Indole-3-acetic acid level in wood,bark and cambial sap of apple rootstocks differing in growth vigour

Free and conjugated IAA levels were determined in wood, bark and cambial sap of M.9, M.26 and MM.106 apple rootstock genotypes differing in growth vigour. The measurements were done on May 15^th, June 15^th and July 15^th. The level of free IAA in bark and wood of the tested trees varied from 27.0 to 52.7 ng·g⁻¹ f.w. while the conjugated hormone content averaged 3–5 times higher. In the bark and wood samples, the differences in auxin content between rootstock genotypes and the time of stem harvesting were insignificant. The level of free IAA in cambial sap was on average 10 to 20 times higher than in both bark and wood tissues, while the conjugated hormone level varied from none (below detection limit) to 37 ng·g⁻¹ f.w. Content of free IAA level in cambial sap from dwarf M.9 rootstock was significantly lower than that in either of the more vigorous genotypes. In both vigorous rootstocks IAA level in cambial sap remained at a similar level at all sampling dates but M.9 cambial sap showed a trend towards decreasing auxin content later in the growing season.     

Collophora hispanica,a New Pathogen and Potential Threat to the Almond Industry in Iran

Trunk diseases are potential threats for almond productivity and longevity worldwide, including Iran. In a recent survey on fungal species associated with trunk diseases of almonds in north‐western Iran, Collophora isolates (tentatively identified as Collophora hispanica) were recovered with high frequency from wood samples with internal necrosis and brown to black vascular streaking of almond trees showing symptoms of decline. However, the pathogenic potential of Collophora isolates on almond trees in Iran remains unproven. In this study, the identity of the isolates was further confirmed as C. hispanica based on a combination of morphological data and sequence data of ITS‐rDNA region, and pathogenicity of C. hispanica isolates on almond was evaluated using excised shoot method and in greenhouse experiments. Collophora hispanica isolates induced lesions statistically different from the control, in both excised shoot method and greenhouse assays. Significant differences were observed among the isolates in the length of the lesion induced on wood. Collophora hispanica should be considered as the main trunk pathogens of almond trees in north‐western region of Iran. The distribution and host range of this new pathogen on almond remains to be studied.     

What is disjunctive xylem parenchyma? A case study of the African tropical hardwood Okoubaka aubrevillei (Santalaceae)

The morphological variation and structure-function relationships of xylem parenchyma still remain open to discussion. We analyzed the three-dimensional structure of a poorly known type of xylem parenchyma with disjunctive walls in the tropical hardwood Okoubaka aubrevillei (Santalaceae). Disjunctive cells occurred among the apotracheal parenchyma cells and at connections between axial and ray parenchyma cells. The disjunctive cells were partly detached one from another, but their tubular structures connected them into a continuous network of axial and ray parenchyma. The connecting tubules had thick secondary walls and simple pits with plasmodesmata at the points where one cell contacted a tubule of another cell. The imperforate tracheary elements of the ground tissue were seven times longer than the axial parenchyma strands, a fact that supports a hypothesis that parenchyma cells develop disjunctive walls because they are pulled apart and partly separated during the intrusive growth of fibers. We discuss unresolved details of the formation of disjunctive cell walls and the possible biomechanical advantage of the wood with disjunctive parenchyma: the proportion of tissue that improves mechanical strength is increased by the intrusive elongation of fibers (thick-walled tracheids), whereas the symplastic continuum of the parenchyma is maintained through formation of disjunctive cells.     

Review on antibacterial biocomposites of structural laminated veneer lumber

In this review, the characteristics and applications of structural laminated veneer lumber made from planted forest wood is introduced, and its preparation is explained, including various tree species and slab qualities, treatments for multiple effects and reinforced composites. The relevant factors in the bonding technology and pressing processes as well as the mechanical properties, research direction and application prospects of structural laminated veneer lumber made from planted forest wood are discussed.     

