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Buchbesprechungen

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HPLC based activity profiling for 5-lipoxygenase inhibitory activity in Isatis tinctoria leaf extracts

In the pursuit of the anti-inflammatory constituents in lipophilic woad extracts, the 5-lipoxygenase (5-LOX) inhibitory activity was investigated by HPLC-based activity profiling. In a low-resolution profiling, two time windows with peaks of activity were found. The first coincided with tryptanthrin, a known dual inhibitor of cyclooxygenase-2 (COX-2) and 5-LOX, whereas the major inhibitory fraction was towards the end of the HPLC run. The active fractions were profiled in a peak-resolved manner, and the compounds analyzed by LC-MS, GC and TLC. The activity in the lipophilic fractions of the Isatis extract could be linked to an unsaturated fatty acid, alpha-linolenic acid.     

Infection of Scots pine seedlings by Gremmeniella abietina during summer under different inoculum potential

The connection between natural conidia dispersal of Gremmeniella abietina (A‐type) and the disease incidence and severity in first and second year conifer seedlings of Pinus sylvestris was studied in central Finland. The seedlings where exposed to natural infection for a 3‐week period throughout the growth season, followed by a 3‐week incubation period in a growth chamber to promote symptom expression. In second year seedlings the infection periods in May–June had a similar effect as regards disease outbreak and roughly half of the successful infections occurred during these periods. However, the first year seedlings were more severely diseased after the infection period in late July/early August, although the inoculum density was lower during this time compared with the period in late June/early July. This result is consistent with earlier studies. The effect of age and growth phase of the seedlings, temperature sum and the number of conidia on the disease occurrence is discussed and compared with the results of earlier studies in which artificial inoculation was employed.     

Radial velocity profiles of water flow in trunks of Norway spruce and oak and the response of spruce to severing

Trunk-tissue heat balance, volumetric and staining methods were used to study xylem water flow rates and pathways in mature Norway spruce (Picea abies (L.) Karst.) and pedunculate oak (Quercus robur L.) trees. The radial profile of flow velocity was confirmed to be symmetrical in spruce, i.e., maximum flow velocity was in the center of the conducting xylem and tailed with low amplitude (about 30 cm h(-1)) in the direction of the cambium and heartwood. Variability around the trunk was high. In contrast, in oak, the radial profile of flow velocity was highly asymmetrical, reaching a peak of about 45 m h(-1) in the youngest growth ring and tailing centripetally for about 10 rings, but variability around the trunk was less, under non-limiting soil water conditions, than in spruce. In spruce, the flow rate increased abruptly within seconds when the tree was severed while immersed in water, and then decreased gradually, showing significant root resistance. We conclude that water flow through an absorbing cut surface differs from the flow higher in a tree trunk because of the presence of hydraulic capacitances in the conductive pathways. The staining technique always yielded higher estimates of flow velocity than the non-destructive tree-trunk heat balance method.     

Effect of wide spacing on increment and branch properties of young Norway spruce

The effects of stand density on increment and branch properties were studied in three spacing experiments of Norway spruce [Picea abies (L.) Karst.]. The stand densities ranged from 350 stems ha⁻¹, regarded as open-grown trees, up to 1,600 stems ha⁻¹, corresponding to the density recommended for forestry practice. Properties of all the branches were measured from the stem apex downwards. The study material included a total of 5,661 branches from 45 trees. Increasing stand density resulted in a decrease in radial increment as well as shorter and narrower crowns, but it had no effect on height increment. The average number of spike knots per tree was 0.87, 0.27, and 0.33 in densities of 350, 700 and 1,600 ha⁻¹, respectively. Additionally, in the widely spaced stands of 350 stems ha⁻¹, the fraction of trees having spike knots was high (over 50%). At a density of 1,600 ha⁻¹, the sample trees had somewhat less branches in a whorl compared with the more widely spaced plots. The most pronounced effect of stand density was the increase in branch diameter with decreasing stand density. At a density of 350 ha⁻¹, the maximum branch diameter of all the sample trees exceeded the diameter limit of quality class B in the European quality requirements for round wood. The results give some indication that trees subjected to severe competition would produce smaller branches per unit of crown projection area. However, the possibilities for reducing branch dimensions relative to stem and crown size through competition appear quite restricted.     

Scots pine responses to elevated temperature and carbon dioxide concentration: growth and wood properties

Growth and wood properties of 20-year-old Scots pine (Pinus sylvestris L.) trees were studied for 6 years in 16 closed chambers providing a factorial combination of two temperature regimes (ambient and elevated) and two carbon dioxide concentrations ([CO2]) (ambient and twice ambient). The elevation of temperature corresponded to the predicted effect at the site of a doubling in atmospheric [CO2]. Annual height and radial growth and wood properties were analyzed during 1997-2002. Physical wood properties analyzed included early- and latewood widths and their proportions, intra-ring wood densities, early- and latewood density and mean fiber length. Chemical wood properties analyzed included concentrations of acetone-soluble extractives, lignin, cellulose and hemicellulose. There were no significant treatment effects on height growth during the 6-year study. Elevated [CO2] increased ring width by 66 and 47% at ambient and elevated temperatures, respectively. At ambient [CO2], elevated temperature increased ring width by 19%. Increased ring width in response to elevated [CO2] resulted from increases in both early- and latewood width; however, there was no effect of the treatments on early- and latewood proportions. Mean wood density, earlywood density and fiber length increased in response to elevated temperature. The chemical composition of wood was affected by elevated [CO2], which reduced the cellulose concentration, and by elevated temperature, which reduced the concentration of acetone-soluble extractives. Thus, over the 6-year period, radial growth was significantly increased by elevated [CO2], and some wood properties were significantly affected by elevated temperature or elevated [CO2], or both, indicating that climate change may affect the material properties of wood.     

Conversion of single-layered Scots pine monocultures into close-to-nature mixed hardwood forests: effects on parasitoid wasps as pest antagonists

In the north Saxon lowlands (near Torgau), effects of conversion of pure pine stands (Pinus sylvestris L.) into mixed stands by planting deciduous trees [Fagus sylvatica L. and Quercus petraea (Matt.) Liebl] were investigated on parasitoid wasps as pest antagonists. The effects of planting deciduous trees in pine stands were investigated using the strategy of space-for-time substitution including advanced plantations of beech and oak of different age classes. Wasps were captured at 4-week intervals by ground photoeclectors (GPE, n=6, 1 m²) and flight-interception traps (FIT, n=8), placed in the tree crown layer during the vegetation period (April–October) of 2000. A total of 32,479 parasitoid wasps belonging to 30 families were caught in the traps. Fifty-nine percent of individuals were representatives of families relevant as antagonists of forest insect pests: Ichneumonidae, Braconidae, Pteromalidae, Eulophidae, Mymaridae, Trichogrammatidae, and Scelionidae. Compared to the pure pine stand, individual numbers of most families of parasitoid wasps were statistically significantly higher in mixed stands with deciduous trees. The clearest promoting effects of deciduous trees on parasitoid wasps were manifested in the oldest age classes of advanced beech and oak plantations. Oak exerted stronger effects than beech. This applied especially to the tree crown layer, the stratum with the highest spatial correlation between important phytophagous pine pests and relevant parasitoids. The increased structural diversity of the stands and the broader spectrum of potential hosts are regarded as key factors for the promoting effects of advanced plantings of deciduous trees in pine stands on the community of parasitoid wasps.