ALBERT

Notizen: Summary Bud break, shoot growth and flowering of trees involve cell expansion, known to be inhibited by moderate water deficits. In apparent contradiction to physiological theory, many trees flower or exchange leaves during the 6 month-long, severe dry season in the tropical dry forest of Guanacaste, Costa Rica. To explore this paradox, changes in tree water status during the dry season were monitored in numerous trees. Water potential of stem tissues (Ψstem) was obtained by a modification of the pressure chamber technique, in which xylem tension was released by cutting defoliated branch samples at both ends. During the early dry season twigs bearing old, senescent leaves generally had a low leaf water potential (Ψleaf), while Ψstem varied with water availability. At dry sites, Ψstem was very low in hardwood trees (〈−4 MPa), but near saturation (〉−0.2 MPa) in lightwood trees storing water with osmotic potentials between −0.8 and −2.1 MPa. At moist sites trees bearing old leaves rehydrated during drought; their Ψstem increased from low values (〈−3 MPa) to near saturation, resulting in differences of 3–4 MPa between Ψstem and Ψleaf. Indirect evidence indicates that rehydration resulted from osmotic adjustment of stem tissues and improved water availability due to extension of roots into moist subsoil layers. In confirmation of physiological theory, elimination of xylem tension by leaf shedding and establishment of a high solute content and high Ψstem were prerequisites for flowering and bud break during drought.

Notizen: Summary Shoot preformation was investigated in buds of four clones of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. at two sites in Manitoba in the second (1988) and third (1989) growing seasons after grafting. More preformed primordia were produced in terminal buds in 1989 compared to 1988 at each site. Both terminal and lateral buds at Morden contained significantly more primordia than those at Winnipeg. The numbers of preformed primordia were significantly different among clones. Clone 3 produced the most and clone 1 the fewest primordia in terminal buds. Despite quantitative variation, the pattern was similar among clones for terminal buds at each site and in each year. A similar pattern was evident for lateral buds at the Winnipeg site in 1989 but at Morden, clones 4 and 1 had the largest number of preformed primordia. Data from 1989 revealed that numbers of primordia were correlated with bud dimensions, parent shoot length, diameter and number of leaves, and location of the bud on the parent. Shoot dry weight was also related to these variables and revealed a non-linear increase in dry weight with shoot length. Multiple regression, with parent shoot length and location of buds along the parent axis as independent variables provided a reliable indicator of preformation in the crown. Although there is a genotypic component to preformation, variation between sites, years and crown locations suggests plasticity in bud development.

Notizen: Summary Strong evidence for the occurrence of pronounced stomatal patchiness in needles of Picea abies (L.) Karst. and Abies alba Mill. was found using various indirect methods. Anatomical investigations revealed a septate leaf anatomy for both species, a phenomenon expected if a patchy distribution of stomatal aperture is present. Calculation of some photosynthetic characteristics (e.g. carboxylation efficiency) from gas exchange measurements is shown to be markedly affected by the patchy distribution of stomatal apertures on the needles. The importance of stomatal patchiness in connection with air pollution related forest decline symptoms as well as an hypothesis suggesting a possible role of the phenomenon as a protective mechanism against photoinhibition are discussed.

Notizen: Summary The level of fruiting in four forest trees species (Picea sitchensis, P. abies, Pinus sylvestris and Fagus sylvatica) was monitored in Great Britain over the period 1989–1991. In addition, assessments of crown transparency were available for many of the trees for 1987 and 1988. The monitoring period encompassed severe summer droughts in 1989 and 1990, with wetter conditions in 1991. Variations in the level of fruiting in spruce and beech (Fagus sylvatica L.) were seen, with a marked peak in 1990. No pattern was apparent in Scots pine (Pinus sylvestris L.). Coning, which was greater in trees with the least transparent crowns, had no discernible effect on the crown transparency of the conifers. Cupule production in beech was greatest in trees with the most transparent crowns, and trees with high numbers of cupules in 1990 tended to have greater crown dieback recorded in 1991.

Notizen: Summary The occurrence of stem deformation in Pinus radiata plantations has been examined previously in terms of the factors leading to the onset of bending symptoms. In this study the influence of seedling family and nitrogen availability on the ability of seedlings to recover from deformation was investigated under glasshouse conditions. Seedlings from four families ranging from resistant to susceptible to stem deformation were used. Stem deformation was induced by loading stems with a known weight and comparing bending moments and rates of recovery. Significant differences between families were found with more susceptible families exhibiting greater initial magnitudes of stem lean. Similarly these families also exhibited greater rates of apical elongation following bending despite the larger stem leans. This resulted in more exaggerated stem bends as a consequence of the recovery of the lower stem pushing the upper stem away from the vertical. The strength characteristics of the stems could not explain differences between families. Susceptibility to stem deformation was explained more by stem slenderness expressed as stem height to root collar diameter.

Notizen: Summary Two experiments were performed to test needle architecture of Scots pine (Pinus sylvestris L.) seedlings when affected by non-shading neighbouring vegetation. Both experiments showed that seedlings reacted to the presence of such adjacent vegetation by changes in needle distribution around the main stem: more needles were found on the opposite side of the main stem to where the vegetation was located. However, this reaction was confined to needles from the main stem. Responses of seedlings to dead neighbours differed from the response to live neighbours and also from the response to a black curtain substituted for plant neighbours. It is suggested that reactions are mediated by the red/far red ratio of incident light.

Notizen: Summary The present study aimed at a physiological understanding of the seasonal changes of the carbohydrate patterns and levels in the various tissues of 8-year-old Scots pine (Pinus sylvestris L.) trees growing under ambient climatic conditions in the botanical garden at Bayreuth. The photosynthates of selected twig sections were labelled by 14CO2 fixation and after chase periods of 1 h up to 8 months, the distribution of radiocarbon in the whole trees was determined and the labelling of identified carbohydrates was compared with the levels of these compounds in the individual tissues. Bud break and sprouting in spring is exclusively supplied by the recent photosynthates of the previous year's needles. During summer assimilates of the old needles were utilized for secondary growth of the axial system while growth of the recent-year's shoots was supported by their own photosynthesis. In autumn, soluble carbohydrates were produced instead of starch, a major part of which in addition to recent photosynthates was utilized for root growth during the cold season. Another part of the autumnal storage material was incorporated into the cell walls of the latest xylem and phloem elements still in winter. A pronounced starch-oligosaccharide interconversion upon frost hardening, and its reversal in spring as has been described for deciduous trees, could not be observed. This was due to maintenance of photosynthetic capability even in the cold season and the replacement of consumed storage material especially in late winter and early spring by new photosynthates.

Notizen: Summary The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (〉1 μmol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.

Notizen: Summary Cuttings of hybrid poplar (Populus × euramericana var. “Dorskamp”) were exposed to ozone (80 μg/m3 from 2100 hours to 0700 hours, 180 μg/m3 from 0700 hours to 2100 hours) for 3 months. Ozone reduced the starch content in leaves and stem bark, whereas starch granules accumulated in bundle sheath cells along small leaf veins. At the same time, sucrose and inositol content increased in the leaves. Mesophyll cells in the vicinity of the stomata were injured first, and droplet-like material appeared on their walls. In the sieve plates of fumigated trees, the pores showed a higher degree of narrowing than those of the control treatment. Cell collapse in the leaves was accompanied by water loss and an increase in air space. In the stems, the ozone treatment led to a reduced radial width, particularly in the xylem tissue. These results are discussed in relation to reduced or inhibited phloem loading and ozone-induced drought stress. The plants injured by ozone showed quite distinct patterns of metabolite responses as well as enzyme activities (PEP- and RubP-carboxylase) in the leaves from the top to the bottom. There were also remarkable differences in the reaction of sucrose and inositol between leaves and stem bark. Future research should therefore increasingly follow a whole-plant approach for a better understanding of complex plant reactions.

Notizen: Summary The NADPH generating enzymes glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), and isocitrate-dehydrogenase (NADP dependent; EC 1.1.1.42) have been characterized in spruce [Picea abies (L.) Karst.] roots. Interference from inherent phenolic compounds was minimized by complexation with borate and insoluble polyvinylpyrrolidone in the presence of 2-mercaptoethanol and NADP. A further addition of protective substances had no (bovine serum albumin) or even an inhibitory effect (ascorbate) on the enzyme activities. The enzymes were shown to be strictly NADP specific. The optimal pH values and the apparent Michaelis constants from spruce roots are in good agreement with data from different photosynthetic organisms and gametophytic tissues of conifers. Native electrophoresis and subsequent activity staining showed the same banding patterns for enzymes both from root and needle tissues. In addition, the applicability of a highly sensitive dot-blot assay for the accurate quantification of the extracted protein is shown.

Notizen: Summary Clusters of 2–4 bare, deciduous hardwood trees and woody vines in a dry upland forest in Costa Rica were surrounded by scaffolding and rehydration was induced during the dry season by irrigation of 9–50 m2 plots with 200 mm water. The resulting changes in water status preceding bud break were monitored. Following irrigation, stem water potentials increased from 〈 −4 MPa to about −1.5 MPa within 24 h and to 〉 −0.3 MPa within 48 h. Rehydration of stem tissues by lateral transport, measured as an increase in electric conductivity, continued for 4–8 days. Terminal flower buds in Tabebuia ochracea began to expand 48 h after irrigation and trees were in full bloom 4 days later. In all experimental species, lateral vegetative buds began to expand 5–7 days after irrigation and leaves were fully expanded 2 weeks later. After the first rains of the rainy season (100 mm in 48 hr) all trees in the dry forest rehydrated and leaves emerged in synchrony slightly faster than after irrigation. In response to rain or irrigation drought-stressed tropical hardwood trees thus rehydrated at rates similar to those of desert succulents and their development resumed much faster than that of deciduous cold-temperate trees in spring.

Notizen: Abstract Enormous quantities of latex are found in over 40 plant families on a worldwide basis. Despite the proportions involved, the role of this substance within plants is still a matter of conjecture. Latex is closely associated with isoprene which may be emitted as a gas from both plants (that may or may not contain latex) and animals. The volume of isoprene expelled into the atmosphere each year is approximately equal to that of total methane emissions. The latter (but not the former), a known “greenhouse gas”, is the subject of considerable concern. It appears reasonable, therefore, that efforts be made to examine more thoroughly the formation and function of latex and associated compounds in order to obtain a better understanding of a number of critical biological and environmental phenomena known to be associated with these phytochemicals. Possible roles played by these substances in both plants and their surrounding environment are described.

