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The Formation of Nodal Adventitious Roots in Salix Cordata
Margery C. Carlson
American Journal of Botany
Vol. 25, No. 9 (Nov., 1938), pp. 721-725
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2436930
Page Count: 5
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Roots arise on stem-cuttings of Salix cordata from definite places at and near the nodes. The nodal roots develop from primordia which are present in the stems before their removal from the tree. A primordium is formed from parenchymatous secondary cells, above a leaf or branch gap. The cells in the outer part of a vascular ray in this region enlarge and become meristematic. Neighboring cells undergo similar changes until the secondary cells outside the cambium, including several rays, are involved in the formation of the primordium. The cambium adds cells to the inner surface of the primordium. A hemispherical protuberance, formed by the enlargement of cells of secondary xylem adjacent to the primordium, pushes the center of the primordium outward, making it dome-shaped. The primordia appear in early June in the lower, but not in the three or four lowermost, nodes of the developing branches. They are formed progressively upward in the nodes of the growing branches during the summer. By autumn they have reached their maximum development except in the youngest nodes. They remain in a dormant condition unless the branches are removed from the tree and placed in conditions favoring the growth of the primordia into roots.
American Journal of Botany © 1938 Botanical Society of America, Inc.