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  • Springer  (339,256)
  • Copernicus
  • 1995-1999  (340,606)
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  • 1
    Electronic Resource
    Electronic Resource
    Allometric analysis of Sitka spruce branches: mechanical versus hydraulic design principles (1995)
    Springer
    Trees 10 (1995), S. 1-12 
    Details
    ISSN: 1432-2285
    Keywords: Sitka spruce ; Geometry ; Allometry ; Branch form ; Architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The geometry of tree branches can have considerable effect on their efficiency in terms of carbon export per unit carbon investment in structure. The purpose of this study was to evaluate different design criteria using data describing the form of Picea sitchensis branches. Allometric analysis of the data suggests that resources are distributed to favour shoots with the greatest opportunity for extension into new space, with priority to the extension of the leader. The distribution of allometric relations of links (branch elements) was tested against two models: the pipe model, based on hydraulic transport requirements, and a static load model based on the requirement of shoots to provide mechanical resistance to static loads. Static load resistance required the load parameter to be proportional to the link radius raised to the power of 4. This was shown to be true within a 95% statistical confidence limit. The pipe model would require total distal length to be proportional to link radius squared but the measured branches did not conform well to this model. The comparison suggests that the diameters of branch elements were more related to the requirements for mechanical load. The cost of following a hydraulic design principle (the pipe model) in terms of mechanical efficiency was estimated and suggested that the pipe model branch would not be mechanically compromised but would use structural resources inefficiently. Resource allocation among branch elements was found to be consistent with mechanical stability criteria but also indicated the possibility of allocation based on other criteria, such as potential light interception by shoots. The evidence suggests that whilst branch topology increments by reiteration of units of morphogenesis, the geometry follows a functional design pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197773
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  • 2
    Electronic Resource
    Electronic Resource
    Anatomical studies of branchlet abscission related to crown modification in Quercus cerris L. (1995)
    Springer
    Trees 10 (1995), S. 20-23 
    Details
    ISSN: 1432-2285
    Keywords: Crown modification ; Oak decline ; Quercus cerris L ; Twig abscission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The basic anatomy of lateral twig insertion onto the main branch in both healthy and damaged Quercus cerris L. trees was studied. An abscission zone is always present: in healthy trees it is formed by a smaller number of cell layers than in damaged ones, where it is more evident with many layers of cells. Cells of the abscission zone are roundish, with many intercellular spaces between them; cell walls are thin, non-lignified and without secondary walls. No starch was found in cells of the abscission zone, where, instead, a few scattered calcium oxalate druses are seen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197775
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  • 3
    Electronic Resource
    Electronic Resource
    Stem annual increments as ecobiological indicators in Turkey oak (Quercus cerris L.) (1995)
    Springer
    Trees 10 (1995), S. 13-19 
    Details
    ISSN: 1432-2285
    Keywords: Volume increment ; Stem analysis ; Dendroclimatology ; Quercus cerris ; Southern Italy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In recent decades, the biostatistical analysis of relationships among tree growth and macroclimatic factors has developed remarkably. In this discipline, the parametrisation of tree growth is generally based on the records of annual ring widths measured on breast height transverse sections of tree stems (ARI). The present research enables the stem volume annual increment (AVI) to be evaluated as a dendroclimatic indicator in comparison with ARI. The research is a part of a broader investigation into the ecobiological characteristics of Turkey oak in the Gargano region (southern Italy). The results indicate that AVI is no better than ARI as a means of highlighting expressive relationships among the examined macroclimatic factors (monthly precipitation and monthly averages of temperature daily maxima and minima) and the Turkey oak annual stem growth. In the examined stands, the most growthinfluencing factors are the autumn and spring rainfalls. Regarding the stem breast height radial increment, the most effective temperature factors are the June averages of daily minima and maxima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197774
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  • 4
    Electronic Resource
    Electronic Resource
    The concentration of Ca, Sr, Ba and Mn in successive needle age classes of Norway spruce [Picea abies (L.) Karst.] (1995)
    Springer
    Trees 10 (1995), S. 31-39 
    Details
    ISSN: 1432-2285
    Keywords: Calcium ; Barium ; Manganese ; Strontium ; Picea abies needles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The concentrations of Ca, Sr, Ba and Mn were determined in up to five successive needle age classes from 54 individual Norway spruce trees [Picea abies (L.) Karst] from nine different sites. The accumulation behaviour was found to be very nonuniform, going from an increase with needle age to a decrease; irregular patterns were also found. The type of accumulation is largely site specific. The increasing behaviour can in most cases be approximated by a simple arithmetic function. All four elements usually show the same accumulation pattern, the similarities being closest between Ca and Mn and least between Ca and Ba. It is postulated that the similarity between the four elements is due to their precipitation and storage as oxalates. The similarity between Ca, Sr and Ba is observed at all concentrations, that with Mn only at concentrations larger than 300 μg/g. Mn at small concentrations (〈 50 μg/g) shows a decreasing pattern and no similarity at all with Ca, Sr and Ba, but behaves similar to mobile elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197777
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  • 5
    Electronic Resource
    Electronic Resource
    Daily dynamics in xylem cell radial growth of Scots pine (Pinus sylvestris L.) (1995)
    Springer
    Trees 10 (1995), S. 24-30 
    Details
    ISSN: 1432-2285
    Keywords: Pinus sylvestris L. ; Wood formation ; Tracheid ; Radial cell expansion ; Daily growth dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Daily dynamics of radial cell expansion during wood formation within the stems of 25-year-old Scots pine trees (Pinus sylvestris L.), growing in field conditions, were studied. The samples of forming wood layers were extracted 4 times per day for 3 days. Possible variations in the growth on different sides of the stem, duration of cell development in radial cell expansion phase and dynamics of cell growth in this phase were taken into account. The perimeters of tracheid cross-sections as a reflection of primary cell wall growth were the criterion of growth in a radial direction. For the evaluation of growing cell perimeters a special system for digital processing and image analysis of tracheid cross-sections of the forming wood was used. Growth rate for certain time intervals was estimated by the change in the relation of the perimeter of each observed cell in each of ten tracheid rows in each of 12 trees to the perimeter of the xylem cell of the same row before the expansion. Temporal differences in average values of the relations were estimated by Analyses of Variance. The existence of daily dynamics of Scots pine xylem cell radial growth has been proved. Intensive growth of pine tracheids has been shown to occur at any time of the day and to depend on the temperature regime of the day and the night as well as water supply of stem tissues. Moreover, reliable differences (P = 0.95) in the increment of cell walls during tracheid radial expansion have been found. Pulsing changes of the water potentials both of the cell and the apoplast, as the reason for the fluctuations of radial cell growth rate, were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197776
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  • 6
    Electronic Resource
    Electronic Resource
    Quinate:NAP(P)+-oxidoreductase from Larix sibirica: purification, characterization and function (1995)
    Springer
    Trees 10 (1995), S. 46-51 
    Details
    ISSN: 1432-2285
    Keywords: Larix sibirica ; Metabolism ; Quinate:NAD(P)+-oxidoreductase ; Quinic acid ; Shikimate pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quinate:NAP(P)+-oxidoreductase (QORase, EC 1.1.1.24), which catalyzes the interconversion of quinic and 3-dehydroquinic acids, was purified from the needles and developing xylem cells of Larix sibirica. The enzymes from these two tissues were partially characterized and compared. QORase from needles had optimum pH at 9.0 and apparent Km values of 1.84 mM for quinic acid and 0.19 mM for NADP+. The enzyme was activated by phosphoenolpyruvate. Gallic and protocatechuic acids were formed in a reaction mixture of purified enzyme from needles as final products of quinic acid transformation. QORase from developing xylem cells showed pH optimum at 10.0 and had apparent Km values of 0.70 mM for quinic acid and 0.05 mM for NADP+. The enzyme was not affected by PEP. The divalent cations Co2+ and Mn2+ at least doubled activity of QORase from both sources but Mg2+ affected the enzyme from needles only. The spatial organization and regulation of quinic acid metabolism in the autotrophic and heterotrophic cells of conifers and the role of QORase in this process are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197779
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  • 7
    Electronic Resource
    Electronic Resource
    Triacylglycerols in the seeds of northern Scots pine, Pinus sylvestris L., and Norway spruce, Picea abies (L.) Karst. (1995)
    Springer
    Trees 10 (1995), S. 40-45 
    Details
    ISSN: 1432-2285
    Keywords: Picea abies ; Pinus sylvestris ; Conifer seeds ; Fatty acids ; Triacylglycerols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The geographical variation in the composition of triacylglycerols in seeds of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.], grown in Finland, was analyzed. The total lipid content of pine seeds was slightly higher in the northernmost provenance (68 °50′N), whereas the lipid content of spruce seeds was not affected systematically by the geographical origin of the seeds. The species studied differed in the proportions of fatty acids in their triacylglycerols, though the three most abundant components were the same, i.e. oleic acid (18∶1 n9), linoleic acid (18∶2n-6) and 5,9,12-octadecatrienoic acid (18∶3 5c9c12c). These fatty acids corresponded to more than 80 mol% of the total fatty acids. According to mass spectrometric analyses, the triacylglycerols of both spruce and pine seeds consisted of the same molecular species with 52–56 acyl carbons, but in different proportions. Molecules with 54 acyl carbons represented approximately 75% of the pine and 85% of the spruce triacylglycerols, with the most abundant molecular species being 54∶5, 54∶6 and 54∶7. Some minor differences in the fatty acid composition of triacylglycerols of pine seeds from different seed collecting areas were found: the proportion of linoleic acid slightly increased whereas that of 5,11,14-eicosatrienoic acid decreased towards the northern origins. Similar differences were not found in the proportions of fatty acids in spruce seed lots. Furthermore, the proportions of triacylglycerols in both pine and spruce seeds from northern and southern collecting areas were not significantly different. The higher content of total lipids in spruce seeds compared with pine seeds may be due to the structure of the seed coat, and the lipophilic layers inside it, acting as a barrier to imbibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197778
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  • 8
    Electronic Resource
    Electronic Resource
    Micronutrient composition of xylem sap and needles as a result of P-fertilization in maritime pine (1995)
    Springer
    Trees 10 (1995), S. 52-54 
    Details
    ISSN: 1432-2285
    Keywords: Forest fertilization ; Micronutrient ; Mineral interaction ; Mineral uptake ; Xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Xylem sap and foliar compositions (P, Cu, Zn, Mn) were examined over 4 months in control and P-fertilized maritime pine in a 7-year-old plantation. The absorption of copper, zinc, and boron appears to be reduced by phosphate fertilization. Manganese concentrations are positively related to P-supply increase. Foliar analysis and sap provides the same type of information in terms of antagonism or synergism between elements but the response to treatment is more often significant with sap throughout the seasons and is completely non-existent on a single classical autumn diagnosis with foliar concentration (i.e. Zn and Cu). In consequence foliar analysis is not sensitive enough for copper or zinc deficiency diagnoses in young plantations where nutritional growth disorders appear in a short period of spring, and xylem chemistry appears to be a convenient tool in monitoring micronutrient disorders in pine plantations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197780
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  • 9
    Electronic Resource
    Electronic Resource
    Seasonal and annual variations of phosphorus, calcium, potassium and manganese contents in different cross-sections of Picea abies (L.) Karst. needles and Quercus rubra L leaves exposed to elevated CO2 (1995)
    Springer
    Trees 10 (1995), S. 55-62 
    Details
    ISSN: 1432-2285
    Keywords: Picea abies ; Quercus rubra ; Nutrients ; Carbon dioxide ; Seasonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Norway spruce and red oak trees were planted directly into the soil and enclosed in open-top chambers. For 2 years the trees were exposed to both ambient and elevated CO2 concentrations (700 μmol mol-1) and during this time variations in nutrient concentrations were studied. CO2-treated plants had decreases in global leaf concentrations of nitrogen, potassium, calcium and manganese for both species. When different areas of the foliage were analysed however, the response showed much variability between the respective sites and between species. Furthermore the nutrient concentrations changed differently as the plant material aged and this change showed inter-treatment differences. These results show how it may be important to analyse plant material of different ages and at different cell sites when studying nutrient levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192184
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  • 10
    Electronic Resource
    Electronic Resource
    Poor stomatal control of water balance and the abscission of green needles from a declining stand of spruce trees [Picea abies (L.) Karst.] from the northern Alps (1995)
    Springer
    Trees 10 (1995), S. 63-73 
    Details
    ISSN: 1432-2285