Notizen: Abstract The seasonal pattern in starch, various sugars, protein, and fat, and their interrelationship, has been followed in 3-year-old branch wood of poplar trees (Populus x canadensis Moench ‘robusta’) under natural site conditions. The deposition of starch, protein and fat proceeds at different times. Starch accumulates from May until October, fat mainly during the summer months, and protein when the leaves are yellowing in September and October. The maximum concentrations in the branch wood were 15–18 μg starch, 6–9 μg protein, 4–8 μg fat, 10–15 μg sucrose, and up to 30 μg total sugars per milligram dry weight (DW). During starch deposition periods no increased sucrose level is found in the tissue. The maximum daily starch deposition rate was 0.2–0.4 μg starch/day/mg DW of wood. During starch hydrolysis in late autumn and winter, a dramatic increase in sucrose and its galactosides is measured (up to 15–27 μg/mg DW in total). In early spring, before budbreak, the concentrations of these sugars diminishes sharply. In contrast to this clear-cut starch-to-sugar conversion in autumn no significant starch-to-fat conversion is detected. An elevated content of free glycerol, however, is found in winter. In spring, starch and storage protein are mobilized completely, or almost completely, in poplar twig wood. A noteworthy pool of maltose is found transiently during autumn (up to 8 μg/mg DW) and again in spring. The results demonstrate that the individual storage materials, e.g. starch, protein, and fat, are accumulated fairly independently in the wood storage parenchyma. Tissue sugar levels, in contrast, appear to be closely related to the seasonal variations in starch content, on the one hand, and to the acclimation and deacclimation of the cells, on the other. The interrelations of the storage materials and sugars are discussed.

Notizen: Abstract Intracanopy variation in net leaf nitrogen (N) resorption and N cycling through leaves in mature walnut (Juglans regia L. cv Hartley) trees were monitored in 3 different years. Differential irradiance among the spurs sampled was inferred from differences among leaves in dry weight per unit area (LW/LA) which varied from 4.0 mg · cm−2 to 7.0 mg · cm−2 in shaded (S) and exposed (E) canopy positions, respectively. Our results, using 15N-depleted (NH4)2SO4 validated the concept that N influx and efflux through fully expanded leaves occurred concurrently during the period of embryo growth. Additionally, it also suggested that N influx into leaves was substantially greater in exposed as compared with shaded canopy positions. Because of its well documented phloem immobility, leaf Ca accumulation was used to better estimate the relative influx of N into exposed and shaded leaves. N cycling varied locally within the tree canopy, i. e. Ca (and presumably N) influx was 100% greater in exposed than shaded tree canopy positions, but influx was not influenced significantly by the proximity of developing fruit. In contrast, both the amount and percentage N efflux was significantly greater during embryo growth in fruit-bearing than defruited spurs. Net leaf N resorption averaged 2–4 times greater (25–30%) in fruit-bearing spurs than the 5–10% decrease in the leaf N content in defruited spurs. Since about 90% of leaf N content reportedly occurs as protein, fruit N demand apparently influenced protein turnover and catalysis in associated spur leaves. The amount of leaf N resorption was greater in exposed than shaded positions in the tree canopy in 2 of the 3 years of data collection. Our data show that like leaf N content, N influx, N efflux and net leaf N resorption vary throughout mature walnut tree canopies under the combined local influences of fruiting and irradiance.

Notizen: Abstract The effects of growing seedlings of red oak (Quercus rubra) and red ash (Fraxinus pennsylvanica) with Hoagland solutions containing five N-regimes, differing in the N-forms (NH4, NO3) and concentrations (High and Low), in relation to light intensity were investigated by the utilization of enzymatic markers of the N assimilation pathway, nitrate reductase (NR) and glutamine synthetase (GS). Red oak and red ash showed different patterns of N-assimilation. Red oak seedlings assimilated NO3 in low amounts in their roots and leaves, whereas red ash seedlings assimilated high amounts of NO3, mostly in the leaves. A significant amount of constitutive NR activity was found in red oak seedlings supplied with NH4 N-regime. This could be characteristic of a species adapted to soils that are poor in nitrogen. Root GS activity was lower in red oak seedlings than in red ash seedlings, indicating that the rate of NH4 assimilation differed in these two hardwood species. Low irradiance reduced growth of both hardwood species, but greatly affected the specific leaf area of red ash and reduced NO3 assimilation (when data are expressed per leaf area). Both species reacted similarly to N-regimes in terms of relative growth rate.

Notizen: Abstract Nitrogen metabolism of the needles of 40-year-old Douglas fir and Scots pine trees, growing in two forest stands on cation-poor and acidic sandy soil with a relatively high atmospheric nitrogen deposition was studied. The composition of the free amino acid (FAA) pool, the concentrations of total nitrogen and soluble protein and the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were determined in the needles. An excessive nitrogen supply by a high atmospheric nitrogen deposition in both forest stands was indicated by the high concentrations of total nitrogen and the amino acids arginine, glutamic acid, glutamine and aspartic acid in control trees. In addition the effect of optimal nutrition and water supply (fertigation) on the needle nitrogen metabolism was evaluated. The total concentration of the FAA pool in needles of both tree species was lower in the fertigated than in the non-fertigated (control) trees, except for 1-year-old needles of Scots pine, in which the concentration after fertigation did not differ from the control. The lower total FAA concentration in the fertigated trees could be attributed to arginine, the concentration of which was on average 60% lower than in the control. Neither the concentration of soluble protein nor the activity of GS were influenced by fertigation. The activity of GDH in fertigated trees only differed significantly from the control in October. Scots pine needles had higher concentrations of protein (50%) and higher activities of GS (44%) and GDH (25%) than Douglas fir needles. Possible explanations for the lower vitality of Douglas fir compared to Scots pine are given.

Notizen: Abstract The formation and vertical distribution of sapwood and heartwood were studied with a 45-year-old Cryptomeria japonica D. Don. The tree was grown at a plantation with 1.5 m × 3.0 m spacing near Miao-Li, Taiwan and was felled on 27 February 1992. The thickness of sapwood and heartwood was expressed by a ring count and a linear measurement. The east-west (E-W) wood strips were collected from 0.3 m above ground upwards to the top of the tree at 2.5 m intervals. The sapwood thicknesses from the base to the 10.3 m tree level height are around 20–22 growth rings and 42±2 mm. At the top of the tree, the sapwood thickness is narrower. The heartwood, which decreases in thickness with increasing tree level heights is not found at the top of the tree. The heartwood appears as a conical shape in the tree trunk. There is no statistical difference in sapwood/heartwood thickness between E-W aspects. Tree level heights and the tree level age were found to be important parameters in determining the thickness of sapwood/heartwood.

Notizen: Abstract Some parts of the xylem can act as a nutrient reserve (or source) to satisfy the plant needs during spring flush or when uptake is insufficient. The distribution patterns have been used to delimit different distribution zones of nutrients in the stem but establishing the limits of the zones can be subjective when a single element is used. In this study, we provide a new methodology for analyzing stem nutrients, taking into consideration the common underlying of nutrients in the different distribution zones. The distribution of P, K, Ca, Mg, Mn and Zn was evaluated on an annual basis, using disks from 8 trees, sampled every 20 cm along the stem, in two 18-year-old plantations of European larch [Larix decidua (Mill.)] and tamarack {Larix laricina [K. Koch (Du Roi)]}. Using principal component analysis, more than 90% of the total variance was explained by the first three components. Based on these components, three groups of nutrients were identified: P and K (mobile), Ca and Mn (immobile), and Mg and Zn (intermediately mobile). Five distribution zones were delimited using factorial scores: bark, apical region, external xylem, transition xylem, and internal xylem. The apical and external xylem zones were characterized by mobile nutrients while the internal zone of the xylem was characterized by immobile and intermediately mobile nutrients. As well as establishing common zones of each nutrient, principal component analysis enabled us to characterize zones based on a group of nutrients. If the different distribution zones are considered, the estimation of the internal reserve contribution to plant's nutritional status and the evaluation of the changes in the distribution patterns of elements following natural or artificial perturbations could be improved. Discriminant functions are provided to classify new observations in the different distribution zones.

Notizen: Abstract The phenology of Quercus suber L., a dominant species of the montados in the Iberian Peninsula, was studied for 2 years in southwest Portugal. The seasonal progression of phenological events was analyzed in seven trees. Selected branches were examined monthly for shoot elongation, leaf number, branching, flowering, and fruiting. Radial stem growth and specific leaf weight were also studied. Active growth was observed from early spring to early summer. Reserves accumulated during winter and high photosynthetic activity in early spring apparently supported this strong development. The growth flush started with stem radial increment, which seemed to be impaired by spring rainfall. Male inflorescence production was the next phenological event. Old leaves were shed during new twig and leaf emergence. Shoot elongation and the number of new leaves produced were well correlated with the previous-year shoot's length, and were not clearly related to climatic factors. Radial growth resumed in autumn at a lower rate than in the previous spring, a possible consequence of a reserve depletion due to lower photosynthetic production in summer and investment on fruit maturation, which was complete by late autumn. Premature and excessive new leaf production were apparently subjected to self-pruning strategies related to the development of each tree's crown. Younger cork-oaks produced shorter and fewer shoots per module, and more sclerophyllous leaves than the older ones. A high intra-specific variability was observed in all the results.

Notizen: Abstract Stems of trees hollowed by agents such as fungal decay, fire or termites have reduced strength and increased likelihood of breakage. This may pose a serious hazard when hollow trees are growing near public places. Previous theoretical studies and field studies of hollow trees, of both hardwood and softwood species, in Europe and America have suggested rules to quantify the risk of breakage of hollow trees. These rules are confirmed and expanded here, using data collected from hollow trees of several species of the hardwood genus Eucalyptus in Australia. It is concluded that where the ratio of the minimum wall thickness of a stem hollow to the total radius of the hollow exceeds 0.3–0.35 and at least one-half of the girth of the tree stem is intact, it is extremely unlikely that the stem of the hollow tree will break. These rules appear to apply for a wide range of tree species throughout the world.

