Sap flow measurements with some thermodynamic methods,flow integration within trees and scaling up from sample trees to entire forest stands

Sap flow measurement techniques and evaluation of data are reviewed. Particular attention is paid to the trunk segment heat balance (THB) and heat field deformation (HFD) methods based on 30 years experience. Further elaboration of sap flow data is discussed in terms of integrating flow for whole stems from individual measuring points, considering variation of radial patterns in sapwood and variation around stems. Scaling up of data from sets of sample trees to entire forest stands based on widely available biometric data (partially on remote sensing images) is described and evaluated with a discussion of the magnitude of errors, the routine procedure applicable in any forest stand and practical examples.     

Sap flow rates of mangrove trees are not unusually low

 In contrast with previous reports, we observed high transpiration rates in mangrove trees. Maximum sap velocities and mean daytime sap flow rates were estimated from heat pulse velocity in entire, field grown trees of Avicennia cf. alba Blume and Rhizophora apiculata Blume. Results were within the range of values measured by identical techniques for trees in lowland dipterocarp and tropical heath forests with a similar climate in Brunei Darussalam (north Borneo). High stomatal conductance (400 mmol m^{–  2} s^{–  1}) was also measured for well insolated leaves of A. cf. alba, with midday water potentials reaching about  – 3 MPa in both species. Received: 11 September 1996 / Accepted: 27 January 1997     

Sap flow as an indicator of transpiration and the water status of young apricot trees

The relationship between water loss via transpiration and stem sap flow in young apricot trees was studied under different environmental conditions and different levels of soil water status. The experiment was carried out in a greenhouse over a 2-week period (November 2–14, 1997) using three-year-old apricot trees (Prunus armeniaca cv. Búlida) growing in pots. Diurnal courses of leaf water potential, leaf conductance and leaf turgor potential also were recorded throughout the experiment. Data from four days of different enviromental conditions and soil water availability have been selected for analysis. On each of the selected days the leaf water potential and the mean transpiration rates were well correlated. The slope of the linear regression of this correlation, taken to indicate the total hydraulic resistance of the tree, confirmed an increasing hydraulic resistance under drought conditions. When the trees were not drought stressed the diurnal courses of sap flow and transpiration were very similar. However, when the trees were droughted, measured of sap flow slightly underestimated actual transpiration. Our heat-pulse measurements suggest the amount of readily available water stored in the stem and leaf tissues of young apricot trees is sufficient to sustain the peak transpiration rates for about 1 hour. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sap flow, gas exchange, and hydraulic conductance of young apricot trees growing under a shading net and different water supplies

The experiment was carried out in a research field near Murcia, Spain, over a 3-week period between September 26 and October 16, 2000. Sixteen trees were used in the experiment, eight of which were placed under a rectangular shading net, while the other eight were maintained in the open air. Trees were irrigated once per day and, after October 5th, water was witheld from eight trees (four shaded and four unprotected for 5 days). The leaf stomatal conductance and the photosynthesis rates were higher in the shaded trees than in the exposed plants, probably because the leaf water potential was lower in the unshaded plants. This higher leaf conductance partially compensated for the effect of low radiation on transpiration, and the reduction of daily sap flow registered in shaded trees was only around 10-20%. The net also affected trunk diameter changes, with the shaded trees showing lower values of maximum daily shrinkage. Soil water deficit and high radiation had a similar effect on plant water parameters, lowering leaf water potential, leaf stomatal conductance, and the photosynthesis rate. The effects of both conditions were accumulative and so the exposed water-stressed plants showed the lowest values of total hydraulic resistance and water use efficiency, while the shaded well-irrigated trees registered the highest values for both parameters. For this reason, we think that net shading could be extended to apricot culture in many areas in which irrigation water is scarce and insolation is high.     

Sap flow measurements in grapevines (Vitis vinifera L.) 2. Granier measurements

The Granier-system, a relatively simple and continuous method for measuring sap flux density, has been adapted and evaluated for its use in older, mature grapevines. The original calibration of Granier (1985, Annales Sciences Forestieres, 42, 193-200) could be extended to a sap flux density of up to 400 10^-6 m³ m^-2 s^-1 with only little error at high flux densities. A time lag of around 20 min was apparent between transpiration and calculated sap flow which was attributed to the thermal mass of the sensors themselves. The time lag and the consequently dampened response of the system caused a very low accuracy over short time periods thus reducing the value for detailed plant physiological investigations. However, when integrating over longer time intervals, much of the error cancelled out. For daily values the maximum error was within ±10% and after a period of 89 days only 1.5% error remained. This method is thus best suited for long term measurements of total water use. This revised version was published online in June 2006 with corrections to the Cover Date.     

