This was the subject of a text conversation between myself and one of my colleagues this morning in the context of this Ted Talk.
Of course, in the context of neural networks that have sensory inputs and motor outputs, the answer is no. But some plants do have excitable cells that fire action potentials. They certainly sense the environment and they can “behave”. That’s because their molecular signal transduction system is based on the same metabolic chart as ours and allows more the individual plant to respond with movement (sometimes even very rapid movement) in response to stimuli.
So plants don’t have brains, but they have the biological toolset to accomplish things that animals with brains accomplish (like counting! see the video).