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1
Toca, Andrei, Pedro Villar-Salvador, Juan A. Oliet, and Douglass F. Jacobs. "Normalization criteria determine the interpretation of nitrogen effects on the root hydraulics of pine seedlings." Tree Physiology 40, no. 10 (June 1, 2020): 1381–91. http://dx.doi.org/10.1093/treephys/tpaa068.
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Abstract Plant hydraulics is key for plant survival and growth because it is linked to gas exchange and drought resistance. Although the environment influences plant hydraulics, there is no clear consensus on the effect of nitrogen (N) supply, which may be, in part, due to different hydraulic conductance normalization criteria and studied species. The objective of this study was to compare the variation of root hydraulic properties using several normalization criteria in four pine species in response to three contrasting N fertilization regimes. We studied four closely related, yet ecologically distinct species: Pinus nigra J.F. Arnold, Pinus pinaster Ait., Pinus pinea L. and Pinus halepensis Mill. Root hydraulic conductance (Kh) was measured with a high-pressure flow meter, and values were normalized by total leaf area (leaf specific conductance, Kl), xylem cross-section area (xylem specific conductance, Ks), total root area (root specific conductance, Kr) and the area of fine roots (fine root specific conductance, Kfr). Controlling for organ size differences allowed comparison of the hydraulic efficiency of roots to supply or absorb water among fertilization treatments and species. The effect of N on the root hydraulic efficiency depended on the normalization criteria. Increasing N availability reduced Kl and Ks, but increased Kh, Kr and especially Kfr. The positive effect of N on Kr and Kfr was positively related to seedling relative growth rate and was also consistent with published results at the interspecific level, whereby plant hydraulics is positively linked to photosynthesis and transpiration rate and fast growth. In contrast, normalization by leaf area and xylem cross-sectional area (Kl and Ks) reflected opposite responses to Kr and Kfr. This indicates that the normalization criteria determine the interpretation of the effect of N on plant hydraulics, which can limit species and treatment comparisons.
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Hacke, U. G. "Variable plant hydraulic conductance." Tree Physiology 34, no. 2 (February 1, 2014): 105–8. http://dx.doi.org/10.1093/treephys/tpu007.
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Calkin, Howard W., Arthur C. Gibson, and Park S. Nobel. "Xylem water potentials and hydraulic conductances in eight species of ferns." Canadian Journal of Botany 63, no. 3 (March 1, 1985): 632–37. http://dx.doi.org/10.1139/b85-079.
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Water potentials, flow rates, and anatomy of xylary elements were studied in eight species of ferns to assess the physical constraints that xylem structure presents to water flow. Comparisons were made among ferns of different leaf morphology as well as between a fern with vessels and ferns with tracheids only. Hydraulic conductance was measured by forcing a solution through excised plant segments. These hydraulic conductances were in close agreement with conductances calculated from water potential gradients and flows measured in intact plants. In three species, backflushing excised segments by forcing a basipetal flow increased subsequently measured conductances two- to six-fold, indicating that the xylem of these three species was partially blocked in intact plants. Hagen–Poiseuille estimates of conductance based on xylary element diameters were 1.8–2.7 times the conductances measured for excised segments. Hydraulic conductances of tracheids and vessels of ferns thus deviate from those of ideal capillaries of similar diameter to about the same extent as has been reported for tracheids in conifers and for vessels in dicotyledons.
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Nguyen, Thuy Huu, Matthias Langensiepen, Jan Vanderborght, Hubert Hüging, Cho Miltin Mboh, and Frank Ewert. "Comparison of root water uptake models in simulating CO<sub>2</sub> and H<sub>2</sub>O fluxes and growth of wheat." Hydrology and Earth System Sciences 24, no. 10 (October 23, 2020): 4943–69. http://dx.doi.org/10.5194/hess-24-4943-2020.
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Abstract. Stomatal regulation and whole plant hydraulic signaling affect water fluxes and stress in plants. Land surface models and crop models use a coupled photosynthesis–stomatal conductance modeling approach. Those models estimate the effect of soil water stress on stomatal conductance directly from soil water content or soil hydraulic potential without explicit representation of hydraulic signals between the soil and stomata. In order to explicitly represent stomatal regulation by soil water status as a function of the hydraulic signal and its relation to the whole plant hydraulic conductance, we coupled the crop model LINTULCC2 and the root growth model SLIMROOT with Couvreur's root water uptake model (RWU) and the HILLFLOW soil water balance model. Since plant hydraulic conductance depends on the plant development, this model coupling represents a two-way coupling between growth and plant hydraulics. To evaluate the advantage of considering plant hydraulic conductance and hydraulic signaling, we compared the performance of this newly coupled model with another commonly used approach that relates root water uptake and plant stress directly to the root zone water hydraulic potential (HILLFLOW with Feddes' RWU model). Simulations were compared with gas flux measurements and crop growth data from a wheat crop grown under three water supply regimes (sheltered, rainfed, and irrigated) and two soil types (stony and silty) in western Germany in 2016. The two models showed a relatively similar performance in the simulation of dry matter, leaf area index (LAI), root growth, RWU, gross assimilation rate, and soil water content. The Feddes model predicts more stress and less growth in the silty soil than in the stony soil, which is opposite to the observed growth. The Couvreur model better represents the difference in growth between the two soils and the different treatments. The newly coupled model (HILLFLOW–Couvreur's RWU–SLIMROOT–LINTULCC2) was also able to simulate the dynamics and magnitude of whole plant hydraulic conductance over the growing season. This demonstrates the importance of two-way feedbacks between growth and root water uptake for predicting the crop response to different soil water conditions in different soils. Our results suggest that a better representation of the effects of soil characteristics on root growth is needed for reliable estimations of root hydraulic conductance and gas fluxes, particularly in heterogeneous fields. The newly coupled soil–plant model marks a promising approach but requires further testing for other scenarios regarding crops, soil, and climate.
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Rejšek, K., P. Holčíková, V. Kuráž, A. Kučera, P. Dundek, P. Formánek, and V. Vranová. "Saturated hydraulic conductance of forest soils affected by track harvesters." Journal of Forest Science 57, No. 8 (August 12, 2011): 321–39. http://dx.doi.org/10.17221/6/2011-jfs.
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The exact data from the field of soil mechanics from specific forest stands exposed to forestry mechanization operation were obtained. Field surveys were performed on four study plots within the Křtiny Training Forest Enterprise, Masaryk Forest, followed by laboratory analyses of the collected soil samples aimed at evaluation of the impacts of Zetor 7245 Horal System, PONSSE ERGO 16 harvester and Gremo 950 forwarder on the compaction of upper soil horizons as well as on the dynamics of soil saturated hydraulic conductivity. A specific objective of the performed investigation was to assess the influence of the used hauling/skidding technology on measurable parameters of soil mechanics with the emphasis on a possibility to apply the Guelph permeameter for direct study of soil saturated hydraulic conductivity. In the measurement points affected by machinery operation, the impact of the changed soil structure on the values of saturated conductivity is very well noticeable – on study plots No. 3 and 4, the values decreased by one order of magnitude from 0.7 × 10<sup>–5</sup> m·s–1 to 0.09 × 10–5 m·s<sup>–1</sup>: specifically, (i) on study plot No. 3 and from 6.9 × 10–5 m·s–1 to 0.7 × 10–5 m·s–1, and (ii) on study plot No. 4; on study plot No. 2 even by two orders, i.e. from 1.6 × 10–5 m·s–1 up to 0.03 × 10–5 m·s–1. After the operation of a universal wheeled tractor at the Babice nad Svitavou locality, the situation partially improved by one order to 0.3 × 10–5 m·s–1, similarly like at the Rudice locality to 1.5 × 10–5 m·s–1. Significant changes were found in both surface and subsurface horizons. Field-saturated hydraulic conductivity indicates also a reduction of the pore volume after machinery traffic; however, tendencies towards restoration of the original state were detectable as soon as after six months.
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Markhart, Albert H., and Barbara Smit. "Measurement of Root Hydraulic Conductance." HortScience 25, no. 3 (March 1990): 282–87. http://dx.doi.org/10.21273/hortsci.25.3.282.
