Xylem cavitation resistance can be estimated based on time-dependent rate of acoustic emissions

In this study, we focused on the use of acoustic activity as a function of time, rather than absolute cumulative emission counts. We hypothesized that the highest acoustic activity should occur near the steepest part of a typical vulnerability curve, that is, near its inflection point (P50), when most embolism is forming within a narrow range of water potential (Ψ). Therefore, the Ψ at maximum AE activity should be correlated to a species’ hydraulically measured P50

Physiological acclimation to drought stress in Solidago canadensis

Solidago canadensis is an invasive species from North America that is spreading across Europe, Australia and temperate Asia. We hypothesized that the species' wide ecological amplitude is also based on its potential in hydraulic acclimation, and analyzed hydraulic and anatomical properties along a transect with decreasing soil humidity. Stem hydraulic conductivity, vulnerability to drought-induced embolism, stomatal closure during dehydration and xylem-anatomical parameters were quantified at three sites. At the humid site, specific hydraulic conductivity of stems (1.0±0.2kgm-1MPa-1s-1) was about twofold higher, and leaf-specific conductivity about 1.5 times higher (3.1±0.5kgm-1MPa-1s-1) than at the dry site. Water potential (Ψ) at 50% loss of conductivity was -3.7±0.1MPa at the dry site and -3.1±0.2MPa at the humid site (September). Vulnerability to drought-induced embolism decreased along the transect and over the vegetation period. At drier sites, stomata started closing at lower Ψ while complete stomatal closure was reached at less negative Ψ (12% of maximum stomatal conductance: -2.5±0.0 and -3.0±0.2MPa at the dry and humid site). The safety margin between stomatal closure and 50% loss of conductivity was 1.2 and 0.2MPa at the dry and humid sites. The observed variability indicated an efficient acclimation in hydraulic conductivity and safety: plants at dry sites exhibited lower specific hydraulic conductivity, higher embolism resistance and broader safety margins, signifying a trade-off between the hydraulic safety and efficiency. The observed intraspecific plasticity in hydraulic and anatomical traits may help to explain the invasive potential of this species

Elevational trends in hydraulic efficiency and safety of Pinus cembra roots

In alpine regions, elevational gradients in environmental parameters are reflected by structural and functional changes in plant traits. Elevational changes in plant water relations have also been demonstrated, but comparable information on root hydraulics is generally lacking. We analyzed the hydraulic efficiency (specific hydraulic conductivity k s, entire root system conductance K R) and vulnerability to drought-induced embolism (water potential at 50 % loss of conductivity Ψ 50) of the roots of Pinus cembra trees growing along an elevational transect of 600 m. Hydraulic parameters of the roots were compared with those of the stem and related to anatomical traits {mean conduit diameter (d), wall reinforcement [(t/b)(2)]}. We hypothesized that temperature-related restrictions in root function would cause a progressive limitation of hydraulic efficiency and safety with increasing elevation. We found that both root k s and K R decreased from low (1600 m a.s.l.: k s 5.6 ± 0.7 kg m(-1) s(-1) MPa(-1), K R 0.049 ± 0.005 kg m(-2) s (-1) MPa(-1)) to high elevation (2100 m a.s.l.: k s 4.2 ± 0.6 kg m(-1) s(-1) MPa(-1), K R 0.035 ± 0.006 kg m(-2) s(-1) MPa(-1)), with small trees showing higher K R than large trees. k s was higher in roots than in stems (0.5 ± 0.05 kg m(-1)s(-1)MPa(-1)). Ψ 50 values were similar across elevations and overall less negative in roots (Ψ 50 -3.6 ± 0.1 MPa) than in stems (Ψ 50 -3.9 ± 0.1 MPa). In roots, large-diameter tracheids were lacking at high elevation and (t/b)(2) increased, while d did not change. The elevational decrease in root hydraulic efficiency reflects a limitation in timberline tree hydraulics. In contrast, hydraulic safety was similar across elevations, indicating that avoidance of hydraulic failure is important for timberline trees. As hydraulic patterns can only partly be explained by the anatomical parameters studied, limitations and/or adaptations at the pit level are likely

