The belief that plants can suffer reflects a pre-scientific animism. A precondition of being a unitary subject of experience is a central nervous system. No selection pressure to evolve an energetically expensive central nervous system could exist on sessile organisms such as plants, which lack the capacity for rapid self-propelled motion. Recall we know how to switch off pain altogether in animals: nonsense mutations of the SCN9A gene cause congenital analgesia. Plants lack a SCN9A gene - or any functional analogue. Even if one believes that individual cells can support rudimentary experience, the encasement of individual plant cells within thick cellulose cell walls prevents any plausible form of phenomenal binding. By contrast, a pig, for example, is at least as sentient (and sapient) as a human prelinguistic toddler - and deserves to be treated accordingly. In practice, the only people who affect concern for plant suffering are meat-eaters who want to rationalise animal abuse. We're not dealing with pre-scientific animists arguing in good faith that plants have souls. Strictly speaking one can't literally disprove the belief that plants (or rocks or mountains etc) suffer pain. Such a conjecture is inconsistent with the scientific world-picture and reductive physicalism. But then we don't understand how creatures with central nervous systems can solve the phenomenal binding problem (cf. http://www.ncbi.nlm.nih.gov/pubmed/10448000). Critically, however, without a unitary subject it makes no sense to say there is a subject of experience who suffers - and can be worthy of moral consideration.