The idea is reasonably simple—place sensors that listen to the electrical signals generated by a plant and then convert those signals to commands carried out by the motorized wheels. The result is a plant that can respond to changes in light direction by moving itself closer to the source.If you are an Aristotelian thinker, this is really an interesting development. Aristotle argues (in De Anima) that the human soul has three parts, the rational, the motive (or animal), and the nutrative (or plant-like). Humans, plants, and animals contain the capacity to take nutrition from the world and put it into our own order: to rebuild our cells, say, with proteins taken from outside us. All of us do that, and it is the distinction between living things and things like rocks that are not alive.
The difference between plants and animals, he thought, was just this capacity to move one's self in order to obtain food. The motive soul was a higher level of soul because it required an ability to distinguish things distant from yourself, rather than simply to absorb things that you came into contact with accidentally. Hans Jonas, in The Phenomenon of Life, argues that this capacity requires a self-conscious mind: a hawk must be able to distinguish that it is different from the rabbit. That isn't necessarily clear, though; there needs to be some sort of process by which the hawk finds the rabbit's presence actionable, but it might not be a conscious process. Still, it makes sense to say it is: certainly, in us, we recognize ourselves as different from the hunted animal. There is no special reason to assume it is otherwise for the hawk, there is just no proof that the hawk experiences consciousness.
(Although, speaking of birds, I think it's at least suggestive that crows not only display advanced problem solving in spite of having brains that contain none of the structures we think humans use for it, they also seem to be able to recognize people who have been mean and to communicate that to others in their murder. But we don't know what their experiences are like, or even if they 'have experiences' at all.)
So anyway, it turns out that plants have the ability to process the information they would need to move around; they just don't, naturally, have the capability to move around. For Aristotle, the soul is the perfection of the thing according to its own nature. Wouldn't the plant be more perfect if it could move, just as an animal would be more perfect if it could reason (as, it seems, crows can)?
If the answer is yes, then we come to another Aristotelian dictum, this one from the Physics: it is the role of art to perfect nature. That is to say that the human soul, which is rational in its highest part, can see where the natural has failed to actualize all of its potential. We can, through art, improve nature by bringing it more fully to its complete perfection. The art of medicine is essentially this, or has been up until now: the eye should see, and see well, but does not, and so the doctor works to try to restore or perfect the sight.
So the question to ask is this: are we perfecting the plants' nature, and if so, does that mean that they really do have an animal (motive) soul that has only existed so far in potency? If so, do they have rational souls in potency as well? We have more reason than Aristotle had to think that animals can reason, at least some of them. Perhaps all animals have rational souls that haven't been fully actualized; perhaps, with art, they could be. Plants as well.
That leads to another ancient view, more Plato's than Aristotle's.