Manipulation of seedling traits with pulsed light in closed controlled environments

•Energy requirements limit sustainable crop growth in closed controlled environments.•Seedling performance is identical under 12 h or 5 s light/dark cycles.•Extending the dark interval does not affect some traits until after 10 s.•Persistent response is triggered by far-red and blue light acting through phyA and cry1, respectively.•Extending the dark interval in a short pulse environment may cut energy costs.