Flowering plants, or angiosperms, are plants of the class of Angiospermae that produces seeds enclosed in an ovary and is characterized by the possession of fruits and flowers. They are adapted to life on land than mosses by several reasons. Adaptations that angiosperms went through to become a more successful terrestrial organism than mosses are the development in their vascular tissues and their specialization in their organ for sexual reproduction, the flower.
Xylem functions in the conduction of water and minerals and also provides mechanical support. In addition to the primary cell wall that all plants have, xylem cells have a secondary cell wall that gives them additional strength. Sometimes, the walls of xylem cells have pits, or places where the secondary cell wall is absent. Most xylem cells are dead at maturity since they are cell walls lacking cellular components, and contain only the material being transported. There are two kinds of xylem cells, tracheids and vessel elements.
In tracheids, which are long and tapered, water passes from one tracheid to another through pits on the overlapping tapered end of the cells. Vessel elements are shorter and wider than tracheids, and have less or no taper at their ends. A column of vessel elements is called a vessel. Water passes from one vessel element to the next through areas without both primary and secondary cell walls. These areas are called perforations and are literally holes between cells. Because of the perforations, water movement through vessel elements is more efficient than through tracheids. As a result, vessels are considered a more evolutionary advanced feature. They are found most prominently among the flowering plants.
Refinements in the vascular tissue of angiosperms, especially the xylem, played a role in spreading flowering plants across diverse terrestrial habitats. The vascular tissue of flowering plants...