Silent Running

Bruce Dern stars as Freeman Lowell, an ecologist on a space station who rebels against his crewmates after they order him to destroy the ship's greenhouse, which contains the last remaining examples of Earth's plant life. He kills his companions and takes control of the ship with the help of three android service robots. With the robots' aid, Lowell sets out into deep space to maintain the forest, but faces a dire situation when he discovers that his greenhouse is dying due to lack of sunlight.