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ONTOGENY AND STRUCTURE OF THE SECONDARY PHLOEM IN EPHEDRA
Author(s) -
Alosi Margaret C.,
Alfieri Frank J.
Publication year - 1972
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1972.tb10156.x
Subject(s) - biology , phloem , sieve tube element , parenchyma , botany , ultrastructure , anatomy
The secondary phloem in Ephedra is atypical of the gymnosperms in general and exhibits several angiosperm‐like characteristics. The ray system of the conducting phloem consists of parenchymatous, multiseriate rays. The axial system contains parenchyma cells, sieve cells, and unusual albuminous cells reminiscent of the specialized parenchyma cells found in some angiosperms. These cell types may intergrade with each other. P‐protein in the developing sieve element appears early in the form of a single, ovoid slime body. Later, smaller slime bodies appear and quickly disperse. In the mature sieve element the single, ovoid slime body is lost, and P‐protein is then evident in the form of a parietal cylinder, thread‐like strands, amorphose globules, or a slime plug. Necrotic‐appearing nuclei are commonly found in mature sieve cells.