    Keywords: Forest decline ; Osmotic potential ; Picea abies ; Stomatal control ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract On a site on the west slope of the Wank in the northern Alps changes in water potential, osmotic potential and transpiration rate were measured in spruce trees during the dry summer months of 1991. The pattern of decrease in water potential and osmotic potential on days of varying evaporative demand from trees of widely different decline conditions was used to describe the relative ability of the trees to withstand drought stress. Stress diagrams served as a tool for interpreting the state of health of each tree. The criterion is independent of the water situation of the tree and the other external conditions of the respective experiment. These diagrams clearly show that the foliage of spruces with high needle losses reaches the limit of endurance relatively early. For equal evaporative demand much lower turgor levels were observed in spruces with high needle loss compared to undamaged trees. Associated with the occurrence of low turgor values was the shedding of green needles. The abscission zone was shown in sections. The accumulation of highly fluorescent substances in the bundle sheath cells of the same material was described. Incomplete to non-existent stomatal control over water loss was attributed to modifications in the cell walls of the stomata which appear to alter the ability of the guard cells to sense changes in either atmospheric or cellular hydration. Our studies point to the following situation: air pollution directly affects stomatal control, the loss of stomatal control changes the drought avoidance abilities of the foliage and, as a consequence, low turgor levels occur and premature needle abscission is induced. As site water balance decreases, either due to a dry year or to poor moisture holding abilities of the soil, these conditions become apparent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192185
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  • 11
    Electronic Resource
    Electronic Resource
    Fatty acids, starch and biomass of Scots pine needles and roots in open-air ozone exposure (1995)
    Springer
    Trees 10 (1995), S. 74-82 
    Details
    ISSN: 1432-2285
    Keywords: Ozone ; Pinus sylvestris (L.) ; Lipids ; Starch ; Biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Scots pine (Pinus sylvestris L.) seedlings were fumigated with 1.2–1.5 x ambient ozone (cumulative exposure) over 2 seasons in an open-air experiment. Starch and fatty acid concentrations were analyzed in needle and root tissue in the summer, autumn and early winter. Seedling growth was determined by measuring the height of the stem and the total shoot and root biomass. Significant decreases in growth were found in exposed seedlings, even though visible symptoms were lacking. Almost significant reductions in needle and root starch concentrations were found. In the ozone treated foliage, significant increases in myristic acid (14∶0) were detected, but the major fatty acids remained unchanged. Fatty acid ratios showed that the degree of unsaturation decreased in treated needles in the summer. In the roots of ozone treated seedlings, changes in fatty acids were different from those in the foliage. Decreases of the main root fatty acids (16∶0, 18∶0, 18∶1, 18:2, 18∶3) were detected in the summer. These results show that Scots pine is susceptible to enhanced levels of ozone. If the tropospheric ozone levels continue to increase it may have deleterious effects on Scots pine forests in Finland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192186
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  • 12
    Electronic Resource
    Electronic Resource
    Restricted lateral gas movement in Pinus strobus branches (1995)
    Springer
    Trees 10 (1995), S. 83-85 
    Details
    ISSN: 1432-2285
    Keywords: Oxygen ; Sap-flow ; Respiration ; Carbon dioxide ; Cambium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Argon gas was incorporated into the sap flowing through xylem of cut branches, or added to the air in a sealed cuvette surrounding a needle-free portion of the branch to investigate lateral movement of gases in Pinus strobus. Microdialysis was used to sample air in the xylem and evacuated vials were used to collect samples of air from cuvettes attached to branches. Argon concentrations of samples of air were measured by GC-MS. When argon was added through the sap, concentrations of argon in the xylem and in air of chambers enclosing needle stumps was greater than that of controls, but argon concentrations of air in cuvettes enclosing a needle-free portion of the branch were not greater than controls. When argon was added to cuvettes enclosing a needle-free portion of the branch, the argon did not enter the xylem and it was not emitted by needle stumps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192187
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  • 13
    Electronic Resource
    Electronic Resource
    Coniferyl alcohol oxidase — a catechol oxidase? (1995)
    Springer
    Trees 10 (1995), S. 102-107 
    Details
    ISSN: 1432-2285
    Keywords: Pinus strobus L ; Polyphenol oxidase ; Tracheid differentiation ; Wood formation ; Cell wall ; Lignin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The physico-chemical properties of coniferyl alcohol oxidase (CAO), a copper containing glycoprotein spatiotemporally associated with lignification in conifers, is reported here. By electron paramagnetic resonance spectroscopy, only type 3 copper was indicated in CAO. CAO oxidizes several laccase substrates; however, it is not a blue-copper protein and monoclonal antibodies against both native and deglycosylated CAO did not recognize any of several laccases. The N-terminal sequence of CAO, H2N-X E L A Y S P P Y X P S, was non-homologous with known enzymes. Transparent copper, tetrameric structure, aminoacid composition, phenylhydrazine and tropolone inhibition, and SDS enhancement of CAO activity indicate that CAO is an o-diphenol oxidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192190
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  • 14
    Electronic Resource
    Electronic Resource
    Carbohydrate content of Eucalyptus gunnii leaves along an annual cycle in the field and during induced frost-hardening in controlled conditions (1995)
    Springer
    Trees 10 (1995), S. 86-93 
    Details
    ISSN: 1432-2285
    Keywords: Carbohydrates ; Eucalyptus gunnii ; Frost resistance ; Hardening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The annual changes in frost hardiness were studied for three Eucalyptus gunnii genotypes. Frost resistance evaluated on leaf discs by the electrolyte leakage method reached a maximum in the coldest period and a minimum in summer demonstrating winter frost hardening. Genotype 634 exhibited a higher intrinsic resistance than the other genotypes both in the hardened and in the non-hardened stages. Plants of this genotype were also frost acclimated in controlled conditions by a progressive decrease of culture temperature (25 to 0 °C) but the degree of hardening appeared to be lower in these conditions. The carbohydrate patterns in leaves varied with acclimation. In controlled conditions the leaves of genotype 634 exhibited a rise in sucrose, fructose and raffinose concentration up to a temperature of 10 to 7 °C which subsequently decreased. In natural conditions a comparison of the three genotypes allowed us to correlate the higher intrinsic resistance of genotype 634 to a higher soluble sugar content. During acclimation fructose and raffinose changes were also correlated to an increase in cold resistance even though the kinetics of these changes differed in controlled and natural conditions. The starch content was very low in the various genotypes in the different conditions but oligosaccharides such as stachyose and possibly verbascose were detected. The results point out the relationships occurring between increased frost resistance and changes in fructose and raffinose concentration in E. gunnii leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192188
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  • 15
    Electronic Resource
    Electronic Resource
    Diurnal changes in the radius of a subalpine Norway spruce stem: their relation to the sap flow and their use to estimate transpiration (1995)
    Springer
    Trees 10 (1995), S. 94-101 
    Details
    ISSN: 1432-2285
    Keywords: Stem radius variation ; Xylem sap flow ; Crown transpiration ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Diurnal changes in the stem radius of a subalpine mature Norway spruce were measured simultaneously with the flow of sap in xylem. Matric potentials in the soil were 〉 -35 kPa. The kinetics of the flow were closely related to the changes in the radius of the stem resulting from depletion of its extensible tissues. The radius of the stem oscillated daily and, fairly independently of this, fluctuated over several days. The daily shrinkage (Δd) was correlated with the daily flow through its base (Qd). When the crown transpired little and was nearly saturated during rainy days, ASd tended to increase relative to Qd. Using a linear relation, the estimates of flow by Δd deviated less than ± 10% from the values measured by heat balance, provided that the periods of calibration in their ratio of dry to rainy days were comparable to those estimated. If the two periods differed in this respect, the estimates of flow deviated up to 42%. A quadratic relation yielded estimates that depended less on weather. It reduced maximal deviations to ±22%. Since Δd additionally may represent the time pattern of the daily transpiration better than Qd, analysing changes in the radius of stems may supplement or partly replace measurements of sap flow in stems.
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    URL: http://dx.doi.org/10.1007/BF00192189
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  • 16
    Electronic Resource
    Electronic Resource
    Growth patterns of early versus late successional multipurpose trees of the western Himalaya (1995)
    Springer
    Trees 10 (1995), S. 108-113 
    Details
    ISSN: 1432-2285
    Keywords: Growth pattern ; Multipurpose ; Successional trees ; Western Himalaya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the mid-western Himalaya (altitude 1350 m, rainfall 1100 mm), multipurpose trees found as escapees in agricultural fields or naturally growing in the forests, play an important role in providing fuel, fooder and small timber to the farmers. Shoot elogation, and tree architecture of 4 year old trees of Grewia optiva, Robinia pseudoacacia and Celtis australis (early successionals), and Quercus leucotrichophora, Q. glauca and Ilex odorata (late successionals), were analyzed. All the late successional species showed a proleptic type of bud and branch production, while the early successional trees made growth through syllepsis. The shoot elongation differed significantly (P 〈0.05) with the crown position, and ranged from 11 to 30 cm in different species. Early successional species tended to maintain a comparatively narrow crown and showed a significantly (P 〈0.05) higher ramification ratio, and multilayered canopy. The late successionals, in contrast, showed a wide crown with monolayered canopy, adapted to the weak light intensity. There was only one flush of leaves in Q. leucotrichophora and Q. glauca while in the rest of the species there were two distinct flush periods. The results are important for the management of agroforestry trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192191
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  • 17
    Electronic Resource
    Electronic Resource
    Altered root growth and plant chemistry ofPinus sylvestris seedlings subjected to aluminum in nutrient solution (1996)
    Springer
    Trees 10 (1996), S. 135-144 
    Details
    ISSN: 1432-2285
    Keywords: Scots pine ; Aluminum ; Pollution ; Photosynthesis ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for 9 weeks in nutrient solutions containing 0, 0.5, 1, 2 and 4 mM aluminum nitrate (Al(NO3)3) at pH 4.2. Nine weeks exposure to Al significantly reduced total plant, shoot and root mass and caused a linear decline in proportional allocation of biomass to roots. Relative growth rate of roots declined to as low as zero. Aluminum treatment decreased calcium and magnesium uptake and increased Al content in roots and needles. After 3 weeks of exposure a 10–60% increase in total phenols in roots and a 20–40% increase in o-diphenols in roots and needles were noted. Roots affected by Al showed degeneration of meristematic cells, fewer cell divisions, deformation in cell walls and higher lignification and suberization. The majority of root apices were structurally similar to dormant roots, and a premature senescence of the entire root system was observed. Net photosynthetic rate after 6 weeks of treatment was negatively correlated with needle Al content and Al/Ca ratio (r 〈 -0.9, P 〈 0.1). The results suggest that Scots pine may be more susceptible to Al than was expected based on previous experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02340765
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  • 18
    Electronic Resource
    Electronic Resource
    Development of needle retention in Scots pine (Pinus sylvestris) in 1957–1991 in northern and southern Finland (1995)
    Springer
    Trees 10 (1995), S. 125-133 
    Details
    ISSN: 1432-2285
    Keywords: Pinus sylvestris ; Needle trace method ; Needle retention ; Long-term variation ; Reindeer browsing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The needle trace method was used to study retrospectively the long-term latitudinal variation in needle retention in Scots pine (Pinus sylvestris L.) in Finland. The mean annual summer needle retention (ANR) along the main stem varied from 3.4 to 6.0 needle sets during the period 1957–1991. The lowest values were observed in southern and the highest in northern Finland. The length of the growing season, expressed as the thermal sum (threshold value +5 °C), was negatively correlated with the mean ANR (r=-0.96). The geographical needle retention pattern (NRP) for the period 1957–1991 showed a clearly increasing trend from 1957 to 1969 (southern Finland) and to 1975 (northern Finland); thereafter, the NRP tended to decrease close to its minimum value recorded in 1991. The general level of the NRP was approximately 5.0 needle sets in northern Finland and 3.5–4.0 needle sets in southern Finland. The NRP, with its 6–12 year cycle for southern Finland, was clearly periodical. Differences in the NRP among the ten stands in southern Finland were small, whereas the said periodicity was missing and the differences were high among the stands in northern Finland. The results indicate that variation in the number of needle sets, viz. defoliation of pines, is a normal phenomenon. The role of net carbon assimilation as a regulator of the number of needle sets is discussed.
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    URL: http://dx.doi.org/10.1007/BF00192193
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    Photosynthetic acclimation to light in juveniles of two cloud forest tree species (1995)
    Springer
    Trees 10 (1995), S. 114-124 
    Details
    ISSN: 1432-2285
    Keywords: Alchornea triplinervia ; Decussocarpus rospigliosii ; Photosynthetic acclimation ; Sun/shade adaptation ; Tropical cloud forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The photosynthetic response of juveniles of Decussocarpus rospigliosii, an emergent primary forest species and shade tolerant in its juvenile stages and Alchornea triplinervia, a gap-colonizing species of tropical cloud forest in Venezuela was studied. Daily courses of microenvironmental variables and gas exchange under contrasting light conditions (gap and understory) were carried out in their natural environment and transplanted to different light regimes (shade and sun) in the field. The photosynthetic response and some anatomical characteristics of plants from different treatments were analyzed in the laboratory. Photosynthetic rates were low for both species, and were negative during some diurnal periods, related to the low photosynthetically active radiation levels obtained at both gap (6% of total radiation) and understory (2%). A. triplinervia shows higher rates (1.5–3.0 μmolm-2 -1) than D. rospigliosii (0.7–1.1 μmolm-2s-1). Both species showed increased photosynthetic rates when grown in gaps. A. triplinervia did not adjust its maximum photosynthetic rates to the prevailing light conditions. In contrast, D. rospigliosii responded to increased light levels. Both species showed low light compensation points when grown under total shade. There was a partial stomatal closure generally during midday in D. rospigliosii. A. triplinervia presented lower leaf conductances, transpiration rates and lesser stomatal control. Some leaf anatomical characteristics, in both species, were affected by variations in the light regime (i.e. increased leaf thickness, leaf specific weight and stomatal density). These results suggest that both species have the ability to respond to variations in their natural light environments, therefore maintaining a favorable carbon balance during the day.
