Silent Running

In a future where all flora is extinct on Earth, an astronaut (Bruce Dern) is given orders to destroy the last of Earth's plant life being kept in a greenhouse on board a spacecraft.

The biggest problem with this film is the music provided by Joan Baez. Maybe in 1972 this was cool, but today (2013) it comes off as obnoxious, and it pushes the film over the boundary from "environmentalist" to "hippie", which may be a serious turn-off for many viewers.

Beyond that, great film with Bruce Dern being his wacky self. I love his little robot pals and how he trains them to be (almost) human. The actors inside the robots deserve a lot more credit than they probably get.