protoxylem


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Related to protoxylem: metaxylem

protoxylem

[¦prōd·ō′zī·ləm]
(botany)
The part of the primary xylem that differentiates from the procambium and is formed during elongation of an embryonic plant organ.
References in periodicals archive ?
Epidermis (Epi), diameter of the root (Root diam), diameter of the vascular cylinder (VC diam), protoxylem (n), coefficient of variation (CV) and simple medium deviation (SMD).
Passage cells are usually aligned with protoxylem poles (Fleet 1961, Peterson & Enstone 1996), so the flow of water through them is more intense and efficient than through the other cells.
Inner wall of epidermic cells are thin; parenchyma composed of polyhedral cells; collateral bundles with a set of sclerenchyma fibers are located at the periphery, each collateral bundle includes two lateral strands of phloem, a central bundle composed of small strands of phloem surrounded with phloematic fibers, a large vessel of metaxylem, several small vessels of protoxylem and xylematic parenchyma.
Reports of such structures in protoxylem of angiosperms other than Limnanthes are not evident to me, although protoxylem is little studied by means of SEM.
However, Souza (2009), who examined seedlings of other eudicots, found that primary roots may present from two (diarch) to five (pentarch) protoxylem poles.
The stele has 8-12 mature protoxylem elements (Figures 1(d), 1(f), and 1(g)) with two to three metaxylem elements (Figures 1(a), 1(d), 1(f), 1(g), and 1(h)), and almost all cells in the stele become lignified as sclerenchyma in aged roots (Figure 1(g)).
In Figure 20, the protoxylem is mature and the center of the stele (the pith) contains a parenchymatous tissue (actually, fiber primordia).
protoxylem: First xylem cells formed in the primary xylem.
In addition to the anatomical description, the root diameter, expansion of the cortex, thickness of the exodermis, and diameter of vascular cylinder were measured, and the numbers of protoxylem poles and metaxylem vessel elements were quantified.
Protoxylem, early metaxylem, and late metaxylem could also be given separate scores on this basis.