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    URL: http://dx.doi.org/10.1007/BF00192192
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    Acceleration of leaf senescence inFagus sylvatica L. by low levels of tropospheric ozone demonstrated by leaf colour, chlorophyll fluorescence and chloroplast ultrastructure (1996)
    Springer
    Trees 10 (1996), S. 145-156 
    Details
    ISSN: 1432-2285
    Keywords: Fagus sylvatica ; Open-top chamber ; Ozone ; Plastoglobuli ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract From April 1988 to October 1991 3-year-old seed propagated beech (Fagus sylvatica L.) trees were exposed in open-top chambers to four different levels of air pollution: (1) charcoal filtered air, (2) ambient air, (3) ambient air plus 30 nl 1-1 ozone during the summer, and (4) ambient air plus 30 nl 1-1 ozone during the summer and 20 nl 1-1 SO2 and NO2 during the winter. Leaf colour was studied in the autumns of 1989 and 1991 and a close relationship between ozone dose and premature senescence was found. A correlation also exists between the colour groups and chlorophyll fluorescence (Fv/Fm). Ozone fumigation increases the size and speeds up the development of the plastoglobules. This is described using an index based on the volume of plastoglobules as a percentage of chloroplast volume. The index was significantly higher for ozone fumigated plants than for control plants during August to November 1989. According to all three methods it is concluded that low levels of ozone accelerate leaf senescence processes inF. sylvatica. There are indications that leaves of the first and the second flush react differently to the ozone treatment. Irrespective of the ozone treatment a special cell wall structure, probably a local suberization, is confined to the subsidiary cells in leaves of the first flush.
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    URL: http://dx.doi.org/10.1007/BF02340766
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    Influence of UV-B radiation on photosynthetic activity and chlorophyll fluorescence kinetics in Norway spruce [Picea abies (L.) Karst.] seedlings (1996)
    Springer
    Trees 10 (1996), S. 172-176 
    Details
    ISSN: 1432-2285
    Keywords: Ultraviolet-B radiation ; Norway spruce ; Picea abies (L.) Karst. ; Photochemical activity ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Norway spruce [Picea abies (L.) Karst.] seedlings were grown in greenhouses with two supplemental levels of ultraviolet-B (UV-B) radiation. Photochemical efficiency of photosystem II and vitality index were determined monthly. At the end of the experiment, growth, chlorophyll content and photosynthetic rates were measured. The data indicate that low temperature in winter affected light dependent processes in experimental plants including control, while the rise of ambient temperatures, moderate this effect. The synergistic effects of UV-B radiation and low temperatures could only be observed in the second winter period. Measurements of net photosynthetic activity in the second winter period showed significant differences between treated and untreated plants.
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    URL: http://dx.doi.org/10.1007/BF02340768
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    Changes in dormancy levels ofFraxinus excelsior L. embryos at different stages of morphological and physiological maturity (1996)
    Springer
    Trees 10 (1996), S. 177-182 
    Details
    ISSN: 1432-2285
    Keywords: Embryo dormancy ; Fraxinus excelsior ; In vitro germination ; Seed development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dormancy status ofFraxinus excelsior embryos at different developmental stages under environmental conditions was examined over a period of 2 years. For each sampling date the length of the fruit, of the seed, and of the embryo were measured, and the embryological stage determined. The depth of dormancy was assayed by the germination behaviour of isolated embryos under aseptic conditions on an agar medium without nutrients. As an approach towards a quantitative estimate of the dormancy status, the degree of inhibiton of germinative growth in the embryonic organs was evaluated on the basis of four categories from none to full germinative growth. From these ratings a dormancy index was calculated, expressing the mean dormancy status of the embryos at a given date. Embryo dormancy already became apparent during embryogenesis and reached its highest level during the later phase of reserve deposition in the seed. A marked loss of embryo dormancy occurred during the phase of maturation drying in autumn, followed by a moderate increase in winter. In hydrated seeds in spring the embryo was gradually released from dormancy and enlarged further. In maintaining the embryo ofF. excelsior in a developmental but not germinative mode, dormancy mechanisms within the embryo and the endosperm, combined with environmental factors, may be involved.
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    Effects of long-term open-air exposure to fluoride, nitrogen compounds and SO2 on visible symptoms, pollutant accumulation and ultrastructure of Scots pine and Norway spruce seedlings (1996)
    Springer
    Trees 10 (1996), S. 157-171 
    Details
    ISSN: 1432-2285
    Keywords: Conifer ; Fluoride ; Nitrogen ; Sulphur dioxide ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of SO2, aqueous fluoride (NaF) and a solution of nitrogen compounds (NH4NO3) on the visible symptoms, pollutant accumulation and ultrastructure of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] seedlings were studied in an open-air experiment lasting for 3 consecutive years. Visible injury symptoms were most pronounced in combination exposures and whenever F was applied. Visible symptoms correlated well with needle pollutant concentrations. Exposure to NaF increased needle F contents particularly when F was applied with SO2 or NH4NO3. This suggests that a reduction in N or SO2 emissions, in F polluted areas, could improve the condition of conifers via decreased accumulation of phytotoxic F in the needles. Norway spruce needles accumulated 2–10 times as much S and F as those of Scots pine. Microscopic observations showed various changes in the needle mesophyll cell ultrastructure. In both species, exposure to SO2 increased significantly the amount of cytoplasmic vacuoles, suggesting detoxification of excess sulphate or low pH. F treatments resulted in a significant enlargement of plastoglobuli in Scots pine and a darkening of plastoglobuli in Norway spruce. All exposures enhanced the accumulation of lipid bodies. An increased portion of translucent plastoglobuli was most pronounced in N treatments. Many of the ultrastructural changes and visible symptoms appeared only as number of years exposed increased, indicating that long-term experiments are needed. Both visible symptoms and ultrastructural changes pointed to the more pronounced sensitivity of Norway spruce compared to Scots pine. Ultrastructural results mostly supported earlier qualitative observations of F, N and SO2 effects on needle mesophyll cell ultrastructure. However, no reduction of thylakoids in SO2 containing exposure or curling of thylakoids in F exposure could be detected in the present study.
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    URL: http://dx.doi.org/10.1007/BF02340767
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    Anaerobic induced ethanol synthesis in the stems of greenhouse-grown conifer seedlings (1996)
    Springer
    Trees 10 (1996), S. 183-188 
    Details
    ISSN: 1432-2285
    Keywords: Anaerobic respiration ; Fermentation ; Hypoxia ; Pseudotsuga menziesii ; Pinus ponderosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ethanol synthesis was induced in stem segments from greenhouse-grown conifer seedlings by placing them in a N2 atmosphere at 30 °C for 24 h. Stems from ponderosa pine,Pinus ponderosa Dougl. ex Laws., sugar pine,Pinus lambertiana Dougl., Pacific silver fir,Abies amabalis Dougl. ex Forbes, and lodgepole pine,Pinus contorta Dougl. ex Loud, produced the highest quantities of ethanol. This group also had the smallest and slowest growing stems. Within each of these species the amount of ethanol produced was inversely related to the stem volume. Stems from western hemlock,Tsuga heterophylla (Raf.) Sarg., grand fir, Abies grandis Dougl. ex Forbes, Douglas-fir,Pseudotsuga menziesii (Mirb.) Franco, and western redcedar,Thuja plicata Donn ex D. Don, all produced equivalent but low ethanol concentrations. These species had the largest and fastest growing stems. In this group only grand fir exhibited an inverse relationship between ethanol concentrations and stem volume. The relative amounts of ethanol synthesized by stems from Douglas-fir, western hemlock and western redcedar seedlings were not the same as subsequently observed in logs from mature trees of the same species under field conditions. Differences in the anaerobic environments for the two stem types could have affected the quantities of ethanol produced. The observed high amounts of ethanol produced by the stems from pine species were discussed in terms of their ability to handle periods of anaerobic stress or hypoxia.
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    URL: http://dx.doi.org/10.1007/BF02340770
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    Effects of N addition rates on the productivity ofPicea sitchensis,Thuja plicata, andTsuga heterophylla seedlings (1996)
    Springer
    Trees 10 (1996), S. 189-197 
    Details
    ISSN: 1432-2285
    Keywords: Nitrogen ; Picea sitchensis ; Relative growth rates ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seedlings ofPicea sitchensis, Thuja plicata andTsuga heterophylla were supplied N hydroponically at one of four exponentially increasing rates of addition (0.09, 0.07, 0.05, or 0.025 gN-1 day-1) for up to 3 months in a naturally illuminated glasshouse. Relative growth rates (RGR) were analyzed as a function of N uptake, the allocation of assimilated N to foliage (LNFR), foliar N concentrations (Nla) and met assimilation rates (NAR), which were combined to estimate N productivity (RGR per unit whole-plant N concentration). Nitrogen accumulation, biomass and N partitioning and RGR and its components varied with species in response to the different N regimes.T. heterophylla had the lowest maximum wholeplant N concentrations (wpN) and specific absorption rates for N and exhibited the least plasticity in root: shoot ratios as wpN increased from 11–21 mg g-1. In all species, RGR increased linearly with wpN, while LNFR increased curvilinearly. Foliar N (Nla) increased linearly with wpN and NAR increased linearly with Nla. The RGRs ofT. heterophylla were highest at wpNs up to 18 mg g-1, a result of higher foliar N use efficiencies (NAR/Nla). However, RGR increased more with wpN inT. plicata andP. sitchensis. Although LNFR increased with wpN in all species, foliar N use efficiency declined, possibly due to an increased partitioning of foliar soluble N to non-photosynthetic compounds. Thus, in each species, N productivity did not increase above intermediate levels of wpN: 14 mg g-1 inT. heterophylla, 16 mg g-1 inP. sitchensis and 17 mg g-1 inT. plicata.
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    Assessing the impact of ozone on photosynthesis of European beech (Fergus sylvatica L.) in environmental chambers (1996)
    Springer
    Trees 10 (1996), S. 268-275 
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    ISSN: 1432-2285
    Keywords: Beech ; Ozone ; Photosynthesis ; Closed chambers ; Critical Levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An exposure — response study with proportionalto-ambient ozone levels was conducted in closed chambers on 3-year-old European beech (Fagus sylvatica L.) of montane origin. The fumigation started in April 1990 and lasted for a single growing season. Climate data and ozone concentrations monitored at an experimental station of the Institute for Applied Plant Biology, Schönenbuch, Switzerland were simulated in the exposure chambers 12 days later (1*O3). To test exposure-response relations three additional treatments were applied, subambient (0.2*O3) and two proportionally increased ozone treatments (1.5*O3 and 2*O3). The photosynthetic behaviour of the trees in August revealed the light reactions to be less affected than parameters which are related to the dark reactions of photosynthesis. Assimilation (A350), apparent carboxylation efficiency (CE), and maximum photosynthetic capacity (A2500) were reduced with increasing ozone concentration. For the ozone response of CE and A2500 ‘Critical Levels’ were calculated.
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    Effects of N addition rates on the productivity ofPicea Sitchensis,Thuja plicata, andTsuga heterophylla seedlings (1996)
    Springer
    Trees 10 (1996), S. 198-205 
    Details
    ISSN: 1432-2285
    Keywords: Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN-1day-1) on photosynthesis, discrimination against13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifersPicea sitchensis, Thuja plicata andTsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g-1 and declined at higher Nlms. Species differences inA resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have causedA to decline at a high Nlm inP. sitchensis andT. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only inP. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness ofA and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
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    Slightly elevated ozone exposure causes cell structural changes in needles and roots of Scots pine (1996)
    Springer
    Trees 10 (1996), S. 207-217 
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    ISSN: 1432-2285
    Keywords: Ozone ; Pine ; Fine structure ; Needles ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Scots pine (Pinus sylvestris L.) seedlings were fumigated with 1.2–1.5 x ambient ozone over 2 seasons in an open-air experiment. Fumigation started in the early spring and continued into late autumn during both years. Needle and root cell structures were analyzed in the summer, autumn and early winter following the second fumigation period. Under the light microscope an increase in the intercellular space and disintegrating cells in the mesophyll tissue near the stomata and stomatal cavities were observed in the ozone-exposed needles. Darkening of chloroplast stroma, increased plastoglobulus size and decreased chloroplast size were characteristic ultrastructural changes associated with ozone exposure. In addition, less dense grouping of the chloroplasts in the needles of elevated ozone-exposed seedlings as compared to the controls (background ozone) was observed in the early winter. Fewer starch grains and an increased accumulation of tannin-like substances were detected in both mycorrhizal and uninfected roots of ozone-exposed seedlings as compared to the control seedlings. For the first time, we were able to show that the ozone-induced darkening of needle chloroplast stroma is a reversible symptom. An increased frequency of frost injury symptoms indicated that the winter hardening process was disturbed in the needles of ozone-treated seedlings.
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    Estimation of canopy density and irradiance in 20- to 40-year-old birch stands (Betula pubescens Ehrh. andBetula pendula Roth) (1996)
    Springer
    Trees 10 (1996), S. 223-230 
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    ISSN: 1432-2285
    Keywords: Betula pubescens Ehrh ; Betula pendula Roth ; Birch ; LAI ; Crown free projection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three different experiments in birch (Betula pubescens Ehrh. andBetula pendula Roth) stands were conducted during summer 1991: an evaluation of the accuracy of the vertical tube method measuring crown free projection (CFP) in four birch stands; a study of relative irradiance (RI; photosynthetically active radiation, PAR), in birch stands differing in stem density and basal area; and an estimation of the CFP in different types of birch stands and the correlation between RI and CFP. The results indicate that the number of observation points well distributed over an area of 0.1 ha can vary between 50 and 200 to achieve sufficient accuracy. There were no significant differences in the CFP estimates made on the same plot by different observers including an untrained observer. CFP was related to basal area, stem number and diameter sum in a non-linear regression, CFP = A*e-BX. The correlations between RI and basal area, density and diameter sum, respectively, were 0.54, 0.57 and 0.67 for PAR. The coefficients of determination for RI (PAR) and CFP were high (0.86).
