metaxylem


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Related to metaxylem: protoxylem

metaxylem

[¦med·ə′zī·ləm]
(botany)
Primary xylem differentiated after and distinguished from protoxylem by thicker tracheids and vessels with pitted or reticulated walls.
References in periodicals archive ?
In most primary walls of monocot metaxylem, networks of primary wall cellulosic fibrils can be seen in preparations in which amorphous wall portions are sectioned away (e.
The only families in which Bierhorst and Zamora note some tracheids (along with vessel elements with scalariform perforation plates) in metaxylem are Aquifoliaceae (Ilex), Buxaceae (Pachysandra), Caprifoliaceae (Weigela), Cornaceae (Comus), Cunoniaceae (Spiraeanthemum), and Ericaceae (Gaultheria).
Could this lead, phylogenetically, to an all-tracheid system if production of late metaxylem was suppressed?
Mayacaceae may merely be forming protoxylem and early metaxylem, in which tracheids and scalariform perforation plates are to be expected.
They may be forming no "late" metaxylem as defined by the presence of wider tracheary elements.
Nodal metaxylem tracheary elements have more densely placed pits, and the pits tend to be polygonal to elongate, with wide borders (Fig.
Pit membranes of metaxylem tracheary elements that are not affected by sectioning appear to be uniform in thickness and non-porose, except for the metaxylem tracheary elements depicted in Fig.
All of the species of Equisetum studied, despite their differing habits, share the basic plan, in both aerial stems and underground stems (rhizomes) of two distinctive types of metaxylem tracheary elements: internodal and nodal.
The dimorphism of metaxylem tracheary elements may be related to conductive patterns.
Scattered small pores were observed in an apparently intact metaxylem tracheid (Fig.
Pits in metaxylem tracheids are oval in shape and prominently bordered in all Lycopodiaceae, as shown in the illustrations of Bierhorst (1960, 1971), Wilder (1970), Cook and Friedman (1998), and Friedman and Cook (2000).
The xylem of Phylloglossum may certainly be regarded as paedomorphic, because it consists of protoxylem only, whereas all other Lycopodiaceae have metaxylem as well as protoxylem.