Understanding Xylem and Phloem

Xylem are water-conducting cells that transport water and nutrients. They die at maturity and leave behind secondary walls. Phloem transports sugars through sieve-tube elements, but do not have nuclei, ribosomes, and vacuoles. However, phloem remains alive at maturity.

Phloem is located in the bark of trees and transports sugars (such as sucrose) and organic compounds to the rest of the plant from the leaves. The other plant vascular tissue is xylem. Xylem is located outer wood of trees, and transports water from the roots to the leaves of trees.

Xylem is a type of tissue present in vascular plants that is responsible for water transport within the organism. Types of cells contained within xylem include tracheids, vessel elements, parenchyma cells, and fibers.

The transport of water through xylem in plants includes the upward movement of water. The forces of transpirational pull and root pressure are responsible for counteracting gravity and producing water’s upward movement. Transpirational pull is defined as the surface tension caused by water evaporation that pulls water upward through xylem. Root pressure is characterized by the difference in water potential between the soil and plant, causing water to travel into plant roots.

Tracheids are elongated cells that are contained within xylem tissue. Tracheids are responsible for water and mineral transport. The thick cell walls of tracheids allow them to hold water against gravitational pull due to the adhesion property of water.

Vessel elements are a cell type contained within xylem tissue of angiosperms. Vessel elements aid in the transport of water and minerals. Morphologically, vessel elements are described as hollow tubular cells that have thick cell walls and are open at both ends.

Phloem is a type of tissue in vascular plants that transports organic nutrients. Among other components, phloem contains sieve elements, parenchyma cells, and supportive cells.

Companion cells are a type of specialized parenchyma cells in vascular plants. They contain a large number of ribosomes and mitochondria and perform cellular functions for sieve-tube elements, which they are connected to by plasmodesmata.

Vessel elements are cells in phloem tissue that are technically dead. Upon maturation, the living material in the cells disappears while the cell wall remains; the cells are dead; however, sieve tube elements contain living tissue.

Xylem is dead at maturity, while phloem is living. All other answer choices are true. Xylem is also thicker and more rigid, which allows for greater pressure during water transport. It provides a strong support structure for the plant, enabling taller growth.