Compensation heat-pulse measurements of sap flow for estimating transpiration in young lemon trees

Potted two-year-old lemon trees [Citrus limon (L.) Burm. f.], cv. Verna grafted on sour orange (C. aurantium L.) rootstock, growing in greenhouse, were subjected to drought for 33 d. Control plants were daily irrigated at field capacity. Values of sap flow (SF) were compared with transpiration (E) rates measured gravimetrically. The results underlined the robustness and high sensitivity of the compensation heat-pulse technique for estimating transpiration on a wide range of SF. Good direct correlations between E and SF rates on an instantaneous and daily basis were obtained in both treatments. On a daily basis, a common calibration curve can be used for both irrigation treatments. On an instantaneous basis, changes in SF were matches by similar changes in E in both treatments, although the relationships between these parameters presented different intercepts in each treatment. Sap flow rates were influenced by weather conditions in trees growing in non-limiting soil water conditions. This makes it possible to evaluate the significance of any sap flow measurement in relation to the reference value calculated for the vapour pressure deficit at the time the measurement was taken.This research was supported by Ministerio de Educacion y Ciencia (MEC), (CICYT/FEDER AGL2003-9387-C05-02 and AGL2004-0794-C03-02), and PETRI (PTR1995-0693-OP-02-01) grants to the authors. M.F. Ortuno was a recipient of a Program I3P research fellowship from CSIC.     

Gas-exchange and sap flow measurements of Salix viminalis trees in short-rotation forest

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.     

Sap tension in flooded trees and bushes of the Amazon

The water relations of the inundated forest of the Rio Negro in the Amazon have been investigated. The sap pressure in trees and bushes standing in several meters of water was found to average between −15 and −20 atm in sunshine. and above −10 in overcast. In rainy weather and at night. the pressure would remain close to ambient. Submerged leaves had ambient or sometimes very slightly positive pressure. Pinnate leaves of legumes folded when the pressure rose above a critical level characteristic of the species. Dehydration curves from full turgor to negative turgor showed 3 characteristic phases: A) a steep decline in pressure when the turgor disappeared; B) a linear decline at zero turgor proportional to the increase in osmotic pressure; and C) a steep decline as negative turgor (intracellular packing) developed. The tensions in the drowned forests were similar to those found in inundated plants of temperate lakes. and hence like many plants in a humid forest. However, in the daytime many flooded plants of the Amazon reached zero turgor without any external sign of wilting.     

Weighted bootstrapping: a correction method for assessing the robustness of phylogenetic trees

Background  

Non-parametric bootstrapping is a widely-used statistical procedure for assessing confidence of model parameters based on the empirical distribution of the observed data [1] and, as such, it has become a common method for assessing tree confidence in phylogenetics [2]. Traditional non-parametric bootstrapping does not weigh each tree inferred from resampled (i.e., pseudo-replicated) sequences. Hence, the quality of these trees is not taken into account when computing bootstrap scores associated with the clades of the original phylogeny. As a consequence, traditionally, the trees with different bootstrap support or those providing a different fit to the corresponding pseudo-replicated sequences (the fit quality can be expressed through the LS, ML or parsimony score) contribute in the same way to the computation of the bootstrap support of the original phylogeny.     

Land-use proximity as a basis for assessing stream water quality in New York State (USA)

The influence of the proximity of urbanization and agriculture to stream water quality is often difficult to quantify. The objectives of this study were to (1) compare the influence of far-field land-use, encompassing a watershed drainage area, to a near-field, 200-m buffer on each side of the stream in an attempt to determine on which zone of influence land-use has the largest impact on water quality, and (2) incorporate the EPA's Rapid Habitat Assessment Protocol (Barbour et al., 1999) to characterize the riparian and channel characteristics of a stream that influence water quality, which can improve New York State's monitoring protocols. Impacts were assessed through biological, chemical, and physical-habitat data from 29 streams located within a variety of land-use categories. Land-use was identified through USGS National Land Cover Data (NLCD). Principal components analysis (PCA) indicated that land-use and water quality variables were associated with non-point source contaminants (e.g. nutrients and specific conductance). Using Spearman's rank correlation coefficient, significant relationships between all three land-use types and stream water quality were determined at the 200-m buffer zone of influence. At the watershed zone of influence, water quality indicators did not correlate significantly with land cover type. DO and BAP values within the 200-m buffer zone varied inversely with the percentage of urban-land cover. The stronger correlation between land cover and stream water quality at the 200-m proximity than that of the watershed suggests that the presence of a riparian buffer zone between streams and agricultural and urban areas is a significant factor in reducing contamination from non-point source loading.     