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    Carbon and water balance in Polylepis sericea, a tropical treeline species (1996)
    Springer
    Trees 10 (1996), S. 218-222 
    Details
    ISSN: 1432-2285
    Keywords: Carbon balance ; Polylepis sericea ; Treeline ; Tropical Andes ; Water balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Polylepis sericea trees grow well above the continuous forest line in the Venezuelan Andes. In these environments, extreme daily temperature ranges can occur at any time of the year and trees experience a 4 month dry period. The purpose of this work was to study carbon and water relations of this species in the field during wet and dry seasons in order to understand this species' success at such high altitudes. Leaf gas exchange (portable system in open mode) and leaf water potential (pressure chamber) were measured at 1–2 h intervals during several daily courses at 4000 m elevation in the Páramo de Piedras Blancas. CO2 assimilation versus leaf temperature curves were also obtained for this species in the laboratory. Clear differences in the measured parameters were observed between seasons. For a wet season day, maximum CO2 assimilation rate was 7.4 μmol m-2 s-1 and leaf conductance was relatively constant (approximately 100 mmol m-2 s-1)In the dry season day, maximum CO2 assimilation rate was 5.8 μmolm-2 s-1 and leaf conductance was close to 60 mmolm-2 s-1. Minimum leaf water potentials measured were -1.3 MPa for the wet and -2.2 MPa for the dry season. The CO2 assimilation-leaf temperature relationship showed a 13.4°C leaf temperature optimum for photosynthesis with maximum and minimum compensation points of 29.5 and -2.8°C, respectively. Maximum night-time respiration was relatively high (2.7 (imol) m-2 s-1)Our results show thatP. sericea maintains a highly positive carbon balance through all daily courses, even though there is a slight water stress effect during the dry season; this suggests that its carbon assimilation machinery is well adapted to the low temperatures and seasonal water stress found in the high tropical mountains.
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    Effects of age and site quality on the distribution of biomass in Scots pine (Pinus sylvestris L.) (1996)
    Springer
    Trees 10 (1996), S. 231-238 
    Details
    ISSN: 1432-2285
    Keywords: Scots pine ; Biomass ; Allocation ; Age ; Single tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The distribution of the above-ground and below-ground biomass of Scots pine in southern Finland were investigated in trees of different ages (18–212 years) from two types of growth site. Secondly, some structural regularities were tested for their independence of age and growth site. Trees were sampled from dominant trees which could be expected to have a comparable position in stands of all ages. All stands were on sorted sediments. The biomass of the sample trees (18 trees) was divided into needles, branch sapwood and heartwood, stem sapwood and heartwood, stem bark, stump, large roots (diameter 〉20 cm), coarse roots (five classes) and fine roots. The amount of sapwood and heartwood was also estimated from the below-ground compartments. Trees on both types of growth site followed the same pattern of development of the relative shares of biomass compartments, although the growth rates were faster on the more fertile site. The relative amount of sapwood peaked after canopy closure, coinciding with the start of considerable heartwood accumulation. The relative amount of needles and fine roots decreased with age. The same was true of branches but to a lesser degree. The relative share of the below-ground section was independent of tree age. Foliage biomass and sapwood cross-sectional area were linearly correlated, but there were differences between the growth sites. Needle biomass was linearly correlated with crown surface area. The fine root to foliage biomass ratio showed an increasing trend with tree age.
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    Effects of bending stress on taper and growth of stems of youngEucalyptus regnans trees (1996)
    Springer
    Trees 10 (1996), S. 239-246 
    Details
    ISSN: 1432-2285
    Keywords: Bending stress ; Stem shape ; Radial growth rate ; Eucalyptus regnans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse experiment investigated the effect of bending stress on stem radial and height growth and stem taper ofEucalyptus regnans seedlings. Eighteen-week-old, potted seedlings were bent continuously for 8 weeks with a static bending stress. The bending treatment was then removed and the seedlings grown for another 12 weeks. Other seedlings were stayed vertically throughout the experiment whilst control seedlings were neither bent nor stayed. Seedlings were rotated every 2 days to prevent reaction wood developing asymmetrically in the stems of bent trees. Bent trees had higher radial growth rates, developed more tapered stems and had higher safety factors (the ratio of stem radius to the minimum radius required to prevent the tree toppling over) than unbent seedlings. They produced a band of tension wood in their stems and ceased height growth whilst bent. When bending ceased, they resumed normal radial and height growth. Unbent trees developed more cylindrical stems. There were no differences in growth behaviour between stayed and control trees. Bent and unbent trees all developed a butt swell, the taper of which was not affected by treatment. It was concluded that bending stress has substantial effects on both the size and taper of tree stems. However, the development of butt swell is independent of the bending stress applied. The results were considered in relation to biomechanical theories of tree stem development.
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    Nutrient dynamics in crown tissues of cork-oak (Quercus suber L.) (1996)
    Springer
    Trees 10 (1996), S. 247-254 
    Details
    ISSN: 1432-2285
    Keywords: Evergreen oaks ; Macronutrients ; “Montado” ; Seasonal patterns ; Tissue nutrient contents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The seasonal fluctuation of N, P, K, Ca and Mg in leaves, young stems and fruits of young and matureQuercus suber trees growing at the same site was studied. Nutrient dynamics within the tree appeared to be linked to phenological events. Leaves maximized their nutrient contents throughout summer whereas stems maintained rather constant values during most of the year. Before the spring growth flush they apparently acted as temporary reservoirs for some nutrients, translocated from leaves or other organs, so that such nutrients would be easily invested in the new tissues. A significant investment was made in sink organs like flowers and fruits. The tree probably relies not only on leaves but also on other nutrient reservoirs like older branches and roots for an adequate supply to those sinks and to the spring growth. The importance of the sampling dates and the basis of expression used for nutrient concentrations has also been emphasized. Nutrient contents and seasonal trends of the studied trees were similar to those of other evergreen oaks, although somewhat higher values for N, K, and Mg were found. Moreover, soil nutrient contents in the studied “montado” were much lower than in other Iberic oak stands. However the nutrient status and requirements of cork-oak suggest high (or at least adequate) nutrient availability to the trees. The mechanisms by which this could be achieved are discussed.
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    Microautoradiographic detection of CO2 fixation in lenticel chlorenchyma of youngFraxinus excelsior L. stems in early spring (1996)
    Springer
    Trees 10 (1996), S. 255-260 
    Details
    ISSN: 1432-2285
    Keywords: CO2 fixation ; Fraxinus excelsior L. ; Lenticels ; Microautoradiography ; Stem chlorenchyma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microautoradiography indicated that 1-year-oldFraxinus excelsior L. stem chlorenchyma assimilated external14CO2 in mid-April, when buds were swollen, but before bud-break. The lenticel regions showed the highest amount of radioactively labeled assimilates. Labeled assimilates declined in the tangential direction with increasing distance from lenticels, suggesting that14CO2 entered the stem through the open intercellular spaces of lenticels. In the radial direction, the amount of radioactively labeled assimilates did not constantly decline with growing distance from the lenticel entrance. It was high in all lenticel phelloderm cells, which had high chlorophyll autofluorescence and very small starch grains, highest in the adjacent 4–6 rows of chlorenchyma, which had larger starch grains that increased in size towards the interior rows, and much lower in the inner cortex chlorenchyma, which had large starch grains. We suggest that the main function of the lenticel chlorenchyma (lenticel phelloderm plus 4–6 rows of adjacent cortex chlorenchyma) is the refixation of respiratory CO2 which could easily leave the stem intercellular spaces, rather than the fixation of external CO2. The lenticel chlorenchyma could reduce the loss of respiratory CO2 by its photosynthetic activity.
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    Uptake of ammonium and nitrate ions from acid mist applied to Sitka spruce [Picea sitchensis (Bong.) Carr.] grafts over the course of one growing season (1996)
    Springer
    Trees 10 (1996), S. 261-267 
    Details
    ISSN: 1432-2285
    Keywords: Wet N inputs ; Labelled N ; N partitioning ; N accumulation ; Per cent incorporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cloned Sitka spruce grafts were subjected to NH4NO3 mist (1 mm day-1 equivalent) acidified with H2SO4, for 4 days a week, from April until November. Three N treatments at pH 5.0 used 0.01 mol m-3 15NH4 15NH3, 1.6 mol m-3 15NH4 NO3 or 1.6 mol m-3 NH4 15NO3. At pH 2.5, the treatments were15NH4 15NO3,15NH4NO3 and NH4 15NO3 all at 1.6 mol m-3. At the end of the growing season,15N was found in every part of the trees, even when NH4NO3 was supplied at 0.01 mol m-3. It was shown that both $$NH_{4^ + } $$ and $$NO_{3^ - } $$ could enter needles to a similar degree and be transported to the roots. No differences between pH treatments or clones could be demonstrated. Entry of labelled N via the roots, in those trees with unprotected compost, was reflected in higher fine root15N content, but no change in shoot15N levels. Per cent incorporation expressed as labelled N as a percentage of total N, was generally at its highest in bark, and in older needles in all treatments, values ranging from 5 to 11%. When15N content was expressed as total content for each tree part on a per tree basis, 25–36% was found in current year needles, with a further 12% in current year bark. The most reproducible data was that for dry weight of tree parts as per cent of the whole tree, where proportions compared closely between treatments and the two clones used. The implications of the results for cuticular transport mechanisms, N storage and internal cycling are discussed.
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    The effect of crown position and date of sampling on biomass, nutrient concentrations and contents of needles and shoots in European larch (1996)
    Springer
    Trees 10 (1996), S. 339-350 
    Details
    ISSN: 1432-2285
    Keywords: European larch ; Nutrient ; Biomass ; Needle ; Shoot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The nutrient concentrations and contents of needles and shoots of 22-year-old European larch (Larix decidua Mill.) were evaluated with respect to crown position, age of tissues and sampling date during a complete growing season. Concentrations of N, P, K, Ca, Mg and Zn in the needles and of N, P and K in the shoots differed significantly among the dates of sampling. The concentrations of N and Mn in the needles and all nutrients in the shoots (except Mg) also differed significantly with crown position. Maximum needle biomass was observed in the middle crown position (55% of the total) and maximum shoot biomass, in the lower crown position (52% of the total). Maximum needle and shoot nutrient contents were observed in the middle position of the living crown for long shoot, short shoot-1, short shoot-2, short shoot-3 and, short shoot-4 age classes while highest contents for short shoot-5 and short shoot-6 age classes were observed in the lower crown position. Biases up to 42% for Mg in the needles and 200% for K in the shoots were obtained when only long shoot tissues are used for content evaluation. For needles and shoots, Mg and K are more difficult nutrients to evaluate. A sampling methodology is proposed for evaluating nutrient contents of the living crown.
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    A model of the gas exchange response ofPicea abies to habitat conditions (1996)
    Springer
    Trees 10 (1996), S. 277-287 
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    ISSN: 1432-2285
    Keywords: Picea abies ; Norway spruce ; Leaf gas exchange ; Net photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Databases describing branch gas exchange ofPicea abies L. at two montane forest sites, Lägeren, Switzerland (National Forschungsprojekt 14 of the Schweizerische Nationalfonds) and Oberwarmensteinach, Germany (Bayerische Forschungsgruppe Forsttoxikologie), were analyzed in conjunction with a physiologically based model. Parameter estimates for describing carboxylase kinetics, electron transport, and stomatal function were derived, utilizing information from both single factor dependencies and diurnal time course measurements of gas exchange. Data subsets were used for testing the model at the branch level. Most of the observed variation in gas exchange characteristics can be explained with the model, while a number of systematic errors remain unexplained. Factors seen as contributing to the unexplained residual variation and not included in the model are light acclimation, degree of damage in adjustment to pollutant deposition, needle age, and cold stress effects. Nevertheless, a set of parameter values has been obtained for general application with spruce, e.g., for use in calculating canopy flux rates and to aid in planning of focused leaf and canopy level experiments. The value of the model for estimating fluxes between the forest and the atmosphere must be evaluated together with measurements at the stand level.
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    Photoinhibition in cork-oak leaves under stress: influence of the bark-stripping on the chlorophyll fluorescence emission inQuercus suber L. (1996)
    Springer
    Trees 10 (1996), S. 288-292 
    Details
    ISSN: 1432-2285
    Keywords: Bark-stripping ; Fluorescence emission ; Quercus suber L. ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quercus suber is the primary source for industrial cork and becomes bark-stripped every 9–10 years. Recurring cork extraction is a major stress factor and the large water loss from the stripped trunk surface may affect the water balance and tree productivity. To evaluate the effect of bark-stripping, fluorescence emission and stomatal conductance of leaves were determined in groups of bark-stripped and control trees. Fv/Fm ratio was found to be significantly lower in bark-stripped trees indicating a reduced photosynthetic efficiency of PSII. Photosynthesis was not found to be stomata limited. The reduction in Fv/Fm resulted from a decline in maximum and variable fluorescence while the initial fluorescence of the dark-adapted state (Fo) remained constant. A general decline in photosynthetic efficiency of PSII was found in all trees during the summer, probably reflecting the prolonged environmental stresses during a hot and dry season. Additional stress caused by the bark-stripping seems to enhance the susceptibility to photoinhibition of the trees.
