Primary Xylem Elements and Element Associations of Angiosperms

Woody Anatomy of Platyopuntias

“…Bierhorst and Zamora ( 1965) have provided some evidence that secondary walls of vessels are deposited in two stages, the first-order framework of secondary thickenings and the second-order framework, which joins the first-formed gyres and produces bordered pits. That one can observe lateral walls transitional between reticulate and transitional in late nonfibrous secondary xylem lends some support to this hypothesis.…”

“…Pitting types change gradually throughout secondary growth; one can observe first-formed elements with transitional pitting (Fig. 20), which show the reticulate firstorder framework of the secondary wall (sensu Bierhorst and Zamora, 1965). Throughout this secondary xylem pit borders are often eliminated where vessels contact parenchyma cells.…”

Wood Anatomy of Calyceraceae and Valerianaceae, with Comments on Aberrant Perforation Plates in Predominantly Herbaceous Groups of Dicotyledons

“…Bierhorst and Zamora ( 1965) report scalariform plates for metaxylem of Lobelia syphilitica L. They also mention a curious primary xylem sequence incorporating tracheids in Lobelia cardinalis L. Patrinia vi!losa does prove to have scalariform pitting in protoxylem and metaxylem vessels, and Solereder's report of scalariform perforation plates in Centranthus ruber very likely refers to metaxylem also. A few scalariform perforation plates have been found in Asteraceae (Bierhorst and Zamora, 1965, report them in Aster novae-angliae L., Centaurea cineraria L., C. nigra L., and Hieracium aurantiacum L.). Aberrant versions of scalariform perforation plates occur in secondary xylem in some Asteraceae, notably two species of Dendroseris sect.…”

Changes in axial hydraulic conductivity along elongating leaf blades in relation to xylem maturation in tall fescue

“…These vessels were apparently transitional between the protoxylem and metaxylem (Esau, 1953). Bierhorst &Zamora (1965) andSavidge (1996) suggested that all primary tracheary elements are constructed initially as annular or helical elements and that reticulated or pitted elements are derived ontogenetically from such elements by the addition of more wall material between the gyres of thickening. According to this hypothesis, the annular pattern of PX elements differentiated in the elongation zone might result from a duration of differentiation shorter than that of elements differentiated beyond the elongation zone.…”