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Related to protoxylem: metaxylem


(Botany) the first-formed xylem tissue, consisting of extensible thin-walled cells thickened with rings or spirals of lignin. Compare metaxylem
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˌproʊ təˈzaɪ ləm, -lɛm)

the part of the primary xylem of a plant that develops first, consisting of narrow, thin-walled cells.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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References in periodicals archive ?
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. 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.
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, respectively.
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 poles.