Smoke actually stifles the photosynthesis process, it hinders a plant's ability to absorb sunlight from the leaves. The tar from the cigarette clogs the pores of the plant. The pores are the gateway that brings carbon dioxide and oxygen into the plant. It's very similar to the tar that gets into a smoker's lungs. Not good for you, not good for plants. Plants have been here longer than we have; most originate from the rain forest across the globe. They did quite well without interference from humans. If we bring them into our own environment, we must give them what they need. There was no tar and nicotine in their original home, don't bring it into their current home.