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.
The vascular cylinder of the cultivare is polyarc, and the average is 36 poles of
protoxylem in U.
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.
The variation in the number of
protoxylem poles varies along the primary root.
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.