Publications

This paper contains a description of the only known non-banded bark in the geologic record. The bark is attached to a branch of the Araucarioxylon arizonicum tree that was found recently in the Late Triassic Chinle Formation (~ 220 Mya) in Arizona. In the fossil the vascular cylinder is almost totally enclosed in rough bark 2–11 mm in thickness. The inner bark is less than 1 mm thick and comprises a very narrow zone of presumed phloem containing infrequent fibers. The outer bark varies in thickness up to 10 mm, and consists of curving lenses of sequent periderm free of both dilation tissue and resin canals but is quite unlike the banded bark of Araucaria heterophylla . Wide zones of very thin-walled rectangular parenchyma cells arranged in radial files and groups of thin-walled spongy parenchyma, and small clusters as well as solitary sclerenchyma occur in the rhytidome. The vascular cambium contains 1–4 fusiform cells per radial file. Uniseriate rays are common in the secondary xylem and extend to the cambial zone. Small (1 mm in diameter), simple tunnels in the bark and wood indicate that the branch was attacked by phytophagous insects. A possible petrified beetle larva similar in form and size to Anobium is associated with these tunnels.

Following cation and anion exchange chromatography, 1-aminocyclopropane-1-carboxylic acid (ACC) was converted to the 2,4-dinitrophenyl derivative and then purified by high-performance liquid chromatography (HPLC). After three HPLC steps, endogenous ACC was identified by GCMS in the vascular cambium on the lower side of Pinus contorta Dougl. ssp. latifolia branches in association with compressionwood differentiation, but ACC was not detected in the opposite wood cambial region on the upper sides of the same branches.The possibility that ACC and ethylene have physiological roles in cambial activity and compressionwood tracheid differentiation is discussed.

Cambial stem chips containing intact cambium between xylem and phloem, or with the phloem layer removed, were cut from the main stem axis of four-year-old Eucalyptus globulus during the winter and grown under controlled environmental conditions for seven weeks on fully defined culture media . Light microscopy revealed that tyloses were induced in sapwood vessels in the region adjacent to the cambium within these stem chips. When incubated in autoclaved double-distilled water (control medium) tyloses were produced in 3.7% and 4.7% of vessels in chips with the phloem layer intact and removed, respectively. When non-hormonal ingredients were included, tyloses developed in 69.5% and 76.1% of vessels in chips with the phloem layer intact and removed, respectively. Addition of 1.0 mg l -1 of l-naphthalene acetic acid (NAA, a synthetic auxin) to the medium had a slight, but significant, inhibitory effect on tylosis formation.

The natural range of Porsild spruce (Picea glauca var. porsildii Raup), a white spruce variety distinguished by its smooth bark and resin blisters, has long been considered to be restricted to northwestern North America, but here it is noted that the same phenotype exists in wild stands in Ontario, Quebec, and Atlantic Canada. No record of Porsild spruce trees yet exists in the region between Alberta and western Ontario, or anywhere in the United States other than Alaska. The forestry community is requested to document any encounters with Porsild spruce in unmanaged stands, in order that its full range can be established. History and potential scientific importance of Porsild spruce are given consideration.

Radial files of tracheids having changing orientations were traced through serial tangential sections to deduce events in fusiform cambial cells (FCCs) associated with spiral grain formation. Within an induction bridge of phloem and cambium sloping diagonally across a stem girdle in Pinus contorta Dougl. ssp. latifolia, repetitive, homologously sloping, pseudo-transverse anticlinal divisions in FCCs were a primary event contributing to FCC orientation changes. Imperfect periclinal divisions (IPDs) in FCCs also contributed. In Picea glauca (Moench.) Voss, IPDs and FCC elongation interacted to change tracheid orientation during natural spiral grain development. In both natural and induced reorientations, small numbers of adjoining FCCs changed their orientation abruptly while the greater population of FCCs changed orientation less rapidly. These sites of abrupt reorientation are termed "microdomains."not available