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    Magnesium deficiency treatment causes reductions in photosynthesis of well-nourished Norway spruce (1996)
    Springer
    Trees 10 (1996), S. 293-300 
    Details
    ISSN: 1432-2285
    Keywords: Norway spruce ; Magnesium deficiency ; Photosynthesis ; Carboxylation efficiency ; Starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to investigate effects of magnesium deficiency on Norway spruce [Picea abies (L.) Karst.] photosynthesis, 100 well-nourished 5-year-old spruce trees were grown in sand culture, individually supplied with circulating nutrient solutions. Mineral nutrients were added to the nutrient solutions in optimal quantities and optimal relations to nitrogen. Magnesium was supplied at 0.203, 0.041 and 0.005 mM in order to simulate optimal nutrition, moderate deficiency and severe deficiency. Parameters of photosynthetic gas exchange, chlorophyll, magnesium and starch concentrations were determined in current-year and 1-year-old needles during one growing season. By mid May — 6 months after onset of the Mg deficiency treatments in late autumn — CO2-assimilation rates of 1-year-old needles were significantly decreased independent of the severity of the deficiency treatment, whereas the chlorophyll concentrations did not differ from the controls. The occurrence of yellowing symptoms during July did not further influence the Mg deficiency effect on photosynthesis. In contrast to 1-year-old needles, significant reductions of photosynthesis and chlorophyll in current-year needles were only caused by severely deficient Mg supply. Mg deficiency affected carboxylation efficiency but not light use efficiency. From the accumulation of starch in the needles, up to 30-fold of the controls, the conclusion has been drawn that reactions of CO2-fixation were affected by reduced carbohydrate export. The light-dependent pigment reduction, leading to the typical tipyellowing of needles, clearly reflects a secondary effect of Mg deficiency.
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    Transpiration and drought resistance of Douglas-fir seedlings exposed to excess ammonium (1996)
    Springer
    Trees 10 (1996), S. 301-307 
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    ISSN: 1432-2285
    Keywords: K ; P ; Pseudotsuga menziesii ; Root/shoot ratio ; Soil acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a pot trial growth and transpiration of 3-year-old Douglas-fir seedlings on an acid, sandy soil was examined at a deficient (30 kg N ha-1 year-1) and an excessive level (120 kg N ha-1 year-1 of NH4 application. Dissolved ammonium sulphate was applied to the pots weekly for two growing seasons. In half of the pots a complete set of other nutrients was applied in optimal proportions to the applied nitrogen. Water supply was optimal and transpiration was recorded. At the end of the second treatment season irrigation was stopped for 2 weeks during dry and sunny weather. Both high application of NH4 and additional nutrients increased shoot growth and transpiration demand in the first treatment year. The root system was smaller at higher N level and this reduced water uptake accordingly. In the second year the combination of high NH4 + and additional nutrients affected root functioning predominantly due to salinity effects and this seriously decreased water uptake capacity and shoot water potentials, finally resulting in tree death. Without addition of other nutrients the high NH4 + application resulted in a high degree of soil acidification, which damaged the roots, that showed a decrease in water uptake capacity. At the low NH4 supply level soil acidification was lower, and root functioning was not affected, and the trees recovered quickly from the imposed drought. Higher needle K and P status depressed transpiration rates at the low NH4 application rate.
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    Differential growth and recovery rates following defoliation in related deciduous and evergreen trees (1996)
    Springer
    Trees 10 (1996), S. 308-316 
    Details
    ISSN: 1432-2285
    Keywords: Herbivory ; Plant-insect interactions ; Leaf lifespan ; Pinus ; Larix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Deciduous larches,Larix spp., and evergreen pines,Pinus spp., are sympatric Pinaceae conifers. Adjacent monocultures of 10-year-oldLarix decidua Mill, andPinus resinosa Ait. were subjected to single-season artificial defoliation by clipping from 0% to 99% of each needle. Survival, above-ground productivity, and architecture were measured for 36 months.P. resinosa andL. decidua exhibited differential relationships with defoliation intensity and recovery time. Two months after treatment, defoliation reduced larch height growth but had no effect on radial growth. By contrast,P. resinosa stem radial growth was reduced immediately, but height growth was not decreased until the following year. Pine leader growth and above-ground biomass following 66% defoliation never recovered to control values or 33% defoliated pines. Conversely, defoliated larch quickly recovered from an initial growth loss to eliminate all treatment effects on biomass. The plasticity in architectural response found in larch, but not pine, might partially account for defoliation tolerance. BothP. resinosa andL. decidua exhibited non-linear responses to defoliation. These patterns may be caused partially by the uneven distribution of nutrients within needles, rather than a simple function of leaf area lost to defoliators. Concentrations of 13 nutrients inP. resinosa were highest either in the mid-(Ca, Mg, S, Zn, B, Mn, Fe, Al and Na) or basal-(N, P, K, and Cu) section. The relatively low nutrient content in needle tips may contribute to similar biomass productivity between trees defoliated 33% and controls. Removal of needle mid-sections significantly reduced whole-plant productivity. In contrast,L. decidua nutrients are concentrated in the distal sections. Nutrient concentrations were generally highest in larch. Our results agree with an emergent prediction of the carbon/ nutrient balance theory that defoliation more severely reduces growth of evergreen than deciduous species. These results are discussed within the physiological, ecological and evolutionary context of allocation theory, with implications for natural resource management and plant-insect interaction theory.
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    Effects of pre-severance light quality on the vegetative propagation ofEucalyptus grandis W. Hill ex Maiden (1996)
    Springer
    Trees 10 (1996), S. 317-324 
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    ISSN: 1432-2285
    Keywords: Carbohydrates ; Eucalyptus grandis ; Photosynthesis ; Propagation ; Red to far-red ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two-leaf, two-node cuttings were taken fromEucalyptus grandis stockplants grown under different light qualities (red to far-red ratios of 0.4, 0.7, 1.3, 3.5 and 6.5) at a constant photon flux density (200 μmol m-2 s-1). Two experiments tested effects of pre-severance light quality on cutting morphology, post-severance gas exchange, carbohydrate status and rooting of cuttings. The best rooting percentage was achieved by cuttings with longer stems and greater stem volume from stockplants grown at lower red to far-red (R∶FR) ratios. Generally, rooting success was associated with low pre-severance starch and water-soluble sugar concentrations, and a greater total water-soluble carbohydrate (TWSC) content per cutting. Rooting was associated with well maintained stem starch and an increase in stem TWSC during the propagation period. Gas exchange of cuttings was measured between 28 and 33 days after severance. Rooting percentages at 35 days after severance were positively and linearly related to net photosynthetic rate and stomatal conductance. In unrooted cuttings there was a net release of CO2 which increased significantly with an increase in pre-severance R∶FR ratio. These results demonstrate that stockplant environment may significantly modify the morphology and physiology of subsequent cuttings, and that cutting morphology, and stored and current photosynthates have a significant influence on rooting.
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    Pyridine nucleotide levels and activities of dehydrogenases in cambial derivatives ofRobinia pseudoacacia L. (1996)
    Springer
    Trees 10 (1996), S. 325-330 
    Details
    ISSN: 1432-2285
    Keywords: Cambial differentiation ; Glucose-6-phosphate dehydrogenase ; 6-Phosphogluconate dehydrogenase ; NAD kinase ; Pyridine nucleotides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Despite the importance of the vascular cambial differentiation, little is known about its regulation. In order to address this problem we attempted to biochemically characterize differentiating xylem and phloem elements during the early stages of development. By applying techniques of quantitative histochemistry we show that the total pool size of pyridine nucleotides is similar in the phloem (PD) and xylem (XD) oriented derivatives of the cambial zone of trees ofRobinia pseudoacacia L. Within the PD zone, the amount of NAD + NADH exceeded that of NADP + NADPH [around 600 versus 200 pmol (mg dry weight)-1], possibly indicative of a preponderance of catabolic pathways (ratio of NADH∶NAD about 1). In contrast, the NADP(H) system dominated in the XD zone. This coincided with a high activity of NAD kinase. In addition, the extractable activities of the key enzymes of the oxidative pentose phosphate pathway, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, were greatly increased. At a ratio of NADPH∶NADP of approximately 1, this could be indicative of increased rates of reductive biosyntheses, and could thus well be involved in early steps of the formation of phenols and lignin monomers. Taken together, this first approach clearly shows that phloem-oriented and xylem-oriented cambial descendents exhibit distinct differences in their biochemical patterns even in early stages of differentiation.
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    Phytohormones in needles of healthy and declining silver fir (Abies alba Mill.): I. Indole-3-acetic acid (1996)
    Springer
    Trees 10 (1996), S. 331-338 
    Details
    ISSN: 1432-2285
    Keywords: Indole-3-acetic acid ; Abies ; Needle senescence ; Forest decline ; SO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Levels of indole-3-acetic acid (IAA) were determined in needles from silver fir (Abies alba Mill.) trees in the northern Black Forest. IAA was quantified by gas chromatography (GC) as 1-heptafluorobutyryl-IAA-methylester (HFB-IAA-ME) using electron capture detection. Prior to GC analysis, extensive purification of needle extracts was performed employing two HPLC steps. Peak identity of HFB-IAA-ME was confirmed by combined gas chromatography-mass spectrometry in selected samples. Levels of IAA in needles belonging to different needle age-classes exhibited a cyclic seasonal pattern with highest concentrations in winter and lowest levels in spring when bud-break occurred. Such a cyclic seasonal pattern of IAA levels was also observed in needles from declining fir trees or fir trees suffering from a strong sulfur impact (S-impact) in the field due to a local SO2 source. Levels of IAA increased with increasing needle age. This age dependency of IAA concentrations was most pronounced in late autumn when IAA levels were high and nearly disappeared in spring when IAA levels reached their minimum. In needles from declining fir trees or fir trees suffering from a strong S-impact in the field, IAA levels hardly increased with increasing needle age. It is suggested that in healthy trees high levels of IAA protect older needles from abscission and that the considerable losses of older needles of declining fir trees or of fir trees under S-impact are a consequence of the low levels of IAA found in older needles of such trees.
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    Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela (1996)
    Springer
    Trees 10 (1996), S. 351-358 
    Details
    ISSN: 1432-2285
    Keywords: Altitude ; Carbon isotope ratio ; Clusiaceae ; Crassulacean acid metabolism ; Deuterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (Δ), hydrogen isotope ratio (δD) and N-levels, and with altitude were assessed. In the samples, where values of Δ above 15‰ indicate predominant performance of C3 photosynthesis, there were slight tendencies of increasing Δ, δD and N-levels with increasing altitude and of increasing Δ with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of Δ with altitude in the samples, where values of Δ below 10‰ indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C3-CAM transitions in C3/CAM intermediate species, low availability of water is the most important.
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    The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM treeClusia hilariana (1996)
    Springer
    Trees 10 (1996), S. 359-365 
    Details
    ISSN: 1432-2285
    Keywords: Chlorophylla fluorescence quenching ; Citric acid ; Malic acid ; Photochemistry ; Photosynthetic electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO2 fixation rates of 28 μmol m-2 s-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (qN) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO2 fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (qA) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of qA throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (Fv/Fm) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in Fv/Fm, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition.
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    Lipids and lipolytic enzymes in the trunkwood ofRobinia pseudoacacia L. during heartwood formation (1996)
    Springer
    Trees 10 (1996), S. 366-375 
    Details
    ISSN: 1432-2285
    Keywords: Acyllipids ; Heartwood formation ; Phospholipids ; Robinia pseudoacacia L. ; Sterols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The radial distribution of membrane and storage lipids was determined in the trunkwood ofRobinia pseudoacacia L. The trees were felled in November at the time of heartwood formation and fluctuations in the amount and composition of phospholipids, free sterols, steryl esters, diand triacylglycerols, and free fatty acids were investigated across the sapwood-heartwood boundary. The individual compounds were identified and quantified by thin layer chromatography, enzymatic and colorimetric assays, and by capillary gas chromatography. Phospholipids show a significant decrease towards the boundary area, and in the heartwood only trace amounts can be detected. The same pattern is observed for free sterols in the sapwood; in the heartwood, however, they reach maximum values with increasing depth of the trunk. Steryl esters exhibit a complementary behaviour by accumulating at the periphery of the heartwood. No concentration changes are found in the total amounts of diacylglycerols and free fatty acids. In contrast, the triacylglycerol concentration declines steadily across the trunk. With regard to qualitative composition, free fatty acids and the fatty acid moieties of the esterified constituents vary in their chain length from 14 to 24 carbon atoms and have up to three double bonds. A radial gradient in the ratio saturated/unsaturated fatty acids can be observed: except for the phospholipid fraction the relative amounts of unsaturated fatty acids increase in centripetal direction. Seven phospholipids were identified: phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, diphosphatidylglycerol, and phosphatidic acid, which constitutes the major proportion. In the sterol group, sitosterol is the most abundant component. The composition of the esterified sterols remains constant across the trunk cross-section, whereas the relative frequencies of individual free sterols change markedly.
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    Lipids and lipolytic enzymes in the trunkwood ofRobinia pseudoacacia L. during heartwood formation (1996)
    Springer
    Trees 10 (1996), S. 376-381 
    Details
    ISSN: 1432-2285
    Keywords: Acylesterhydrolase ; Heartwood formation ; Lipase ; Robinia pseudoacacia L. ; Phospholipases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The radial profile of lipase and phospholipase activities was determined in the trunkwood ofRobinia pseudoacacia L. The trees were felled in November at the time of heartwood formation and alterations in the enzymatic activities were investigated across the sapwood and heartwood. Methods employed include gaschromatographic, colorimetric and enzymatic assays. On a dry weight basis, the hydrolysis of the artificial substrate pnitrophenylpalmitate shows a maximum activity in growth ring 4; however, the assay has proved not to be specific for lipase. In contrast, lipase analyses (triacylglycerol acylhydrolase; E.C. 3.1.1.3) with an authentic substrate show activity peaks in growth rings 1 and 4. With protein as a reference the highest activity is found in growth ring 5. A similar tendency is observed for phospholipase A1 (E.C. 3.1.1.32) and phospholipase A2 (E.C. 3.1.1.4). Phospholipase C (E.C. 3.1.4.3) activity decreases towards the sapwood-heartwood boundary; negligible traces of activity are detected in the heartwood, whereas, based on the protein content, growth ring 4 yields maximal activity. Phospholipase D (3.1.4.4) exhibits the same radial pattern with regard to protein content as a reference. On a dry weight basis there is a significant increase within the sapwood area, while in the heartwood the activity drastically decreases. The enzyme activities are discussed in relation to degradative processes within the plasma membranes and the hydrolysis of reserve lipids during heartwood formation.