Notizen: Abstract The hypothesis that the frequently observed shedding of older needle age classes in stands of Norway spruce suffering from atmospheric pollutants has minimal effect on photosynthetic primary production was assessed. Using structural parameters of young Norway spruce [Picea abies (L.) Karst.] trees, an existing 3-dimensional canopy photosynthesis model was adapted and validated for conifer canopies. This model was employed to quantitatively demonstrate that, depending on the stand density, the loss in photosynthetic active foliage area may be compensated by higher photosynthetic rates of the remaining younger foliage age classes due to higher levels of photosynthetically active radiation (PAR) within the thinned tree crowns. Under certain circumstances, beneficial effects on the tree's water use efficiency may be expected. Extrapolating the model results to mature tree stands is addressed. The potential effects of higher PAR levels on abundance and species diversity of the epiphytic and understory vegetation, as well as the general importance of the older foliage age classes for spruce trees on a long term scale, are discussed.

Notizen: Abstract Morphological and histological observations were made on eight dwarf mutants arising either as seedlings from sexual reproduction or from somatic bud mutations (witches'-brooms in the crowns of normal trees). The most predominate morphological trait contributing to the expression of dwarfism in all taxa was the reduction of final internode lengths along the shoot axis. In taxa of sexual origin, with the exception of Prunus, there was a consistent reduction in the number of preformed leaves contained in the winter buds. In addition, in two taxa (Liquidambar and Tsuga) there was an almost complete absence of neoformed leaves and sylleptic branches on current year shoots. Conversely, in mutants of somatic origin there was no apparent reduction in the number of preformed leaves. Genetic dwarfness in this group resulted solely from decreases in final internode length. Significant differences in the cellular basis of dwarfism between mutants of different genetic origins are clearly evident. In dwarf trees arising from sexual reproduction, reduction in final internode length is attributed predominately to inhibition of mitotic activity in developing internodes resulting in highly significant decreases in final cell number, and not cell length. In mutants of somatic origin, the reduction in length of mature internodes results from a decrease in final cell length, rather than a decrease in cell number. Physiological mechanisms associated with the genetic expression of these morphogenetic differences are suggested.

Notizen: Abstract Seasonality in nitrogen (N) and phosphorus (P) concentration in soil and shoots of five Brachystegia-Julbernardia (miombo) woodland trees was studied from September 1991 to March 1993 at two regrowth miombo sites in central Zambia. Shoot growth started in the dry season (September–November) and lasted until April during the 1991/92 season but had virtually ceased by January 1993 during the 1992/93 season. The shoot growing season was associated with low foliar N/P ratios. These ratios were much lower (〈5) during the 1991/92 season than in the 1992/93 season (12–15). The increase in foliar N/P ratios after the shoot growing season was caused by a sharp drop in foliar P concentration, apparently due to reabsorption before leaf fall. There were no annual variations in biomass N concentration in contrast to P. During the 1992/93 growing season P concentrations in foliage and wood were a quarter and a third, respectively, of the 1991/ 92 levels. Since the short shoot growing season observed during the 1992/93 season is typical of savanna woodland trees in southern Africa, the high biomass P concentration and longer growing season in 1991/92 season were exceptional and may have been related to reduced competition by shallow rooting herbaceous plants caused by the severe drought of that season.

Notizen: Abstract The classification of chromosomal aberrations was used to characterize different factors affecting chromosomes in the root meristem of Norway spruce [Picea abies (L.) Karst.] trees. It is important to know the most significant factor affecting the chromosomes in the root meristem of plants at natural sites. The results suggest that an intensive site effect is more significant than the soil or the provenance of the individual. This cytogenetic plant test system was also used to investigate 5-year-old spruce trees exposed in environmental chambers to elevated concentrations of carbon dioxide (750 cm3m−3) and ozone (0.08 cm3m−3) as single variables or in combination, and then transferred to a field for observation of a “memory effect”. The fumigated variants showed an increased number of chromosomal aberrations compared to the controls, which carried on as a memory effect in the root meristems far beyond the fumigation period.

Notizen: Abstract Poplar branches were ringed in late spring to determine whether the interruption of the phloem flow could induce the accumulation of vegetative storage proteins (VSPs) in the bark of adult trees. Eight days after ringing, an increased deposition of starch as well as a premature rise in the soluble-protein level occurred in the bark tissues located 1 cm above the ring. Changes in the SDS-PAGE pattern of bark proteins were characterized by the accumulation of three polypeptides (32, 36 and 38 kDa), which exhibited the same molecular weight as VSPs described in poplar bark during winter, cross-reacted to antibodies raised against a poplar VSP, and bound to several lectins in the same way as poplar bark VSPs. These results indicate that during the vegetative period, ringing induces the accumulation of VSPs in the bark of poplar.

Notizen: Abstract Cuticular wax composition of healthy and and declining mature Norway spruce trees [Picea abies (L.) Karst.] was investigated in five European forest areas. The amount of extracted wax and the content of alkanes and secondary alcohols were analysed as a function of the factors “sample area” (five areas, detailed below), “needle age” (current year to 2 years) and “decline class” (Class O to Class 2). Using a GC-MS, alkanes from C20 to C31 and the following alcohols were quantified: 10-nonacosanol, 5,10-nonacosandiol, 4,10-nonacosandiol and the triterpenol 24-methylenecycloartanol. According to our results, the total wax content as well as the alkane and alcohol content of waxes show a large variation corresponding to sample area and needle age. Ageing caused a highly significant increase in alkane content and a highly significant decrease in total wax and alcohol content. The decline class significantly influenced only the content of the long chain alkane C31 (increase), the secondary alcohol 10-nonacosanol (decrease), and the triterpenic alcohol (decrease). Total wax weight was not influenced by tree damage. Thus, according to our results, needle ageing and progressive tree damage are correlated to different changes in the examined parameters.

Notizen: Abstract The effects of different nutrient availabilities on growth and biomass partitioning in seedlings from the tropical deciduous forest in Mexico were compared. The tree species studied were Heliocarpus pallidus, a species associated with disturbed parts of the forest, and Caesalpinia eriotachys, Jacquinia pungens and Recchia mexicana, species from mature, undisturbed habitats. The tropical deciduous tree seedlings were grown in pure silica sand for 50 days inside growth chambers under four nutrient regimes; 5, 20, 100 and 200% Long Ashton nutrient solutions. Data showed contrasting responses among species to different nutrient availabilities. Except Jacquinia pungens, all species had increased growth and productivity as nutrient level increased from 5 to 100%; however, no significant differences in these parameters were detected between 100 and 200% in all species. Compared with mature forest species, pioneer species showed higher variations in biomass production, relative growth rate and net assimilation rate. In contrast to mature forest species, root/ shoot ratios in Heliocarpus pallidus were greater and thus showed higher biomass allocation to roots when nutrient supply was limited. This response suggests higher phenotypic plasticity in pioneer species. Species from mature parts of the forest (Caesalpinia eriostachys, Recchia mexicana) showed less dependency on nutrient supply than pioneer species. These responses appear to support observations from studies with temperate plants investigating growth responses to soil fertility.

Notizen: Abstract Effects of water stress on needle ultrastructure of 2-year-old Scots pine (Pinus sylvestris L.) and 5-year-old Norway spruce [Picea abies (L.) Karst.] seedlings were studied in greenhouse experiments. Drought stress was induced by leaving seedlings without watering, and waterlogging stress was produced by submerging the seedling containers in water. Needle samples for ultrastructural analyses were collected several times during the experiments, and samples for nutrient analyses at the end of the experiments. In drought stress, plasmolysis of mesophyll and transfusion parenchyma tissues, aggregation of chloroplast stroma and its separation from thylakoids and decreased size and abundance of starch grains in needles of both species were observed. The concentration of lipid bodies around the chloroplasts were detected in pine needles. Calcium and water concentrations in spruce needles were lower by the end of the experiments compared to controls. In waterlogging treatment, swelling of phloem cells in pine needles and large starch grains, slight swelling of thylakoids and increased translucency of plastoglobuli in chloroplasts of both species studied were observed. The phosphorus concentration in pine needles was higher while phosphorus, calcium and magnesium concentrations in spruce needles were lower in the waterlogging treatments compared to controls. Typical symptoms induced by drought stress, e. g. aggregation of chloroplast stroma and its separation from thylakoids, were detected, but, in waterlogging stress, ultrastructural symptoms appeared to be related to the developing nutrient imbalance of needles.

Notizen: Abstract Quantification is a major problem when using histology to study the influence of ecological factors on tree structure. This paper presents a method to prepare and to analyse transverse sections of cambial zone and of conductive phloem in bark samples. The following paper (II) presents the automated measurement procedure. Part I here describes and discusses the preparation method, and the influence of tree age on the observed structure. Highly contrasted images of samples extracted at breast height during dormancy were analysed with an automatic image analyser. Between three young (38 years) and three old (147 years) trees, age-related differences were identified by size and shape parameters, at both cell and tissue levels. In the cambial zone, older trees had larger and more rectangular fusiform initials. In the phloem, sieve tubes were also larger, but their shape did not change and the area for sap conduction was similar in both categories. Nevertheless, alterations were limited, and demanded statistical analysis to be identified and ascertained. The physiological implications of the structural changes are discussed.

Notizen: Abstract Image analysis provides the means to overcome quantification problems in plant science. Part I of this study (Vollenweider et al. 1994) presented a method of preparing transverse views of the cambial zone and conductive phloem in bark samples. Part II of the study presents computerized analysis of the images thus obtained. The equipment and procedures are described, and we show that presently available software can be sufficiently versatile and easily customized to perform automated histological measurements. The program allows the user considerable interactivity. The automated treatment requires particularly high quality standards in both sample preparation and image capture, but provides numerical results able to reveal fine histological differences.

Notizen: Abstract A direct algorithm for computing constrained Delaunay triangulation in 2-D is presented. The algorithm inserts points along the constrained edges (break lines) to maintain the Delaunay criterion. Since many different insertions are possible, the algorithm computes only those that are on the Delaunay circles of each intersected triangle. A shelling procedure is applied to put triangles together in such a way that completeness and correctness are guaranteed.

Notizen: Abstract A method for generating a smooth voxelbased model from an arbitrary polygon mesh is presented. It is based on a polygonal subdivision process which takes an irregular polygon mesh as input and creates a finer and smoother mesh. The mesh is recursively refined down to or close to the voxel level, and then voxelized (digitized) into a voxel-based representation. A local subdivision approach has been developed in order to ease the computationally expensive subdivision process. The voxelization of the mesh maintains topological and fidelity requirements which are pre-defined and application dependent.