BIOCHEMISTRY OF SEASONAL CAMBIAL GROWTH AND WOOD FORMATION - AN OVERVIEW OF THE CHALLENGES. Introduction. Practical significance of biochemistry research into cambial growth. Woods: chemically heterogeneous biosynthetic end products. General and specific pathways of development during wood formation. Distinguishing and isolating cells of the cambial region. Manipulating cells of the cambial region. Some of the research challenges. Conclusions. References. CYTOSKELETON, CELL WALLS AND CAMBIUM: NEW INSIGHTS INTO SECONDARY XYLEM DIFFERENTIATION. Introduction. Role of the cytoskeleton in wood formation. A cytoskeletal approach to designer wood. The future. References. ETHYLENE, OXYGEN AND CARBON DIOXIDE IN WOODY STEM DURING GROWTH AND DORMANCY. Introduction. Methods for sampling, identification and quantification of carbon dioxide, oxygen and ethylene. The source of carbon dioxide, oxygen and ethylene. Physiological effects of carbon dioxide, oxygen and ethylene. Conclusions and perspectives for the future. References. CAMBIAL CONIFERIN CONTENT AS AN INDICATOR OF HEALTH STATUS OF CONIFERS. Introduction. Materials and methods. Results and discussion. References. SEASONAL VARIATION IN THE K, Ca AND P CONTENT AND DISTRIBUTION OF PLASMA MEMBRANE H+-ATPase IN THE CAMBIUM OF POPULUS TRICHOCARPA. Introduction. Seasonal variation in the fine structure of the vascular cambium. Seasonal changes of the K, Ca and P content in the cambium. Immunolocalization of PM-H+ATPase activity in the cambium. Conclusions. References. PHOTOSYNTHATE ALLOCATION TO THE VASCULAR CAMBIUM: FACTS AND PROBLEMS. Introduction. The structural relationship of rays and cambium. Accumulation pattern of storage materials and flow rates of sugars and N compounds. Sucrose synthase activity of the cambium zone. References. SYMPLASMIC ORGANIZATION OF THE TRANSPORT PHLOEM AND THE IMPLICATIONS FOR PHOTOSYNTHATE TRANSFER TO THE CAMBIUM. Introduction. The different tasks of the phloem in seed plants. Ultrastructure of the companion cells in dicotyledons. Translocation of photosynthate and lateral release from the transport phloem in dicotyledons. Experimental assessment of the symplasmic organization of the transport phloem. The organization of the transport phloem and the post-phloem pathways. Conclusions on the symplasmic organization of transport phloem. The battle for photosynthates in the apoplast and the consequences for photosynthate supply to the cambium. Speculations on the consequences of the phloem design for photosynthate allocation between axial and terminal sinks. Concluding remarks. References. WATER AND SOLUTE RELATIONS OF THE CARROT CAMBIUM STUDIES AT SINGLE-CELL RESOLUTION. Introduction. Techniques of study. Results. Discussion. References. INFLUENCE OF SUCROSE ON CAMBIAL ACTIVITY. Introduction. Species investigated and general approach. Dynamics of sucrose concentration in cambial tissue. Identification and characterization of cambial derivatives. Conclusions. References. DARK FIXATION BY THE CAMBIUM AND ITS DERIVATIVES. Introduction. Sources of carbon dioxide. Enzymes of dark fixation. Dark fixation in pine cambium. Implications of dark fixation. Conclusion. References. WOOD FORMAITON IN HYBRID ASPEN (POPULUS TREMULA L. X POPULYS TREMULOIDES MICHX) GROWTH UNDER DIFFERENT NITROGEN REGIMES. Introduction. Materials and methods. Results. Discussion. References. THE FORMATION OF CAMBIUM FROM CALLUS IN GRAFTS OF WOODY SPECIES. Introduction. The anatomy of the developing graft union. Factors involved in cambium formation. Consequences for understanding of the cambium. References. CAMBIAL GROWTH AND AUXIN GRADIENTS. Introduction. IAA and cambial growth. Earlier models explaining the role of IAA in seasonal and spatial control of cambial growth. Towards a new concept of the role of IAA in cambial growth. Spatial and seasonal variation of IAA and its control of cambial growth pat

