Silent Running: The original WALL-E?
I watched this film again recently because I was reminded of it after watching "WALL-E". "Silent Running" tells the story of several ships preserving various earth ecosystems, waiting for a time when they can be returned to the polluted planet. One crewman (Bruce Dern) becomes agitated when the order comes to terminate the program because the earth is beyond recovery. He kills his crewmates, and tends to the remaining ecosystems with the help of three, boxy robot drones.
After watching this movie again thirty years later, my instincts were correct! Many of these plot points found there way into "WALL-E"... in a twisted sort of way. In "Wall-E", the boxy robot drone tends to the polluted earth, while the ship preserves human life until the planet is able to sustain it. The presence of plant life is the signal that the ship can return. However, a robot caretaker on the ship becomes agitated and confines the ship's captain so that he can continue to care for the human cargo.
As always, I monitored the movie for smoking content. Good news! Tobacco was not one of the plants preserved on the ships. "Silent Running" earned a SmokeScreeners rating of No Butts! www.smokescreeners.org