Light-scattering polarization measurements as a new parameter in flow cytometry

Polarization measurement of orthogonal light scattering is introduced as a new optical parameter in flow cytometry. In the experimental setup, the electrical field of the incident laser beam is polarized in the direction of the sample flow. The intensity of the orthogonal light scattering polarized along the direction of the incoming laser beam is called depolarized orthogonal light scattering. Theoretical analysis shows that for small values of the detection aperture, the measured depolarization is caused by anisotropic cell structures and multiple scattering processes inside the cell. Measurements of the orthogonal depolarized light scattering in combination with the normal orthogonal light scattering of human leucocytes revealed two populations of granulocytes. By means of cell sorting it was shown that the granulocytes with a relatively high depolarization are eosinophilic granulocytes. Similar experiments with human lymphocytes revealed a minor subpopulation of yet-unidentified lymphocytes with a relative large orthogonal light-scattering depolarization. The results were obtained with an argon ion laser tuned at different wavelengths as well as with a 630-nm helium neon laser. These results show that measurement of depolarized orthogonal light scattering is a useful new parameter for flow-cytometric cell differentiation.     

开发木本油料植物作为生物柴油原料的研究

本文根据德国、欧盟和美国制定的生物柴油标准制定了以碘值、十六烷值和脂肪酸组成等参数作为植物油质量的评价体系。通过四条标准,即51<十六烷值<65、碘值<115、亚麻酸<12%和十八碳四烯酸<1%、碳链长度为C12-C22,对国产118种种子含油量超过30%的木本油料植物进行评估,共筛选出53种木本油料植物的种子油可作为发展生物柴油最适合的原料。其中油茶、杏、无患子、臭椿、白檀、海州常山分布广,是值得推广种植的生物柴油植物。富油大科山茶科和无患子科植物的种子油一般都适合发展生物柴油,而富油大科樟科、松科和卫矛科植物的种子油不适合作生物柴油原料。我国各省区可因地制宜选择合适的能源树种,发展生物柴油产业。     

Continuous flow cultures of a HeLa cell line as a basis for a steady supply of Rubella virus

A HeLa cell line was propagated in semicontinuous suspension culture, 85 liters final volume, and in continuous flow culture with a volume of 300 ml. or 5 liters in an autoclavable medium to which 8% calf serum had been added. A medium containing 0.1% Methocel and 2% calf serum was also tested. Maximum productivity was obtained at a dilution rate of 0.33 day^?1 with a cell density of about 1.0 × 10⁶ cells/ml. The same cell line was also infected with Rubella virus and the production of virus was followed at the 5-liter cultivation level.     

Structural basis for profilin-mediated actin nucleotide exchange

Actin is a ubiquitous eukaryotic protein that is responsible for cellular scaffolding, motility, and division. The ability of actin to form a helical filament is the driving force behind these cellular activities. Formation of a filament depends on the successful exchange of actin's ADP for ATP. Mammalian profilin is a small actin binding protein that catalyzes the exchange of nucleotide and facilitates the addition of an actin monomer to a growing filament. Here, crystal structures of profilin-actin have been determined to show an actively exchanging ATP. Structural analysis shows how the binding of profilin to the barbed end of actin causes a rotation of the small domain relative to the large domain. This conformational change is propagated to the ATP site and causes a shift in nucleotide loops, which in turn causes a repositioning of Ca(2+) to its canonical position as the cleft closes around ATP. Reversal of the solvent exposure of Trp356 is also involved in cleft closure. In addition, secondary calcium binding sites were identified.     

