There are several types of vascular tissue in a typical gymnosperm plant. Two of the most important are the xylem and phloem, which conduct water and nutrients up the body of the tree. Gymnosperms are most generally plants that have exposed seeds, as opposed to angiosperms, which have enclosed seeds. Typical gymnosperms are conifers, which are cone bearers, such as pine trees, spruce trees, and fir trees. The vascular tissue is like a system of pipes, or straws, all hooked together. They conduct the flow of water and nutrients into the main stem of the gymnosperm and get both to the leaves where photosynthesis may take place. Photosynthesis is the process by which all green plants produce their own food. This process takes sunlight and combines it with carbon dioxide and water to produce glucose, a simple sugar, and oxygen as a waste product. Another important vascular tissue in the stem of gymnosperms is the cork cambium.