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1.
Stem water storage capacity and efficiency of water transport: their functional significance in a Hawaiian dry forest 总被引:17,自引:3,他引:14
We investigated the contribution of internal water storage and efficiency of water transport to the maintenance of water balance in six evergreen tree species in a Hawaiian dry forest. Wood‐saturated water content, a surrogate for relative water storage capacity, ranged from 70 to 105%, and was inversely related to its morphological correlate, wood density, which ranged between 0·51 and 0·65 g cm?3. Leaf‐specific conductivity (kL) measured in stem segments from terminal branches ranged from 3 to 18 mmol m?1 s?1 MPa?1, and whole‐plant hydraulic efficiency calculated as stomatal conductance (g) divided by the difference between predawn and midday leaf water potential (ΨL), ranged from 70 to 150 mmol m?2 s?1 MPa?1. Hydraulic efficiency was positively correlated with kL (r2 = 0·86). Minimum annual ΨL ranged from ? 1·5 to ? 4·1 MPa among the six species. Seasonal and diurnal variation in ΨL were associated with differences among species in wood‐saturated water content, wood density and kL. The species with higher wood‐saturated water content were more efficient in terms of long‐distance water transport, exhibited smaller diurnal variation in ΨL and higher maximum photosynthetic rates. Smaller diurnal variation in ΨL in species with higher wood‐saturated water content, kL and hydraulic efficiency was not associated with stomatal restriction of transpiration when soil water deficit was moderate, but avoidance of low minimum seasonal ΨL in these species was associated with a substantial seasonal decline in g. Low seasonal minimum ΨL in species with low kL, hydraulic efficiency, and wood‐saturated water content was associated with higher leaf solute content and corresponding lower leaf turgor loss point. Despite the species‐specific differences in leaf water relations characteristics, all six evergreen tree species shared a common functional relationship defined primarily by kL and stem water storage capacity. 相似文献
2.
John S. Veres 《American journal of botany》1990,77(12):1610-1625
Hydraulic conductivities of stems, stipes, and elongate leaf stipes were determined for greenhouse-grown Blechnum (B. fraxineum, B. fragile, B. buchtienii, B. sprucei) and Salpichlaena (S. volubilis) plants collected in tropical rain forests of Costa Rica. Organ conductivity was examined in relation to morphology and tracheid characteristics in order to gain an understanding of factors influencing water flow. Hydraulic conductivity of plant organs was determined by measurement of transpiration rates, leaf areas, and water potential gradients. Erect stemmed species develop larger whole plant water potential gradients than elongate stemmed species for a similar transpiration rate. Elongate leaves develop even smaller water potential gradients for a given transpiration rate. Stems have larger hydraulic conductivities but smaller leaf-specific conductivities (LSCs) than stipes. Small conductivities and small LSCs are associated with short, erect stems. Elongate structures have large conductivities and large LSCs. Of the tracheid characteristics examined, the most important characteristics determining the magnitude of organ hydraulic conductivity are diameter, pit aperture area between tracheids, taper length, and cell length. Large conductivities of S. volubilis climbing leaf stipes are associated with very large-diameter tracheids (some > 200 μm), large tracheid number, exceptionally long tracheids (some > 4 cm), large pit aperture area between tracheids, short tracheid taper, and smooth tracheid lumen walls. Hagen-Poiseuille estimates of hydraulic conductivity range from 1.1 to 3.3 times the measured values. Conductivity of stipes is highly correlated with leaf area supplied by stipes. Conductivities of stems and elongate leaf stipes also correlate with leaf area supplied by these structures. Estimated hydraulic conductivities of field-grown Blechnum and Salpichlaena demonstrate that larger conductivities are associated with larger plants. This study contributes toward our knowledge of fern water relations and extends previous growth form/hydraulic architecture characterizations by providing a more comprehensive comparison of closely related species. In addition, this study provides evidence for the relative importance of tracheid characteristics in determining the magnitude of organ hydraulic conductivity. 相似文献
3.
