Silent Running

Plant-loving botanist Freeman Lowell happily carries out his duties on the spaceship Valley Forge, a giant orbiting greenhouse which contains the last remaining samples of flora from a now-barren Earth. When Lowell is ordered to destroy his cargo and return home, he mutinies, kills his more obedient shipmates, and sets out for the far reaches of space with his robot companions Huey and Dewey in tow.