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Development and Organization of the Primary Vascular System in Populus deltoides According to Phyllotaxy
Philip R. Larson
American Journal of Botany
Vol. 62, No. 10 (Nov. - Dec., 1975), pp. 1084-1099
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2442125
Page Count: 16
You can always find the topics here!Topics: Meristems, Cylinders, Cardiovascular system, Phyllotaxis, Phloem, Developmental biology, Plants, Seedlings, Leaves, Botany
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An actively growing cottonwood bud was embedded in epon-araldite and serially sectioned at 2 μ m. The sections were analyzed microscopically with the optical shuttle system of Zimmermann and Tomlinson, and all data were quantitatively recorded relative to the apex and to leaf plastochron index (LPI). Analysis of the sections revealed an acropetally developing procambial system organized according to a precise phyllotaxy. Six procambial strands could be recognized and followed long before the leaf primordia that they would enter were evident at the apex. Origin of these strands coincided with developmental events both in the parent trace and its primordium and in the antecedent leaf on the same orthostichy. Once a primordium and its trace attained a certain stage of development, trace bundles began to develop basipetally from the primordium base. These trace bundles appeared to be the earliest progenitors of wood formation in cottonwood. It was concluded that the concept of residual meristem and its corollary, the hypothesis that acropetally developing procambial strands determine the inception sties of new primordia, apply to the cottonwood apex.
American Journal of Botany © 1975 Botanical Society of America, Inc.