Notizen: Abstract This paper describes a new system for controlling the animation of gases, liquids, and volume density functions. This system is extremely powerful and flexible. It allows for the control of animation effects ranging from physically based motion of gases to the choreographed motion of gases. These techniques make extensive use of three-dimensional tables, including both flow vectors and motion functions for controlling gas animation. This new system uses aninverse particle system, where each point in three-dimensional screen space (image space discretized to pixel locations) is moved through a gas space to determine which portion of the gas occupies the current location in screen space.

Notizen: Abstract A new triangulation scheme for the Marching Cubes algorithm is proposed. The scheme allows the extraction of continuous isosurfaces from volumetric data without the need to use disamgiguation techniques.

Notizen: Abstract This paper describes an algorithm for ray tracing general parametric surfaces. After dividing the surface adaptively into small parts, a binary tree of these parts is built. For each part a bounding volume is calculated with interval arithmetic. From linear approximations and intervals for the partial derivatives it is possible to construct parallelepipds that adapt the orientation and shape of the surface parts very well and form very tight enclosures. Therefore we can develop an algorithm for rendering that is similar to that used with Bèzier and B-spline surfaces, where the bounding volumes are derived from the convex hull property. The tree of enclosures (generated once in a preprocessing step) guarantees that each ray that hits the surface leads to an iteration on a very small surface part; this iteration can be robustly (and very quickly) performed in real arithmetic.

Notizen: Summary The cerebrally innervated larval eyes of Aporrhais sp. and Bittium reticulatum are investigated by means of transmission electron microscopy. Each organ consists of a pigmented cup containing an acellular lens. The cornea overlaps the anterior portion of the eye. The retina is composed of sensory cells and supportive cells. The sensory cells of Aporrhais sp. bear one cilium and in Bittium reticulatum two cilia, the ciliary membrane being folded into numerous finger-shaped evaginations. The supportive cells contain the pigment granules and most of them bear one or two cilia, the plasmalemma of which is likewise folded. It is supposed that: (a) these cilia have a transportive function for lens material and (b) that the ciliary photoreceptor of Aporrhais sp. and Bittium reticulatum is a functional adaptation to a relatively long larval period.

Notizen: Summary Using sulfur dioxide (SO2) as catalyst, wood specimens were treated with nonformaldehyde cross-linking reagents such as glyoxal, glutaraldehyde and dimethylol dihydroxy ethyleneurea (DMDHEU). The results of dimensional stability, acoustic properties, and mechanical strength tests were compared with those obtained from formaldehyde treatment. With glyoxal and glutaraldehyde treatments, antiswelling efficiency (ASE) reached around 70%, which is comparable to the values attained by formaldehyde treatment, although the accompanying weight gain was much larger than for the latter, whereas DMDHEU did not give sufficiently high ASE. None of the treatments, significantly increased specific dynamic Young's modulus (E/ρ) with the exception of the DMDHEU treatment, loss tangent (tan δ) decreased substantially, about 50 and 60% in longitudinal and radial directions respectively, which were somewhat exceeding the formaldehyde treatment. The results suggested that the improvement of the dimensional stability and acoustic properties is partly attributed to the formation of cross-links.

Notizen: Summary A mathematical model for describing the structure of a randomly formed flake layer network is presented. The structural properties of the flake network are random variables in essence characterized by Poisson and exponential distributions. The model predicts distribution of: flake centres, flake area coverage, free flake length, and void size over the flake layer network. A computer program for simulating the random flake network and rapidly evaluating structural properties is developed as well. In addition, the structural properties of hand-formed flake layers are experimentally measured. Close agreement is found between mathematical model prediction, computer simulation and experimental measurements.

Notizen: Summary The process of absorption of methanol in liquid state by a wood sample, as well as the following step of desorption, is studied. A 3-dimensional transfer takes place within a cubic wood sample, this cube being cut in such a way that the sides of the cube are parallel with the longitudinal, radial and tangential axes of diffusion. A numerical model taking into account all the facts, e. g. diffusion within the solid and constant concentration on the surface during the stage of absorption, and diffusion within the solid and evaporation from the surface during the stage of desorption, is built and successfully tested. A pseudo-equilibrium of absorption is attained after an immersion time of about 3 hours in the liquid, and the whole amount of methanol is evaporated during the stage of desorption. The process can be described by a 3-dimensional diffusion with constant principal diffusivities.

Notizen: Summary Thermal movement of wood and wood composites was studied and compared with that of random and oriented phenolic foams. Cell orientation was a dominate factor determining the thermal response of these structures. In dried wood, thermal movement in the direction parallel to the cells (longitudinal) decreased in dimension during heating while the radial and tangential directions expanded under similar heating condition. Oriented foams showed more restraint in thermal movement in the parallel to orientation direction. These findings indicate constraining forces act on the direction parallel to the cells while more flexibility exists in perpendicular directions. Wood element size and orientation and the manufacturing process also influence the thermal response in wood composites. The experimental results also revealed the potential fire hazard of waferboard type of composites.

Notizen: Summary The features of the reaction between sitka spruce wood and non-formaldehyde reagents, i. e. glyoxal, glutaraldehyde, and dimethylol dihydroxy ethyleneurea (DMDHEU), were investigated from the aspects of moisture adsorption and bending creep properties. To the moisture adsorption data, Hailwood-Horrobin adsorption equation was applied, and whole adsorbed water was separated into hydrated water and dissolved water which correspond to monolayer and multilayer adsorption, respectively. In the treatments with non-formaldehyde reagents, the decrease of equilibrium moisture content was mainly attributed to the decrease of dissolved water, but not largely to that of hydrated water. This suggested that the reagent in the multilayer adsorption region contributed pronouncedly to suppress the moisture adsorption by the bulking and cross-linking effects, but that the reagent in the monolayer adsorption region did not considerably. The creep deformation and remaining strain of the specimens treated with glyoxal and glutaraldehyde were as small as those of formaldehyde treatment. Also by the DMDHEU treatment, creep deformation was restrained to some extent. The eminent creep restraint effect by these treatments showed the formation of cross-linkings, although the crosslinkings were not stable to the drastic water leaching.

Notizen: Summary The structure of a randomly-formed flake-type wood composite mat is further defined and characterized. A model for the prediction of horizontal mass density distribution in a random flake mat is presented through application of two-dimensional random field theory. This model predicts the small-scale mass density variance and the spatial correlation of flake coverage. The predictions agree well with experimental results and computer simulations. Significance and implications of the model development towards practical manufacturing applications are discussed. In addition, equations for the calculation of general structural properties such as overall mat thickness, between-flake void volume content and maximum potential inter-flake bonded areas are presented.

Notizen: Summary Acoustic Emission (AE) was measured in 30 mm-thick backsawn and quartersawn Tasmanian Oak (Eucalyptus regnans F. muell) boards drying at temperatures in the vicinity of 20 °C. By varying the diffusion coefficient used in a non-linear drying simulation program, calculated half-thickness moisture profiles were matched to measured profiles in a sample board. Once the measured and calculated drying behaviour was satisfactorily matched, the AE measured in an endmatched board closely followed the surface instantaneous strain calculated with the program. The AE activity increased once the surface instantaneous strain attained the proportional limit. The AE is not simply related to drying temperature or humidity but rather to a complex interaction between the two parameters.

Notizen: Summary In this paper the method of fractal dimension is applied to characterize the wood surface by using water-sorption data. Three different methods are implemented to determine the fractal dimension. These methods are based on polymolecular sorption and capillary condensation and are found to estimate the fractal dimension in the range of 2.5–2.8. This implies that the estimation of the surface area of wood by determining the number of molecules of water corresponding to monolayer formation is not true. The surface in fact is far from two dimensional as being closer to a three dimensional one.

Notizen: Summary In part 1 of this series, a three-dimensional, structural analysis, finite element program has been developed to predict the stress distribution in wood poles with and without spiral grain and variable material properties. This program serves as a basis for a model to predict the strength and failure location in full-size wood poles. Fundamental to this model is the ability to quantify the effects of key material and geometric properties of the pole. This paper deals with the enhancement of the program to quantify the effect of knots and their associated cross grain on the stress distribution of wood poles. The technique is based on the theoretical behavior of laminar fluid flow around an elliptical obstruction. The flow-grain analogy was employed to develop empirical relationships between knot diameter and pertinent variables (grain deviation angle near the knot and area of influence of the knot). Prior to the development of the empirical relationships, a study was conducted to determine the size and distribution of knots in Douglas-fir and western redcedar poles. The validity of the technique to describe knot behavior is reflected in the ability of the finite element model to predict the strength and failure location of wood poles. The results suggested that the flow-grain analogy is a rational mechanism to quantify the fiber orientation near a knot. Furthermore, this technique could have meaningful implication in improving visual grading methods for wood poles.

Notizen: Summary The behaviour of lignin-polysaccharide complex of spruce wood in soda pulping was studied by the characterization of lignin-saccharide fractions isolated from a series of soda pulps. The dioxane pulp lignins contain 8–14% of carbohydrates in which glucose was the predominant component. Its content increased with increasing degree of delignification indicating the formation of secondary lignin-carbohydrate linkage. Both glycosidic and ether type of bond between residual lignin and cellulose in pulp was proved by methylation analysis of the pulp dioxane lignin.

Notizen: Summary Pinus pinaster wood samples were treated with NaOH solutions in order to improve their susceptibility to enzymatic hydrolysis. The variations caused by pretreatments on the chemical composition of treated samples and on the extent of enzymatic saccharification were correlated with the experimental variables studied (temperature, liquor/wood ratio and alkali concentration). Empirical models were used to assess the extraction and the hydrolysis steps. The reliability of the mathematical models was confirmed by further experimentation. Additional aspects affecting the studied process (such as selectivity of extraction and kinetics of enzymatic hydrolysis) are discussed.

Notizen: Summary A non-linear fracture mechanics model, the Fictitious Crack Model (FCM), is utilised for a theoretical study of the Compact Tension (CT) specimen. The complete stress-displacement curve for the material is used in the FCM, even the descending branch after maximum stress. The analysis shows that the computed load-displacement curve is sensitive to modulus of elasticity perpendicular to the grain, tensile strength and fracture energy. The theoretically obtained results agree well with experimentally determined curves.

