What is the difference between xylem and phloem?

• Buffer
• Tweet

The difference between xylem and phloem is that xylem transports water from the roots of a plant up through the plant whereas phloem transports nutrients, including sugars, proteins and RNA, either up or down the entire plant. This is determined by where there are more nutrients. An example of phloem is the sap in a tree, which flows up from the roots in the spring and down from the leaves in the fall before the leaves fall off the tree.

Xylem is made up of two kinds of cells, tracheids and vessel elements. These cells are dead when they transport water from the roots throughout the plant. Vessel elements are hollow vessels that are formed when the cells are joined end to end. There are perforations in their end walls so that water can flow through. In simple plants like ferns and conifers the cells are called tracheids. There is also primary and secondary xylem. Xylem is what makes a tree or a plant strong. Since xylem must be very strong to support the plant, they have secondary cell wall thickening which form into rings. Wood is made of secondary xylem. Every year the plant grows a new ring of xylem tissue. This can be seen when a tree is cut down and its trunk reveals rings of old xylem tissue. The number of rings shows the age of the tree.

The other part of the vascular system is phloem. Phloem, as opposed to xylem, is composed of living tissue and is made of soft wall cells. It forms tube cells called sieve tubes. These run parallel to the plant organ’s long axis and are formed from long cells called sieve elements that are joined end to end. The end walls of these sieve elements and their companion cells are broken down. They then transport organic products that derive from the process of photosynthesis to the lower parts of a plant. Photosynthesis makes a kind of sugar from the plant’s green leaves. This sugar produces energy that enables the plant to grow.

In each plant, xylem and phloem are usually placed in vascular bundles in various relations to each other. There is a collateral arrangement, where xylem and phloem lie next to each other, with phloem lying on the outside and xylem on the inside. Another arrangement is known as bicollateral. Here xylem lies pressed between two layers of phloem. A third arrangement is called amphivasal. Here a ring of xylem surrounds the phloem.

Xylem and phloem develop in a young plant from the tip of the shoot, which is called the apical meristem. New cells change and differentiate into yellow procambrium. Then this procambrium itself divides and becomes differentiated into xylem and phloem. The vascular tissue needs to become properly aligned so that separate columns are created to enable the cells of the xylem and the phloem to form into hollow vessels that can transport the water and the other nutrients efficiently throughout the plant.

Resource by Will

I am the editor for TheFreeResource.com, and owner of LinchpinSEO, a small business content creation company. The Free Resource has a select community of talented writers, teachers, and business people (and we are always looking for more) that bring you the most trusted resources on the web and credible articles about many topics.

Related Research For Teachers, Students, and Kids