Black spruce (Picea mariana) reproduces sexually from seeds and asexually by layering. There is a prevalent concept that clonal reproduction maintains populations of this species in the subarctic and arctic regions. We used microsatellite DNA markers of the nuclear genome to investigate the genetic structure of montane and subalpine black spruce populations from the Western Yukon Plateau in relation to this concept. Sixty individual trees at a minimum distance of 4 m from each other were sampled from each of four populations and individual trees were genotyped for eight microsatellite loci. Each of the 60 individuals from three montane pure black spruce populations growing on flat terrain at relatively low elevations had unique multilocus genotypes, indicating an absence of clonal structure in those populations. However, in an anthropologically undisturbed climax white spruce-dominated subalpine black spruce population on a northwest slope near Mount Nansen, the majority of the sampled individuals belonged to eight genetically distinct clones (genets). Clone size differed by altitude, the dominant genet being nearest the timberline–tundra ecotone. The results indicate that black spruce reproduction is variable and adaptive, being primarily sexual in flat-terrain montane populations previously subjected to fire disturbance, but mixed vegetative–sexual in the anthropogenically undisturbed subalpine population. This study is the first to employ molecular markers a priori to examine the mode of reproduction in natural black spruce populations.

Between the Klondike Plateau and Yukon–Tanana highlands of Yukon and Alaska, respectively, current maps explain glaciated alpine locales and periglacial areas in terms of localized Pliocene–Pleistocene montane ice caps, alpine glaciers, and periglacial changes. However, this region’s plateau topography is populated with long undulating ridges having wide flattened tops; it contrasts with relief of other regions of northwestern North America also affected by ice caps, cryoplanation, and erosion over similar duration during the same epochs. This region has received minimal research and appears to present a new opportunity for resolving outstanding glaciological and stratigraphy issues. The glaciological history is reviewed, placing particular emphasis upon the low-elevation ridges within the “unglaciated” region, suggesting that those ridges are relict arête/cirque remnants. Sites of subalpine glacial grooving and mountaintop planing are also identified, and a conglomeratic red bed containing erratic clasts is described. All indications point to the “unglaciated” region having been glaciated before late Pliocene. Two working hypotheses are proposed: (1) The landscape once supported a range of young mountains that became glaciated then overridden and pared to a plateau by an ice sheet. (2) Following deglaciation, an extended period of paraglacial activity removed most of the former drift and excised new valleys to give the region an unglaciated appearance, which thereafter became modified into its present state by local montane/alpine glaciations, interglacial cryoplanation, periglacial gelifraction, and erosion. In addition to Pliocene–Pleistocene glaciations, a northeastward advancing Miocene ice sheet seems plausible and, on the basis of paleographic considerations and lithology, a Cretaceous glaciation evidently is also not out of the question.

Endogenous indol-3yl acetic acid (IAA) was characterized by combined gas chromatography – mass spectroscopy (GC–MS) in inactive cambia of Pinus contorta Dougl. and Larix decidua Mill, during winter, and IAA levels were estimated by GC–MS in buds, needles, and the tissues comprising the inactive cambial region of P. contorta during late autumn and winter. Supplementary IAA estimates were obtained for cambia of Acer pseudoplatanus L., L. decidua, Populus × canadensis 'Robusta,' and Quercus robur L. IAA levels in cambial tissue of lodgepole pine were higher than those in similar-aged tissue of hardwoods throughout the winter.Both winter disbudding and defoliating treatments reduced levels of endogenous IAA in the cambial region of lodgepole pine. Moreover, exogenous [ 14 C]IAA and [ 14 C]sucrose were transported downward in the stem during winter. Microscopy suggested functional sieve cells to be present during winter, and the moisture content of the cambial region of lodgepole pine was more than twice that of overwintering hardwoods.Thus, the vascular cambium of P. contorta probably is not dependent upon a supply of IAA from extending shoots and growing needles for its reactivation in spring. The findings also suggest that IAA production and export from metabolically active buds and mature needles may occur during winter.