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Judd, Lesley A., Brian E. Jackson, William C. Fonteno, and Jean-Christophe Domec. "Measuring Root Hydraulic Parameters of Container-grown Herbaceous and Woody Plants Using the Hydraulic Conductance Flow Meter." HortScience 51, no. 2 (February 2016): 192–96. http://dx.doi.org/10.21273/hortsci.51.2.192.
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Root hydraulic conductance and conductivity are physiological traits describing the ease with which water can move through the belowground vascular system of a plant, and are used as indicators of plant performance and adaptability to a given environment. The ability to measure hydraulic conductance of container-grown herbaceous and semiwoody plants with soft conductive tissue was tested using a hydraulic conductance flow meter (HCFM). Although the HCFM is a hydraulic apparatus that has been used on woody plants to measure hydraulic conductance of intact roots, it has never been reportedly used on container-grown horticultural plants. Two herbaceous species, Chrysanthemum L. and Solenstemon scutellarioides Thonn., were grown in containers and hydraulic parameters were measured, including root conductance and root conductivity, as well as physical traits such as stem diameter and dry root mass. The HCFM was easily connected to intact roots even on herbaceous stems and was used to determine hydraulic conductance and conductivity directly on container-grown plants with minimal disturbance on the root system. Chrysanthemums, Buddleja davidii Franch., and Hibiscus moscheutos L. were grown in three different substrates, and both root mass and root hydraulic parameters were determined. Chrysanthemums showed a positive response with increasing root hydraulic conductance with increasing root mass. The substrates used in these studies only had an effect on root biomass of chrysanthemums, but substrates had no differential effect on root hydraulic conductivity.
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Choudhary, Sunita, and Thomas R. Sinclair. "Hydraulic conductance differences among sorghum genotypes to explain variation in restricted transpiration rates." Functional Plant Biology 41, no. 3 (2014): 270. http://dx.doi.org/10.1071/fp13246.
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Sorghum (Sorghum bicolor L.) is an important crop for production in dryland regions of the globe. Traits identified in many sorghum lines that apparently make them adapted for dryland conditions are restricted transpiration rate both early in the soil drying cycle and under high atmospheric vapour pressure deficit. It was hypothesised that these responses could be a result of differences in hydraulic conductance of the plants: those with low hydraulic conductance would be more likely to express restricted transpiration rates. The location of the lower hydraulic conductance in the plant could also be important with a low conductance in the leaf xylem to stomata pathway possibly being more advantageous than in the root. In this study, the amount and location of the hydraulic conductance was measured in 20 sorghum genotypes. Those genotypes that expressed an early decrease in transpiration rate with soil drying had greater plant and leaf hydraulic conductance than those genotypes that had the later decreases in transpiration rate, which was in contrast with what was hypothesised. However, sorghum genotypes that segregated between two groups based on expression of a maximum transpiration trait also segregated based on their hydraulic conductance. Those genotypes that expressed the maximum transpiration trait had lower hydraulic conductance for the intact plant and in the leaves.
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Schulte, Paul J., and Arthur C. Gibson. "Hydraulic conductance and tracheid anatomy in six species of extant seed plants." Canadian Journal of Botany 66, no. 6 (June 1, 1988): 1073–79. http://dx.doi.org/10.1139/b88-153.
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Hydraulic conductance of tracheids was studied in either petioles or young stems of six species of seed plants having various types of intertracheid pitting. Measured conductances were compared with estimates based on Hagen–Poiseuille flow through ideal capillaries and with predictions from a biophysical model incorporating observed anatomical characteristics of tracheids and intertracheid pits. Conductance of the xylem, expressed as a percentage of the ideal capillary flow prediction, varied from an average of 88% for a species containing only very narrow tracheids to less than 35% for species with large-diameter tracheids. The biophysical model allowed fairly close predictions of conductance for all species except one, where an estimate of the pit membrane resistance could not be experimentally obtained. For individual tracheids, conductance was largely a function of lumen diameter, pit membrane resistivity, and the exposed area of the pit membranes, as determined by pit shape, size, and frequency. For wide tracheids, scalariform-pitted elements showed a linear increase in conductance with an increase in lumen diameter; however, for tracheids with large circular pits, the conductance increase afforded by a wider lumen declines as lumen diameter increases. These model simulations demonstrate the increasing significance of intertracheid pitting in obstructing flow as lumen diameter increases.
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Meinzer, FC, DA Grantz, and B. Smit. "Root Signals Mediate Coordination of Stomatal and Hydraulic Conductance in Growing Sugarcane." Functional Plant Biology 18, no. 4 (1991): 329. http://dx.doi.org/10.1071/pp9910329.
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Root hydraulic conductance and total stomatal conductance on a per plant basis changed in parallel during growth of sugarcane. Changes in root system water and solute transport properties were evaluated to determine the role of changes in root xylem sap composition in this coordination of vapour and liquid phase conductances. Stomatal conductance of excised leaf strips supplied with root exudate declined with increasing leaf area of the exudate donor plants. Leaf strips from plants of different sizes responded similarly to exudate from each donor plant, indicating that there were no inherent differences in leaf stomatal properties. The effect of xylem sap from plants of increasing size paralleled the decline in stomatal conductance of intact plants of similarly increasing plant size. Delivery rates per unit leaf area of K+, Ca2+, abscisic acid, and zeatin riboside (ZR) in xylem sap declined with increasing plant size. Patterns of delivery of ZR and K+ were consistent with a role in the plant size-dependent regulation of stomatal conductance, although additional xylem constituents are likely to be involved. Developmental patterns of stomatal conductance in intact sugarcane plants may be linked to plant hydraulic properties by the composition and flux of xylem sap arriving at the stomatal complexes in leaves.
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Myers, BA. "The Influence of the Lignotuber on Hydraulic Conductance and Leaf Conductance in Eucalyptus behriana Seedlings." Functional Plant Biology 22, no. 5 (1995): 857. http://dx.doi.org/10.1071/pp9950857.
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Hydraulic conductances of stem segments and stem-plus-lignotuber segments were estimated for 3-year-old seedlings of the mallee eucalypt Eucalyptus behriana F. Muell. Stems of seedlings were cut underwater and either above or below the lignotuber. Cutting the stem of intact seedlings underwater and above the lignotuber resulted in rapid increases in leaf water potential (Ψ); 1.1 MPa in 10-15 min with a concomitant decrease in leaf conductance. Cutting the stem below the lignotuber did not significantly affect leaf Ψ or leaf conductance. Transpirational flow through whole seedlings and segments of seedlings was about 10-9 m3 s-1. The hydraulic conductance of the lignotuber (2.27 × 10-9 m3 s-1 Mpa-1) was about half that of the stem. This work suggests that resistance to water flow through the lignotuber accounts, in part, for the persistently low dawn Ψ of the foliage of mature trees of E. behriana.
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Aasamaa, Krõõt, and Anu Sõber. "Light sensitivity of shoot hydraulic conductance in five temperate deciduous tree species." Functional Plant Biology 39, no. 8 (2012): 661. http://dx.doi.org/10.1071/fp12047.
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The light sensitivity of the shoot hydraulic conductance in five temperate deciduous tree species was measured using two methods to clarify the role of light sensitivity and the suitability of the methods used to study it. The light sensitivity measured using a method that included an interruption of ≤10 min in shoot light acclimation did not differ from that measured using a method with continuous illumination. The ‘noncontinuous light’ methods are suitable for measuring hydraulic conductance and its light response. Light sensitivity correlated with other leaf water traits as follows: positively with the ion-mediated increase in xylem hydraulic conductance; a relative decrease in the hydraulic conductance of the laminae in response to HgCl2; a relative change in stomatal conductance in response to changes in PAR intensity or atmospheric CO2 concentration, or to a decrease in air humidity or leaf water potential; and with instantaneous water use efficiency. The traits correlated negatively with shoot hydraulic conductance, stomatal conductance and relative increases in stomatal conductance in response to increases in leaf water potential. We suggest that high light sensitivity should be considered as one of the characteristics of conservative water use in trees. Low blue light increased shoot hydraulic conductance to a similar extent to moderate white light and twice as much as moderate red light. Blue light perception is important in the light sensitivity mechanism.
