Freeze-induced fluctuations in xylem sap pressure in Acer pseudoplatanus

1983 ◽  
Vol 61 (12) ◽  
pp. 3100-3106 ◽  
Author(s):  
P. E. R. O'Malley ◽  
J. A. Milburn
Keyword(s):  
Field Experiments ◽  
Freezing Point ◽  
Xylem Sap ◽  
Acer Pseudoplatanus ◽  
Freezing And Thawing ◽  
Pressure Potential ◽  
Mature Trees ◽  
Ambient Temperatures ◽  
Stem Wood ◽  
Stem Segments

Xylem sap pressures in response to temperature changes were investigated in Acer pseudoplatanus L., the British sycamore. Mature trees were used for field experiments; excised seedling stem segments were used in the laboratory. A general correlation was observed between changes in pressure potential (ψp) of the xylem sap of mature trees and ambient temperatures above zero (freezing point). More outstanding, however, were the characteristic decreases in pressure potential observed in response to subzero air temperatures. Investigation of this phenomenon under controlled conditions using excised stem segments revealed that rapid decreases in sap pressure occurred simultaneously with freezing. Freezing caused the stem wood to absorb water. This is a surprising response because water expands on freezing. Subsequently exudation of sap was triggered by thawing. Freezing and thawing responses appeared to be similar whether stem segments were collected during summer, when the xylem sap contained no detectable sugars, or during winter, when sugars were present in the sap. Apparently water uptake or replenishment (termed "conditioning") during cooling is of paramount importance in determining the capability of maple wood to exude sap. The freeze-induced uptake of sap under negative pressures described here is considered to be the process fundamental to conditioning.

Accuracy and Usefulness of Psychrometer and Pressure Chamber for Evaluating Water Potentials of Pinus radiata Needles

1982 ◽  
Vol 9 (5) ◽  
pp. 499 ◽  
Author(s):  
BD Millar
Keyword(s):  
Water Potential ◽  
Pinus Radiata ◽  
Xylem Sap ◽  
Pressure Chamber ◽  
Pressure Potential ◽  
Pine Trees ◽  
Average Water ◽  
Potential Gradients ◽  
Fundamental Uncertainty ◽  
The One

Pressure chamber evaluations of xylem sap pressure potential (P) and thermocouple psychrometric evaluations of average water potential (Ψl) in needles from both transpiring and non-transpiring pine trees (Pinus radiata D. Don) were compared in order to determine the relative accuracy and usefulness of these methods for assessing Ψl. Markedly different but linear P v. Ψl relationships were obtained for pine needles of different age and also for the case where resin exudation masked the xylem and led to a 'resin error'. Evidence suggests that these differences are mainly due to injection and resin errors in pressure chamber determinations totalling as much as 1 MPa (a 10 bar). The psychrometric method appears to be the much more accurate. Radial water potential gradients across leaves did not result in differences between evaluations of P and Ψl, at least in P. radiata. The need for multiple 'calibrations' of the pressure chamber and the fundamental uncertainty about the constancy of such calibrations on the one hand and the slowness of the excised-needle psychrometer on the other can restrict the usefulness of these methods.

Textural and mineralogical controls on temperature dependent SIP behavior during freezing and thawing

2021 ◽  
Author(s):  
Jonas K. Limbrock ◽  
Maximilian Weigand ◽  
Andreas Kemna
Keyword(s):  
Freezing Point ◽  
Pore Space ◽  
Thermal Characterization ◽  
Complex Frequency ◽  
Freezing And Thawing ◽  
Temperature Dependent ◽  
Measured Resistance ◽  
Ice Content ◽  
Water Saturated ◽  
Geoelectrical Methods

<p>Geoelectrical methods are increasingly being used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties are sensitive to the phase change of liquid to frozen water. Here, electrical resistivity tomography (ERT) is most commonly applied, using resistivity as a proxy for various quantities, such as temperature or ice content. However, it is still challenging to distinguish between air and ice in the pore space of the rock based on resistivity alone due to their similarly low electrical conductivity. Meanwhile, geoelectrical methods that utilize electrical polarization effects to characterize permafrost are also being explored. For example, the usage of the spectral induced polarization (SIP) method, in which the complex, frequency-dependent impedance is measured, can reduce ambiguities in the subsurface conduction properties, considering the SIP signature of ice. These measurements seem to be suitable for the quantification of ice content (and thus the differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites. However, to improve the interpretation of SIP measurements, it is necessary to understand in more detail the electrical conduction and polarization properties as a function of temperature, ice content, texture, and mineralogy under frozen and partially frozen conditions.</p><p>In the study presented here, electrical impedance was measured continuously using SIP in the frequency range of 10 mHz to 45 kHz on various water-saturated solid rock and loose sediment samples during controlled freeze-thaw cycles (+20°C to -40°C). These measurements were performed on rock samples from different alpine permafrost sites with different mineralogical compositions and textures. For all samples, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperature. Also, hysteresis between freezing and thawing behavior is observed for all measurements. During freezing, a jump within the temperature-dependent resistance is observed, suggesting a lowering of the freezing point to a critical temperature where an abrupt transition from liquid water to ice occurs. During thawing, on the other hand, there is a continuous decrease in the measured resistance, suggesting a continuous thawing of the sample. The spectra of impedance phase, which is a measure for the polarization, exhibit the same qualitative, well-known temperature-dependent relaxation behaviour of ice at higher frequencies (1 kHz - 45 kHz), with variations in shape and strength for different rock texture and mineralogy. At lower frequencies (1 Hz - 1 kHz), a polarization with a weak frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, which likewise depends on the texture as well as on the mineralogy of the respective sample. This polarization response partially vanishes during freezing. Overall, the investigated SIP spectra do not only show a dependence on texture and mineralogy, but mainly a dependence on the presence of ice in the sample as well as temperature. This indicates the possibility of a thermal characterization, as well as a determination of the ice content, of permafrost rocks using SIP.</p>

