45 minutes: That’s how long watercress plants, embedded with nanoparticles, glowed in the dark during an early series of trials by MIT researchers looking to change the way we illuminate our lives. Glowing trees to replace street lights? A plant as a desk lamp? Not yet, but becoming increasingly possible. In subsequent tests with watercress, arugula, kale, and spinach, the plants glowed for 3.5 hours. Researchers also figured out a way to turn off the glow during daylight hours.Alex Kingsbury can be reached at firstname.lastname@example.org.