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Saliendra, NZ, and FC Meinzer. "Relationship Between Root/Soil Hydraulic Properties and Stomatal Behaviour in Sugarcane." Functional Plant Biology 16, no. 3 (1989): 241. http://dx.doi.org/10.1071/pp9890241.
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Stomatal conductance, leaf and soil water status, transpiration, and apparent root hydraulic conductance were measured during soil drying cycles for three sugarcane cultivars growing in containers in a greenhouse. At high soil moisture, transpiration and apparent root hydraulic conductance differed considerably among cultivars and were positively correlated, whereas leaf water potential was similar among cultivars. In drying soil, stomatal and apparent root hydraulic conductance approached zero over a narrow (0.1 MPa) range of soil water suction. Leaf water potential remained nearly constant during soil drying because the vapor phase conductance of the leaves and the apparent liquid phase conductance of the root system declined in parallel. The decline in apparent root hydraulic conductance with soil drying was manifested as a large increase in the hydrostatic pressure gradient between the soil and the root xylem. These results suggested that control of stomatal conductance in sugarcane plants exposed to drying soil was exerted primarily at the root rather than at the leaf level.
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Sangsing, Krissada, Hervé Cochard, Poonpipope Kasemsap, Sornprach Thanisawanyangkura, Kumut Sangkhasila, Eric Gohet, and Philippe Thaler. "Is growth performance in rubber (Hevea brasiliensis) clones related to xylem hydraulic efficiency?" Canadian Journal of Botany 82, no. 7 (July 1, 2004): 886–91. http://dx.doi.org/10.1139/b04-083.
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Hydraulic efficiency, xylem pressure, and stomatal conductance were measured in two Hevea clones having contrasting growth performances in their immature phase. Hydraulic efficiency was estimated by the xylem resistance on a leaf area basis on stem, petiole segments, and whole branches. The fast-growing clone exhibited significantly higher xylem efficiency, higher stomatal conductance, and higher xylem pressure. The difference in xylem pressure between the two clones was quantitatively consistent with the differences in hydraulic resistance and leaf transpiration rates. Our results suggest that variations in xylem efficiency may explain variations in stomatal conductance and xylem pressure, and hypothetically, growth performance between Hevea clones.Key words: xylem, hydraulic conductance, hydraulic architecture, water relations, rubber tree, Hevea.
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Aasamaa, Krõõt, Anu Sõber, and Märt Rahi. "Leaf anatomical characteristics associated with shoot hydraulic conductance, stomatal conductance and stomatal sensitivity to changes of leaf water status in temperate deciduous trees." Functional Plant Biology 28, no. 8 (2001): 765. http://dx.doi.org/10.1071/pp00157.
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Some anatomical characteristics in leaves relating to hydraulic conductance and stomatal conductance were examined in six temperate deciduous tree species. The fourth power of the radius of the conducting elements in xylem (r4) and the area of mesophyll and epidermal cells per unit length of leaf cross-section (u) were high in leaves with high hydraulic conductance (L). Stomatal conductance (gs) and stomatal sensitivity to an increase in leaf water potential (si) correlated positively with the length of stomatal pore (l), but negatively with the guard cell width (z) and the length of the dorsal side of the guard cells (ld). Stomatal sensitivity to a decrease in leaf water potential (sd) correlated negatively with l and positively with z and ld. The anatomical characteristics associated with hydraulic conductance (r4 and u) and those associated with stomatal conductance and sensitivity to changes of leaf water potential (l, z and ld) were correlated. We conclude that hydraulic conductance may depend on anatomical characteristics of xylem, mesophyll and epidermis, and stomatal conductance and its sensitivity to changing water potential may depend on anatomical characteristics of stomata. The correlation of shoot hydraulic conductance with stomatal conductance and its sensitivity may be based largely on the correlation between the anatomical characteristics of the water conducting system and stomata in these trees.
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Jin, Ying, Chuankuan Wang, Zhenghu Zhou, and Zhimin Li. "Co-ordinated performance of leaf hydraulics and economics in 10 Chinese temperate tree species." Functional Plant Biology 43, no. 11 (2016): 1082. http://dx.doi.org/10.1071/fp16097.
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Exploring relationships between leaf hydraulics and economic traits is important in understanding the carbon–water coupling and in extending the leaf economics spectrum. In this study, leaf hydraulics, photosynthesis, structural and nutrient traits and photosynthetic resource use efficiency were measured for 10 temperate tree species in the north-eastern China. Leaf hydraulic conductance was positively correlated with photosynthetic traits, specific leaf area, leaf nitrogen concentration, photosynthetic water and nitrogen use efficiencies, suggesting co-ordination between leaf hydraulics and economic traits. Principal component analysis revealed that significant correlations existed among leaf hydraulic, photosynthetic and resource use traits (axis 1), and axis 2 was strongly associated with leaf structural and nutrient traits. The 10 species were distributed along the diagonal line between axis 1 and axis 2. Species displaying the ‘fast’ strategy tended to have higher photosynthetic rates, leaf hydraulic conductance and photosynthetic water and nutrient use efficiencies; however, they also had lower carbon investment and faced a greater risk of embolism. These findings indicate that leaf hydraulics, economics and resource uses together play an important role in determining species ecological strategies, and provide supports for the ‘fast–slow’ leaf economics spectrum.
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Karatassiou, Maria, Panagiota Karaiskou, Eleni Verykouki, and Sophia Rhizopoulou. "Hydraulic Response of Deciduous and Evergreen Broadleaved Shrubs, Grown on Olympus Mountain in Greece, to Vapour Pressure Deficit." Plants 11, no. 8 (April 8, 2022): 1013. http://dx.doi.org/10.3390/plants11081013.
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In this study, leaf hydraulic functionality of co-occurring evergreen and deciduous shrubs, grown on Olympus Mountain, has been compared. Four evergreen species (Arbutus andrachne, Arbutus unedo, Quercus ilex and Quercus coccifera) and four deciduous species (Carpinus betulus, Cercis siliquastrum, Coronilla emeroides and Pistacia terebinthus) were selected for this study. Predawn and midday leaf water potential, transpiration, stomatal conductance, leaf temperature and leaf hydraulic conductance were estimated during the summer period. The results demonstrate different hydraulic tactics between the deciduous and evergreen shrubs. Higher hydraulic conductance and lower stomatal conductance were obtained in deciduous plants compared to the evergreens. Additionally, positive correlations were detected between water potential and transpiration in the deciduous shrubs. The seasonal leaf hydraulic conductance declined in both deciduous and evergreens under conditions of elevated vapor pressure deficit during the summer; however, at midday, leaf water potential reached comparable low values, but the deciduous shrubs exhibited higher hydraulic conductance compared to the evergreens. It seems likely that hydraulic traits of the coexisting evergreen and deciduous plants indicate water spending and saving tactics, respectively; this may also represent a limit to drought tolerance of these species grown in a natural environment, which is expected to be affected by global warming.
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Richardson, Freya, Gregory J. Jordan, and Timothy J. Brodribb. "Leaf hydraulic conductance is linked to leaf symmetry in bifacial, amphistomatic leaves of sunflower." Journal of Experimental Botany 71, no. 9 (January 23, 2020): 2808–16. http://dx.doi.org/10.1093/jxb/eraa035.
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Abstract The hydraulic implications of stomatal positioning across leaf surfaces and the impact on internal water flow through amphistomatic leaves are not currently well understood. Amphistomaty potentially provides hydraulic efficiencies if the majority of hydraulic resistance in the leaf exists outside the xylem in the mesophyll. Such a scenario would mean that the same xylem network could equally supply a hypostomatic or amphistomatic leaf. Here we examine leaves of Helianthus annuus to determine whether amphistomaty in this species is associated with higher hydraulic efficiency compared with hypostomatic leaves. We identified asymmetry in the positioning of minor veins which were significantly closer to the abaxial than the adaxial leaf surface, combined with lower Kleaf when transpiration was driven through the adaxial rather than the abaxial surface. We also identified a degree of coordination in stomatal behaviour driven by leaf hydraulics, where the hydraulic conditions experienced by an individual leaf surface affected the stomatal behaviour on the opposite surface. We found no advantage to amphistomaty based on efficiencies in construction costs of the venous system, represented by vein density:stomatal density, only limited hydraulic independence between leaf surfaces. These results suggest that amphistomaty does not substantially increase whole-leaf hydraulic efficiency.