Notizen: Summary A model that predicts heat and moisture transfer through wood in the hygroscopic range and which is based on the principles of irreversible thermodynamics, was evaluated with unsteady-state nonisothermal moisture desorption experimental data. The model predicted the phenomenon of thermal diffusion during the initial stages of desorption and results in a very good simulation of the desorption curve and the center's temperature change with time.

Notizen: Summary The ultrastructural characteristics of fracture surfaces from southern pine and Douglas-fir specimens tested in tension at various angles to grain were examined. The fracture surace morphology was inspected using scanning electron microscopy. Three anatomical failure types were recognized: intercell failure, transwall failure, and intrawall failure. Certain failure characteristics were ascribed as a function of the magnitudes of paralleland perpendicular-tograin tension and parallel-to-grain shear present in the specimen. In specimens tested in paralleland perpendicular-to-grain tension, the thick-walled latewood cells were found to fail in a combination of transwall and intrawall failure. The intrawall failures were usually at the S1–S2 interface. The more thin-walled earlywood cells were more likely to exhibit abrupt, transwall failures. At intermediate angles of load to grain, surfaces indicative of the type found in pure shear tests were predominant. Perpendicularto-grain tension failures resulted in mostly intercell failures. Ray cells consistently exhibited transwall failures. The failure surface frequently changed planes in all loading modes. This path transfer was inevidably associated with material discontinuities in the wood. When the path did transfer, all three failure types were observed. No significant species effect was observed.

Notizen: Summary Iodine in water is of great interest in some undeveloped countries, and wood can be used as a iodine reservoir capable of releasing it with a controlled rate. The problem of iodine release from a wooden beam is considered in this paper in a rather complex case. The beam is immersed in a finite volume of pure water for a given time, and then reimmersed successively in the same way. Equilibrium of desorption is not attained at the end of each stage of immersion. A numerical model with finite differences was built and successfully tested, providing the kinetics of release and the profiles of iodine concentration in the wood.

Notizen: Summary We are investigating wood decay biocides that are both effective in protecting wood from decay and more environmentally compatible than other biocides. A series of halophenyl sulfonamides were synthesized and characterized by infrared and neuclear magnetic resonance spectroscopy. Wood impregnated with these compounds was tested for resistance to decay as well as water leaching. Wood impregnated with para-iodophenyl or para-fluorophenyl para-tolyl sulfonamides resisted decay by brown- and white-rot fungi. For wood impregnated with para-iodophenyl para-tolyl sulfonamide, threshold retention with the brown-rot fungus Gloeophyllum trabeum was 9.1 mmol/ 100 g solution for unleached blocks. For leached blocks, weight loss was very high (24.6%), which indicated that threshold retention will be substantially higher than 9.1 mmol/100 g solution. With the white-rot fungus Coriolus versicolor, threshold retentions were 2.9 and 5.6 mmol/100 g solution, respectively, for unleached and leached blocks. Leaching of the blocks treated with the iodo compound slightly decreased resistance to decay by C. versicolor. For wood impregnated with parafluorophenyl para-tolyl sulfonamide, threshold retentions with both G. trabeum and C. versicolor were very close to 9.0 and 9.2 mmol/100 g solution, respectively, for leached and unleached blocks. Leaching had a little effect on resistance to decay by both fungi. Wood impregnated with parachlorophenyl or bromophenyl para-tolyl sulfonamide was ineffective in resisting decay by both fungi.

Notizen: Summary Kraft delignification kinetics has been modelled on the basis of a first order decay process with a time-dependent rate constant. A generalized severity parameter derived from this kinetic model, Roh, has been applied to describe the lignin solubilization during alkaline (soda and Kraft) and bisulphite pulping of different wood species. The model has been succesfuly applied to data sets available from the literature. Our approach has combined the main process variables (temperature, time and chemical load) into a single parameter, Roh, which is then used as a reaction ordinate to map the changes in chemical composition and physical properties. An extension of the initial formulation of the Roh parameter has been made to cover the situations where the catalytic system is composed by two active chemical species, as in the Kraft process.

Notizen: Summary The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Based on this review a constitutive model is proposed for the case of uniaxial stress in the longitudinal direction. The validity of the model is checked independently against test results. The calculations show that the model is capable of describing the response of wood with reasonable accuracy. Simulations indicate that the response of small test specimens is more difficult to describe than that of larger beams. Some differences in behaviour are found to depend on loading mode and nature of moisture cycling. Very large and fast moisture cycles seem to give larger mechano-sorption than smaller variations. The results of the simulations show that there is a significant influence of strain on the shrinkage and swelling response.

Notizen: Summary The validity of the following equation of water adsorption into wood substance which was derived in the previous report, is examined: d(δW)/dt = k0(1 − exp(-k1/t))δW(l − δW), which can approximately be written as: d(δW)/d(logt) = rδW(l − δW), where δW is moisture content; t is time (t 〉 0); k0, k1 and r are constants. After measuring dimensional change with change in time under various relative humidities, the change of moisture content was indirectly calculated from the proportional relationship between dimensional change and moisture content. It was found that the theoretical equation satisfactorily agreed with the experimental results. These results lead to the conclusion that the equation was valid. Furthermore, the properties of the equation, whose constants are determined from experimental results, is discussed. The rate of water adsorption of wood shows interesting and systematical properties, especially near relative humidities corresponding to the fiber-saturation point.

Notizen: Summary The organisation of the spermatozoa ofAnthopharynx sacculipenis is described, based on electron-microscopical observations. The male gametes are fili-form in shape. They are totally enclosed by cortical microtubules and possess two free cilia. Special features are dot-like dense granules arranged in regular rows and terraced elaborations of the nuclear membrane. Such terraced elaborations are not known in any other species of flatworms whereas dot-like dense granules are described for some other taxa of the Rhabdocoela. Male gametes do not show synapomorphic correspondences between the Solenopharyngidae and the Prolecithiphora.

Notizen: Summary The morphology of the complex tibial organs in the forelegs of two bushcricket species belonging to the Phaneropterinae and Decticinae (Tettigoniidae) is described comparatively. In both species the tibial organs are made up of the subgenual organ, the intermediate organ and the crista acustica; the latter are parts of the tympanal organs and serve as auditory receptors. The very thin tympana in the forelegs ofPholidoptera griseoaptera (Decticinae) are protected by tympanal covers whereas inLeptophyes punctatissima (Phaneropterinae) the tympana are thicker and fully exposed. The overall auditory sensitivity ofL. punctatissima is lower and the sensitivity maximum of the hearing threshold lies at higher frequencies compared toP. griseoaptera. The number of scolopidia in the three scolopale organs and the dimensions of parts of the sound conducting system differs in the two species. In the crista acustica ofL. punctatissima a higher number of scolopidia is distributed in a smaller range than inP. griseoaptera; the scolopidia are especially concentrated in the distal part. Morphometrical analyses indicate that the dimensions of the spiracles, the acoustic trachea and the tympana determine the overall auditory sensitivity and that the arrangement of the scolopidia and the dimensions of structures in the crista acustica affect the frequency tuning of the hearing threshold.

Notizen: Summary A whole-mount fluorescence technique using rhodamine-labeled phalloidin was used to demonstrate for the first time the whole muscle system of a free-living plathelminth, Macrostomum hystricinum marinum. As expected, the body-wall musculature consisted of circular, longitudinal, and diagonal fibers over the trunk. Also distinct were the musculature of the gut and of the mouth and pharynx (circular, longitudinal, and radial). Dorsoventral fibers where restricted in this species to the head and tail regions. Circular muscle fibers in the body wall were often grouped into bands of up to four parallel strands. Surprisingly, diagonal fibers formed two distinct sets, one dorsal and one ventral. Certain diagonal muscle fibers entered the wall of the mouth and were continuous with some longitudinal muscles of the pharynx. Dorsoventral fibers in the rostrum occurred partly in regularly spaced pairs, a fact not known for free-living Plathelminthes. All muscle fibers appeared to be mononucleated. During postembryonic development, the number of circular muscle fibers can be estimated to increase by a factor of 3.5 and that of longitudinal muscles by a factor of 2. Apparently as many as 700–800 circular muscle cells must be added in the region of the gut alone during postembryonic development. Stem cells (neoblasts), identified by TEM in the caudalmost region of the gut, lie along the lateral nerve cords. In the same body region most perikarya of circular muscle cells occurred in a similar position. This suggests that the nucleus-containing part of the cell remains in the position where differentiation starts.

Notizen: Summary An ultrastructural comparison between the unistellate spermatozoa of the shrimps Penaeus kerathurus and P. japonicus reveals a number of similarities that are common among dendrobranchiates, but also some marked differences which would confirm the validity of a potential use of sperm structure in systematic and phylogenetic studies. Typical morphological features shared by the spermatozoa of P. kerathurus and P. japonicus are: a membrane-bound acrosomal vesicle consisting of a cap and spike; non-membrane-bound filamentous chromatin; a perinuclear cytoplasmic band including degenerative membranous organelles (mostly mitochondria), small vesicles with a dense core and parallel membrane lamellae. Discordant spermatozoal characteristics between both species involve a significantly different size (ca. 5 μm in length by ca. 3 μm in diameter in P. kerathurus; ca. 8 μm in length by ca. 4.7 μm in diameter in P. japonicus), the occurrence of intranuclear lipid droplets only in P. kerathurus and the presence of a deeper subacrosomal space in this species as compared to P. japonicus. It is very likely that the most significant difference between both species is, however, the appearance of microtubule bundles in the spermatozoon of P. japonicus. So far, the occurrence of spermatozoal microtubules in decapod crustaceans appears to be restricted to reptantian species, whereby the finding of such elements in sperm of a dendrobranchiate shrimp could be of phylogenetic interest.

Notizen: Summary Radiographs of live, unanesthetized snakes were used to document the position of the heart in the body cavity during horizontal, head-up, and head-down postures. The extent of cardiac displacement observed during these postural changes differed substantially among the snakes examined, ranging from virtually none in a thin-bodied arboreal snake to as much as three vertebral lengths (=half the length of the heart) in a heavy-bodied terrestrial Crotalus. The basis of this differential cardiac displacement is attributed to the anatomical “packaging” of the pericardial sac. In some snakes the pericardial sac is loosely suspended in the body cavity by the great vessels and connective tissue sheets. In contrast, in other snakes the pericardial sac is buttressed against the body wall, the lung, or the liver. We hypothesize that cardiac displacement during postural change may alter the pattern of blood flow in the aortae of snakes.