Distribution of the eucalypt-defoliating sawfly Perga affinis affinis (Hymenoptera)

1965 ◽  
Vol 13 (4) ◽  
pp. 593 ◽  
Author(s):  
PB Carne
Keyword(s):  
Field Experiments ◽  
Climatic Factors ◽  
Leaf Shape ◽  
Mature Trees ◽  
Leaf Production ◽  
Study Region ◽  
Sawfly Larvae ◽  
Litter Accumulation ◽  
Large Trees ◽  
Individual Trees

The distribution of the sawfly is discussed at several levels, ranging from that within a study region which comprised a substantial proportion of the known range of the insect, to that within the crowns of individual trees. A mosaic of areas was recognized within the region, each characterized by a degree of ecological uniformity and in which saivfly populations maintained relatively high or low levels of abundance during 6 yr of observation. The distribution of the insect is influenced strongly by climatic factors, the rainfall and temperature statistics for the critical period October-March for all areas in which it occurs being closely grouped. Such grouping is even more marked for those areas in which the sawfly was consistently most abundant. The cool wet limit of the sawfly's distribution coincides with that of a favoured host species, but the hot dry limit appears to be determined by the insect's susceptibility to desiccation. Although many naturally occurring and planted eucalypts will support sawfly larvae, persistent infestations were recorded only where one or more of three species grew - Eucalyptus blakelyi, E. camaldulensis, or E. melliodora. The sawfly is an inhabitant of river valley woodland, rarely becoming abundant in other situations and being absent from sclerophyll forest formations. Survival of the insect is greatly influenced by the ease with which it can penetrate into the soil for cocoon formation; it tends to be most abundant in areas of light soil, or where large trees provide a deep litter accumulation. The susceptibility of trees to infestation is influenced by seasonal production of new foliage. Those growing in sites where the water table is high, and whose leaf production is to a large extent independent of rainfall patterns, may be subject to chronic attack. Distribution between trees is affected by their leaf shape and texture, and by their history of previous defoliation. Small trees are particularly prone to attack, and infestation of mature trees is generally an indication of outbreak abundance of the insect. Similarly, marginally favoured species are attacked only when oviposition sites on more favoured trees are virtually saturated. Field experiments indicated that an observed contagious distribution of sawfly eggs in portions of the crowns of individual trees is not the result of overt gregariousness on the part of the females, but results from the attraction of the latter to foliage of certain physical characteristics and position on the tree.

scholarly journals Comparison of Rootability of Stem Cuttings from Seedlings of Aesculus sp. and Mature Aesculus × arnoldiana ‘Autumn Splendor’

1988 ◽  
Vol 6 (2) ◽  
pp. 69-71
Author(s):  
B.A. Bergmann ◽  
W.P. Hackett ◽  
H. Pellett
Keyword(s):  
Butyric Acid ◽  
Developmental Stages ◽  
Stem Cuttings ◽  
Mature Tree ◽  
Mature Trees ◽  
Old Growth ◽  
Rooting Of Cuttings ◽  
Root Suckers ◽  
Stem Segments

Rootability was evaluated for stem cuttings taken at varying positions and developmental stages from seedlings of Aesculus and from the mature trees of Aesculus × arnoldiana ‘Autumn Splendor’. Rooting was 100% for cuttings taken from 2-week-old seedlings and 0% for those obtained from the crown of the mature tree 2 months after commencement of spring growth flush. Intermediate rootability was found for cuttings taken from 1-month-old seedlings and from the 2 week-old growth of suckers at the base of the mature tree. Rooting of cuttings with intermediate rooting potential was increased by a quick dip treatment with 2500 ppm indole-3-butyric acid (IBA) or by using apical rather than basal stem segments. Commercially acceptable rooting was not achieved using cuttings from root suckers or the crown of Aesculus ‘Augumn Splendor’.