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Aasamaa, Krõõt, and Anu Sõber. "Seasonal courses of maximum hydraulic conductance in shoots of six temperate deciduous tree species." Functional Plant Biology 32, no. 12 (2005): 1077. http://dx.doi.org/10.1071/fp05088.
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The seasonal course of maximum hydraulic conductance of leaf laminae (K lamina) of shoots correlated strongly with the seasonal course of the maximum hydraulic conductance of leaf laminae of HgCl2-treated shoots (K lamina(HgCl2)), and with the seasonal course of the difference (dK lamina) between K lamina and K lamina(HgCl2). However, it did not correlate strongly with the seasonal course of the hydraulic conductance of stem and petioles of the shoot (K stpt) in six temperate deciduous tree species. The species ranked according to K lamina as follows: Populus tremula L. > Salix caprea L. > Padus avium Mill. > Quercus robur L. > Tilia cordata Mill. > Acer platanoides L. The species-specific maxima of K lamina correlated positively with the simultaneous values of K lamina(HgCl2), dK lamina and K stpt; the correlation was strongest with K lamina(HgCl2). It was concluded that the seasonal dynamics of maximum hydraulic conductance of leaf laminae was determined almost equally by the seasonal dynamics of the hydraulic conductance of foliar protoplasts and apoplast, but the inter-specific differences in K lamina were mainly caused by the different apoplastic hydraulic conductance in leaves of these species. The relative contribution of dK lamina (in K lamina) was highest in slow-growing species (~55% in A. platanoides) and the lowest in fast-growers (~30% in S. caprea).
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Li, Duan, Jianhua Si, Xiaoyou Zhang, Yayu Gao, Huan Luo, Jie Qin, and Guanlong Gao. "Comparison of Branch Water Relations in Two Riparian Species: Populus euphratica and Tamarix ramosissima." Sustainability 11, no. 19 (October 2, 2019): 5461. http://dx.doi.org/10.3390/su11195461.
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Water relations in plants maintain healthy tree branches and drought conditions during plant growth may affect water relations, but the mechanisms are poorly known. In our study, we determined the stomatal conductance, hydraulic conductance, water potential and ion concentration of xylem sap to increase the understanding of changes in water relations in branches of Populus euphratica (P. euphratica) and Tamarix ramosissima (T. ramosissima), which are the dominant plant species in the lower reaches of the Heihe River Basin in China. The results showed that both species responded to vapor pressure deficit (VPD) during the growing season by adjusting stomatal conductance to achieve homeostasis in leaf water potentials. The leaf-specific hydraulic conductance (LSC) of the branch was determined using water status in the branch, and the LSC of the leaf was determined using water status in the leaf. Because of homeostasis in leaf water potentials, hydraulic conductance in leaves remained stable. As a result, branch dieback, which might be induced by deficits in water supply, could rarely be seen in T. ramosissima owing to the homeostasis in branch and leaf water status. The ion sensitivity of xylem hydraulic conductance in P. euphratica induced an increase in hydraulic conductance caused by the deficits in the water supply which might lead to branch dieback. The evaluation of water relations provides a further understanding of the internal mechanisms of drought acclimation for riparian plants.
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Mencuccini, Maurizio, and Jonathan Comstock. "Variability in hydraulic architecture and gas exchange of common bean (Phaseolus vulgaris) cultivars under well-watered conditions: interactions with leaf size." Functional Plant Biology 26, no. 2 (1999): 115. http://dx.doi.org/10.1071/pp98137.
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In a greenhouse study, 12 common bean cultivars from a wide geographical range were compared for their morphological, gas exchange and hydraulic architecture characters. Cultivars bred for cultivation in hot and dry regions had significantly smaller leaves and crowns, but higher stomatal conductances and transpiration rates per unit of leaf area. Short-term variability in gas exchange rates was confirmed using leaf carbon isotope discrimination. A literature survey showed that, although previously unnoticed, the strong inverse coupling between leaf size and gas exchange rates was present in three other studies using the same set of cultivars. Several measures of ‘leaf-specific hydraulic conductance’ (i.e. for the whole plant and for different parts of the xylem pathway) were also linearly related to rates of water loss, suggesting that the coupling between leaf size and gas exchange was mediated by a hydraulic mechanism. It is possible that breeding for high production in hot regions has exerted a selection pressure to increase leaf-level gas exchange rates and leaf cooling. The associated reductions in leaf size may be explained by the need to maintain equilibrium between whole-plant water loss and liquid-phase hydraulic conductance.
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Sober, A. "Hydraulic conductance, stomatal conductance, and maximal photosynthetic rate in bean leaves." Photosynthetica 34, no. 4 (December 1, 1998): 599–603. http://dx.doi.org/10.1023/a:1006834119588.
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Darlington, Alan B., and Michael A. Dixon. "The hydraulic architecture of roses (Rosa hybrida)." Canadian Journal of Botany 69, no. 4 (April 1, 1991): 702–10. http://dx.doi.org/10.1139/b91-095.
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The presence of an abscission zone in the stem of greenhouse roses (Rosa hybrida) between the vegetative and reproductive components was verified. This led to a description of the hydraulic architecture of the rose stem. The structural aspects of the xylem conducting system in stem, abscission zone and peduncle were examined to define their relative roles in the delivery of water via the stem to the transpiring plant surfaces and the extent to which their functional capacity may be influenced by environmental variables such as humidity. The stem exhibited a highly developed xylem with many large-diameter tracheary elements. Contrary to this the distal segment of the peduncle was poorly vascularized. The remainder of the peduncle, which included the abscission zone, was a transition between these two extremes. The abscission zone was a site of reduced hydraulic conductance that was not due to a reduction in the number or size of xylem conduits but to changes in the alignment of the elements. The variable conductances across the abscission zone and peduncle regions may play an important role in floral development and the response of the plant to water stress. Rose plants grown at constantly high humidity (77% RH) did not exhibit significantly different internal anatomical features of the xylem conducting system relative to roses grown in ambient, uncontrolled humidity (30 to 60% RH). Key words: abscission zone, hydraulic conductance, humidity.
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Keller, Markus, Laura S. Deyermond, and Bhaskar R. Bondada. "Plant hydraulic conductance adapts to shoot number but limits shoot vigour in grapevines." Functional Plant Biology 42, no. 4 (2015): 366. http://dx.doi.org/10.1071/fp14206.
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The rate of shoot growth (vigour) in grapevines tends to decrease as the number of shoots per plant increases. Because the underlying causes of this relationship remain unclear, they were studied by variable pruning of field-grown, deficit-irrigated Merlot grapevines (Vitis vinifera L.). Shoot number ranged from 11 to 124 per vine and was inversely correlated with shoot growth rate, leaf appearance rate, axillary bud outgrowth, internode length, leaf size, shoot leaf area, carbon partitioned to the fruit (Cfruit) per shoot, average daily maximum photosynthesis (Amax), stomatal conductance (gmax), and leaf-specific hydraulic conductance (Kl). Shoot number was positively correlated with canopy leaf area, whole-vine Cfruit, whole-plant hydraulic conductance (Kv), and canopy conductance (Kc). Higher shoot vigour was associated with higher Amax, gmax, predawn leaf water potential (Ψpd), shoot hydraulic conductance (Ks), Kl, and Kv. Vigorous shoots supported both more vegetative growth and more reproductive growth; thus fruit growth did not compete with shoot growth for photosynthates. These results indicate that the hydraulic capacity of grapevines adapts to varying shoot numbers to support leaf physiology, growth, and carbon partitioning, but adaptation may be limited, putting upper bounds on the growth of individual shoots and fruit.
