Silent Running depicts a future in which all plant life on Earth has been made extinct. Only a few specimens have been preserved in enormous, greenhouse-like geodesic domes attached to a fleet of American Airlines space freighters, just outside the orbit of Saturn. Freeman Lowell (Bruce Dern), one of four crewmen aboard the Valley Forge, is the resident botanist and ecologist who preserves the forests for their eventual return to Earth and the reforestation of the planet. Lowell spends most of his time in the forests, cultivating the plant and animal life. When orders come from Earth to jettison and destroy the domes (with nuclear charges) and return the freighters to commercial service, Lowell rebels and opts instead to save the forests and animals on his ship. After four of the six domes on the Valley Forge are jettisoned and destroyed, Lowell kills one of his crewmates in a struggle, and his right leg is seriously injured in the process. Nevertheless, he prevents the destruction of one of the remaining domes by trapping the other two crewmen in the other dome, which he jettisons and destroys. Enlisting the aid of the ship's three service robots, which he later nicknames Huey, Dewey, and Louie (for the cartoon characters), Lowell stages a fake premature explosion as a ruse and sends the Valley Forge careening away from the space freighter fleet towards Saturn in an attempt to hijack the ship and flee with the last forest dome.
Now alone, Lowell reprograms the drones to perform surgery on his leg and sets the Valley Forge on a risky course through Saturn's rings. As the ship endures a rough passage, Drone 3 (Louie) is ripped away from the ship. The ship and its remaining dome emerge relatively undamaged on the other side of the rings. Lowell and the other drones set out into deep space to maintain the forest. Lowell teaches Huey and Dewey to plant trees and play poker. Drone 2 (Huey) is damaged when Lowell accidentally collides with him while driving a buggy recklessly. During a scene where Drone 2 (Huey) is being repaired, Drone 1 (Dewey) sentimentally refuses to leave the side of Drone 2. As time passes Lowell is horrified when he learns that his forest is dying, but is unable to come up with a solution to the problem. When the Berkshire eventually reestablishes contact with Lowell, he knows that his acts will soon be discovered. It is then that he realizes a lack of light has restricted plant growth, and he races to install lamps to correct this situation. In an effort to save the last forest before the Berkshire catches up to him, Lowell jettisons the dome to safety. He then detonates nuclear charges, destroying himself, drone 2 (Huey) and the Valley Forge. The final scene is of the well-lit forest greenhouse drifting into deep space, with Drone 1 (Dewey) tenderly caring for it, holding a battered old water can. - From Wikipedia
DOUGLAS TRUMBULL (1972)