d) Xylematic arch showing the exarch protoxylem
--full arrow--and the centralized metaxylem--traced arrow (bar = 100 [micro]m).
An obvious but infrequently mentioned function of axial parenchyma in stems and roots is its relationship to protoxylem
vessel elements and tracheids are extensible, and thereby require contact with equally extensible parenchyma cells (Fig.
Some of the undifferentiated vascular bundles contained only protoxylem
transport tissues (Fig.
They quantitatively assessed: (1) diameter of the root; (2) thickness of the root epidermis; (3) count of cores of protoxylem
; (4) diameter of the vascular cylinder of the root; (5) proportion of the stomata and (6) subsidiaries cells; (7) size of the bulliform cells; (8) thickness of the foliar mesophyll; (9) thickness of the group of fibers of the abaxial and adaxial foliar rib; (10) diameter of the central vascular bundle of the foliar blade.
(A) Primary root (en = endodermis; arrows indicate protoxylem
praecox was characterized with xylem vessels with helical secondary wall, that is, the protoxylem
and some unusual outgrowths.
There is also a reduction in the size of the root cap and derangement of the meristematic tissue, besides the formation of protoxylem
and endoderm in regions close to the root apex with high contents of lignin (Miguel et al., 2010).
(4,11) In particular, VND6 and VND7 are specifically expressed in differentiating tracheary elements of the metaxylem and protoxylem
The xylem is the principal water-conducting tissue of vascular plants and is divided in primary xylem which consists of protoxylem
that has an active stretch in its youth and the metaxylem which begins in the mature plant, but after elongation it is stretched and is destroyed.
Trigalet, "Microscopic studies of intercellular infection and protoxylem
invasion of tomato roots by Pseudomonas solanacearum," Molecular Plant-Microbe Interactions, vol.
secundum dealt with plants cultivated in greenhouse conditions, and described roots with five-six layered velamen, exodermal cells with wall thickenings, 10-12 layered cortex, O-thickened endodermis, and 17 protoxylem