Impacts of long‐term precipitation manipulation on hydraulic architecture and xylem anatomy of piñon and juniper in Southwest USA
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P. J. Hudson J. M. Limousin D. J. Krofcheck A. L. Boutz R. E. Pangle N. Gehres N. G. McDowell W. T. Pockman 《Plant, cell & environment》2018,41(2):421-435
Hydraulic architecture imposes a fundamental control on water transport, underpinning plant productivity, and survival. The extent to which hydraulic architecture of mature trees acclimates to chronic drought is poorly understood, limiting accuracy in predictions of forest responses to future droughts. We measured seasonal shoot hydraulic performance for multiple years to assess xylem acclimation in mature piñon (Pinus edulis ) and juniper (Juniperus monosperma ) after 3+ years of precipitation manipulation. Our treatments consisted of water addition (+20% ambient precipitation), partial precipitation‐exclusion (?45% ambient precipitation), and exclusion‐structure control. Supplemental watering elevated leaf water potential, sapwood‐area specific hydraulic conductivity, and leaf‐area specific hydraulic conductivity relative to precipitation exclusion. Shifts in allocation of leaf area to sapwood area enhanced differences between irrigated and droughted K L in piñon but not juniper. Piñon and juniper achieved similar K L under ambient conditions, but juniper matched or outperformed piñon in all physiological measurements under both increased and decreased precipitation treatments. Embolism vulnerability and xylem anatomy were unaffected by treatments in either species. Absence of significant acclimation combined with inferior performance for both hydraulic transport and safety suggests piñon has greater risk of local extirpation if aridity increases as predicted in the southwestern USA. 相似文献
4.
Shunsuke Adachi Yukiko Tsuru Motohiko Kondo Toshio Yamamoto Yumiko Arai-Sanoh Tsuyu Ando Taiichiro Ookawa Masahiro Yano Tadashi Hirasawa 《Annals of botany》2010,106(5):803-811
Background and Aims
The rate of photosynthesis in paddy rice often decreases at noon on sunny days because of water stress, even under submerged conditions. Maintenance of higher rates of photosynthesis during the day might improve both yield and dry matter production in paddy rice. A high-yielding indica variety, ‘Habataki’, maintains a high rate of leaf photosynthesis during the daytime because of the higher hydraulic conductance from roots to leaves than in the standard japonica variety ‘Sasanishiki’. This research was conducted to characterize the trait responsible for the higher hydraulic conductance in ‘Habataki’ and identified a chromosome region for the high hydraulic conductance.Methods
Hydraulic conductance to passive water transport and to osmotic water transport was determined for plants under intense transpiration and for plants without transpiration, respectively. The varietal difference in hydraulic conductance was examined with respect to root surface area and hydraulic conductivity (hydraulic conductance per root surface area, Lp). To identify the chromosome region responsible for higher hydraulic conductance, chromosome segment substitution lines (CSSLs) derived from a cross between ‘Sasanishiki’ and ‘Habataki’ were used.Key Results
The significantly higher hydraulic conductance resulted from the larger root surface area not from Lp in ‘Habataki’. A chromosome region associated with the elevated hydraulic conductance was detected between RM3916 and RM2431 on the long arm of chromosome 4. The CSSL, in which this region was substituted with the ‘Habataki’ chromosome segment in the ‘Sasanishiki’ background, had a larger root mass than ‘Sasanishiki’.Conclusions
The trait for increasing plant hydraulic conductance and, therefore, maintaining the higher rate of leaf photosynthesis under the conditions of intense transpiration in ‘Habataki’ was identified, and it was estimated that there is at least one chromosome region for the trait located on chromosome 4. 相似文献5.
Independence of stem and leaf hydraulic traits in six Euphorbiaceae tree species with contrasting leaf phenology 总被引:1,自引:0,他引:1
Hydraulic traits and hydraulic-related structural properties were examined in three deciduous (Hevea brasiliensis, Macaranga denticulate, and Bischofia javanica) and three evergreen (Drypetes indica, Aleurites moluccana, and Codiaeum variegatum) Euphorbiaceae tree species from a seasonally tropical forest in south-western China. Xylem water potential at 50% loss of
stem hydraulic conductivity (P50stem) was more negative in the evergreen tree, but leaf water potential at 50% loss of leaf hydraulic conductivity (P50leaf) did not function as P50stem did. Furthermore, P50stem was more negative than P50leaf in the evergreen tree; contrarily, this pattern was not observed in the deciduous tree. Leaf hydraulic conductivity overlapped
considerably, but stem hydraulic conductivity diverged between the evergreen and deciduous tree. Correspondingly, structural
properties of leaves overlapped substantially; however, structural properties of stem diverged markedly. Consequently, leaf
and stem hydraulic traits were closely correlated with leaf and stem structural properties, respectively. Additionally, stem
hydraulic efficiency was significantly correlated with stem hydraulic resistance to embolism; nevertheless, such a hydraulic
pattern was not found in leaf hydraulics. Thus, these results suggest: (1) that the evergreen and deciduous tree mainly diverge
in stem hydraulics, but not in leaf hydraulics, (2) that regardless of leaf or stem, their hydraulic traits result primarily
from structural properties, and not from leaf phenology, (3) that leaves are more vulnerable to drought-induced embolism than
stem in the evergreen tree, but not always in the deciduous tree and (4) that there exists a trade-off between hydraulic efficiency
and safety for stem hydraulics, but not for leaf hydraulics. 相似文献
6.
