Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. Xylem's main function is to transport water, but it also transports some nutrients and provides physical support. C. Sunflower D. Potato Ans: A - C₄ photosynthesis is an adaptation that improves carbon fixation efficiency in certain environmental conditions. - Other common C₄ plants include maize, sorghum, millet, and many tropical grasses.