Xylem vs. Phloem

Xylem and phloem are special tissues that comprise the vascular system of plants. They work together to transport food, water, nutrients, and minerals to all parts of the plant. Together, they form a vascular bundle, with xylem in the center and phloem around the outside.

Xylem composes the woody or stem part of a plant. Its job is to transport water and dissolved minerals from the roots to the other parts of the plant. Xylem is made up of long, hollow cells that create water-conducting tissue. These tissues also provide mechanical support for the plant, often holding it straight up off the ground (as in the case of tall trees and even short flowers). As xylem grows, the innermost part of the plant stem dies, providing only mechanical support, and new cells grow on the outermost part to continue transporting water.

Phloem is found throughout a plant. Its job is to transport food that is made in the plant's leaves to other parts of the plant (a process called translocation). Therefore, phloem is made up of long, flexible fibers that contain many different specialized types of cells and structures (sieve tubes, companion cells, bast fibers, and others).

While phloem allows for movement up or down the plant's stem, xylem only allows for movement upward. Plants can be 'girdled' in order to produce larger than normal fruits or vegetables. Girdling a plant involves stripping away a section of its outer phloem, but leaving the xylem intact. Xylem and phloem are generally not used in everyday conversation, but in specialized discussion of plants.