scholarly journals The acropetal effects of indole-3-acetic acid in isolated shoot segments of Acer pseudoplatanus L. II. Possible regulation by a vectorial fieid of auxin waves

2014 ◽  
Vol 60 (1-2) ◽  
pp. 51-66
Author(s):  
Jacek A. Adamczyk
Keyword(s):  
Acetic Acid ◽  
Phase Shift ◽  
Direct Action ◽  
Lateral Branch ◽  
Stem Segment ◽  
Acer Pseudoplatanus ◽  
Basipetal Transport ◽  
Indole 3 Acetic Acid ◽  
Stem Segments ◽  
Growing Shoot

The acropetal effects of auxin on elongation of axillary buds and on modulation of the wave-like pattern of basipetal efflux of natural auxin to agar from <i>Acer pseudoplatanus</i> L. shoots were studied. When synthetic IAA was applied to cut surfaces of one of two branches the elongation growth of buds situated on the opposite branch was retarded, suggesting regulation independent of the direct action of the molecules of the applied IAA. Oscillations in basipetal transport of natural auxin along the stem segments were observed corroborating the results of other authors using different tree species. Apical application of synthetic IAA for 1 hour to the lateral branch caused a phase shift of the wave-like pattern of basipetal efflux of natural auxin, when the stem segment above the treated branch was sectioned. The same effect was observed evoked by the laterally growing branch which is interpreted as an effect of natural auxin produced by the actively growing shoot. These modulations could be propagated acropetally at a rate excluding direct action of auxin molecules at the sites of measurement. The results seem to corroborate the hypothesis suggesting that auxin is involved in acropetal regulation of shoot apex growth through its effect upon modulation of the vectorial field which arises when the auxin-waves translocate in cambium.

The thermal insulation properties of hightech sportswear fillings

2015 ◽  
Vol 27 (4) ◽  
pp. 549-560 ◽  
Author(s):  
Antonin Havelka ◽  
Viera Glombikova ◽  
Zdenek Kus ◽  
Michal Chotebor
Keyword(s):  
Thermal Resistance ◽  
Thermal Insulation ◽  
Freezing Point ◽  
Weather Conditions ◽  
Modern Method ◽  
Content Type ◽  
Ambient Temperatures ◽  
Real Application ◽  
Actual Application ◽  
Humidity Change

Purpose – The purpose of this paper is to deal with performance verification of thermal insulation fillings that are used for outer clothes into cold environments. Thermal properties of filling materials (down and three sophisticated fillings) were tested under condition approaching real weather conditions in Middle Europe. Design/methodology/approach – In the paper, modern method of thermal resistance Rct measurement, by Sweating Guarded-Hotplate system, was compared with method of Technical University of Liberec (TUL method). The TUL method shows good results and it is applicable even at ambient temperatures below zero, which fully corresponds to real application of the insulation filling. Findings – Evaluation of fibre battings were carried out even at temperatures below the freezing point, which is important for simulation of actual application of these filling structures. The highest thermal resistance of goose down confirm that natural materials have their irreplaceable position, especially in application into clothes for extreme conditions. Research limitations/implications – There does not include effect of the humidity change on thermal insulation properties. It will be subject of further research of authors. Originality/value – The investigation of thermal insulation properties were carried out under conditions approaching real application of tested materials, namely, at low ambient temperature.

scholarly journals Life cycle expression of inbreeding depression in Eucalyptus regnans and inter-generational stability of its mixed mating system

2019 ◽  
Vol 124 (1) ◽  
pp. 179-187 ◽  
Author(s):  
A Rod Griffin ◽  
Brad M Potts ◽  
René E Vaillancourt ◽  
J Charles Bell
Keyword(s):  
Life Cycle ◽  
Mating System ◽  
Inbreeding Depression ◽  
Field Experiments ◽  
Natural Populations ◽  
Forest Tree ◽  
Mixed Mating ◽  
Mature Trees ◽  
Mixed Mating System ◽  
Eucalyptus Regnans