Herb hydraulics : inter- and intraspecific variation in three Ranunculus species

The requirements to the water transport system of small herbaceous species differ considerably from those of woody species. Despite their ecological importance for many biomes, knowledge regarding herb hydraulics remains very limited. We compared key hydraulic features (vulnerability to drought-induced hydraulic decline, pressure-volume relations, onset of cellular damage, in situ variation of water potential and stomatal conductance) of three Ranunculus species differing in their soil humidity preferences and ecological amplitude. All species were very vulnerable to water stress (50 % reduction in whole-leaf hydraulic conductance (kleaf) at -0.2 to -0.8 MPa). In species with narrow ecological amplitude, the drought-exposed R. bulbosus was less vulnerable to desiccation (analysed via loss of kleaf and turgor loss point (TLP)) than the humid-habitat R. lanuginosus. Accordingly, water stress exposed plants from the broad-amplitude R. acris revealed tendencies of lower vulnerability to water stress (e.g. osmotic potential at full turgor, cell damage, stomatal closure) than conspecific plants from the humid site. We show that small herbs can adjust to their habitat conditions on inter- and intraspecific levels in various hydraulic parameters. Coordination of hydraulic thresholds (50 and 88% loss of kleaf, TLP, minimum in situ water potential) enabled the study species to avoid hydraulic failure and damage to living cells. Reversible recovery of hydraulic conductance, desiccation-tolerant seeds, or rhizomes may allow them to prioritise towards a more efficient but vulnerable water transport system while avoiding the severe effects that water stress poses on woody species

Stem and leaf hydraulic properties are finely coordinated in three tropical rainforest tree species

Coordination of stem and leaf hydraulic traits allows terrestrial plants to maintain safe water status under limited water supply. Tropical rainforests, one of the world's most productive biomes, are vulnerable to drought and potentially threatened by increased aridity due to global climate change. However, the relationship of stem and leaf traits within the plant hydraulic continuum remains understudied, particularly in tropical species. We studied within-plant hydraulic coordination between stems and leaves in three tropical lowland rainforest tree species by analyses of hydraulic vulnerability (hydraulic methods and ultrasonic emission (UE) analysis), pressure-volume relations and in situ predawn and midday water potentials (Ψ).\ud \ud We found finely coordinated stem and leaf hydraulic features, with a strategy of sacrificing leaves in favour of stems. Fifty percent of hydraulic conductivity (P50) was lost at -2.1 to -3.1 MPa in stems and -1.7 to -2.2 MPa in leaves. UE analysis corresponded to hydraulic measurements. Safety margins (leaf P50 – stem P50) were very narrow at -0.4 to -1.4 MPa. Pressure-volume analysis and in situ Ψ indicated safe water status in stems but risk of hydraulic failure in leaves. Our study shows that stem and leaf hydraulics were finely tuned to avoid embolism formation in the xylem

AMIDE: A Free Software Tool for Multimodality Medical Image Analysis

Amide's a Medical Image Data Examiner (AMIDE) has been developed as a user-friendly, open-source software tool for displaying and analyzing multimodality volumetric medical images. Central to the package's abilities to simultaneously display multiple data sets (e.g., PET, CT, MRI) and regions of interest is the on-demand data reslicing implemented within the program. Data sets can be freely shifted, rotated, viewed, and analyzed with the program automatically handling interpolation as needed from the original data. Validation has been performed by comparing the output of AMIDE with that of several existing software packages. AMIDE runs on UNIX, Macintosh OS X, and Microsoft Windows platforms, and it is freely available with source code under the terms of the GNU General Public License

Xylem cavitation resistance can be estimated based on time‐dependent rate of acoustic emissions

Acoustic emission (AE) analysis allows nondestructive monitoring of embolism formation in plant xylem, but signal interpretation and agreement of acoustically measured hydraulic vulnerability with reference hydraulic techniques remain under debate. We compared the hydraulic vulnerability of 16 species and three crop tree cultivars using hydraulic flow measurements and acoustic emission monitoring, proposing the use of time‐dependent AE rates as a novel parameter for AE analysis. There was a linear correlation between the water potential (Ψ) at 50% loss of hydraulic conductivity (P(50)) and the Ψ at maximum AE activity (P(maxrate)), where species with lower P(50) also had lower P(maxrate) (P < 0.001, R (2) = 0.76). Using AE rates instead of cumulative counts for AE analysis allows more efficient estimation of P(50), while excluding problematic AE at late stages of dehydration

Monitoring freezing dynamics in timberline trees

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