In the Buddhist view, the difference between the plant, animal and the humans is in the level of intelligence; and all possess subtle consciousness. Any sentient being that can experience pain and pleasure is thought to possess consciousness. Therefore, the subtle consciousness is not uniquely human.
Consciousness of eye which arises in the mind is dependent upon the sensory organ of the eye. The eye detects light and passes it on to the brain, where the input is processed. Buddha did not teach that eye consciousness was dependent upon a brain, but dependent upon mind which is independent of a brain, that is to say not a part of the brain. (By the way, I have never subscribed to this theory/teaching. It is my understanding and training that mind arises from complex biochemical and electrochemical processes made possible by the neurochemical processes of the organ we call a brain.)
The other five conciousnesses: smell, taste, touch, hearing, mentality are all made possible due to organs which make contact with the exterior world and find residence in the mind, forming consciousnesses integrated by the mental consciousness.
Plants can do all of this as previously stated. The question is, "Do plants have a mental consciousness?", which I can't demonstrate. But, neither can I demonstrate if anyone on this board has a mental consciousness. You each have to volunteer that information to me when asked. The problem with demonstrating that plants have a consciousness is that we aren't smart enough to speak "plant" to raise the question.