This movie was prescient: Plants pilot UFOs [Redux]
The Thing (from Another World) was an intelligent carrot.
This book [Prentice Hall, inc. Englewood Cliffs, N.J. 1970] tells us why and how:
“It [is] only a small step from the first one-celled plants to the first one-celled animals …
Even in the complex plants and animals of today the fundamental processes are the same and the genes to control them carry the same codes. Human beings are thus more like plants than you might think, and in fact, many of our genes are identical to those of the plants growing in our gardens …” [Page 15]
Page 18 provides the math for planets (not plants!) in the known Universe, postulating that after all the caveats are taken into account, 100 million evolutions could have taken place on planets with suns.
“ … how can one imagine the variety of life forms that might have come about through 100 million processes? Some would still be quite primitive while others would have advanced far beyond ourselves. If the one-in-a-thousand ratio were projected further, it would n\mean that there might be 100 thousand that had reached a stage of civilization perhaps at least the equal of our own.”
Then there is this:
“ … plants … aid … in their own salvation …” [Page 239]
“ … plants have now been found to produce chemicals similar to juvenile hormones …” [Page 239]
“Algae, the most ancient of the earth’s flora … [have] cells … held together in colonies, and [the] most advanced are the multicellular ones such as kelp in which cells have specialized functions – some (“holdfasts”) to anchor the plant, others to form a stalk, and still others to form expanded leaflike structures.” [Pages 21-22]
These books and a video take the topic further:
With the need for chlorophyll and water, one can see why a civilization of evolved, thinking plants might seek out the Earth.