No my last point was not addressed. The whole concept of suffering is a human one. It is not permissible to judge the "subjective plant reality" based on concepts from subjective human reality (note that I do not use the term "subjective" to imply consciousness in a human sense). There's no way to infer that similarity or dissimilarity makes killing wrong in one case (animals) but right in another case (plants).
Most plants are cultivated (ill-breeded, genetically mutilated and grown in unnatural habitats) only to serve human consumption. This is in no way less condemnable than what humans do to animals.
The essence: Surviving sometimes means killing.
ya.ya.yo!
Plants are passive beings, feeling pain would not have helped them in any way for evolution's sake, and thus they can't feel pain. They don't have a nervous system like animals do, so all their reactions occur for no other sake than optimal growth and distribution of genes. Why would any plant adapt to feel complex sensations like pain, especially when none of them have the required nervous system to do so? It would be a waste of energy, and in nature, a waste of energy means the end of the specie.