Throughout the entire movie the seedling is visual motif of hope and a new beginning for humankind after destroying the earth over 700 years ago. When wall-e finds the seedling in an old refrigerator it is the camera zooms in on it, slightly blurry as its alien like that doesn't belong on earth and the first sign of green. As the film progresses the seedling grows larger and larger because it's the driving force of the whole movie and the whole idea of bringing humanity back to earth. In the movie EVE is always seen carrying the last remnant of life on earth (the plant), thus showing how EVE is symbolic of hope and a new beginning for humanity. At the end of the movie, the plant has grown into a tree on earth symbolising that humanity is doing