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    Interactive effects of elevated CO2 and O3 on photosynthesis and biomass production of clonal 5-year-old Norway spruce [Picea abies (L.) Karst.] under different nitrogen nutrition and irrigation treatments (1996)
    Springer
    Trees 10 (1996), S. 382-392 
    Details
    ISSN: 1432-2285
    Keywords: CO2 ; Ozone ; Norway spruce ; Gas exchange ; Biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To study the single and combined effects of elevated carbon dioxide (CO2), ozone (O3), nitrogen nutrition, and water supply on photosynthetic gas exchange and biomass accumulation of Norway spruce, a four-factorial experiment was conducted in closed environmental chambers. Each factor was applied at two levels: (i) ambient and elevated (ambient + 200 μl 1-1) CO2, (ii) 20 and 80 nl 1-1 O3, (iii) low and high nitrogen fertilization, and (iv) a well watered and a drought treatment. Neither elevated O3 nor CO2 significantly changed stomatal conductances of spruce needles. Adverse effects of elevated O3 on photosynthetic parameters such as net assimilation rate and carboxylation efficiency occurred only when the plants were well watered and in a good nutritional status. After 6 weeks enhanced atmospheric CO2 resulted in increased net assimilation rates provided that nutrition was well balanced and plants were well watered. Acclimation processes became apparent and are interpreted as a consequence of sink regulation. While O3-effects were apparent only in biomass of 1-year-old plant material, elevated CO2 resulted in higher biomass of the buds expanding during the exposure and increased root biomass significantly. Above and below-ground biomass were strongly influenced by the water and nutrition treatments.
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    The effect of long term CO2 enrichment on the growth, biomass partitioning and mineral nutrition of Sitka spruce (Picea sitchensis (Bong.) Carr.) (1996)
    Springer
    Trees 10 (1996), S. 393-402 
    Details
    ISSN: 1432-2285
    Keywords: Elevated CO2 ; Sitka spruce ; Growth ; Allocation ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings were grown for 3 years in an outside control plot or in ambient (∼355 μmol mol-1) or elevated (ambient + 350 μmol mol-1) atmospheric CO2 environments, within open top chambers (OTCs) at the Institute of Terrestrial Ecology, Edinburgh. Sequential harvests were carried out at the end of each growing season and throughout the 1991 growing season, five in all. Plants grown in elevated CO2 had, (i) 35 and 10% larger root/shoot ratios at the end of the first and third season, respectively, (ii) significantly higher summer leader extension relative growth rates, which declined more rapidly in early autumn than ambient grown plants, (iii) after three growing seasons a significantly increased mean annual relative growth rate, (iv) consistently lower foliar nutrient concentrations, and (v) after two growing seasons smaller total projected needle areas. Plants grown inside OTCs were taller, heavier and had a smaller root/shoot ratio than those grown outside the chambers. There was no effect of CO2 concentration on Sitka spruce leaf characteristics, although leaf area ratio, specific leaf area and leaf weight ratio all fell throughout the course of the 3 year experiment.
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    URL: http://dx.doi.org/10.1007/BF02185643
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    Changes in root growth patterns of (Picea abies) spruce roots by inoculation with an ectomycorrhizal fungusPisolithus tinctorius and jasmonic acid treatment (1996)
    Springer
    Trees 10 (1996), S. 410-414 
    Details
    ISSN: 1432-2285
    Keywords: Ectomycorrhiza ; Jasmonic acid ; Picea abies ; Pisolithus tinctorius ; Spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Symbiosis between fungi and plant roots forming a mycorrhiza involves extensive interactions at the molecular level between both partners. The role of plant hormones in the regulation of mycorrhizal infection is not known to involve jasmonates. Their endogenous levels increase during pathogen attack; however, little has been done on their involvement in mycorrhizae. In our recent work, root growth patterns of 2-month-old spruce seedlings after inoculation withPisolithus tinctorius and/or jasmonic acid (JA) treatment were studied using a paper-sandwich technique. Changes in root length, the degree of branching, presence and length of root hairs, and infection parameters were followed using a stereomicroscope. The first mycorrhizal contact of hyphae with roots was significantly accelerated upon treatment with 0.5 μM JA. Interactions between root hairs and fungal hyphae were seen by scanning electron microscopy. The multiplication of root hairs of non-mycorrhized seedlings treated with 5.0 μM JA and changes of the root surface were observed by the same technique.
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    Early season cuticular conductance and gas exchange in two oaks near the western edge of their range (1996)
    Springer
    Trees 10 (1996), S. 403-409 
    Details
    ISSN: 1432-2285
    Keywords: Cuticular conductance ; Gallery forests ; Leaf development ; Photosynthesis ; Quercus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seasonal changes in minimum leaf conductance to water vapor (gmin), an estimate of cuticular conductance, and photosynthetic gas exchange in two co-occurring oak species in north-east Kansas (USA) were examined to determine if leaf gas exchange characteristics correlated with differences in tree distribution. Bur oak (Quercus macrocarpa Michx.) is more abundant in mesic gallery forest sites, whereas chinquapin oak (Quercus muehlenbergii Englm.) is more abundant in xeric sites. Early, during leaf expansion, gmin was significantly lower in chinquapin oak than in bur oak, though midday water potentials were similar. After leaves had fully expanded, gmin decreased to seasonal minimum values of 4.57 (±0.274) mmol m-2 s-1 in bur oak, and 2.66 (±0.156) mmol m-2 s-1 in chinquapin oak. Water potentials at these times were significantly higher in chinquapin oak. As leaves were expanding, photosynthesis (Anet) was significantly higher in chinquapin oak than in bur oak. Later in the growing season, Anet and gleaf increased dramatically in both species, and were significantly higher in bur oak relative to chinquapin oak. We concluded that bur and chinquapin oak have a number of leaf gas exchange characteristics that minimize seasonal water loss. These characteristics are distinct from trees from more mesic sites, and are consistent with the distribution patterns of these trees in tall-grass prairie gallery forests.
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    Hydrogen fluoride effects on plasma membrane composition, ATPase activity and cell structure in needles of eastern white pine (Pinus strobus) seedlings (1995)
    Springer
    Trees 9 (1995), S. 190-194 
    Details
    ISSN: 1432-2285
    Keywords: Plasma membrane ; Fluoride ; ATPase ; Sterols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Eastern white pine (Pinus strobus L.) seedlings were grown in controlled environment growth cabinets and fumigated with 0.4 and 1.6 μg m−3 hydrogen fluoride for 2–28 days. Plasma membranes were isolated from needles of treated and control seedlings and their chemical composition and ATPase activity examined to determine early effects of hydrogen fluoride action. In plants treated for 2 days with both fluoride levels, ratios of plasma membrane free sterols:phospholipids and sterols:proteins were drastically higher than ratios in control plants. Seedlings treated with hydrogen fluoride for 8 days contained plasma membranes with elevated phospholipid:protein and sterol:protein ratios and their plasma membrane ATPase activity was higher than that of control plants. Prolonged, 28-day hydrogen fluoride treatment with 1.6 μg m−3 level was the only treatment which produced a drastic inhibition of plasma membrane ATPase activity. During the initial stages of hydrogen fluoride treatment, treated cells did not show alterations of ultrastructure which were previously shown in cells of plants treated with soil applied sodium fluoride. The results of the present study indicate that the plasma membranes may be among the initial sites of hydrogen fluoride injury to plants as well as initial sites of defense reaction.
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    Detection and features of wetwood in Quercus mongolica var. grosseserrata (1995)
    Springer
    Trees 9 (1995), S. 261-268 
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    ISSN: 1432-2285
    Keywords: Quercus mongolica var. grosseserrata ; Wetwood ; Moisture content ; Cryo-SEM ; Soft x-ray photography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To elucidate the location of water in wetwood, variations in moisture content within a tree of Quercus mongolica var. grosseserrata were observed macroscopically by determination of moisture content and by soft x-ray photography. Then the typical wetwood, which had been precisely located by such macroscopic analysis, was examined further by cryo-scanning electron microscopy. The moisture content varied considerably within the tree trunk, and typical wetwood was detected in limited regions of the heartwood. The distribution of the wetwood did not always correspond to the discoloration of the wood. In the wetwood, almost all the lumina of vessels and fibers were filled with water, while the lumina of ray and axial parenchyma cells were often cavitated. Intercellular spaces produced by deformation of cell walls and radial shakes were filled with water. In addition, tyloses were collapsed and torn in the wetwood, and they did not block the vessel lumina. These results suggest the possibility that vessels and fibers might serve as effective pathways for the accumulation of water in the wetwood.
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    Immunogold localization of pectins and glycoproteins in tissues of peach with reference to deep supercooling (1995)
    Springer
    Trees 9 (1995), S. 253-260 
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    ISSN: 1432-2285
    Keywords: Prunus persica ; Deep supercooling ; Xylem ; Pectins ; Glycoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Living xylem tissues and floral buds of several species of woody plants survive exposure to freezing temperatures by deep supercooling. A barrier to water loss and the growth of ice crystals into cells is considered necessary for deep supercooling to occur. Pectins, as a constituent of the cell wall, have been implicated in the formation of this barrier. The present study examined the distribution of pectin in xylem and floral bud tissues of peach (Prunus persica). Two monoclonal antibodies (JIM5 and JIM7) that recognize homogalacturonic sequences with varying degrees of esterification were utilized in conjunction with immunogold electron microscopy. Results indicate that highly esterified epitopes of pectin, recognized by JIM7, were the predominant types of pectin in peach and were uniformly distributed throughout the pit membrane and primary cell walls of xylem and floral bud tissues. In contrast, un-esterified epitopes of pectin, recognized by JIM5, were confined to the outer surface of the pit membrane in xylem tissues. In floral buds, these epitopes were localized in middle lamellae, along the outer margin of the cell wall lining empty intercellular spaces, and within filled intercellular spaces. JIM5 labeling was more pronounced in December samples than in July/August samples. Additionally, epitopes of an arabinogalactan protein, recognized by JIM14, were confined to the amorphous layer of the pit membrane. The role of pectins in freezing response is discussed in the context of present theory and it is suggested that pectins may influence both water movement and intrusive growth of ice crystals at freezing temperatures.
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    The significance of structure for imbibition in seeds of the Norway spruce, Picea abies (L.) Karst. (1995)
    Springer
    Trees 9 (1995), S. 269-278 
    Details
    ISSN: 1432-2285
    Keywords: Picea abies (L.) Karst ; Seed coat ; Morphology ; Imbibition ; Permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Since the observations of those regularly handling Norway spruce [Picea abies (L.) Karst.] seeds with regard to their imbibition frequently disagree with earlier opinions that this process is markedly inhibited by the seed coat, we decided to examine the morphological factors influencing imbibition in seeds of different colour and different provenances. The seed coat, consisting of the sarcotesta, sclerotesta and endotesta, was found to have little influence on the passage of water, despite the presence of sclereids full of wax lamellae. No differences in seed coat structure were observed between provenances or colours of seeds. The cells of the endotesta were lignified in the area of the micropyle, however, and stood out lip-like on the outer surface of the micropyle after imbibition. An opening in the sclerotesta filled with parenchyma cells was also seen at the chalazal end of the seed. Neither of these openings, which were covered by accumulations of wax, served as the main route for the passage of water, though the micropyle opened up slightly after only 24 h incubation, when the lignified cells bordering it swelled differently from the rest of the endotesta. The progress of water into the seed soon discontinued, however, as the tip of the nucellar cap, covered with wax and crystals, effectively plugged the micropyle. This opening of the micropyle may be the reason why the IDS method does not always succeed in separating viable from non-viable spruce seeds sufficiently well by their density. Imbibition was mostly regulated by the lipophilic layers surrounding the endosperm, which are mainly of nucellar origin, and particularly the megaspore membranes, the outer and inner exine. Imbibition was further hampered by the impermeable nucellar cap, which covered about 3/4 of the length of the endosperm and had merged with the outer exine at its edges. Deposits of wax were observed both between the exines and between the endotesta and the nucellar layers at the edges of the nucellar cap. Waxes may serve as a defence against diseases at the sites of water penetration, while simultaneously increasing the significance of the nucellar endosperm covers as regulators of imbibition.
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    Gas-exchange and sap flow measurements of Salix viminalis trees in short-rotation forest (1995)
    Springer
    Trees 9 (1995), S. 289-294 
    Details
    ISSN: 1432-2285
    Keywords: Sap flow ; Transpiration ; Open-top chamber ; THB method ; Leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Simultaneous field measurements of transpiration and sap flow were performed on short-rotation Salix viminalis trees ranging in diameter from 1.5 to 3.5 cm (2-year-old shoots on 8-year-old stumps). Transpiration was measured using an open-top ventilated chamber enclosing the whole foliage of a tree. Sap flow was measured using a tree-trunk heat balance (THB) technique with a constant temperature difference and variable heat input. Both the instantaneous and daily values of water flux measured by the two absolute techniques agreed well with a difference of up to about 5%. In July, the hourly transpiration reached a maximum of about 0.2 kg m−2 (leaf area) or 0.45 kg tree−1, whereas maximum daily integrals reached 4 kg tree−1. The response of sap flow rate to abrupt flux change when inducing emboli by cutting-off the stem was very rapid: the registered signal dropped by 85% within 10 min for a specimen with a projected leaf area of 2 m2. For S. viminalis trees, transpiration was linearly correlated with stem cross-sectional area and with leaf area.
