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The stem makes up the largest parts of some kinds of plants. For example, the trunk, branches, and twigs of trees are all stems. Other plants, such as cabbage and lettuce, have such short stems and large leaves that they appear to have no stems at all. The stems of still other plants, including potatoes, grow partly underground.
Most stems suport the leaves and flowers of plants. The stems hold these parts up in the air so they can receive sunlight. Stems also carry water and minerals from the roots to the leaves, and they carry food from the leaves to the other parts of the plant. The cells that carry water make up what is called the xylem tissue of a plant. Cells that transport food form the plant's phloem tissue.
Stems that grow above ground are called aerial stems, and those underground are known as subterranean. Aerial stems are either woody or herbaceous. Plants with woody stems include trees and shrubs. These plants are rigid because they contain large amounts of woody xylem tissue. Most herbaceous stems are soft and green because they contain only small amounts of xylem tissue.
Many common flowers sprout from underground stems. Some of these subterranean stems are rootlike structures called bulbs, corms, rhizomes, or tubers. Jonquils, lilies, and tulips grow from bulbs, crocus and gladiolus plants from corms. Many grasses and wild flowers grow from rhizomes, which are long and slender and spread horizontally. Tubers, such as those of the familiar potato plant, are shorter and thicker.
At the tip of each stem or twig is a terminal bud. When these buds grow, the plant grows taller. Other buds, called lateral buds, form farther back along the stem. Some of these buds grow into branches, and other become leaves or flowers. The place at which a lateral bud forms is called a node. Tiny leaflike coverings known as bud scales protect the growing ends of some buds.
World Book Encyclopedia Chicago: World Book-Childcraft International, Inc., 1979
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This page was last updated on 09/03/2018.