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Quiescent 6-year-old lodgepole pine (Pinus contorta Dougl. var. latifolia) were transferred in midwinter from outdoors to warm, long-day greenhouse conditions. Vascular cambia from these trees were harvested on the day of transfer and weekly thereafter until xylem development became apparent. The stage of cambial reactivation in each tree was assessed by microscopy. Cambial extracts were then analyzed quantitatively by high-performance liquid chromatography (HPLC) at four ultraviolet wavelengths. A major HPLC peak, at 254 nm, was associated with radial expansion of cambial derivatives and increased markedly with secondary-wall formation and lignification in differentiating tracheids. The presence of this peak suggests a facile means for assessing commitment to tracheid differentiation in lodgepole pine.

Conference Article| May 01 1992 Evidence for coniferyl-alcohol oxidase promotion of lignification in developing xylem of conifers Rodney A Savidge; Rodney A Savidge 1Dept Forest Resources, Univ New Brunswick, Fredericton, NB, E3B 6C2, Canada Search for other works by this author on: This Site PubMed Google Scholar Preethi V Randeniya Preethi V Randeniya 1Dept Forest Resources, Univ New Brunswick, Fredericton, NB, E3B 6C2, Canada Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1992) 20 (2): 229S. https://doi.org/10.1042/bst020229s Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation Rodney A Savidge, Preethi V Randeniya; Evidence for coniferyl-alcohol oxidase promotion of lignification in developing xylem of conifers. Biochem Soc Trans 1 May 1992; 20 (2): 229S. doi: https://doi.org/10.1042/bst020229s Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1992 Biochemical Society1992 Article PDF first page preview Close Modal You do not currently have access to this content.

At present, a carbon (C) content of 50% (w/w) in dry wood is widely accepted as a generic value; however, few wood C measurements have been reported. We used elemental analysis to investigate C content per unit of dry matter and observed that it varied both radially and vertically in boles of two old-growth tree species: sugar maple (Acer saccharum Marsh.) and giant sequoia (Sequoiadendron giganteum (Lindl.) Bucholz). In sugar maple there was considerable variation in tree ring widths among four radii for particular annual layers of xylem, revealing that the annual rate of C assimilation differs around the circumference and from the base of each tree to its top, but the observed variation in C content was unrelated to diameter growth rate and strongly related to the calendar year when the wood was formed. Carbon content in sugar maple wood increased in an approximately linear fashion, from < 50 to 51% from pith to cambium, at both the base and top of the boles. In giant sequoia, C was essentially constant at > 55% across many hundreds of years of heartwood, but it declined abruptly at the sapwood-heartwood boundary and remained lower in all sapwood samples, an indication that heartwood formation involves anabolic metabolism. Factors that may be responsible for the different C contents and trends with age between sugar maple and sequoia trees are considered. Tree-ring data from this study do not support some of the key assumptions made by dendrochronology.

A critique is provided of the physical and chemical control of primary and secondary xylem development in terms of mechanics, genetics, phylogenetics, and the larger field of plant physiology. Strengths and weaknesses of the phytohormone theory of vascular development are analyzed. Homeobox genes, sub-cellular phytohormone localization, anatomical responses to varied phytohormone ratios and dosages, polar auxin transport, second messengers, radial fluxes in water potential, intercellular signalling, lignin biochemistry, and the phylogenetic position of bryophytes in relation to xylogenesis are identified as some areas for future research. Homeodomain proteins are addressed in terms of cambial initials and cell-fate determination, and other genetic and environmental factors controlling differentiation of diverse cellular phenotypes are reviewed. As a 'continuum hypothesis', it is proposed that the extent of secondary wall sculpturing during tracheary element differentiation is a function of the duration of homeotic gene expression.

Several new developments are noted since publication of “Porsild spruce in Canada” in The Forestry Chronicle in January 2013. Firstly, Porsild spruce has been found in northeastern Quebec. Secondly, although researchers were unaware of the fact until now, the Porsild spruce phenotype has been found to be a common component in the New Brunswick tree improvement program’s second-generation seed orchard in support of reforestation. Thirdly, a wild tree discovered in New Brunswick displays morphological features of Engelmann spruce and, based on observed similarities between Yukon Beringia Porsild spruce phenotypes and the accepted Engelmann spruce phenotype, it is possible that the New Brunswick Engelmann spruce tree was derived from the local Porsild spruce population.