Abstract Background and Aims Many plants exhibit a mixed mating system. Published models suggest that this might be an evolutionarily stable rather than a transitional state despite the presence of inbreeding depression, but there is little empirical evidence. Through field experimentation, we studied the role of inbreeding depression in eliminating inbred progeny from the reproductive cohort of the forest tree Eucalyptus regnans, and demonstrate a stable mixed primary mating system over two successive generations. Methods Two field experiments were conducted using seed from natural populations. We sowed open-pollinated seeds to simulate a natural regeneration event and determined isozyme genotypes of dominant and suppressed individuals over 10 years. We also planted a mixture of open-pollinated, outcross and selfed families with common maternal parentage; monitored survival of cross types over 29 years; and determined the percentage of outcrosses in open-pollinated seed from a sample of reproductively mature trees using microsatellite analysis. Key Results Both experiments demonstrated progressive competitive elimination of inbred plants. By 29 years, the reproductive cohort in the planted experiment consisted only of outcrosses which produced seed which averaged 66 % outcrosses, similar to the estimate for the parental natural population (74 %). Conclusions Selective elimination of inbred genotypes during the intense intra-specific competition characteristic of the pre-reproductive phase of the life cycle of E. regnans results in a fully outcrossed reproductive population, in which self-fertility is comparable with that of its parental generation. The mixed mating system may be viewed as an unavoidable consequence of the species’ reproductive ecology, which includes the demonstrated effects of inbreeding depression, rather than a strategy which is actively favoured by natural selection.

The hydraulic architecture of Thuja occidentalis

1983 ◽  
Vol 61 (8) ◽  
pp. 2105-2111 ◽  
Author(s):  
M. T. Tyree ◽  
M. E. D. Graham ◽  
K. E. Cooper ◽  
L. J. Bazos
Keyword(s):  
Water Potential ◽  
Water Flow Rate ◽  
Potential Gradient ◽  
Pressure Potential ◽  
Thuja Occidentalis ◽  
Unit Leaf ◽  
Leaf Surface Area ◽  
Potential Gradients ◽  
Evaporative Flux ◽  
Stem Segments

Leaf specific conductivities (LSC's) were measured on stem segments excised from various points within the canopy of eastern white cedar trees, Thuja occidentalis L. LSC is defined as the water flow rate (kilograms per second) through a stem caused by a unit of pressure potential gradient (megapascals per metre) per unit leaf surface area supplied by the stem (square metres). LSC's were measured on stems of various diameters and were found to vary over a factor of 30 in magnitude from 1 × 10−5 kg s−1 m−1 MPa−1 for stems 1 mm in diameter to 3 × 10−4 kg s−1 m−1 MPa−1 for stems 100 mm in diameter. LSC was found to be related to stem diameter (D (millimetres)) by the following empirical formula: LSC = 9.58 × 10−6 × D0.727. LSC's measured on stem segments including a node had significantly lower LSC's than internodal stem segments of the same length. Various water relations parameters were measured on cedar trees on a diurnal basis including evaporative flux, leaf resistance to evaporation, shoot water potential, air temperature, and air humidity. Water potential isotherms were also measured on excised green shoots. From the above data, we estimate that about 15% of the total water evaporated from green shoots comes from stored water while the shoot water potentials are growing progressively negative. The typical peak evaporative flux in midday was 1.5 × 10−5 kg s−1 m−2; using this value and our measured LSC's we estimate that the pressure potential gradients in the stems must be 50 kPa m−1 in stems 100 mm in diameter and 1500 kPa m−1 in stems 1 mm in diameter. Pressure potential gradients were measured in stems 30 to 50 mm in diameter by the pressure bomb technique and were found to be 69 kPa m−1 during a typical afternoon and this confirms the accuracy of the above estimates.

Pressure Chamber and Air Flow Porometer for Rapid Field Indication of Water Status and Stomatal Condition in Wheat

1977 ◽  
Vol 13 (4) ◽  
pp. 341-351 ◽  
Author(s):  
R. A. Fischer ◽  
M. Sanchez ◽  
J.R. Syme
Keyword(s):  
Field Experiments ◽  
Water Status ◽  
Air Flow ◽  
Pressure Chamber ◽  
Plant Responses ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Plant Water Potential ◽  
Key Features

SUMMARYPlant water potential and leaf diffusive conductance, key features of plant responses to water stress in field experiments, can be estimated, respectively, by xylem pressure potential measured with the pressure chamber apparatus, and leaf permeability measured with the air flow porometer. This paper describes modifications to these two techniques in order to increase the rapidity of measurements in wheat to 60/h with the pressure chamber, and 200/h with the porometer. Rapid measurements are needed because of the large within-and between-plot errors encountered with daytime measurements in typical field experiments, examples of which are presented.

scholarly journals Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

2012 ◽  
Vol 8 (6) ◽  
pp. 1006-1011 ◽  
Author(s):  
Joe Quirk ◽  
David J. Beerling ◽  
Steve A. Banwart ◽  
Gabriella Kakonyi ◽  
Maria E. Romero-Gonzalez ◽  
...  
Keyword(s):  
Mycorrhizal Fungi ◽  
Atmospheric Carbon Dioxide ◽  
Field Experiments ◽  
Carbon Dioxide Concentration ◽  
Arbuscular Mycorrhizal ◽  
Mineral Weathering ◽  
Mineral Surfaces ◽  
Mature Trees ◽  
Silicate Mineral ◽  
Climate History

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO 2 and climate history.

Sign in / Sign up

Export Citation Format

Share Document