Notizen: Summary A mechanosensitive ciliated cell type of the polyp Stauridiosarsia producta (Hydrozoa) was investigated by means of electron microscopy. These cells bear at their apical cell surface a modified cilium, a set of seven stereovilli, a so-called pseudovillar system and a large vacuole. Cilium and stereovilli are interconnected like the cnidocil apparatus of hydrozoan nematocytes which is responsible for mechanoelectric transduction. The vacuole is enclosed by and linked to the pseudovillar system by a microtubular basket. Considering its structural organization and physiological activities the ciliated sensory cell closely resembles a nematocyte that has lost its ability ot produce a nematocyst.

Notizen: Summary In this paper we present evidence for the presence of actin-related junctions between neighboring Sertoli cells and between Sertoli cells and spermatids in the testis of the guppy (Poecilia reticulata). In the guppy, spermatogenesis occurs in spermatocysts that are lined by a simple squamous to cuboidal epithelium formed of Sertoli cells. At a certain stage of differentiation, elongate spermatids occur in Sertoli cell recesses in the apical surface of Sertoli cells. When evaluated by electron microscopy, junctions occur between Sertoli cells and spermatids situated in the recesses. In these regions, obvious linkages occur between the plasma membrane of Sertoli cell recesses and the adjacent spermatids. Moreover, large concentrations of microfilaments occur in the Sertoli cell cytoplasm immediately underlying the crypts. Also, junctional complexes are apparent between neighboring Sertoli cells near the apical surface of the epithelium. These complexes consist of microfilament-related components (probably contributing to both tight and adhesion junctions), which occur closest to the lumen, and intermediate-filament related desmosomes, which occur more basally. In fixed frozen sections of guppy testis, probes for filamentous actin (rhodamine phalloidin) and myosin II (polyclonal antisera raised against human platelet myosin II) react with function regions between neighboring Sertoli cells and between Sertoli cells and spermatids. We conclude that actin-related junctions occur at both these sites and that the actin networks have contractile properties because they contain myosin II.

Notizen: Summary In this study, ASAM method was modified by the use of ethanol instead of methanol. This new organosolv pulping method is referred to as ASAE. Brutia pine (Pinus brutia Ten.) was chosen as raw material in cooking because of its wide-spread usage in Turkish sulphate mills. 28 cooks were made by changing the cooking conditions systematically to achieve the most effective cooking parameters for yield and physical properties of ASAE pulps. Also, a control sulphate cook was made. After statistical evaluations of the data optimum pulping conditions were determined to be 20% Na2SO3 with 50% ethanol ratios and 150 min cooking time at maximal temperature. It was found that ASAE pulps had higher yield, viscosity, brigthness and strength properties than sulphate control pulps with the exception of breaking length. Furthermore bad-odour problems were absent during the blowing and washing process in the laboratory trials.

Notizen: Summary The rate and maximum swelling of several North American wood species in water have been obtained with a computer interfaced linear variable displacement transformer. Since wood swells extremely fast in water even at room temperature, this apparatus made it possible for the first time, to obtain accurate rate data on the swelling of wood in water. The strict linear dependence of swelling on the temperature suggests a chemical mechanism. The activation energies obtained from Arrhenius plots ranged from 32.2 KJ/mole for sitka spruce to 47.6 KJ/mole for sugar maple. Although the two hardwoods exhibited greater maximum tangential swelling compared with the two softwoods, the maximum swelling appears to be correlated with the wood density. Generally both the rate and maximum swelling of the woods were increased by removal of extractives and the activation energies were reduced.

Notizen: Summary The ultrastructure of lignifying cell walls in Pinus radiata D.Don was investigated using potassium permanganate staining and transmission electron microscopy. Lignin deposition occurred at numerous discrete sites within various cell wall regions, suggesting the presence of some initiating agent at these sites. In the middle lamella region, lignin deposition occurred by addition of protolignin monomers to spherical particles of lignin. Lignification was completed by expansion of these spherical particles, initially forming irregular patterns of lignification followed by infilling of adjacent areas. In contrast, lignification in the secondary wall occurred by deposition of protolignin monomers onto the ends of expanding lignin lamellae between cellulose microfibrils leading to greatly elongated patches of lignin due to the greater rate of deposition along the microfibril axis compared to that across it. It is concluded that the cellulose matrix in which lignin deposition occurs, in the secondary wall, can exert a mechanical influence which limits the rate of lignin deposition in the direction perpendicular to the microfibril axis.

Notizen: Summary Mode I fracture energy of premature plantation-grown red pine is discussed, for crack growth in the longitudinal direction. It is demonstrated that fracture energy is influenced by moisture content at test and the direction that stress is applied in the radial-tangential plane. Secondary influences of moisture conditioning and density on fracture energy were observed, with the severity related to the moisture content of the material at test. Discrepancies with findings in the literature are identified and discussed. It is likely that results of this study apply to other conifer species with low extractive contents.

Notizen: Summary When lines of constant moisture content (isosteres) are plotted on axes of In r (r, relative humidity) versus In ps (ps, pressure of water vapour at saturation), approximately straight lines result. Other axes with the same property are discussed. The slope of lines of constant Gibbs free energy of water vapour is derived for the above chart and it is shown that the basic equation of sorption is represented by this slope and that of the isostere.

Notizen: Summary For the assessment of many different aspects of growth processes in trees millions of annual rings are being measured all over the world every year. Other studies dealing with the prediction or explanation of wood properties also require numerous density measurements. While the density of a wood sample is relatively easy to determine by stereogravimetric methods, density relationships or variations within a piece of wood and within individual annual rings can only be detected by time-consuming techniques, e.g. radiodensitometry. A new, simplified method for ring analysis was developed with the aid of the sandblasting and laser sensor method. This process permits the automatic recording of annual radial increment and simultaneously provides results on the mean and intra-annual density of the wood specimens. Sandblasting of cross-sections of stems or of radial strips produces hardness profiles. Due to the hardness variations in these profiles individual annual rings can be more or less easily identified macroscopically, depending on the wood species. Furthermore, density variations are also macroscopically visible on account of the relationship between abrasion depth and density: Sandblasting can be said to provide a three-dimensional representation of the density relationships in wood. Following the numerical recording of these surface profiles with the aid of a laser sensor and upon conversion of abrasion depth profiles into density profiles radial increment and density parameters for stem radii, segments of radii or even individual annual rings can be determined. A comparison with the conventional radiodensitometric ring analysis method shows very good correlations with the results achieved in this study. The advantage of the laser-sandblasting method is that large samples can be investigated without great preparatory effort and in a single processing step.

Notizen: Summary A new type of soft rot of southern pine longitudinal tracheids is described. In this type, soft-rot cavities form by diffuse degradation of the S2 cell wall layer by hyphae growing within the cell wall. Cavity formation is diffuse and irregular as opposed to the restricted, periodic cavity formation typical of type 1 soft rot. Proboscis hyphae are small (diameter 0.6 to 0.9 μm) and rapidly autolyse. These proboscis hyphae are not easily recognizable with light microscopy, especially at later stages of decay, but require transmission electron microscopy to confirm their presence. This may be an alternative interpretation of the type 2 soft rot of softwoods described previously as being caused by lumenal hyphae through an intact S3. Chemical analysis of pine test blocks revealed a greater loss of glucose and an increase of galactose with diffuse type 1 species compared to typical type 1 soft rot species. The term “diffuse type 1” is suggested to describe this soft rot.

Notizen: Summary This is the first of two papers designed to describe the most recent efforts in using contemporary technology to predict strength and failure location in wood poles. In this report, a three-dimensional finite element model is presented which was developed to provide a rational stress analysis tool for wood poles. Due to practical considerations, only critical pole segments were subjected to stress analyses. Twelve-inch (30.5 cm) segments were selected for analysis which contained knots or knot clusters deemed consequential. The linear elastic model assumes small-deflection theory, and exploits linear strain, 15-node wedge and 20-node parallelepiped, isoparametric finite elements. Element geometry was selected to reflect knot size distribution found in full-size wood poles used in North America. Boundary conditions represented both applied loading and support considerations. Model verification studies were conducted on poles with isotropic (steel) and anisotropic (wood) material properties with and without spiral grain and variable longitudinal elastic properties along the pole radius. The results showed excellent agreement between theoretical and numerically-predicted pole stresses. The effect of boundary conditions on predicted stress distribution was defined, and the element geometry was appropriately modified. The developed model proved to be a rational basis for a more enhanced version to predict the mechanical behavior of wood poles with several inherent growth characteristics.

Notizen: Summary This paper highlights a number of articles on research and development on wood composites. The coefficient of variation in the mechanical properties of wood components tends to decrease when the thickness of the wood elements decreases. This finding was utilized in the manufacture of hollow cylindrical columns of laminated veneer lumber (LVL) from Cryptomeria plantation thinnings. In the future, the marketing of wood composite boards will tend toward two types: thick boards with low density properties and thin boards with fiber orientation. For the production of thick boards, fundamental parameters and application of steam-injection pressing have been studied, and continuous steam-injection pressing has been developed. For thin board production, generation principles of aligning torque in high-voltage system and the application has been studied. A new oriented mat former with electrodes positioned only at the reverse side of a forming belt has been developed. Various synthetic resins of low-molecular weight have been applied to improve dimensional stability of laminated products, such as LVLs and particleboards. Acetylation and formalyzation of fibers and particles were investigated to provide stabilized panels. High pressure steam treatment during pressing of wood composites has been studied and the process has been found effective and promising.

Notizen: Summary In order to control the compression effectively, the main processing parameters for hot-pressing of poplar LVL were investigated in this study. Results from an orthogonal experiment show qualitatively that compression of poplar LVL is influenced by pressing pressure and moisture content of the veneers. High press pressure and veneer moisture content lead to high compression during hot pressing. It is shown that compression has significant effects on modulus of elasticity, modulus of rupture, specific gravity and thickness swelling of poplar LVL. Modulus of elasticity, modulus of rupture and specific gravity appear to be directly proportional to compression within the compression range of 5% to 20%. Horizontal shear strength results indicate that, due to inadequate contact, proper glue bond may not be achieved between veneers of LVL with low compression. Thickness swelling appears not sensitive to compression between the compression range of 4% to 10%.

