Naturally durable heartwoods, where available, continue to be used as support structures in environments considered hazardous, particularly in ground contact. However, durability of heartwoods against wood decay microorganisms varies. Therefore, it is important to evaluate heartwood products for their in-service performance in order to maximise benefits derived from this valuable natural resource of limited supply. In the work presented, wood pieces from a kempas (Koompassia malaccensis) utility pole that had been placed in service in an acidic soil in Malaysia, and in time had softened at the ground-line position, were examined by light and transmission electron microscopy to evaluate the cause of deterioration.
Light microscopy (LM) provided evidence of extensive attack on fibre cell walls by cavity-producing soft rot fungi. Transmission electron microscopy (TEM) revealed in greater detail the distribution and micromorphologies of cavities as well as their relationships to the fine structure of fibre cell walls, which consisted of a highly electron dense middle lamella, a moderately dense S1 layer and a multilamellar S2 layer with variable densities, reflecting differences in lignin concentration. The resistance of the moderately dense S1 layer to soft rot was a feature of particular interest and is the main focus of the work presented. The resistance appeared to be correlated with high lignification of the outermost region of the S2 wall, interfacing with the S1 layer, an unusual cell wall feature not previously described for normal wood.
Xylem traits such as xylem vessel size can influence the efficiency and safety of water transport and thus plant growth and survival. Root xylem traits are much less frequently examined than those of branches despite such studies being critical to our understanding of plant hydraulics. In this study, we investigated primary lateral and sinker roots of six co-occurring species of semi-arid Australia. Two species are restricted to a floodplain, two were sampled only from the adjacent sand plain, and two species co-occur in both habitats. We assessed root wood density, xylem traits (i.e., vessel diameter, fibre and vessel wall thickness), outer pit aperture diameter and calculated theoretical hydraulic conductivity and vessel implosion resistance. We hypothesized that (1) roots have larger xylem vessel diameters and lower wood density than branches of the same species and that (2) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance for roots. Variation in root wood density was explained by variations in xylem vessel lumen area across the different species (r2 = 0.73, p = 0.03), as hypothesized. We rejected our second hypothesis, finding instead that the relationship between theoretical hydraulic conductivity and vessel implosion resistance was not maintained in roots of all of our studied species, in contrast to our previous study of branches from the same species. Xylem traits were found to depend upon habitat and eco-hydrological niche, with the groupings including (i) arid-adapted shrubs and trees with shallow lateral roots (Acacia aneura and Psydrax latifolia), (ii) trees restricted to the floodplain habitat, both evergreen (Eucalyptus camaldulensis) and deciduous (Erythrina vespertilio) and (iii) evergreen trees co-occurring in both floodplain and adjacent sand plain habitats (Corymbia opaca and Hakea sp.).
The structure and development of interxylary phloem (IP) and external phloem in Aquilaria sinensis were investigated using light and scanning electron microscopy. Complete IP strands were isolated, measuring 14 ± 4 mm in length and 417 ± 124 μm in width. The outer margin of IP was composed of two to three layers of fusiform parenchyma cells. The development of IP can be divided into five stages: 1) Locally IP starts its differentiation within a small segment of a broad cambial zone, at the cost of xylem differentiation. 2) Inward growth of IP advances, and fibres and sieve tubes differentiate. 3) IP is constricted by the encroachment of immature xylem cells between cambium and immature IP. 4) IP is isolated from the cambium and surrounded by immature, non-lignified xylem tissue. 5) IP is surrounded by lignified xylem tissue, and the fibres within IP become lignified.
In all the phloem islands in a ten-year-old stem, sieve elements showed positive staining of callose with aniline blue. However, no staining of callose was observed in the external secondary phloem of agarwood trees collected from two different sites. No sieve tubes or sieve pores were detected by SEM observation of numerous serial cross and radial sections of the external phloem. We therefore conclude that sieve tubes are absent from the external phloem or extremely rare and that the transport of photosynthetic products in the stem of A. sinensis takes place in the interxylary phloem.
Betula species have phellems with distinctive features such as stratification into thin paper-like layers, which are easily split in the tangential direction, and linear lenticels. We aimed to clarify the structure and development of the characteristic phellems of B. maximowicziana. In a normal periderm, phellem, phellogen, and phelloderm consist of tangentially elongated cells that are arranged in radial files. The phellem consists of layers of 1.4 ± 0.5 cells thick of very thin-walled phellem cells alternating with layers of 7.1 ± 1.5 thick-walled phellem cells. Seasonal sampling showed that the former and the latter were formed in the early and middle-to-late stages of the growing period, respectively. In lenticels, filling tissues alternated with closing layers. Most cells were collapsed and loosely packed in the filling tissue while all cells were intact and arranged in radial files in the closing layers. The filling tissue cells had unique walls that appeared to be easily deformed. Each annual increment of phellem in Betula is composed of a thin-walled cell layer (early phellem) and a thicker layer of thick-walled cells (late phellem). It is likely that the combination of filling tissue and closing layer in lenticels helps to perform the dual functions of gas exchange and protection, and that the collapse of the cells in filling tissue effectively contributes to gas permeability.
In his ‘Project of the New Testament’ Erasmus also wrote a running commentary on all New Testament books, except Revelation, in the form of a paraphrase. In this volume, the Paraphrase on Luke – Latin text with critical apparatus, and English introduction and commentary, is edited. In the paraphrase, Erasmus turns out to be a mature interpreter of the Bible, who advocated a new Christianity, which he called ‘the philosophy of Christ’, and implicitly criticized the clergy of his own age.
Silicified wood preserved in the Güdül fossil forest site in the Galatian Volcanic Province (GVP) near Ankara in Central Anatolia is described. The material comprises six petrified wood samples that date from early to middle Miocene. The woods have very low rays (2–5 cells high), bordered tracheidal pitting (9–10 μm), pinoid cross-field pits and very thin, unpitted, smooth walls of axial parenchyma and rays. This combination of characters indicates affinity to the fossil-genus Glyptostroboxylon. The presence of this wood genus suggests that the local environment was either riparian or wetland forest.
We describe a new fossil wood from the El Bosque Formation (Eocene) in Chiapas, southern Mexico. It has a combination of features found in the Anacardiaceae, including distinct growth rings, diffuse porosity, vessels solitary and in radial multiples of 2–3, simple perforation plates, medium to large alternate intervessel pits, vessel-ray parenchyma pits rounded and elongate with reduced borders, septate and non-septate fibers, axial parenchyma scanty paratracheal, vasicentric, apotracheal diffuse, Kribs heterogeneous rays type IIA, and multiseriate rays with radial canals. The mosaic of features of this wood supports the erection of a new genus, Bosquesoxylon Pérez-Lara, Castañeda-Posadas et Estrada-Ruiz. This new genus of anacardiaceous fossil wood extends our knowledge of this family’s history and offers hints on the possible relationships with floras from other localities worldwide, especially North America and Asia.
The systematics of a fossil wood assigned to Duabangoxylon (family Lythraceae) is described from the Deccan Intertrappean beds of Kutch, Gujarat, western India considered to be late Maastrichtian to early Danian in age. This fossil is the oldest record of Duabanga as its previous records are not older than Eocene. As the intertrappean flora of Kutch is poorly known, the present fossil not only enriches this flora but also helps in the reconstruction of palaeoclimate.