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    Gas-exchange and sap flow measurements of Salix viminalis trees in short-rotation forest (1995)
    Springer
    Trees 9 (1995), S. 295-301 
    Details
    ISSN: 1432-2285
    Keywords: Mesophyll conductance ; Stomatal conductance ; Allocation ; Growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water use efficiency was estimated for Salix viminalis (L.) trees growing in the field under non-limiting nutrient and soil water conditions. Gas exchange measurements were used to calculate conductances to water vapour and CO2 fluxes. Sap flow was measured using a tree-trunk heat balance technique. Transpiration and CO2 uptake were estimated using an open-top ventilated chamber enclosing the whole foliage of a tree. Mesophyll conductance to CO2 (gm ′) was modelled as a non-linear function of global radiation (R g) and air temperature. Stomatal conductance (gs) was modelled as a function of R g and vapour pressure deficit (δe). The models explained 92 and 88% of the variation of gm′ and gs, respectively. The net photosynthetic capacity of S. viminalis was high compared to a number of broad-leaved species. The optimum temperature for photosynthesis was found to be 20.5 °C. The instantaneous water use efficiency (WUEi) was high: it reached a maximum of 15 g (CO2) kg−1 (H2O) for small rates of E, and decreased down to 9 g kg−1 for peak rates of E. Water use efficiency calculated from above-ground biomass measurements and from net carbon assimilation revealed a specific carbon allocation pattern during the season. The combination of gas exchange and dendrometric measurements was found to be a promising approach of non-destructive estimation of root/shoot allocation of carbon.
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    Solutes and succulence in southern African mistletoes (1995)
    Springer
    Trees 9 (1995), S. 303-310 
    Details
    ISSN: 1432-2285
    Keywords: Parasitic angiosperm ; Succulence ; Cations ; Organic osmolytes ; Cyclitols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The inorganic ion and organic solute composition of Tapinanthus oleifolius (Loranthaceae) and Viscum rotundifolium (Viscaceae) growing on various host trees in Namibia were investigated. Organic osmolytes accounted for 22.8–45.1% of the total solutes determined in leaves of the mistletoes parasitizing Acacia nebrownii, Catophractes alexandri, Grewia flava and Ziziphus mucronata. On other hosts (Acacia karroo, Euphorbia virosa, Salvadora persica and Tamarix usneoides) T. oleifolius showed distinct succulence with increasing leaf age, with leaves more than 3 mm thick on E. virosa. In the more succulent leaves (〉 1.1 kg H2O m−2 leaf area) organic solutes were only of minor importance. Water content per leaf area was significantly correlated with chloride content per leaf area, suggesting that succulence served as a means to keep ion concentration at a physiological tolerable level. At whole plant levels 93.7% of the total sodium of the mistletoe bush was located in leaves thicker than 1 mm for T. oleifolius parasitizing Tamarix usneoides. This pronounced sequestration of sodium in older leaves as well as the high variability of the K/Na ratio in various parts of the parasite-host system point to highly selective ion distribution processes in this association.
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    Chemical composition and ultrastructural changes in Scots pine needles in a forest decline area in southwestern Finland (1995)
    Springer
    Trees 9 (1995), S. 311-317 
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    ISSN: 1432-2285
    Keywords: Forest decline ; Pinus sylvestris ; Nutrition ; Needle ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tree decline and deaths have been observed among 15 to 20-year-old Scots pines (Pinus sylvestris L.) in a dry heath forest in southwestern Finland. The sudden decline in height growth, the dieback of leading shoots and the yellowing of needles in young shoots in the upper part of the tree are typical symptoms of the decline of these young pines. Needle ultrastructure and chemical composition of Scots pines with or without decline and fluctuations of them in different seasons were studied. Afflicted trees were found to suffer from a deficiency in calcium and magnesium with low concentration of foliar nitrogen and phosphorus observed in all the trees studied. Ultrastructural study revealed changes characteristic of different seasons and measured nutrient status of needles. A clear reduction of membrane system in chloroplasts, especially related to Mg deficiency, was observed in most samples. The symptoms related to N deficiency, the translucent appearance of the cytoplasm and chloroplast stroma, and the elongated chloroplasts, as well as swelling of mitochondria, indicating P deficiency, were also found in the needles sampled from this forest decline area. The present study showed that it is possible to detect specific nutrient deficiency symptoms in needle ultrastructure in field samples and for use as sensitive indicators of unbalanced nutrient status.
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    Changes in enzyme activities involved in malate metabolism in oak leaves during rhythmic growth (1995)
    Springer
    Trees 9 (1995), S. 318-323 
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    ISSN: 1432-2285
    Keywords: Quercus robur L. ; Leaf development ; Malate metabolism ; Nitrogen assimilation ; Rhythmic growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Amide content, ATP level and activities of enzymes linked to malate metabolism were determined in leaves of three successive flushes of common oak during the development of the third flush. In the expanding leaves, all studied enzymes showed a maximum activity around the 7th day after budbreak. Phosphoenolpyruvate carboxylase (PEPc), NAD-malate dehydrogenase (MDH) and NADP-malic enzyme (ME) maintained high activity up to full leaf expansion. In contrast, fumarase (FUM), pyruvate kinase (PK) and NADP-MDH activities sharply decreased to reach, on the 10th day after budbreak, the same low activity levels as those measured in mature leaves. Two patterns were observed in oak leaves during growth. Firstly (7th–10th day after budbreak), PK, FUM and NADP-MDH could contribute to the supply of ATP through glycolysis and Krebs cycle; the ATP profile corroborated those results. Secondly (after the 10th day), the maintenance of an active PEPc pathway led to a respiratory CO2 refixation and provided carbon skeletons for amino acid synthesis. Furthermore, nitrate reductase (NR) activity was high in young oak leaves. Slight changes in activities of NR as well as NAD(P)-ME, NAD(P)-MDH can be noted on days 7 and 10 after budbreak in the mature leaves. These changes could be necessary in supplying the third flush with amino acids. These data suggest that MDH, ME, PK and PEPc have important functions in the young leaves which are not directly linked to C3 photosynthesis but rather to nitrate assimilation and malate provision to mitochondria.
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    Structure and identification of root bark of Quercus robur L. (1995)
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    Trees 9 (1995), S. 341-347 
    Details
    ISSN: 1432-2285
    Keywords: Bark structure ; Bark anatomy ; Root bark ; Identification ; Quercus robur L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The root bark structure of Quercus robur L. was analysed at different stages of root development and compared to the structure of stem bark. Root bark thickness varied considerably between different roots. Sclereid quantity decreased with increasing distance from the stem, which means it increased with age. Visible growth increments diminished with increasing distance from the stem. In lateral roots crystal quantity decreased with increasing distance from the stem. In lateral roots secondary phloem fibre length, sieve tube member length, and sieve tube diameter showed no regular trend. There were only a few basic structural differences between root and stem bark. The zone of cell differentiation (cell expansion, lignification) was wider in root bark; sieve tube collapse was delayed. In lateral root bark fewer sclereids were formed. The first-formed periderm often originated from deeper cell layers. Thus, primary elements were lacking after periderm formation. In root bark the phellem cell walls were of equal thickness. Thus, phellem lacked visible growth increments. Root bark phellem cells were slightly larger. The root phelloderm was more distinct. The secondary phloem fibres were slightly shorter than those in stem bark. Sieve tube members of stem and root bark were of similar length and diameter. The qualitative bark anatomical characters of oak root bark are suitable for root identifications. Due to minor structural differences between root and stem bark the characters must be used with care.
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    Effects of phosphorus supply on growth and nitrogen fractions in xylem sap and foliage of Eucalyptus regnans (F.Muell.), E. nitens (Maiden) and E. globulus (Labill.) seedlings: implications for herbivory (1995)
    Springer
    Trees 9 (1995), S. 324-331 
    Details
    ISSN: 1432-2285
    Keywords: Amino acids ; Arginine ; Eucalyptus ; Foliage ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rates of growth of seedlings of E. globulus, E. regnans and E. nitens were related to phosphorus supply in two soils but concentrations of total nitrogen and total phosphorus in most plant tissues did not vary significantly among soil or phosphorus treatments. Differences in concentrations of nitrogen and phosphorus and in the composition of the pool of free amino-acids among leaves at different stages of development were far greater than differences between treatments. The most significant of these differences were several-fold greater concentrations of arginine in the oldest leaves and these are most likely due to protein degradation and/or in situ synthesis since arginine is not generally phloem mobile. The concentration of reduced nitrogen in xylem sap was inversely related to growth and glutamine was by far the dominant nitrogenous solute. We suggest that specific nitrogenous solutes may be useful indices of the nitrogen status of eucalypt tissues for insect herbivores.
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    Events (1995)
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    The visual computer 11 (1995), S. 276-276 
    Details
    ISSN: 1432-2315
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/BF01901046
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    Nonlinear ray tracing: visualizing strange worlds (1995)
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    The visual computer 11 (1995), S. 263-274 
    Details
    ISSN: 1432-2315
    Keywords: Key words: Ray tracing ; Visualization ; Nonlinearity ; Chaotic dynamical system ; Strange attractors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/s003710050020
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    Ray-cast volume rendering accelerated by incremental trilinear interpolation and cell templates (1995)
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    The visual computer 11 (1995), S. 297-308 
    Details
    ISSN: 1432-2315
    Keywords: Direct volume rendering ; Ray casting ; Projection ; Forward difference ; Cell template
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Two related ideas for improving the speed of ray-cast volume rendering are studied in this paper. The first is an incremental algorithm for trilinear interpolation, a method commonly used in ray-cast volume rendering to calculate sample values. The incremental algorithm can expedite trilinear interpolation when many samples along a ray are located in one cell. The second is an efficient hybrid volume rendering restricted to parallel projection. In the preprocessing stage, acell template is created to store the information used by the incremental trilinear interpolation. When a cell is parallel projected, the information is retrieved from the template to compute the cell contribution. Because the algorithm with only one template may cause aliasing, an antialiasing technique exploiting multiple cell templates is proposed. With our method, ray-cast volume rendering can be accelerated considerably.
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    Data-parallel, volumerendering algorithms (1995)
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    The visual computer 11 (1995), S. 319-338 
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    ISSN: 1432-2315
    Keywords: Parallel volume rendering ; Data-parallel approach ; Combining ; Splatting ; Z-buffer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this presentation, we consider the image-composition scheme for parallel volume rendering in which each processor is assigned a portion of the volume. A processor renders its data by using any existing volume-rendering algorithm. We describe one such parallel algorithm that also takes advantage of vector-processing capabilities. The resulting images from all processors are then combined (composited) in visibility order to form the final image. The major advantage of this approach is that, as viewing and shading parameters change, only 2D partial images, and not 3D volume data, are communicated among processors. Through experimental results and performance analysis, we show that our parallel algorithm is amenable to extremely efficient implementations on distributed memory, multiple instruction-multiple data (MIMD), vector-processor architectures. This algorithm is also very suitable for hardware implementation based on image composition architectures. It supports various volume-rendering algorithms, and it can be extended to provide load-balanced execution.
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    Approximate conversion of a rational boundary gregory patch to a nonuniform B-spline surface (1995)
    Springer
    The visual computer 11 (1995), S. 360-368 
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    ISSN: 1432-2315
    Keywords: Rational boundary Gregory patch ; Gregory patch ; Nonuniform B-spline surface ; Approximation ; Conversion ; C 1 continuity ; Least squares
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A rational boundary Gregory patch is characterized by the facts that anyn-sided loop can be smoothly interpolated and that it can be smoothly connected to an adjacent patch. Thus, it is well-suited to interpolate complicated wire frames in shape modeling. Although a rational boundary Gregory patch can be exactly converted to a rational Bézier patch to enable the exchange of data, problems of high degree and singularity tend to arise as a result of conversion. This paper presents an algorithm that can approximately convert a rational boundary Gregory patch to a bicubic nonuniform B-spline surface. The approximating surface hasC 1 continuity between its inner patches.
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    Process modelling — An approach to two-dimensional image creation (1995)
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    The visual computer 11 (1995), S. 399-400 
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    URL: http://dx.doi.org/10.1007/BF01909881
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    Approximate conversion of a rational boundary Gregory patch to a nonuniform B-spline surface (1995)
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    The visual computer 11 (1995), S. 360-368 
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    ISSN: 1432-2315
    Keywords: Key words: Rational boundary Gregory patch ; Gregory patch ; Nonuniform B-spline surface ; Approximation ; Conversion ; C1 continuity ; Least squares
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: n -sided loop can be smoothly interpolated and that it can be smoothly connected to an adjacent patch. Thus, it is well-suited to interpolate complicated wire frames in shape modeling. Although a rational boundary Gregory patch can be exactly converted to a rational Bézier patch to enable the exchange of data, problems of high degree and singularity tend to arise as a result of conversion. This paper presents an algorithm that can approximately convert a rational boundary Gregory patch to a bicubic nonuniform B-spline surface. The approximating surface has C 1 continuity between its inner patches.
