Cedroxylon shakhtnaense (Blokhina 2010) Dolezych, Mantzouka et L.Kunzmann comb. nov.; A fossil Abies wood from the late early Miocene Mastixioideae flora of Wiesa (east Germany)

We describe the first evidence of fossil Abies wood from the late early Miocene fossil plant assemblage of Wiesa in east Germany. The comparatively well-preserved piece of xylitic wood was recovered in the kaolin quarry at Hasenberg hill in Wiesa. The Wiesa assemblage is characterized as being allochthonous and partly parautochthonous mass deposits of diaspores, leaves, and wood. The latter component is rather incompletely studied so far. The described fossil is characterized by high rays, mostly uniseriate bordered pits, generally thick and pitted horizontal and tangential ray cell walls, but also partly smooth horizontal ray cell walls, absence of ray tracheids, the occurrence of traumatic resin canals, and rare occurrence of axial parenchyma of two types. This type of fossil wood has been described as Abietoxylon shakhtnaense Blokhina from the Oligo-Miocene of Sakhalin, Russia. Due to nomenclatural issues of Abietoxylon a recombination to Cedroxylon Kraus emend. Gothan is proposed following common practice for affiliation of abietoid fossil wood of Cenozoic age. Cedroxylon shakhtnaense comb. nov. shares anatomical characteristics with the wood of extant Abies Mill., in particular with sections Abies and Grandis, and is most closely related to section Grandis. The properly preserved fossil wood from Wiesa provides the opportunity of applying qualitative and quantitative analyses for testing and discussing its placement in relationship to intra-tree variability and ontogenetic aspects. The first evidence of fossil wood of Abies from Wiesa confirms again the presence of the genus in mid-latitude subtropical zonal vegetation during the beginning of the Miocene Climatic Optimum.

Geographic variation in resin canal defenses in seedlings from the Sitka spruce × white spruce introgression zone

Seedlings from 18 provenances along a coast-interior transect in the Picea sitchensis (Bong.) Carrière × Picea glauca (Moench) Voss introgression zone in northwestern British Columbia were mechanically wounded at the beginning of their third growing season to simulate natural attack by the white pine weevil, Pissodes strobi (Peck). Constitutive resin canals (CRC) in the cortex and traumatic resin canals (TRC) in the xylem of terminal shoots were characterized microscopically 4 months after wounding. Wounding resulted in a large increase in CRC size and in TRC number and density. Provenances differed significantly in TRC number and in CRC number, size, total area, and the proportion of total bark area occupied by CRC. CRC number and size, TRC number, and provenance weevil resistance (obtained from previously published data) increased with increasing latitude, elevation, and distance from the Pacific Ocean (i.e., towards the P. glauca end of the introgression zone) and decreased with increasing longitude (i.e., towards P. sitchensis). These traits also increased with aridity and continentality and decreased with most temperature, precipitation, and growing season length variables. Statistically significant multiple regression models related variation in some resin canal traits to geographic (r2 = 0.71) and climatic (r2 = 0.62) variables. Provenance mean values for weevil resistance were positively associated with predicted values for TRC number and CRC size. These results indicate that it is possible to predict locations in the introgression zone containing trees that possess desirable resin canal traits using geographic or climatic variables.

Seasonal Variation in Traumatic Resin Canal Formation in Chamaecyparis Obtusa Phloem

Trunks of Chamaecyparis obtusa were injured to examine seasonal differences in traumatic resin canal formation in secondary phloem. Even after wounding during winter, differentiation of axial parenchyma into epithelium was initiated, and vertical resin canals formed. After winter wounding, resin canal development was slower and the tangential extent of resin canals was narrower than after spring wounding, and it took one to two months until resin secretion began. After spring wounding, the sites of resin canal formation were the 1- and 2-year-old annual rings of phloem. In August, the location of resin canal formation shifted into the current and 1-year-old annual ring. Resin canals never formed in secondary phloem areas that were 3 or more years old. In C. obtusa trunks that are affected by the resinous stem canker, numerous tangentiallines of resin canals are found throughout the phloem, not just recent and 1- to 2-year-old phloem. The present research indicates that these many lines of resin canals were not formed at one time, and that the stimuli that induce traumatic resin canals must occur repeatedly over many years. The data on artificial wounding effects are useful for understanding resinous stem canker.

