What Does Phloem Do?

phloem Credit: Science Photo Library/Getty Images

Phloem tissue transports and distributes sucrose and nutrients produced by the plant during photosynthesis to the rest of the plant tissue. In stemmed woody plants, such as trees, phloem is the inner bark tissue layer.

Plants have two types of transport tissue, xylem and phloem. Xylem tissue distributes water and minerals gathered by the roots to the rest of plant, but it is primarily dead cells. In contrast, phloem consists primarily of living cells. Botanists use the name translocation for the process of moving foods through the phloem using hydrostatic forces and active transport.

The sugar solution produced in the leaves is sap. In addition to providing nutrition for other cells, sap is stored in other structures including tubers. Tubers, such as potatoes, allow the plant to survive extreme weather. When the exposed portions of the plant die due to the conditions, a new sprout forms from the energy stored in the tuber.

Removal of a circle of bark from the circumference of the plant prevents food transport to the root. This process, known as girdling, is an effective means of killing a tree. Girdling a limb of a fruit tree and removing all but one fruit results in a single large, show-quality fruit. Since sugars no longer pass to the remainder of the tree, they are stored in the remaining fruit.