Effects of fructose on human fibroblast metabolism: the application of DNA measurements as a basis for interpretation

Summary A fluorometric procedure for measuring DNA was used to study growth and metabolic responses of eight cell strains of human foreskin fibroblasts. In preliminary studies this procedure gave more precise specific activity changes inN-acetyl-β-d-glucosaminidase (NAG) than did a protein activity basis, when changes in this enzyme's specific activity were investigated as a function of experimental cell manipulation. When fibroblast growth in eight cell strains was compared in 134 mM d-fructose vs. 13.4 mM glucose-supplemented minimum essential media, a significant increase in cellular DNA (50%) and protein (45%) occurred over an 11-d period. No significant differences in media pH change, lactate production, or carbohydrate uptake occurred on a DNA basis when cell metabolism was compared over the last 24 h of culture in the two media. Cells grown in fructose-containing media tended to show a reduction in NAG specific activity when compared with those grown in glucose-containing media.     

Staphylococcal DNA as a basis for classification

The genome characterization of the typing strains for all 13 species of the genus Staphylococcus, included into the Approval List of the Names of Bacterial (1980), is presented. The nucleotide composition of DNA (28-33% of GC) did not permit the differentiation between staphylococcal species, but some of the groups of these species could be differentiated by the size of their genome (0.6-1.6 X 10(9) daltons). Differences in the degree of similarity between the nucleotide sequences of the DNA of all species (5-6% of DNA homology) made it possible to suggest raising the genus Staphylococcus to the rank of the family Staphylococcaceae fam. nov. The hypothetical classification scheme of this family is presented for discussion.     

A microhistological survey on the trees of a relict subtropical laurel forest from the Macaronesian Islands as a base for assessing vertebrate plant diet

A microhistological collection and its respective key on the leaves and fleshy fruits produced by the mostly endemic trees that integrate the relict laurel forest in the Macaronesian Islands are presented. Epidermal tissues from the adaxial and abaxial surfaces of leaves and fruits of 23 species were extracted by scraping and prepared on individual microscope slides. An optical microscope with a camera lucida fixed at magnifications of ×400 was used to analyse and to draw the morphological traits of epidermal tissues to the same scale. Furthermore, quantitative data for those congeneric species were also obtained by using an image analysis program system. The results indicate that this microhistological method permits the differentiation of practically all species of trees present in the Macaronesian laurel forest. Furthermore, most species belonging to the same taxa (genus or family) show a general common pattern in the morphology of the different epidermal traits. Lastly, despite the effort that constitutes the preparation of plant microhistological collections of a determined ecosystem, it is of basic importance because it makes possible the performance of feeding ecological studies of several herbivorous and frugivorous vertebrate species. These results provide crucial information that elucidates the functioning of the food web and energetic flux dynamics of the Macaronesian laurel forest ecosystem.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 409–426.     

Classification trees as a tool for predicting cyanobacterial blooms

Nutrient enrichment of aquatic ecosystems caused dramatic increase in the frequency, magnitude and duration of cyanobacterial blooms. Such blooms may cause fish kills, have adverse health effects on humans and contribute to the loss of biodiversity in aquatic ecosystems. Some 50 eutrophic to hypereutrophic ponds from the Brussels Capital Region (Belgium) were studied between 2003 and 2009. A number of the ponds studied are prone to persistent cyanobacterial blooms. Because of the related health concerns and adverse effects on ecological quality of the affected ponds, a tool for assessment of the risk of cyanobacterial bloom occurrence was needed. The data acquired showed that cyanobacteria have threshold relationships with most of the environmental factors that control them. This is negatively reflected on the predictive capacity of conventional statistical methods based on linear relationships. Therefore, classification trees designed for the treatment of complex data and non-linear relationships were used to assess the risk of cyanobacterial bloom occurrence. The main factors determining cyanobacterial bloom development appeared to be phytoplankton biomass, pH and, to a lesser degree, nitrogen availability. These results suggest that to outcompete eukaryotic phytoplankters cyanobacteria need the presence of environmental constraints: carbon limitation, light limitation and nitrogen limitation, for which they developed a number of adaptations. In the absence of constraints, eukaryotic phytoplankters appear to be more competitive. Therefore, prior build up of phytoplankton biomass seems to be essential for cyanobacterial dominance. Classification trees proved to be an efficient tool for the bloom risk assessment and allowed the main factors controlling bloom development to be identified as well as the risk of bloom occurrence corresponding to the conditions determined by these factors to be quantified. The results produced by the classification trees are consistent with those obtained earlier by probabilistic approach to bloom risk assessment. They can facilitate planning management interventions and setting restoration priorities.