Fungal diversity and deterioration in mummified woods from the ad Astra Ice Cap region in the Canadian High Arctic

Non-permineralized or mummified ancient wood found within proglacial soil near the ad Astra Ice Cap (81°N, 76°W), Ellesmere Island, Canada was investigated to ascertain the identification of the trees, current morphological and chemical characteristics of the woods and the fungi within them. These woods, identified as Betula, Larix, Picea and Pinus, were found with varying states of physical and chemical degradation. Modern microbial decomposition caused by soft rot fungi was evident and rDNA sequencing of fungi obtained from the samples revealed several species including Cadophora sp., Exophiala sp., Phialocephala sp., as well as others. Analytical ¹³C-labeled tetramethylammonium hydroxide thermochemolysis showed the lignin from the ancient wood was in a high degree of preservation with minor side chain alteration and little to no demethylation or ring hydroxylation. The exposure of these ancient woods to the young soils, where woody debris is not usually prevalent, provides carbon and nutrients into the polar environment that are captured and utilized by unique decay fungi at this Arctic site.     

Leaching potential and forms of phosphorus in deep row applied biosolids underlying hybrid poplar

Biosolids deep row incorporation (DRI) offers an alternative recycling approach for bioenergy crop production, but phosphorus additions in excess of the vegetation requirements can potentially impair water quality. The effects of DRI of anaerobically digested (AD) and lime-stabilized (LS) biosolids at four rates (213, 426 Mg ha⁻¹ for AD and 328, 656 Mg ha⁻¹ for LS) and a single rate of conventional P fertilizer on leaching of PO₄-P, and TKP were investigated in a hybrid poplar plantation in a coastal plain heavy mineral mine reclamation site. The effects of AD and LS biosolids aging on the transformations and losses of P applied with the biosolids were also studied. Zero tension lysimeters were installed at the site to collect leachate. Samples were collected at least monthly for 30 months between July 2006 and December 2008. We also analyzed biosolids P (labile P, Al-, Fe-bound-P, Ca-bound-P, total P, Mehlich 1 P) fractions. The loss of P was determined and P binding constituents were described via regression analysis. Orthophosphate and TKP from the DRI biosolids leached in negligible amounts, and were similar to leaching from conventional P fertilization. Most of the P was Al- and Fe-bound in the AD biosolids and Ca-bound in the LS biosolids. Labile P decreased with decrease in organic C, which indicated that P leaching potential from the DRI biosolids decreased with aging. Our results indicated that P mobility from biosolids of the type used should not pose a water quality risk.     

Pit membrane remnants in perforation plates and other vessel details of Cornales

Perforation plates and other vessel details as studied with scanning electron microscopy (SEM) have been reported for four species of Cornaceae (s.l.): similar features are shown by the four, suggesting that a more extensive sampling of the family might reveal similar phenomena. Perforation plates contain pit membrane remnants in the form of threads or, less commonly, laminar portions perforated by pores. When least well-represented, the pit membrane remnants are restricted to lateral ends of perforations and to the perforations transitional to lateral wall pitting. Perforations are all clearly bordered. Helical thickenings that do not form a continuous gyre are reported for the vessel walls ofAucuba. The presence of pit membrane remnants in vessel elements of Cornaceae correlates with the mesic habitats occupied by species in this family. The presence and type of pit membrane remnants reported by us in the three genera is very similar, although pit membrane remnants are doubtless a symplesiomorphy and thus not an indicator of relationships. The presence of pit membrane remnants in the three genera, however, does attest to the primitiveness of wood and other features of Cornaceae s.l.     

人工林青梅木材构造的初步研究

解剖了人工林青梅木材.用切片、显微摄影的方法,通过观测,得到如下结果:⑴导管、木纤维、轴向薄壁组织和射线薄壁组织的比例相近,但木纤维最多.⑵管孔数目随生长轮数的增加而减少,而导管切向直径却增加.⑶树木的实际生长年龄比生长轮数少得多.⑷木材解剖特征的演化不均一.同时,对木材性质与构造的关系、解剖特征的系统发育、木材生长的规律进行了初步探讨.     

Adaptive Growth of Gymnosperm Branches-Ultrastructural and Micromechanical Examinations

The top, the lateral and the underside of basal branch segments of two gymnosperm species, spruce (Picea abies [L.] Karst.) and yew (Taxus baccata L.), were studied with respect to possible adaptation in structural and mechanical properties. Microtensile tests were performed on thin wet foils, which were removed from the periphery of the branches. Structural parameters such as density and the microfibril angle in the S2-layer were examined to investigate the structure-function relationships of the branch wood. The top, the lateral and the underside of both branches showed significant differences in their structural and mechanical properties. However, no significant variations were observed as a function of age and size development. The findings were discussed in view of adaptive growth strategies of trees, including biomechanical constraints of a horizontally growing branch.