Originally Posted by
OrphanPip
Not quite, all sorts of machines react to external input in complex ways. Sentience is certainly difficult to define, but we know just from relatedness that most other chordates have brains sufficiently like ours that they probably have the same basic feelings of pain and fear. Plants lack the actual organs involved in sense. What good would it do for a plant to feel anyway: they can't move away from what is hurting them, they can't fight back, they can't perceive their environment to any great extent. Plants not only lack the sensory organs that would explain how they would feel, they lack the impetus to evolve such a response.
Insects are more problematic because they are more similar to chordates than plants, but it is difficult to say for sure how their brains function.