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Mohamed, Johar, Hazandy A. Hamid, Ahmad A. Nuruddin, and Nik M. N. A. Majid. "Anatomical characteristics of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance." BioResources 14, no. 4 (September 30, 2019): 9082–99. http://dx.doi.org/10.15376/biores.14.4.9082-9099.
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Structural development and modification of bamboo culm’s anatomical characteristics occur during the maturation period. This process affects the conductivity efficiency in individual bamboo culms (above ground). The present study clarified this process in the sympodial type of bamboo rhizome (belowground). This study aimed to observe the anatomical characteristics of Gigantochloa scortechinii rhizome, examine their relationship with different study sites and rhizome ages, and investigate their relationship with hydraulic conductance. Destructive sampling on four consecutive rhizomes was conducted using a selective random sampling method. All rhizome anatomical characteristics were significantly different between study sites except parenchyma diameter, parenchyma lumen diameter, and fiber cell wall thickness. The results also indicated that the vascular bundle diameter, parenchyma diameter, parenchyma lumen diameter, parenchyma cell wall thickness, fiber diameter, fiber cell wall thickness, and fiber length increased with age, but radial to tangential ratio decreased with age. All measured characteristics including the conductance elements had no relationship with hydraulic conductance, except parenchyma diameter and parenchyma lumen diameter. The sizes parenchyma diameter and lumen diameter did not imply a determinant factor in hydraulic conductance. Further studies on rhizome chemical attributes should be carried out to isolate the cause of decreasing hydraulic conductance.
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Schenk, H. J., K. Mocko, J. M. Michaud, A. Hunt, G. Roldan, M. Catalan, A. Downey, and K. Steppe. "In situ measurement of plant hydraulic conductance." Acta Horticulturae, no. 1300 (December 2020): 169–78. http://dx.doi.org/10.17660/actahortic.2020.1300.22.
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Tucker, V. L., and V. H. Huxley. "O2 modulation of single-vessel hydraulic conductance." American Journal of Physiology-Heart and Circulatory Physiology 254, no. 2 (February 1, 1988): H317—H323. http://dx.doi.org/10.1152/ajpheart.1988.254.2.h317.
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To investigate the response of the microvascular endothelial barrier to O2 lack, hydraulic conductivities (Lp) were compared under control and hypoxic conditions. In 29 decerebrate frogs (Rana pipiens) the mesentery was exposed and continuously superfused with room air-equilibrated frog Ringer (14 degrees C, pH 7.4). Single mesenteric microvessels (15- to 50-microm diam) were cannulated and perfused with frog Ringer containing 5-40 mg/ml bovine serum albumin and 5-10% (vol/vol) human erythrocytes. The modified Landis technique was used to measure transmural water flux per unit area (Jv/S) from marker red cell movement at pressures ranging from 15 to 45 cmH2O. In 21 vessels, a 10-min superfusion with 100% N2-equilibrated Ringer increased Lp 2.4-fold (+/- 0.72 SD) over control (P less than or equal to 0.05). In an additional six vessels, simultaneous exposure to 100% N2-equilibrated perfusate and superfusate resulted in a 10-fold (+/- 3.0) increase in Lp (P less than or equal to 0.05). In 15 of the vessels, a 10- to 75-min reexposure to control conditions decreased Lp, averaging a 77% recovery toward base line. These data support an active role for O2 in the regulation of microvascular membrane permeability, which appears to be sensitive to the severity of O2 lack. The rapid increase in capillary water conductivity following exposure to hypoxic conditions may be the initial process in the events leading to edema formation.
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Baldwin, A. L., L. M. Wilson, and B. R. Simon. "Effect of pressure on aortic hydraulic conductance." Arteriosclerosis and Thrombosis: A Journal of Vascular Biology 12, no. 2 (February 1992): 163–71. http://dx.doi.org/10.1161/01.atv.12.2.163.
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Bolger, T. P., D. R. Upchurch, and B. L. McMichael. "Temperature effects on cotton root hydraulic conductance." Environmental and Experimental Botany 32, no. 1 (January 1992): 49–54. http://dx.doi.org/10.1016/0098-8472(92)90029-2.
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Anderegg, William R. L. "Quantifying seasonal and diurnal variation of stomatal behavior in a hydraulic-based stomatal optimization model." Journal of Plant Hydraulics 5 (December 22, 2018): e001. http://dx.doi.org/10.20870/jph.2018.e001.
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Plant responses to drought occur across many time-scales, with stomatal closure typically considered to be a critical short-term response. Recent theories of optimal stomatal conductance linked to plant hydraulic transport have shown promise, but it is not known if stomata update their hydraulic “shadow price” of water use (marginal increase in carbon cost with a marginal drop in water potential) over days, seasons, or in response to recent drought. Here, I estimate the hydraulic shadow price in five species – two semi-arid gymnosperms, one temperate and two tropical angiosperms – at daily timescales and in wet and dry periods. I tested whether the shadow prices varies predictably as a function of current and/or lagged drought conditions. Diurnal estimates of the hydraulic shadow price estimated from observed stomatal conductance, while variable, did not vary predictably with environmental variables. Seasonal variation in shadow price was observed in the gymnosperm species, but not the angiosperm species, and did not meaningfully influence prediction accuracy of stomatal conductance. The lack of systematic variation in shadow price and high predictive ability of stomatal conductance when using a single set of parameters further emphasizes the potential of hydraulic-based stomatal optimization theories.
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Gibson, Arthur C., Howard W. Calkin, and Park S. Nobel. "Hydraulic Conductance and Xylem Structure in Tracheid-Bearing Plants." IAWA Journal 6, no. 4 (1985): 293–302. http://dx.doi.org/10.1163/22941932-90000957.
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To understand water flow in tracheary elements, hydraulic conductances per unit length were measured and then compared with theoretical values calculated from xylem anatomical measurements using the Hagen -Poiseuille relation for nine species of pteridophytes, including Psilotum and eight species of ferns. In ferns the water potential gradients were essentially constant from the root tips to the distal portion of the leaf rachises, although somewhat larger gradients were found from the petiolule onward. Although tracheid number and diameter apparently controlled water flow in xylem, estimates of hydraulic conductance per unit length predicted from tracheid numbers and diameters were generally twice those actually measured from plants under steady-state conditions. A model was developed to account for this discrepancy for Pteris vittata, indicating that pit membrane resistances may contribute 70% of the total resistance to water flow in this fern. This may account for the generally observed deviation of tracheid performance from that predicted for ideal capillaries of uniform diameter.
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Bréda, N., H. Cochard, E. Dreyer, and A. Granier. "Water transfer in a mature oak stand (Quercuspetraea): seasonal evolution and effects of a severe drought." Canadian Journal of Forest Research 23, no. 6 (June 1, 1993): 1136–43. http://dx.doi.org/10.1139/x93-144.
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The reactions of sessile oak (Quercuspetraea (Mattuschka) Liebl.) to drought were studied under natural conditions in a 32-year-old stand near Nancy (northeastern France) during the summers of 1989 (strongly rain deficient) and 1990. A plot of five trees was subjected to imposed water shortage, while a group of irrigated trees was used as a control. Measurements of xylem sap flows and water potential enabled the computation of plot transpiration, canopy conductance, and specific hydraulic conductance in the soil–tree continuum. Stomatal conductance was measured directly with a porometer. Specific hydraulic conductance of our oaks was of the same order of magnitude as that reported for other species. It decreased significantly during spring because of a time lag between cambial growth and leaf area expansion. Measured transpiration was close to potential evapotranspiration, except during days with high vapor pressure deficits, which promoted stomatal closure in the absence of soil water deficits. Imposed drought caused predawn leaf water potentials to reach values as low as −2.0 MPa and a progressive decline in hydraulic conductance, which was probably attributable to modifications in hydraulic properties at the soil–root interface. This gradual decline in conductance was attributed to their deep rooting (1.40 m). This study revealed that Q. petraea may be considered as drought tolerant because of adaptations like deep rooting, efficient and safe xylem sap transport, maintenance of significant stomatal conductance, and significant transpiration, even during strong drought stress.