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    Creativity and simplicity (1995)
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    The visual computer 11 (1995), S. 447-452 
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    ISSN: 1432-2315
    Keywords: Accumulation ; Brain ; Chaos ; Conformal mapping ; Convolution ; Creativity ; Fast Fourier transform ; Fractal geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract For many scientists, human intelligence and, in particular, its creative potential seem to consist of processes that cannot be automated by means of a computer. As already shown with fractal geometry, this short note tries to show that the iteration and combination of very elementary operations can give very complex behaviors and shapes. It gives some practical examples to encourage reader involvement and new experiments, particularly in classroom settings.
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    Feature matching and affine transformation for 2D cell animation (1995)
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    The visual computer 11 (1995), S. 419-428 
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    ISSN: 1432-2315
    Keywords: Key words: Inbetweening ; Key frames (2D) ; Cell animation ; 2D ; Feature matching ; Affine transform
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    Conference announcement and call for papers (1995)
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    The visual computer 11 (1995), S. A5 
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    Ray-cast volume rendering accelerated by incremental trilinear interpolation and cell templates (1995)
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    The visual computer 11 (1995), S. 297-308 
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    ISSN: 1432-2315
    Keywords: Key words: Direct volume rendering ; Ray casting ; Projection ; Forward difference ; Cell template
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: cell template is created to store the information used by the incremental trilinear interpolation. When a cell is parallel projected, the information is retrieved from the template to compute the cell contribution. Because the algorithm with only one template may cause aliasing, an antialiasing technique exploiting multiple cell templates is proposed. With our method, ray-cast volume rendering can be accelerated considerably.
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    Is the fractal Golden Curlicue cold ? (1995)
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    The visual computer 11 (1995), S. 309-312 
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    Keywords: Key words: Spirals ; Curlicues ; Fractals ; Thermodynamics ; Plane curves
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    Function representation in geometric modeling: concepts, implementation and applications (1995)
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    The visual computer 11 (1995), S. 429-446 
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    ISSN: 1432-2315
    Keywords: Geometric modeling ; Solid modeling ; Real functions ; Implicit surfaces ; R functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Concepts of functionally based geometric modeling including sets of objects, operations, and relations are discussed. Transformations of a defining real function are described for set-theoretic operations, blending, offsetting, bijective mapping, projection, cartesian products, and metamorphosis. Inclusion, point membership, and intersection relations are also described. We use a high-level geometric language that can extend the interactive modeling system by input symbolic descriptions of primitives, operations, and predicates. This approach supports combinations of representational styles, including constructive geometry, sweeping, soft objects, voxel-based objects, deformable and other animated objects. Application examples of aesthetic design, collisions simulation, NC machining, range data processing, and 3D texture generation are given.
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    Creativity and simplicity (1995)
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    The visual computer 11 (1995), S. 447-452 
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    Keywords: Key words: Accumulation ; Brain ; Chaos ; Conformal mapping ; Convolution ; Creativity ; Fast Fourier transform ; Fractal geometry
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    Topics: Computer Science
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    URL: http://dx.doi.org/10.1007/s003710050035
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    Fast collision detection between complex solids using rasterizing graphics hardware (1995)
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    The visual computer 11 (1995), S. 497-511 
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    ISSN: 1432-2315
    Keywords: Computer animation ; Virtual environment ; Collision detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We present an efficient method for detecting collisions between complex solid objects. The method features a stable processing time and low sensitivity to the complexity of contact between objects. The algorithm handles both concave and convex objects; however, the best performance is achieved when at least one object is convex in the proximity of the collision zone (our techniques check the required convexity property as a byproduct of the calculations). The method achieves real-time performance when calculations are supported by the standard functionality of graphics hardware available on high-end workstations.
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    A functional presentation of Fourier series convergence (1996)
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    The visual computer 12 (1996), S. 350-359 
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    Keywords: Key words: Functional presentation ; Functional proofs ; Visualization ; Mathematica
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    Ratioquadrics: an alternative model for superquadrics (1996)
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    The visual computer 12 (1996), S. 420-428 
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    ISSN: 1432-2315
    Keywords: Geometric modeling ; Parametric surfaces ; Implicit surfaces ; Superquadrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a new family of 2D curves and its extension to 3D surfaces, respectively, calledrationconics andratioquadrics that have been designed as alternatives to the well-known superconics and superquadrics. This new model is intended as an improvement to the original one on three main points: first, it involves lower computation cost and provides better numerical robustness; second, it offers higher order continuities (C 1/G 2 orC 2/G 2 instead ofC 0/G 0); and third, it provides a greater variety of shapes for the resulting curves and surfaces. All these improvements are obtained by replacing the signed power function involved in the formulation of superconics and superquadrics by linear or quadratic rational polynomials.
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    Hamiltonian triangulations for fast rendering (1996)
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    The visual computer 12 (1996), S. 429-444 
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    Keywords: Triangulations ; Hamiltonian paths ; Quadrangulation ; Rendering ; Computer graphics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract High-performance rendering engines are often pipelined; their speed is bounded by the rate at which triangulation data can be sent into the machine. An ordering such that consecutive triangles share a face, which reduces the data rate, exists if and only if the dual graph of the triangulation contains a Hamiltonian path. We (1) show thatany set ofn points in the plane has a Hamiltonian triangulation; (2) prove that certain nondegenerate point sets do not admit asequential triangulation; (3) test whether a polygonP has a Hamiltonian triangulation in time linear in the size of its visibility graph; and (4) show how to add Steiner points to a triangulation to create Hamiltonian triangulations that avoid narrow angles.
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    A note on visualizing the Omega Prism (1996)
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    The visual computer 12 (1996), S. 451-454 
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    Keywords: Key words: Visualization ; Puzzles ; Smooth numbers ; Lattices ; Perception ; Factorization
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    A parallel scaled conjugate-gradient algorithm for the solution phase of gathering radiosity on hypercubes (1997)
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    The visual computer 13 (1997), S. 1-19 
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    Keywords: Key words: Gathering radiosity ; Scaled conjugate-gradient method ; Parallel algorithms ; Hypercube multicomputer ; Data redistribution
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    CFFD: a tool for designing flexible shapes (1998)
    Springer
    The visual computer 14 (1998), S. 271-287 
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    Keywords: Key words: Solid deformation ; B-spline FFD ; Unbounded control lattice ; 3D design ; Animation
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    An intuitive and device-independent method of generating color atlases for electronic displays (1998)
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    The visual computer 14 (1998), S. 328-342 
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    Keywords: Key words: CIE UCS ; CIE L*u*v* ; 3D Color gamut ; Color atlas ; Color scheme ; Device-independent color description ; CRT ; Displays ; device colorimetric characterization
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    Image morphing: a survey (1998)
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    The visual computer 14 (1998), S. 360-372 
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    Keywords: Key words: Image morphing ; Feature specification ; Warp generation ; Transition control
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    Self-intersection elimination in metamorphosis of two-dimensional curves (1998)
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    The visual computer 14 (1998), S. 415-428 
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    Keywords: Key words: Computer-aided geometric design ; Freeform parametric curves and surfaces ; Homotopic curves and surfaces ; Matching ; Morphing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: H :[0, 1]× 3→ 3, where H(t, r) for t=0 and t=1 are two given planar curves C 1(r) and C 2(r). The first t parameter defines the time of fixing the intermediate metamorphosis curve. The locus of H(t, r) coincides with the ruled surface between C 1(r) and C 2(r), but each isoparametric curve of H(t, r) is self-intersection free. The second algorithm suits morphing operations of planar curves. First, it constructs the best correspondence of the relative parameterizations of the initial and final curves. Then it eliminates the remaining self-intersections and flips back the domains that self-intersect.
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    A note on a linear time algorithm for constructing adjacency graphs of 3D FEA data (1996)
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    The visual computer 12 (1996), S. 445-450 
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    Keywords: Adjacency graph ; Finite element analysis (FEA) data
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    Topics: Computer Science
    Notes: Abstract In this paper, we present an algorithm for constructing adjacency graphs of 3D finite element analysis (FEA) data. Adjacency graphs are created to represent the connectivities of FEA data cells. They are used in most visualization methods for FEA data. We stress that in many engineering applications FEA data sets do not contain the adjacency information. This is opposite to computer-aided geometric design where, e.g., the winged edge geometrical representation is usually generated and utilized. By establishing intermediate data structures and using bin-sorting, we developed an efficient algorithm for constructing such graphs. The total time complexity of the algorithm is linear in the number of data cells.
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    A constrained finite element method for modeling cloth deformation (1999)
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    The visual computer 15 (1999), S. 90-99 
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    Keywords: Key words: Cloth deformation ; Geometric constraint ; Geometric physical method ; Constrained finite element method
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    A new antialiasing approach for image compositing (1997)
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    The visual computer 13 (1997), S. 218-227 
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    Keywords: Key words: Image compositing ; Antialiasing ; Discrete regions ; Discrete contours ; Euclidean paths
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    Scattered data fitting with simplex splines in two and three dimensional spaces (1997)
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    The visual computer 13 (1997), S. 295-315 
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    Keywords: Key words: α-Hull ; Fitting ; Simplex spline
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    A note on computing the saddle values in isosurface polygonization (1997)
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    The visual computer 13 (1997), S. 342-344 
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    Keywords: Key words: Volume visualization ; Marching cubes ; Topology consistency ; Saddle value
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    Acute shapes preserved by constructing arc-line-arc splines for machining (1998)
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    The visual computer 13 (1998), S. 401-411 
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    Keywords: Key words: Zigzag data ; Local approximation ; Arc-line-arc spline
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    A marching method for the triangulation of surfaces (1998)
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    The visual computer 14 (1998), S. 95-108 
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    Keywords: Key words: Triangulation ; Marching method ; Numerical implicitization ; Parametric surface ; Implicit surface ; Offset surface ; Blend surface
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    Shadow generation for volumetric data sets (1998)
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    The visual computer 14 (1998), S. 83-94 
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    ISSN: 1432-2315
    Keywords: Key words: Volume visualization ; Scientific visualization ; Medical imaging ; Shadow Z-buffer ; Shadow map
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    Topics: Computer Science
    Notes: Z -buffer technique for fast and efficient shadow generation. Volumetric data contain information about the grid points only. Such data do not provide surface information that could be projected immediately onto the shadow map. To solve this problem, we have implemented two techniques. The first uses a modified adaptive version of the well-known marching cubes algorithm for the special characteristics of medical data sets. The algorithm uses material properties for a precise representation of object boundaries, generating volumetric objects quickly and effectively. There are two representations of the same data set: we use a view-independent approximation to display shadows and the original representation of the volume for object visualization in full precision. The second algorithm uses a ray-tracing approach to create shadow maps. The same routine is used for object rendering, but is restricted to depth-value generation. Semitransparent objects are handled by storing an intensity profile in addition to the depth value.
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    A comparison of four visibility acceleration techniques for radiosity (1996)
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    The visual computer 12 (1996), S. 307-316 
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    ISSN: 1432-2315
    Keywords: Radiosity ; Ray tracing ; 3D axis-aligned bounding boxes ; 3D convex hulls ; Illumination volumes
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    Topics: Computer Science
    Notes: Abstract Four visibility acceleration techniques for speeding up the form-factor computation are presented and compared in this paper. Three-dimensional axis-aligned bounding boxes (BB), illumination volumes (IVs), and 3D convex hulls (CHs) are some of the methods described. A new method that enhances IVs with 3D axis-aligned BBs (BBIVs) is also proposed. The results of these methods are compared with the uniform space subdivision (USSD) method, which is used as a basis of comparison of the effectiveness of these acceleration methods. In addition, the advantages and the disadvantages of each of the proposed techniques is discussed.
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    A comparison of four visibility acceleration techniques for radiosity (1996)
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    The visual computer 12 (1996), S. 307-316 
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    Keywords: Key words: Radiosity ; Ray tracing ; 3D axis-aligned bounding boxes ; 3D convex hulls ; Illumination volumes
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    Kepler, von Neumann and God (More rounding-off error visualizations) (1996)
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    The visual computer 12 (1996), S. 346-349 
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    Keywords: Key words: Numerical simulation ; Sensitivity to initial conditions ; Sensitivity to numerical accuracy ; Rounding-off errors ; Scientific visualization
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    Topics: Computer Science
    Notes: N -body problem is used to display the sensitivity to numerical accuracy.
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    A Monte Carlo approach for Galerkin radiosity (1996)
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    The visual computer 12 (1996), S. 390-405 
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    ISSN: 1432-2315
    Keywords: Global illumination ; Radiosity ; Galerkin methods ; Monte Carlo methods ; Particle tracing ; Progressive refinement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Galerkin radiosity solves the integral rendering equation by projecting the illumination functions into a set of higher-order basis functions. This paper presents a Monte Carlo approach for Galerkin radiosity to compute the coefficients of the basis functions. The new approach eliminates the problems with edge singularities between adjacent surfaces present in conventional Galerkin radiosity, the time complexity is reduced fromO(K 4) toO(K 2) for aK-order basis, and ideally specular energy transport can be simulated. As in conventional Galerkin radiosity, no meshing is required even for large or curved surfaces, thus reducing memory requirements, and no a posteriori Gouraud interpolation is necessary. The new algorithm is simple and can be parallelized on any parallel computer, including massively parallel systems.
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    A type-merging algorithm for extracting an isosurface from volumetric data (1996)
    Springer
    The visual computer 12 (1996), S. 406-419 
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    ISSN: 1432-2315
    Keywords: Key words: Volume visualization ; Surface modeling ; Marching cubes ; Iso- surface
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    Topics: Computer Science
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