Sucrose (JrSUT1) and hexose (JrHT1 and JrHT2) transporters in walnut xylem parenchyma cells: their potential role in early events of growth resumption

Scanning electron microscopy has been used to examine silica isolated by chemical means from the wood of 32 species of woody perennial. The silica consists of aggregate grains lying free in the lumina or in ray and xylem parenchyma cells in 24 of the species. It occurs as dense silica in the other species, filling the lumina or lining the internal surfaces of vessels (and fibres) in all cases except Gynotroches axillaris where it is deposited in ray parenchyma cells. Infrared spectra and X-ray diffraction diagrams, obtained for specimens of both sorts of silica, are indistinguishable from those for amorphous silica. Aggregate grain and dense silicas are also alike in that their differential thermal analysis curves show a rather broad endothermic peak between 175° and 205°C. The results are discussed in relation to possible modes of deposition of the two sorts of silica and the tendency for silica in ray parenchyma cells to be associated with polyphenols.

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Presence of supercooling-facilitating (anti-ice nucleation) hydrolyzable tannins in deep supercooling xylem parenchyma cells in Cercidiphyllum japonicum

Planta ◽

10.1007/s00425-011-1536-3 ◽

2011 ◽

Vol 235 (4) ◽

pp. 747-759 ◽

Cited By ~ 18

Author(s):

Donghui Wang ◽

Jun Kasuga ◽

Chikako Kuwabara ◽

Keita Endoh ◽

Yukiharu Fukushi ◽

...

Keyword(s):

Ice Nucleation ◽

Xylem Parenchyma ◽

Hydrolyzable Tannins ◽

Cercidiphyllum Japonicum ◽

Parenchyma Cells ◽

Deep Supercooling

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Properties of the K+ inward rectifier in the plasma membrane of xylem parenchyma cells from barley roots: Effects of TEA+, Ca2+, Ba2+ and La3+

The Journal of Membrane Biology ◽

10.1007/bf00233442 ◽

1994 ◽

Vol 142 (3) ◽

pp. 363-379 ◽

Cited By ~ 34

Author(s):

L. H. Wegner ◽

A. H. De Boer ◽

K. Raschke

Keyword(s):

Plasma Membrane ◽

Inward Rectifier ◽

Xylem Parenchyma ◽

Parenchyma Cells

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The Protective Layer as an Extension of the Apoplast

IAWA Journal ◽

10.1163/22941932-90001312 ◽

1993 ◽

Vol 14 (2) ◽

pp. 163-171 ◽

Cited By ~ 14

Author(s):

J. R. Barnett ◽

P. Cooper ◽

Lynda J. Bonner

Keyword(s):

Cell Wall ◽

Protective Layer ◽

Xylem Parenchyma ◽

Pit Membrane ◽

Parenchyma Cells ◽

Deep Supercooling ◽

Dying Cells ◽

Tylose Formation ◽

Universal Application

The protective layer between the cell wall and plasmalemma of xylem parenchyma cells has variously been suggested to be involved in protection of the protoplast from attack by autolytic enzymes from neighbouring, dying cells, tylose formation, deep supercooling of xylem, and strengthening of the pit. None of these ideas has universal application to all species in which parenchyma cells possess a protective layer. It is proposed instead, that the protective layer is primarily laid down in order to preserve apoplastic continuity around the protoplast of a lignified cell, bringing the entire plasmalemma surface, and not just that part of it in contact with the porous pit membrane, into contact with the apoplast. If this is so, then other functions may be coincidental, or have arisen secondarily.

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NITROGEN IN WOOD AND ITS ROLE IN WOOD DETERIORATION

Canadian Journal of Botany ◽

10.1139/b66-167 ◽

1966 ◽

Vol 44 (11) ◽

pp. 1539-1554 ◽

Cited By ~ 156

Author(s):

Ellis B. Cowling ◽

William Merrill

Keyword(s):

Cell Wall ◽

Continuous Process ◽

Wood Fiber ◽

Significant Loss ◽

Chemical Form ◽

Present Knowledge ◽

Xylem Parenchyma ◽

Fiber Cells ◽

Parenchyma Cells ◽

Wood Deterioration

Based on present knowledge of the origin, amounts, chemical form, and distribution of nitrogen (N) in wood, hypotheses are proposed to explain radial gradients in N content that exist across the xylem cylinder of tree stems: (1) N in the cytoplasm of developing wood cells is diluted by apposition of cell wall substances; (2) after maturation of wood fiber cells, N in their cytoplasm is removed by elution into the transpiration stream; (3) death of xylem parenchyma cells during aging of sapwood and formation of heartwood is accompanied by removal of much of the N in their cytoplasm. Hypotheses 2 and 3 above suggest strongly that trees possess an internal recycling mechanism for conservation and reuse of the N in the cytoplasm of xylary cells.Although the supply of N in wood is meager, wood-destroying fungi readily metabolize the carbon-rich constituents of wood and produce large fruiting structures that release vast numbers of spores in nature. To account for these capacities, we postulate that these fungi employ one or more of the following three mechanisms: (1) preferential allocation of N obtainable from wood to substances and pathways highly efficient in the use of wood constituents; (2) reuse of N obtainable from wood by a dynamic and continuous process of autolysis and reuse without significant loss of N; (3) utilization of N sources outside the wood itself, for example, by fixation of atmospheric N.

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