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Trifilò, Patrizia, Maria Assunta Lo Gullo, Fabio Raimondo, Sebastiano Salleo, and Andrea Nardini. "Effects of NaCl addition to the growing medium on plant hydraulics and water relations of tomato." Functional Plant Biology 40, no. 5 (2013): 459. http://dx.doi.org/10.1071/fp12287.
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This work reports on experimental evidence for the role of ion-mediated changes of xylem hydraulic conductivity in the functional response of Solanum lycopersicum L. cv. Naomi to moderate salinity levels. Measurements were performed in fully developed 12-week-old plants grown in half-strength Hoagland solution (control, C-plants) or in the same solution added with 35 mM NaCl (NaCl-plants). NaCl-plants produced a significantly less but heavier leaves and fruits but had similar gas-exchange rates as control plants. Moreover, NaCl-plants showed higher vessel multiple fraction (FVM) than control plants. Xylem sap potassium and sodium concentrations were significantly higher in NaCl-plants than in control plants. When stems were perfused with 10 mM NaCl or KCl, the hydraulic conductance of NaCl plants was nearly 1.5 times higher than in control plants. Accordingly, stem hydraulic conductance measured in planta was higher in NaCl- than in control plants. Our data suggest that tomato plants grown under moderate salinity upregulate xylem sap [Na+] and [K+], as well as sensitivity of xylem hydraulics to sap ionic content, thus, increasing water transport capacity.
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Wang, Yujie, and Christian Frankenberg. "Technical note: Common ambiguities in plant hydraulics." Biogeosciences 19, no. 19 (October 5, 2022): 4705–14. http://dx.doi.org/10.5194/bg-19-4705-2022.
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Abstract. Plant hydraulics gains increasing interest in plant ecophysiology and vegetation modeling. However, the hydraulic properties and profiles are often improperly represented, thus leading to biased results and simulations, e.g., the neglection of gravitational pressure drop results in overestimated water flux. We highlight the commonly seen ambiguities and/or misunderstandings in plant hydraulics, including (1) the distinction between water potential and pressure, (2) differences among hydraulic conductance and conductivity, (3) xylem vulnerability curve formulations, (4) model complexity, (5) stomatal-model representations, (6) bias from analytic estimations, (7) whole-plant vulnerability, and (8) neglected temperature dependencies. We recommend careful thinking before using or modifying existing definitions, methods, and models.
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SPERRY, J. S., N. N. ALDER, and S. E. EASTLACK. "The Effect of Reduced Hydraulic Conductance on Stomatal Conductance and Xylem Cavitation." Journal of Experimental Botany 44, no. 6 (1993): 1075–82. http://dx.doi.org/10.1093/jxb/44.6.1075.
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Zhao, Xiao-wei, Lei Ouyang, Ping Zhao, and Chun-fang Zhang. "Effects of size and microclimate on whole-tree water use and hydraulic regulation inSchima superbatrees." PeerJ 6 (July 6, 2018): e5164. http://dx.doi.org/10.7717/peerj.5164.
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BackgroundPlant-water relations have been of significant concern in forestry and ecology studies in recent years, yet studies investigating the annual differences in the characteristics of inter-class water consumption in trees are scarce.MethodsWe classified 15 trees from aSchima superbaplantation in subtropical South China into four ranks using diameter at breast height (DBH). The inter-class and whole-tree water use were compared based on three parameters: sap flux density, whole-tree transpiration and canopy transpiration over two years. Inter-class hydraulic parameters, such as leaf water potential, stomatal conductance, hydraulic conductance, and canopy conductance were also compared.Results(1) Mean water consumption of the plantation was 287.6 mm over a year, 165.9 mm in the wet season, and 121.7 mm in the dry season. Annual mean daily water use was 0.79 mm d−1, with a maximum of 1.39 mm d−1. (2) Isohydrodynamic behavior were found inS. superba. (3) Transpiration was regulated via both hydraulic conductance and stoma; however, there was an annual difference in which predominantly regulated transpiration.DiscussionThis study quantified annual and seasonal water use of aS. superbaplantation and revealed the coordinated effect of stoma and hydraulic conductance on transpiration. These results provide information for large-scale afforestation and future water management.
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Gibson, A. C., H. W. Calkin, D. O. Raphael, and P. S. Nobel. "Water relations and xylem anatomy of ferns." Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 86 (1985): 81–92. http://dx.doi.org/10.1017/s0269727000007995.
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SynopsisThe entire soil-plant-atmosphere continuum must be analysed to elucidate how xylem anatomy relates to water flow in plants. Measurements of water potential gradients and volume of water flow per unit time are needed to obtain values of hydraulic conductance per unit length. By comparing values of hydraulic conductance per unit length along the plant, the regions where xylem structure restricts water flow can be determined. Previous studies of fern water relations demonstrated that very large water potential gradients occurring in stipes of certain ferns were closely correlated with reduced conducting area of stipe xylem. A new study on Cyrtomium falcatum showed that the water potential gradient was relatively small and constant along the stipe and rachis; however, a much larger gradient occurred from the rachies into the pinnae. Hydraulic conductance per unit length varied with the leaf area to be supplied, leading to the fairly constant water potential gradient along the rachis.. The measured hydraulic conductance per unit length was only half the value predicted from the Hagen-Poiseuille equation. Although the Hagen-Poiseuille equation overestimated the measured value by a factor of 2, it did support the assumption that conduit number and lumen diameter are the principal determinants of water conductance in the xylem.
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Maurel, Marion, Cécile Robin, Thierry Simonneau, Denis Loustau, Erwin Dreyer, and Marie-Laure Desprez-Loustau. "Stomatal conductance and root-to-shoot signalling in chestnut saplings exposed to Phytophthora cinnamomi or partial soil drying." Functional Plant Biology 31, no. 1 (2004): 41. http://dx.doi.org/10.1071/fp03133.
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The effects of root infection by Phytophthora cinnamomi on stomatal conductance in Castanea sativa L. saplings were investigated to determine the potential role of root-derived chemical signals. A split-root experiment was carried out, in which inoculation of the pathogen or drought was applied to the root systems in either one or both compartments. At the end of the experiment plant sap extracts were collected and their effects on stomatal conductance were determined by leaf bioassay. Inoculation or drought imposed in both compartments resulted in decreases in stomatal conductance (gs), transpiration rate, soil-to-leaf specific hydraulic conductance, leaf water potential, xylem [ABA] and root biomass, but not in the ratio of root-to-leaf mass in inoculated plants. Conversely, only gs and xylem [ABA] were affected in plants inoculated or droughted in one compartment, and no changes were detectable in leaf water potential and soil-to-leaf specific hydraulic conductance. The leaf bioassay showed that gs in chestnut was sensitive to ABA but not to Phytophthora elicitins. Stomatal conductance was reduced by some sap extracts, both from control and inoculated plants. Our results suggest the involvement of different signals, chemical and hydraulic, in regulating stomatal conductance of chestnut at different stages of stress.
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Scoffoni, Christine, Grace John, Herve Cochard, and Lawren Sack. "Testing for ion-mediated enhancement of the hydraulic conductance of the leaf xylem in diverse angiosperms." Journal of Plant Hydraulics 4 (April 26, 2017): e004. http://dx.doi.org/10.20870/jph.2017.e004.
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Replacing ultra-pure water solution with ion solution closer to the composition of natural xylem sap increases stem hydraulic conductance by up to 58%, likely due to changes in electroviscosity in the pit membrane pores. This effect has been proposed to contribute to the control of plant hydraulic and stomatal conductance and potentially to influence on carbon balance during dehydration. However, this effect has never been directly tested for leaf xylem, which constitutes a major bottleneck in the whole plant. We tested for an ion-mediated increase in the hydraulic conductance of the leaf xylem (Kx) for seven species diverse in phylogeny and drought tolerance. Across species, no significant changes in Kx were observed between 0 and 15 mM KCl. We further tested for an effect of ion solution during measurements of Kx vulnerability to dehydration in Quercus agrifolia and found no significant impact. These results for leaf xylem contrast with the often strong ion effect reported for stems, and we suggest several hypotheses to account for the difference, relating to the structure of xylem conduits across vein orders, and the ultrastructure of leaf xylem pores. A negligible ion response in leaves would weaken xylem sap ion-mediated control of plant hydraulic conductance, facilitating modeling of whole plant hydraulic behavior and its influence on productivity.