An induced defense reaction in white spruce to attack by the white pine weevil, Pissodesstrobi

An induced defense reaction in the leaders of white spruce, Piceaglauca (Moench) Voss, occurs in response to attack by the white pine weevil, Pissodesstrobi Peck. The response was initiated shortly after feeding and oviposition in the attacked shoot and consisted of the cambium switching from producing normal tracheids and parenchyma ray cells to producing traumatic resin canals, arranged in a ring fashion in the developing xylem. In sectioned leaders, these traumatic resin canals could be seen emptying their contents into feeding and oviposition cavities dug by the adults, and into the larval galleries. This defense reaction killed eggs and larvae. When the leader survived the attack, the cambium reverted to producing normal xylem tissue, leaving one or more rings of traumatic resin canals embedded in the xylem annual ring.

Seasonal Characteristics of Wood Formation in Hopea Odorata and Shorea Henryana

Seasonal characteristics of wood formation were investigated using the pinning method in Hopea odorata and Shorea henryana in a natural dry evergreen forest of eastern Thailand. The position of cells having initiated S1-layer formation at the time of pinning was estimated in the zone where cells were directly injured by the pinning and consequently destroyed. The position of cambial initials at the time of pinning was estimated in the zone where cells were indirectly affected by the pinning and continued their physiological activity resulting in the formation of aberrant cells. Traumatic resin canals were occasionally formed in Shorea. These canals were formed after pinning and could, therefore, not record the exact time of the pinning. Diameter growth of both species was greatest in the rainy season and decreased in the dry season.

Control of fusiform initial orientation in the vascular cambium of Abies balsamea stems by indol-3-ylacetic acid

Fusiform initial reorientation, deduced from changes in tracheid arrangement, was investigated in helical bridges left after Abies balsamea stems were girdled. The first responses included an increase in the number of S- and Z-oriented anticlinal divisions without any change in their ratio, a decrease in fusiform initial length, and the formation of traumatic resin canals. Subsequently, normal tracheid differentiation resumed, the frequency of anticlinal divisions further increased, and there was an increase in the number of oriented intrusive growth events. The orientations of the anticlinal wall and of the intrusive growth were predominantly in the direction that eventually would result in the fusiform initials being aligned parallel to the bridge angle. The application of exogenous indol-3-ylacetic acid to the upper edge of a helical bridge inhibited fusiform initial reorientation, mainly by decreasing the frequency of oriented intrusive growth events. However, immediately below the application point, exogenous indol-3-ylacetic acid also induced the fusiform initials to begin temporarily to realign so as to be perpendicular to the bridge angle. The transport of a pulse of [1-14C]indol-3-ylacetic acid applied to the shoot apex was inhibited 1 day after girdling in both helical and longitudinal bridges, particularly the former, whereas it was inhibited only in helical bridges at the end of a subsequent 11-week growing period. The degree of inhibition in the helical bridges was greater the day after girdling than at the end of the growing period, during which interval fusiform initial reorientation occurred at the bottom of the bridge width. The results support the conclusion that the orientation of fusiform initials is parallel to the direction of indol-3-ylacetic acid transport.

The pathogenicity of Diplodia pinea to Pinus radiata D. Don

In the Pinus radiata stands of north-eastern Victoria the symptom "dead top" is common and consistently associated with the fungus Diplodia pinea. In order to resolve the pathogenic status of D. pinea, its association with disease symptoms has been studied by histological examination and tissue isolations following greenhouse and field inoculations. Malformations were associated with infection by D. pinea and although the amount of tissue killed was small, the defect induced was considerable. Damage to the leader caused the greatest loss in wood quality. The fungus attacked the pith very readily after gaining access to this tissue through injuries and via needle or cone traces. In the pith, the fungus spread slowly downwards and was protected from changes in the external environment. Injection of D. pinea spores into the pith resulted in a very high percentage of infection, and caused the malformations and other symptoms associated with attack by this fungus in the field. Histological studies showed that the fungus spread rapidly in the pith tissues, causing alterations in cambial function which produced traumatic resin canals, parenchymatous cells, and compression wood. Field trials showed that fast-growing trees were more severely affected than slower-growing ones, and the latter recovered more quickly. The fungus persisted in the infected tissues for up to 400 days.