Michael Marder considers the vegetal souls on our plate:
For example, studies have found evidence of "deliberate behavior" in plants: foraging (note that the botanists themselves use this word usually associated with animal behavior) for nutrients, the roots can drastically change their branching pattern when they detect a resource-rich patch of soil, or they can grow so as to avoid contact with roots of other members of the same species, in order to prevent detrimental competition. Of course, plants are not capable of deliberation or of making decisions in the human sense of the term. But they do engage with their environments and with one another in ways that are incredibly sophisticated, plastic and responsive — in a word, intelligent, though not perhaps conscious.
Adam Kolber isn't buying Marder's call for "plant liberation":
[T]he signaling mechanism Marder describes is common to lots of systems that have no moral claim to our actions. I suspect, for example, that the advanced heating and cooling systems in modern buildings have the kinds of abilities that pea plants have. Yet surely we can assemble and disassemble such systems without worry that we are hurting anyone by doing so. Now, if plants could feel pain, that might be a different story. It wouldn't mean we'd have to stop eating plants, but we might at least have to think differently about the issue.