In this investigation, the effects of exogenous indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and 1-aminocyclopropane-1-carboxylic acid (ACC) on anatomical development within cultured segments of <i>Abies balsamea</i> (L.) Mill. were compared, using debudded and defoliated leaders produced in the preceding year as bioassay material. In stem apical regions, IAA promoted radial enlargement of pre-existing cortical resin ducts and attending parenchyma enlargement, whereas IBA promoted cell division and expansion of parenchyma on the outer edge of phloem without altering cortical duct shape. Cortical woody ducts, each partially surrounded by cambium, were observed as a novel but infrequent feature. A single cortical woody duct was spatially associated with each mature leaf as its vascular trace, and they were not encountered elsewhere in the cortex, nor were they induced to form in response to any hormone application. An unknown leaf factor induces the development of cortical woody ducts. Both IAA and IBA promoted cell division in the vascular cambium. The common cellular response at the interface between the latewood boundary and cambial zone was the radial expansion of primary-walled fusiform cambial cell derivatives with little if any ensuing tracheary element (TE) differentiation. Enhanced TE production at basal stem positions occurred when ACC was provided with IAA and/or IBA, and an IAA + IBA + ACC combination produced a basal stem response similar to that in untreated segments having intact leaves. The data support the conclusion that IAA, IBA, and ACC have distinct but complementary roles in the overall regulation of the types of cellular differentiation that contribute to cortex histogenesis and diameter growth of balsam-fir leaders.

Endogenous E-coniferin was characterized chemically and found to accumulate in cambia of Picea glauca, Pinus banksiana, Pinus strobus, and Larix laricina at the time of resumption of springtime cell-division activity and well before the initiation of lignification in differentiating tracheids. Coniferin content, quantified by high performance liquid chromatography, was highest on the centripetal side of the cambium, in developing xylem, at time of radial expansion of cambial derivatives. Stem ringing resulted in coniferin accumulation above the ring and disappearance below the ring. Coniferin was absent from leaves and dormant cambia. Exogenous coniferin was metabolized rapidly by in vitro cultures of P. strobus cambium grown on a defined medium containing the auxins 1-naphthalene acetic acid and indol-3-yl acetic acid and the cytokinin benzylaminopurine. The evidence suggests coniferin content of the cambium will be of practical value for determining commitment to and competence for wood formation in conifers.

Coniferin, the 4-O-β-D-glucopyranoside of trans-coniferyl alcohol, occurs as a dominant metabolite in conifers and has also been reported in woody angiosperms. Coniferin has long been considered as a storage precursor of gymnosperm lignin, and more recently coniferin content of the cambial zone has been suggested as a biochemical indicator for wood formation in conifers. However, coniferin is not present in the cambium except during cambial growth. Moreover, coniferin content rises well before lignification commences in springtime and disappears prior to completion of lignification at the end of the growing season.Appearance and activity of UDP-glucose: coniferyl alcohol glucosyltransferase (CAGT), the enzyme catalysing production of coniferin from coniferyl alcohol, is not specifically linked to lignification but rather specifically associated with the annual cycle of growth and dormancy. Progress in genetic engineering of lignin content and composition has raised questions about the basic concept of lignin biosynthesis, indicating that the metabolic flexibility may be broader than previously thought. The incorporation of labelled coniferin into syringyl units of angiosperm wood as well as interconversions between cinnamyl alcohols and cinnamyl aldehydes have indicated that the turnover of lignin precursors may occur distantly downstream from the phenylpropanoid acid and/ or cinnamyl CoA-ester stages. We found in vitro that CAGT could convert cinnamyl alcohols as well as cinnamaldehydes. Our results support the view that CAGT has a regulatory influence and lignin modulating function exceeding mere substrate supply in support of guaiacyl lignification.

Coniferyl alcohol oxidase (CAO), a catechol oxidase (o-diphenol:oxygen oxidoreductase, E.C.1.10.3.1) specifically associated with lignification during wood formation in conifers, is described and its activity is compared with that of peroxidase. CAO activity is not affected by provision of H2O2, and although CAO is an O2-requiring enzyme able to oxidize substrates in common with laccase, CAO is distinct from laccase in catalytic rate, amino acid composition, response to effectors, copper content and type, protein size, and immunodetectability. Peroxidase activity, readily detected in phloem, cambium and xylem, was inversely correlated with lignification. In contrast, CAO activity was restricted to the lignifying zone. Peroxide and superoxide anion were found in the phloem and cambial zone, respectively, but a pool of H2O2 in support of lignification could not be detected in lignifying xylem or elsewhere. Additional evidence has indicated that coniferin hydrolysis may be the rate limiting step in the supply of coniferyl alcohol for oxidation by CAO.