I saw this movie when I was a kid.
At the end of the movie, the robot was left behind in a broken space ship taking care of the plants.
That is Silent Running, from 1972.
It would be easier if you told us a bit more, when were you a kid. But My google-fu threw up this.
It does have the broken space-ship, the robot and the plants.
Kind regards, Jennifer
I agree. Sounds like Silent Running, starring Bruce Dern. I saw it on TV, yes, years ago. Green apocalypse type of film, with all Earth's plants on a spaceship after Earth got to polluted to sustain them. When the crew gets the order to blow the ship and come home, Dern's character kills the other crew members and takes off into space with the plants and the robot helpers on board.