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Lauri, Pierre-Éric, Antoine Marceron, Frédéric Normand, Anaëlle Dambreville, and Jean-Luc Regnard. "Soil water deficit decreases xylem conductance efficiency relative to leaf area and mass in the apple." Journal of Plant Hydraulics 1 (April 23, 2014): e003. http://dx.doi.org/10.20870/jph.2014.e003.
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It is generally postulated that at the tree scale a drought-related decrease in hydraulic conductance is balanced by a decrease of leaf area. We hypothesized that, at the individual leaf scale, drought affects the allometry between leaf area or mass and hydraulics, leading to a non-linear relationships between these traits. The study was conducted on well-watered and on water-stressed shoots of several apple genotypes covering an extended range of leaf area. Working on dried leaves, we measured leaf lamina area and mass and analyzed their relationships with the maximal xylem hydraulic conductance of the water pathway through the parent shoot and the petiole connected to the leaf lamina. Drought decreased leaf area and mass in absolute values. It also changes the allometric relationships between these two variables: for a same decrease of leaf dry mass the water-stressed shoot had a lower decrease of leaf dry area than the well-watered shoot. Our study also showed that drought affected the stem-to-petiole hydraulics with a higher hydraulic efficiency in the well-watered shoot compared to the water-stressed shoot. We discuss that, compared to the well-watered condition, drought not only decreased leaf size, but also reduced xylem efficiency through the stem-to-petiole pathway with regard to the leaf area and mass supplied.
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Wang, Yong-Qiang, Ming-Yuan Ni, Wen-Hao Zeng, Dong-Liu Huang, Wei Xiang, Peng-Cheng He, Qing Ye, Kun-Fang Cao, and Shi-Dan Zhu. "Co-ordination between leaf biomechanical resistance and hydraulic safety across 30 sub-tropical woody species." Annals of Botany 128, no. 2 (April 30, 2021): 183–91. http://dx.doi.org/10.1093/aob/mcab055.
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Abstract Background and Aims Leaf biomechanical resistance protects leaves from biotic and abiotic damage. Previous studies have revealed that enhancing leaf biomechanical resistance is costly for plant species and leads to an increase in leaf drought tolerance. We thus predicted that there is a functional correlation between leaf hydraulic safety and biomechanical characteristics. Methods We measured leaf morphological and anatomical traits, pressure–volume parameters, maximum leaf hydraulic conductance (Kleaf-max), leaf water potential at 50 % loss of hydraulic conductance (P50leaf), leaf hydraulic safety margin (SMleaf), and leaf force to tear (Ft) and punch (Fp) of 30 co-occurring woody species in a sub-tropical evergreen broadleaved forest. Linear regression analysis was performed to examine the relationships between biomechanical resistance and other leaf hydraulic traits. Key Results We found that higher Ft and Fp values were significantly associated with a lower (more negative) P50leaf and a larger SMleaf, thereby confirming the correlation between leaf biomechanical resistance and hydraulic safety. However, leaf biomechanical resistance showed no correlation with Kleaf-max, although it was significantly and negatively correlated with leaf outside-xylem hydraulic conductance. In addition, we also found that there was a significant correlation between biomechanical resistance and the modulus of elasticity by excluding an outlier. Conclusions The findings of this study reveal leaf biomechanical–hydraulic safety correlation in sub-tropical woody species.
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Bonan, G. B., M. Williams, R. A. Fisher, and K. W. Oleson. "Modeling stomatal conductance in the Earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum." Geoscientific Model Development Discussions 7, no. 3 (May 7, 2014): 3085–159. http://dx.doi.org/10.5194/gmdd-7-3085-2014.
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Abstract. The empirical Ball–Berry stomatal conductance model is commonly used in Earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must both be empirically parameterized. We evaluated the Ball–Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil–plant–atmosphere continuum (SPA) to numerically optimize photosynthetic carbon gain per unit water loss while preventing leaf water potential dropping below a critical minimum level. We evaluated two alternative optimization algorithms: intrinsic water-use efficiency (Δ An/Δ gs, the marginal carbon gain of stomatal opening) and water-use efficiency (Δ An/Δ El, the marginal carbon gain of water loss). We implemented the stomatal models in a multi-layer plant canopy model, to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using: (1) leaf analyses; (2) canopy net radiation, sensible heat flux, latent heat flux, and gross primary production at six AmeriFlux sites spanning 51 site–years; and (3) parameter sensitivity analyses. Without soil moisture stress, the performance of the SPA stomatal conductance model was generally comparable to or somewhat better than the Ball–Berry model in flux tower simulations, but was significantly better than the Ball–Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from the physiological theory linking leaf water-use efficiency and water flow to and from the leaf along the soil-to-leaf pathway rather than being imposed a priori, as in the Ball–Berry model. Similar functional dependence of gs on Ds emerged from the water-use efficiency optimization. Sensitivity analyses showed that two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal conductance model. The critical stomatal efficiency for optimization (ι) was estimated from leaf trait datasets and is related to the slope parameter (g1) of the Ball–Berry model. The optimized parameter value was consistent with this estimate. Optimized root hydraulic conductivity was consistent with estimates from literature surveys. The two central concepts embodied in the stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.
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Sharipova, Guzel, Ruslan Ivanov, Dmitriy Veselov, Guzel Akhiyarova, Oksana Seldimirova, Ilshat Galin, Wieland Fricke, Lidiya Vysotskaya, and Guzel Kudoyarova. "Effect of Salinity on Stomatal Conductance, Leaf Hydraulic Conductance, HvPIP2 Aquaporin, and Abscisic Acid Abundance in Barley Leaf Cells." International Journal of Molecular Sciences 23, no. 22 (November 18, 2022): 14282. http://dx.doi.org/10.3390/ijms232214282.
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The stomatal closure of salt-stressed plants reduces transpiration bringing about the maintenance of plant tissue hydration. The aim of this work was to test for any involvement of aquaporins (AQPs) in stomatal closure under salinity. The changes in the level of aquaporins in the cells were detected with the help of an immunohistochemical technique using antibodies against HvPIP2;2. In parallel, leaf sections were stained for abscisic acid (ABA). The effects of salinity were compared to those of exogenously applied ABA on leaf HvPIP2;2 levels and the stomatal and leaf hydraulic conductance of barley plants. Salinity reduced the abundance of HvPIP2;2 in the cells of the mestome sheath due to it being the more likely hydraulic barrier due to the deposition of lignin, accompanied by a decline in the hydraulic conductivity, transpiration, and ABA accumulation. The effects of exogenous ABA differed from those of salinity. This hormone decreased transpiration but increased the shoot hydraulic conductivity and PIP2;2 abundance. The difference in the action of the exogenous hormone and salinity may be related to the difference in the ABA distribution between leaf cells, with the hormone accumulating mainly in the mesophyll of salt-stressed plants and in the cells of the bundle sheaths of ABA-treated plants. The obtained results suggest the following succession of events: salinity decreases water flow into the shoots due to the decreased abundance of PIP2;2 and hydraulic conductance, while the decline in leaf hydration leads to the production of ABA in the leaves and stomatal closure.
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Chen, Yapeng, Xingming Hao, and Chenggang Zhu. "Comparative Apparent Hydraulic Conductance, Leaf Gas Exchange, and Water Resource Partitioning of Populus euphratica Trees and Saplings." Forests 13, no. 12 (November 24, 2022): 1982. http://dx.doi.org/10.3390/f13121982.
