Plant sentience and the case for ethical veganism

Does the possibility of plant sentience pose a problem for ethical veganism? It has not yet been demonstrated that plants are sentient (i.e., that they can feel). Moreover, even if it were demonstrated that plants could feel, it would also have to be demonstrated that they can feel the affectively “valenced” feelings that are ethically significant, such as pain and fear, rather than just neutral sensations such as darker/lighter, or wetter/drier. Finally, if plants could feel valenced feelings, veganism would likely still be the ethical option, on the principle of causing the least harm.