Notizen: Summary A method for measuring the complete stress-displacement relation in both tension and shear and some experimental results on Nordic redwood (Pinus sylvestris) are presented. The complete stress-displacement relation also includes the post-peak behaviour, i.e. the descending branch of the curve. The influence of annual ring orientation and moisture content on the form of the stress-displacement curve for the fracture process zone has been examined, and the results show that the normalised curve in tension is independent of annual ring orientation and moisture content.

Notizen: Summary Load-duration (creep-rupture) effects in wood are often modeled using cumulative damage theory. In application, such as for duration of load reliability analyses, incremental damage owing to stochastic load pulse models is summed over an assumed reference period (e.g., 50 years), with failure defined in terms of the damage state variable. The effect of load pulse shape on cumulative damage is examined herein through the use of one such proposed damage accumulation model. An exponential damage rate model (EDRM) is used to calculate the damage owing to a rectangular load pulse (RECT), a triangular load pulse (TRI), and two trapezoidal load pulses (TRAP1 and TRAP2). The differences in the calculated damage predicted by the EDRM and resulting from the four load pulse shapes are presented and the effect of critical load parameters (e. g., load intensity and duration) are illustrated. Also, the effect of neglecting ramp loading and unloading is discussed; that is, the error in assuming RECT versus either TRAP1 or TRAP2 load pulses is assessed.

Notizen: Summary A rate equation of non-steady state adsorption for wood is theoretically discussed, and an adsorption equation is solved. This will clarify the mechanism of the mechano-sorptive process. Non-steady state water adsorption of wood cannot be represented by an equation which is derived from Fick's law, because the equation by Fick's law is similar to that of Langmuir's adsorption theory. Therefore, the adsorption process in non-steady state was discussed, based on the assumption that water molecules create a new secondary internal surface as the water adsorption proceeds. That is, the process of water adsorption was regarded as an auto-catalyzed reaction. Additionally, the effect of the ultra-structure of wood was also considered. Consequently, a rate equation of adsorption and an adsorption equation could be theoretically obtained which satisfactorily represented the process of water adsorption.

Notizen: Summary Properties of wood can be improved by reacting chemicals with hydroxyl groups of wood cell wall polymers. To achieve this improvement in wood properties, bioactive compounds containing hydroxyl groups, such as pentachlorophenol, 3,5-dimethyl phenol, and 2-naphthol, can be reacted with epichlorohydrin to give corresponding glycidyl ethers. The new epoxide formed during this reaction can be used to bond bioactive compounds to wood. This bonding may result in improved wood properties. The objective of this study was to develop a simple procedure for synthesizing glycidyl ethers. The alcohol was reacted with epichlorohydrin and a catalyst and monitored by thin-layer chromatography. Shortwave ultraviolet light was used to detect spots. Resulting products were analyzed for carbon, hydrogen, and in one case, chlorine. Reaction of pentachlorophenol with epichlorohydrin formed only one enantiomeric glycidyl ether, whereas reaction of 3,5-dimethyl phenol with epichlorohydrin led to two enantiomeric glycidyl ethers in a 1 to 3 ratio. Reaction of 2-naphthol with epichlorohydrin also led to two enantoimeric glycidyl ethers in equal amounts. In future research, these glycidyl ethers will be reacted with wood, and their toxicity to wood-destroying fungi in bonded form will be determined.

Notizen: Summary The observed kinetics of Pinus pinaster bark with acetic acid after alkali treatment, with or without intervening acid prehydrolysis, are satisfactorily explained by a model involving both solubilization and condensation reactions.

Notizen: Summary High-yield pulps have been obtained by means of steam explosion pulping. This process was carried out as follows: 1) chips soak impregnation (60 °C, 24 h, L/C = 6) in solutions containing 8% Na2SO3 and a variable concentration of either Na2CO3 or NaHCO3, ranging from 0 to 2%; 2) cooking at high temperature (190–200 °C) for short time (2-1 min); 3) rapid pressure release. This work shows that mechanical properties were substantially improved when adding a second chemical to the Na2SO3 impregnation solution. Moreover, refining energy requirement was significantly reduced. However, the higher chemical charge used made the optical properties drop. In this paper, mathematical models have been proposed in order to accurately predict specific refining energy and paper properties from sulfonate content and pulp yield. In addition, the relative importance of these two parameters has been studied.

Notizen: Abstract Structural grade chipboard was subjected to fatigue and creep loads in four-point bending, the peak fatigue stress being equal to the constant creep stress. Peak fatigue stresses of 50, 60, 70 and 80% of the static bend strength were selected and an S-N (stress versus log10 (cycles)) curve was generated. Stress versus strain hysteresis loops were captured automatically throughout fatigue tests so that underlying creep strain, dynamic modulus and energy dissipated per cycle were continuously monitored. The possibility of superimposing creep and fatigue data was investigated. The S-N curve generated at R = 0.01 demonstrates that for lives of less than 107 cycles chipboard does not show a fatigue endurance limit. The 70 and 80% samples experience a gradual decrease in dynamic modulus and an increase in the area of the hysteresis loop during fatigue tests. Samples at the 50 and 60% levels show an initial increase in dynamic modulus before a decline to failure is observed. Creep samples never failed before fatigue samples at the same peak stress level, but until close to the point of failure, creep strains were nearly always greater than fatigue strains on elapsed time. It is concluded that the mechanism of fatigue damage accumulation differs from the mechanism of creep deformation.

Notizen: Summary The muscles of the metathoracic segment are described for the larva and imago of the beetleZophobas morio. In the search for possible homonomous and ontogenetic persistent structures, we further employed muscles served by the first segmental nerve in the thoracic and abdominal segments. In the larva, eight muscles per hemisegment are associated with this nerve. Based on topological criteria they may be characterized as homonomous for all tested segments. In the adult, the topology of the dorsal muscles seems to be different compared to the larval situation, due to the complex structural remodelling during metamorphosis. However, a supplementary analysis employing the innervation pattern allows us to equate larval with adult muscles, even down to the level of individual motor units. Comparison of different orthopteran and coleopteran species provides some evidence that these muscles are homologous, apparently representing part of a basic pattern common in pterygote insects.

Notizen: Summary The ontogeny of the cranium of Dipnoi is restudied. The investigation especially refers to the basic components of the dipnoan cranium and several functional and developmental aspects of the structure of the larval skull ofNeoceratodus. There are fundamental differences even in the early development and composition of the chondrocranium ofNeoceratodus and Lepidosirenidae. This result, and comparison with several osteichthyans and Tetrapoda, requires a reinterpretation of the components of the dipnoan skull base. The pterygoid processes are not reduced, but incorporated into the cranial base early in ontogeny. The characteristic elongate trabecular rods, which in Gnathostomata usually bridge the ethmoidal plate and the orbito-temporal base of the chondrocranium, are much delayed in development inNeoceratodus, or even seem absent inLepidosiren andProtopterus. Accordingly, in Dipnoi no typical basitrabecular junction is formed in early ontogeny. Instead, the pars quadrata is fused to the mesodermal basis cranii posteriorly. InNeoceratodus a mesially directed basal process of the palatoquadrate is recognizable, which topographically corresponds to the basal process of Urodela and the pseudobasal process of anuran larvae. The ethmosphenoid region of the dipnoan skull also develops quite differently. In Lepidosirenidae, the palatoquadrates are interconnected anteriorly by a distinct commissura palatoquadrati, whereas inNeoceratodus a continuous planum ethmoidale (“trabecular plate”) is formed. The primary embryonic quadrato-trabecular connection persists as a commissura quadratocranialis anterior below the foramen opticum, at the root of the ectethmoid process. The formation of the skull base in living Amphibia appears to provide the best model for comparison, though it is difficult to propose any undisputable shared derived character states of the cranium of Dipnoi and Tetrapoda beyond this similarity. A similar difficulty presents the phylogenetic interpretation of the hyoid arch. In contrast to the absence of any dorsal hyoid arch elements inLepidosiren, the small hyomandibula ofNeoceratodus is surprisingly complete. In larvae it consists of a laterohyale, an epihyal part, and a processus symplecticus. A stylohyal cartilage is present, which forms rather late in ontogeny. The major chondral components of the hyoid arch are thus comparable to those of living Actinopterygii, except that a distinct symplecticum is not separated off, the components are relatively smaller, and they do not ossify. In view of the early-immobilized palatoquadrate, the hyomandibula ofNeoceratodus has no suspensorial function, but represents part of an opercular hinge and opening mechanism. The hamuloquadrate knob at the posterior face of the quadrate body is comparable to the processus hyoideus in some Urodela. It provides a pivoting joint for the ceratohyale, and therefore functions in buccal expansion. The closed spiracular canals include mechanoreceptive lateral line organs, which probably represent proprioreceptive organs for adjustment of mandibular, hyoid, and opercular movements. It is concluded that considerable differences between the skull architecture of Dipnoi and other Osteognathostomata (Teleostomi) can be assigned to the fact that palatoquadrate and trabecular anlagen fail to separate, resulting in a dramatic and highly adaptive change of palatoquadrate development in early ontogeny. Though these differences include several characters that suggest a plagiostomate condition of the jaw apparatus, this can be explained as a secondary acquisition. The multitude of retained plesiomorphies observed in the cranium of Dipnoi do not exclude a sister group-relationship to Tetrapoda. However, the ancestral osteognathostome suspensorial pattern still presents a problem of interpretation, for we lack a detailed survey of the development and significance of different quadrato-neurocranial connections.

Notizen: Summary The feeding mechanisms of four species of the teleostean family Labridae (Cheilinus fasciatus, C. trilobatus, Oxycheilinus bimaculatus, and O. unifasciatus) were modeled using four-bar linkage theory from mechanical engineering. The predictions of four-bar linkage models regarding the kinematics of feeding were compared to the movements observed with high speed cinematography (200 frames/s). A four-bar linkage was an accurate model of the mechanism by which upper jaw protrusion, maxillary rotation, and gape increase occur in each species. A four-bar mechanism of hyoid depression was an accurate predictor of hyoid depression when simultaneous cranial elevation and sternohyoideus contraction were simulated. Morphometrics of the linkage systems of the jaws and hyoid were collected for 12 labrid species. These data were used to calculate the transmission of force and motion through the musculoskeletal linkages. Several measures of mechanical advantage and displacement advantage were compared, including both traditional lever ratios and transmission coefficients of four-bar linkages. Alternative designs of the feeding mechanisms maximize force or velocity for the capture of different prey types. High velocity transmission of both the jaw and hyoid systems is characteristic of those species that feed on evasive prey, whereas species that feed on benthic invertebrates favor increased force transmission in both systems. Quantitative models of biomechanical systems supply criteria for functionally relevant morphometrics, and aid in calculating the capacity for transmission of force and velocity in musculoskeletal systems.

