Q:Generate a question about the following movie plot: Silent Running takes place in the not-so-distant future, at a time in which Earth's plant life has been decimated. Only a few specimens of flora have been preserved, and are currently in space in a fleet of orbiting greenhouses.Freeman Lowell (played by Bruce Dern) is the main character, one of four extraterrestrial forest rangers aboard the Valley Forge, one of the 2,000 metre-long green house freighters. He is passionately dedicated to preserving the orbiting forests and their natural inhabitants, and eventual returning them to Earth for reforestation of his now-barren planet more so than his crewmates, whose main priority seems to be returning to Earth after their one-year deployment to space.The main conflict comes when Lowell and his crew are ordered to destroy the orbiting greenhouses and redeploy the freighters to commercial service. Lowell decides to disobey orders and save the forests he has worked so hard to preserve.Lowell's crewmates manage to jettison and detonate four of the six greenhouse domes on the Valley Forge. Lowell kills one of his crewmates in a struggle to save the two remaining domes, during which he seriously injures his leg. He then manages to trap the other two crewmen in the other remaining dome, which he then jettisons and destroys.With help from the ship's three robots, Lowell feigns a premature dome detonation to fool his superiors, then alters the orbit of the Valley Forge , redirecting it towards Saturn in an attempt to preserve the last forest dome. Injured and alone with three robots, Lowell programs them to perform surgery on his leg.Still in communication with the rest of the fleet, Lowell is informed that the Valley Forge is on a collision course with Saturn's rings, and there is nothing he can do to stop the catastrophic event. The ship will likely be destroyed. With communications failing due to the distance now between the Valley Forge and the rest of the fleet, the ship passes through the rings of Saturn. While the three robots are outside the ship on maintenance...
A:
What is restricitng plant growth?