That is a supposition, but the converse, that no living thing except human beings is conscious is a vastly greatly "stretch" of the imagination. I do not suppose we are anywhere near actually experimentally verifying that trees, e.g. are conscious, but the burden-of-proof is on the nay-sayers, because everything alive acts as if it is conscious.

As far as nerves-and-brains go: consider the first computers, which operated in a gaseous-mode (vacuum tubes) and their modern, solid-state descendents. The first computers filled basements and required their own air conditioners, and pocket-calculators can now run circles around them. But despite the fact that the technology of computers has evolved in leaps-and-bounds, the principle of operation is still the same!!!

The technology is completely different, but "what they are doing" is still the same. Ditto for consciousness.

Just because a computer lacks solid-state devices does not mean, "it is not computing." And just because plants lack brains does not mean, "they are not aware." We do not understand the principle-of-operation of consciousness in human brain, and until we actually understand what gives rise to consicousness in us, you cannot say (with any certainty) that the same thing is not happening in plants.

Well, you can say it, but it don't mean a thing

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PW -- Plant Whisperer