Notizen: Summary The hepatopancreas of the freshwater crayfish Astacus astacus was reinvestigated by means of light and electron microscopy using refined techniques of tissue preservation. The results contribute significantly to the solution of controversial problems of the decapod hepatopancreas such as cell genealogy, cellular interdependences, elimination of senescent cells and functional interpretation of the cell types. The three mature cell types of the organ, R-, F- and B-cells, are shown to originate independently from embryonic E-cells which are located at the blind-ending tips of the hepatopancreatic tubules. The less abundant M-cells are supposedly of non-hepatopancreatic origin since they are also found in other epithelia of the digestive tract. Differentiating cells can be assigned at an early stage to one of the three hepatopancreatic cell lines if the ultrastructural appearance and distribution pattern of their organelles are used as distinguishing features. The most sensitive markers are the Golgi bodies which have a cell-specific architecture and secretion product not only in mature cells but also in early differentiating stages. Later conversion of one cell type into another, as has often been proposed in literature, does not occur. Senescent cells are preferably expelled from the epithelium at the junction of neighbouring hepatopancreatic tubules and at the antechamber which links the hepatopancreas to the main digestive tract. Cellular discharge in the antechamber occurs by sliding of the oldest parts of the hepatopancreatic epithelium across a particular antechamber epithelium that was thus far unknown. New ultrastructural findings are described with respect to the absorptive apparatus of nutrient absorbing R-cells, the formation of Golgi vesicles and retrieval of membranes in digestive enzyme synthesizing F-cells, and the involvement of Golgi body and endoplasmic reticulum in the formation of heterophagic vacuoles in B-cells. The discovery of these ultrastructural features enables a more sophisticated functional interpretation of the hepatopancreatic cells of Decapoda.

Notizen: Summary The spermatozoan from testes of Cephalothrix rufifrons consists of an elongated, straight head 13–14 μm long with a flattened anterior acrosome and a 12.5-μm-long nucleus. Placed along one side of the nucleus, is a single tubular 7-μm-long mitochondrion. There is no midpiece, but immediately posterior to the nucleus are two centrioles. The tail is at least one and a half times the length of the head. Mature sperm cells were also found in the oviducts of mature females which, combined with the modified structure of the sperm cell, indicates that sperm is transferred during pseudocopulation.

Notizen: Summary A novel glandular structure is described within the mandibles of a series of representatives of the Formicidae. It consists of a variable number of secretory cells with their accompanying duct cells, located in the vicinity of the mandibular cuticle. Because of its localization inside the mandibles, we propose to designate this structure as the intramandibular gland of ants. Ultrastructural observations reveal the development of smooth endoplasmic reticulum in the glandular cells. Several electron-lucid and electron-dense inclusions occur in the cytoplasm. Until now, the function of this widespread gland among the Formicidae remains unknown.

Notizen: Abstract Response of senescing leaves of wheat seedlings to ultraviolet A (UVA) radiation (365 nm) has been examined. The results indicate that senescence-induced disorganization of thylakoid membrane, decline in carotenoid-to-chlorophyll energy transfer, and enhancement of lipid peroxidation are furthered by radiation. The senescence-induced decline in photochemical activity of photosystem II further declines on irradiation. UVA does not specifically alter any site other than those damaged by senescence.

Notizen: Abstract An experimental setup using static-field gel electrophoresis (SFGE) was developed to determine radiation-induced DNA double-strand breaks (DSBs) in CHO-K1 cells after exposure to X-rays or heavy charged particles. The fraction of DNA eluted into the gel matrix depends on the quantity of DSBs introduced. In agreement with a recent report, SFGE and pulsed-field electrophoresis were found to be equally sensitive in DSB detection. With radiolabeled DNA from cell cultures, the absolute amount of DNA migrating out of agarose plugs into the gel was quantified by determining the radioactivity in the gel lane. Alternatively, relative measurements of the amount of DNA released into the gel were achieved with a standardized protocol for both SFGE and a subsequent densitometric scanning of photographic negatives from gels stained with ethidium bromide. After calibration with the radioactive method, the fractions of DNA retained could be calculated directly from the data obtained with the densitometric assay to set up classical dose-effect curves. This procedure was validated for its application with heavy ions using an 500 MeV/u lead beam.

Notizen: Abstract Based on the results of131I thyroid activity measurements in three districts of the Chernigov region (Ukraine), individual doses were calculated and an approach of the age dependence of the average thyroid exposure was derived. Using the relationships between the thyroid doses and the137Cs deposition as well as the location relative to the Chernobyl Nuclear Power Plant (NPP), age-dependent average thyroid doses were extrapolated also for those settlements of this region where no monitoring measurements have been carried out. The highest doses were found in the west of the region with the lowest distance to the Chernobyl NPP. In this part, the highest mean of the thyroid dose in a settlement was 3.3 Gy for infants and 0.5 Gy for adults. The collective thyroid dose was 31000 and 27 000 person-Gy for children and adults, respectively. Based on this assessment, 140 and 21 excess thyroid cancer cases are predicted for children and adults, respectively. In the years 1989 to 1991, in the whole contaminated territory of the Ukraine 0.4–1.2 cases per 100000 children were observed. Although the absolute numbers are very small, this indicates the possibility of an increase in thyroid cancer morbidity among children. The same trend also seems to be indicated in the Chernigov region. A careful epidemiological study in the future is necessary to enable a final evaluation of radioinduced cancers in this region.

Notizen: Abstract Cell inactivation, mutation and DNA strand-break induction by γ-radiation have been investigated at very low temperatures (−78° C, −196° C, and −268° C). InEscherichia coli Y mel ,lacI + →lacI − andSalmonella typhimurium TA102,his −→his + dose-modifying factors determined for low radiation doses are similar for both mutation induction and cell inactivation. The sensitivity of repair-deficient strainsE. coli polA − andE. coli recA − was also reduced at low temperature to a comparable extent. This suggests that the lesions which are responsible for cell inactivation and mutagenesis could be strongly mutually related and/or that different types of lesions which are responsible for cell inactivation and mutation induction in bacteria are reduced at low temperature to the same or similar extent. Likewise, a lower yield of DNA strand breaks in plasmids irradiated at low temperature was observed.

Notizen: Abstract The procedure to extract caesium from seawater developed by Mann and Casso (1984) has been slightly modified and applied to the determination of radiocaesium originating from the Chernobyl accident in the waters of a Bavarian chain of lakes. Activity concentrations and estimated water inventories are given for 15 lakes 5 years after the accident, and depth profiles of the137Cs activity concentration in the water column of three selected lakes are presented. The activity concentrations in water of the different lakes show a high variability from 1.2 to 93 mBq 1−1. The calculated inventory of dissolved radiocaesium has decreased over the 5 years to 0.03% and 2% of the deposited activity, respectively.

Notizen: Abstract Long-term variation of outdoor radon equilibrium equivalent concentration was investigated from 1982 to 1992 at a semi-natural location 10 km north of Munich, southern Germany. For this period the continuous measurement yielded a long-term average of 8.6 Bq·m−3 (arithmetic mean) and 6.9 Bq·m−3 (geometric mean), from which an average annual effective dose of 0.14 mSv due to outdoor radon can be derived. A long-term trend of the radon concentration was not detectable over the whole period of observation. However, by time series analysis, a long-term cyclic pattern was identified with two maxima (1984–1986, 1989–1991) and two minima (1982–1983, 1987–1988). The seasonal pattern is characterized by an autumn maximum and an early summer minimum. On average, the seasonal maximum in October was found to be higher by a factor of 2 than the June minimum. The diurnal variation of the radon concentration shows a maximum in the early morning and a minimum in the afternoon. On average, this maximum is a factor of 2 higher than the minimum. In the long term a seasonal pattern was observed for diurnal variation, with an average diurnal maximum to minimum ratio of 1.5 in winter compared with 3.5 in the summer months. The radon concentration is correlated with a meteorological parameter (stagnation index) which takes into account horizontal and vertical exchange processes and the wash-out of aerosols in the lower atmosphere.

Notizen: Abstract This paper explores the feasibility of the acoustoelastic birefringence method for monitoring the axial stresses in the railroad rails. An electromagnetic-acoustic transducer (EMAT) is incorporated with a superheterodyne-phase-sensitive detector to accomplish noncontacting stress measurements. Two different measurement techniques are employed and compared to each other, both of which use the polarized shear waves propagating transversely to the rail axis. One is the pulsed resonance spectroscopy technique applied to the web, where the surfaces are nearly parallel to each other and support the thickness oscillations. The other method detects the small phase shift that occurs along with the stress application. The phase shifts were measured for the discrete reflection echoes that traveled long distances (top-to-bottom echo and multiple echoes in the head of the rail). The compressive axial load was raised up to 60 tons with the Shinkansen (bullet train) rail samples, which exceeds the buckling load of long rails. Both techniques showed a linear response to stress with a sufficient sensitivity and robustness, which promise the development of a practical railroad maintenance technology. The effects of the liftoff and the residual stress distribution are determined.

Notizen: Abstract A family of highly dispersed repetitive elements, designated PREM-1, which are transcribed primarily during pollen development, has been identified in maize. Sequence data from six PREM-1-containing genomic clones suggest that the PREM-1 sequences are the LTRs of a family of putative retroelements. PREM-1 LTRs are estimated to be present in about 10 000 to 40 000 copies in the maize genome. Although related sequences have been detected in sorghum and crab grass, highly homologous sequences appear to be specific to the genus Zea (maize and teosinte). A diverse group of RNAs that contain portions of the PREM-1 sequence at their 3′ ends are transcribed in pollen; highest levels appear in early uninucleate microspores. The PREM-1-containing cDNAs do not appear to code for protein products since stop codons are present in all three reading frames. The possible significance of expression of retroelements in the male gametophyte, in terms of transposition of DNA, is discussed.