leaf, while the smaller particles carrying luciferase enter the cells that make up the mesophyll. The PLGA particles gradually release luciferin, which then enters the plant cells, where luciferase performs the chemical reaction that makes luciferin glow.
The light generated by one 10cm watercress seedling is currently about one-thousandth of the amount needed to read by, but the researchers believe they can boost the light emitted, as well as the duration of light, by further optimising the concentration and release rates of the components. For future versions of this technology, the researchers hope to develop a way to paint or spray the nanoparticles onto plant leaves, which could make it possible to transform trees and other large plants into light sources. The researchers are also working towards creating plants that shut off their light emission in response to environmental conditions such as sunlight.

Related Story