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THE THICKENED LEPTOID (SIEVE ELEMENT) WALL OF DENDROLIGOTRICHUM (BRYOPHYTA): CYTOCHEMISTRY AND FINE STRUCTURE
Author(s) -
Scheirer Daniel C.
Publication year - 1977
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.1537-2197.1977.tb15739.x
Subject(s) - cytochemistry , cell wall , biology , ultrastructure , sieve (category theory) , toluidine , sieve tube element , botany , middle lamella , plasmodesma , biophysics , chemistry , phloem , organic chemistry , mathematics , combinatorics
Leptoids (sieve elements) of Dendroligotrichum exhibit unevenly thickened lateral walls. The thickened wall areas are predominantly confined to the radial walls. With the light microscope the thickened wall cannot be resolved into distinct layers, but rather is optically homogeneous. Standard histochemical tests reveal that these walls are rich in cellulose (birefringent; IKI‐H 2 SO 4 ‐positive) with small amounts of polyuronides (toluidine blue‐positive) and pectins (hydroxylamine‐positive) and are non‐lignified. They also contain abundant natural aldehydes as revealed by the Schiff, silver hexamine, and silver proteinate reagents. Aldehyde blockades (sodium borohydrate, sodium chlorite) confirmed the presence of aldehyde groups in the cell wall. At the ultrastructural level, the lateral walls of sieve elements react strongly with uranyl and lead salts and yield little fine structural information. Electron cytochemical localization of aldehydes with silver proteinate revealed three distinct wall regions: outer, middle and inner. The outer and middle regions appeared polylamellate while the inner region contained no reaction product. The nacreous sieve elements of vascular plants are compared to the thickened sieve elements in bryophytes.