We can't stop all suffering, but that doesn't mean we shouldn't stop any. There is currently no reason to believe that plants experience pain, devoid as they are of central nervous systems, nerve endings, and brains. It is theorized that the main reason animals have the ability to experience pain is as a form of self-protection. If you touch something that hurts and could possibly injure you, you will learn from the pain it produces to leave it alone in the future. Since plants cannot locomote and do not have the need to learn to avoid certain things, this sensation would be superfluous.
Plants are completely different physiologically from mammals.
Unlike animals' body parts, many perennial plants, fruits, and vegetables can be harvested over and over again without resulting in the death of the plant or tree. If one is concerned about the impact of vegetable agriculture on the environment, a vegetarian diet is still preferable to a meat-based one, since the vast majority of grains and legumes raised today are used as feed for cattle. Although the Nazis purported to pass an anti-vivisection bill, they did not. In fact, they were required by law to first perform their experiments on animals before carrying them out on humans. All were in continuation of or complementary to experiments on animals.