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Water acquisition via the root system of woody species is a key factor governing plant physiology. In order to compare the impact of water acquisition on the hydraulic and photosynthetic characteristics of different-sized Populus euphratic, which is a desert riparian tree species, we quantified leaf hydraulic conductance (KL), stomatal conductance (gs), net photosynthetic rate (PN), predawn and midday leaf water potential (Ψ), and the stem δ18O of the saplings and mature trees. The results showed that the saplings had a lower predawn leaf water potential (Ψpd) and soil-to-leaf water potential gradient (ΔΨ) and a higher KL than the mature trees but had a similar gs and PN to the mature trees. In arid zones, probably due to root limitation, the saplings were more likely to use unreliable topsoil water (<80 cm), whereas the mature trees typically uptake reliable deep soil water (>80 cm) and groundwater due to having deeper root systems. The unreliability of the water supply might make saplings hold a higher hydraulic conductance to ensure that the water is transported efficiently to the leaves and to satisfy their transpiration need. In contrast, the mature trees, which uptake the more reliable deeper water resources, had a relatively low leaf-specific hydraulic conductance because of the increased path length versus the saplings. However, adult trees can maintain stomatal conductance by upregulating ΔΨ, thereby facilitating their ability to maintain a carbon assimilation rate similar to that of the saplings. This regulating behavior benefits mature trees’ net carbon gain, but it comes at the expense of an increased risk of hydraulic failure. These results imply that the top priority for saplings should be to maintain hydraulic system functioning, whereas, for mature trees, the priority is to assure stable net carbon gain for their growth.
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Raimondo, Fabio, Francesco Raudino, Santa Olga Cacciola, Sebastiano Salleo, and Maria Assunta Lo Gullo. "Impairment of leaf hydraulics in young plants of Citrus aurantium (sour orange) infected by Phoma tracheiphila." Functional Plant Biology 34, no. 8 (2007): 720. http://dx.doi.org/10.1071/fp07065.
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Phoma trachephila (Petri) Kantschaveli et Gikachvili causes dieback of several Citrus species. The impact of this fungus on leaf hydraulics was studied in Citrus aurantium L. (sour orange) with the aim of identifying the primary mechanism of damage to leaves. Leaves inoculated with a conidial suspension were measured for conductance to water vapor (gL) and specific hydraulic conductance (Kleaf) every 3 days after inoculation. The earliest symptom of infection consisted of vein chlorosis. Functional vein density (FVD) was monitored and microscopic observations were made of major vein conduits. Impairment of vein hydraulics started 25 days after inoculation with a losses of Kleaf of 40% and gL of ~60%. Most minor veins within chlorotic areas were no longer functioning and some conduits of the major veins showed digested interconduit pits leading to vein cavitation. The close Kleaf–FVD relationship revealed that vein impairment caused drop of Kleaf and, consequently, of gL at chlorotic areas. Leaf infection was focused to veins that were first forced to embolise and then invaded by fungal hyphae. The vein embolism due to the Phoma amplifies the native dominant hydraulic resistance of leaf veins, and leads ultimately to early shedding of infected leaves.
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Liu, Xiaorong, Hui Liu, Sean M. Gleason, Guillermo Goldstein, Shidan Zhu, Pengcheng He, Hao Hou, Ronghua Li, and Qing Ye. "Water transport from stem to stomata: the coordination of hydraulic and gas exchange traits across 33 subtropical woody species." Tree Physiology 39, no. 10 (July 17, 2019): 1665–74. http://dx.doi.org/10.1093/treephys/tpz076.
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Abstract Coordination between sapwood-specific hydraulic conductivity (Ks) and stomatal conductance (gs) has been identified in previous studies; however, coordination between leaf hydraulic conductance (Kleaf) and gs, as well as between Kleaf and Ks is not always consistent. This suggests that there is a need to improve our understanding of the coordination among hydraulic and gas exchange traits. In this study, hydraulic traits (e.g., Ks and Kleaf) and gas exchange traits, including gs, transpiration (E) and net CO2 assimilation (Aarea), were measured across 33 co-occurring subtropical woody species. Kleaf was divided into two components: leaf hydraulic conductance inside the xylem (Kleaf-x) and outside the xylem (Kleaf-ox). We found that both Kleaf-x and Kleaf-ox were coordinated with gs and E, but the correlations between Kleaf-ox and gs (or E) were substantially weaker, and that Ks was coordinated with Kleaf-x, but not with Kleaf-ox. In addition, we found that Ks, Kleaf-x and Kleaf-ox together explained 63% of the variation in gs and 42% of the variation in Aarea across species, with Ks contributing the largest proportion of explanatory power, whereas Kleaf-ox contributed the least explanatory power. Our results demonstrate that the coordination between leaf water transport and gas exchange, as well as the hydraulic linkage between leaf and stem, were weakened by Kleaf-ox. This highlights the possibility that water transport efficiencies of stem and leaf xylem, rather than that of leaf tissues outside the xylem, are important determinants of stomatal conductance and photosynthetic capacity across species.
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Esin Koksal, Suheyla, Gokhan Gunduz, and Menderes Kalkat. "Installation of Test Setup and Measurement Procedures in Fir Wood Hydraulic Conductance Measurement." Drvna industrija 72, no. 2 (May 7, 2021): 111–19. http://dx.doi.org/10.5552/drvind.2021.1945.
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For a hydraulic conductor, through which liquid flows, hydraulic conductance (K, ml·s-1·MPa-1) is defined as the ratio of pressure difference at the inlet and outlet to the fluid amount passing through the hydraulic conductor in a unit time period. This property is one of the key functions of the wood, and is obtained by the flow rate (F – Flow, ml·s-1) along the wood sample divided by the pressure difference driving the flow (DP, MPa). This study aimed to establish a test setup to determine the hydraulic conductance values of Uludağ Fir (Abies bornmulleriana Mattf.). A test setup was established to measure the amount of water that flows in samples and pressure difference in characterized capillary tubes. In addition, calibration of the test apparatus is explained in detail. Fir wood samples taken from Yedigoller, which is affiliated to Kale Operation Chieftainship and Bolu Forest Regional Directorate, of 4 mm in diameter and 3 cm in length were prepared and hydraulic conductance measurements were performed, and the results are presented in this article. The installed test setup was used to obtain the following information about trees: operation of the hydraulic conduction system, the amount of needed water, seasonal effects and stress-related changes.
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Xiong, Dongliang, Jaume Flexas, Tingting Yu, Shaobing Peng, and Jianliang Huang. "Leaf anatomy mediates coordination of leaf hydraulic conductance and mesophyll conductance to CO2inOryza." New Phytologist 213, no. 2 (September 22, 2016): 572–83. http://dx.doi.org/10.1111/nph.14186.
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Hubbard, R. M., M. G. Ryan, V. Stiller, and J. S. Sperry. "Stomatal conductance and photosynthesis vary linearly with plant hydraulic conductance in ponderosa pine." Plant, Cell & Environment 24, no. 1 (January 2001): 113–21. http://dx.doi.org/10.1046/j.1365-3040.2001.00660.x.
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Lloyd, J., T. Trochoulias, and R. Ensbey. "Stomatal Responses and Whole-Tree Hydraulic Conductivity of Orchard Macadamia integrifolia Under Irrigated and Non-Irrigated Conditions." Functional Plant Biology 18, no. 6 (1991): 661. http://dx.doi.org/10.1071/pp9910661.
Full textAbstract:
Diurnal patterns of stomatal conductance (gs) and leaf water potential (Ψ1) were determined for leaves on irrigated and non-irrigated 5-year-old Macadamia integrifolia trees over a 4-month period from September to December 1989. An empirical model for stomatal conductance was developed for irrigated trees using relationships to photon irradiance (I), leaf temperature (T1) and vapour mole fraction difference (D). This model accounted for 69% of the variance in gs, and was not improved by the inclusion of Ψ1 as an independent variable. Fitted parameters led to the effective prediction of gs for untried combinations of environmental variables. By using a simple expression to link leaf water potential to transpiration rate (E), the model was extended to prediction of Ψ1 from measurements of I, T1 and D. Stornatal conductances were significantly lower on non-irrigated trees after a 2-month dry period. Lower stornatal conductances were not accompanied by more negative Ψ1 indicating that soil rather than leaf water status may control gs in macadamia trees under non-irrigated conditions.