Plant water relations of nine woody species were studied in a lower montane rain forest in Panama. These data provide a partial
test of the hypothesis that hydraulic architecture of lower montane species might limit transpiration and thus leaf size or
nutrient transport (as suggested by J. Cavelier and E. G. Leigh, respectively). Diurnal variation in leaf transpiration was
closely correlated with changes in net radiation. Peak transpiration rates (7 × 10–5 kg s–1 m–2) were as high as peak transpiration rates from tropical lowland forests but mean daily water use [0.39 ± 0.08 (SEM) kg m–2 day–1] were mostly lower than comparable data from tropical lowland forests. Thus transpiration rates are sufficiently high for
sufficiently long periods to make it unlikely that nutrient transport is limited by transpiration. Another objective of this
study was a comparison of two different methods to measure hydraulic conductance (Kh = flow rate per unit pressure gradient) and leaf specific conductance of stem segments (KL = Kh/leaf area distal to the segment). The results obtained with the traditional conductivity apparatus and the high pressure
flow meter method, yielded similar results in six out of seven cases.
Received: 20 March / Accepted: 21 October 1997 相似文献
7.
Patricia A. Iogna Sandra J. Bucci Fabián G. Scholz Guillermo Goldstein 《Oecologia》2013,173(3):675-687
Phenotypic plasticity in morphophysiological leaf traits in response to wind was studied in two dominant shrub species of the Patagonian steppe, used as model systems for understanding effects of high wind speed on leaf water relations and hydraulic properties of small woody plants. Morpho-anatomical traits, hydraulic conductance and conductivity and water relations in leaves of wind-exposed and protected crown sides were examined during the summer with nearly continuous high winds. Although exposed sides of the crowns were subjected to higher wind speeds and air saturation deficits than the protected sides, leaves throughout the crown had similar minimum leaf water potential (ΨL). The two species were able to maintain homeostasis in minimum ΨL using different physiological mechanisms. Berberis microphylla avoided a decrease in the minimum ΨL in the exposed side of the crown by reducing water loss by stomatal control, loss of cell turgor and low epidermal conductance. Colliguaja integerrima increased leaf water transport efficiency to maintain transpiration rates without increasing the driving force for water loss in the wind-exposed crown side. Leaf physiological changes within the crown help to prevent the decrease of minimum ΨL and thus contribute to the maintenance of homeostasis, assuring the hydraulic integrity of the plant under unfavorable conditions. The responses of leaf traits that contribute to mechanical resistance (leaf mass per area and thickness) differed from those of large physiological traits by exhibiting low phenotypic plasticity. The results of this study help us to understand the unique properties of shrubs which have different hydraulic architecture compared to trees. 相似文献
8.
Hydraulic architecture of deciduous and evergreen dry rainforest tree species from north-eastern Australia 总被引:6,自引:0,他引:6
Brendan Choat Marilyn C. Ball Jon G. Luly Joseph A. M. Holtum 《Trees - Structure and Function》2005,19(3):305-311
Hydraulic conductivity and xylem anatomy were examined in stems of two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret., and two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., from a seasonally dry rainforest in north Queensland, Australia. The deciduous species possessed hydraulic architecture typical of drought-sensitive plants, i.e. low wood density, wider xylem vessels, higher maximal rates of sapwood specific hydraulic conductivity (Ks) and high vulnerability to drought-induced embolism. In contrast, the evergreen species had lower rates of Kh and leaf specific conductivity (KL) but were less susceptible to embolism. The evergreen species experienced leaf water potentials <–4.0 MPa during the dry season, while the deciduous species shed their leaves before leaf water potentials declined below –2.0 MPa. Thus, the hydraulic architecture of the evergreens allows them to withstand the greater xylem pressure gradients required to maintain water transport to the canopy during the dry season. Our results are consistent with observations made in neotropical dry forests and demonstrate that drought-deciduous species with low wood density and high water storage capacity are likely to be more hydraulically efficient, but more vulnerable to embolism, than coexisting evergreens. 相似文献
9.
Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems 总被引:1,自引:0,他引:1
Hao GY Hoffmann WA Scholz FG Bucci SJ Meinzer FC Franco AC Cao KF Goldstein G 《Oecologia》2008,155(3):405-415
Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed
of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there
were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats
were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood
area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species.
However, maximum leaf hydraulic conductance (K
leaf) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also
higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves
were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K
leaf values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An
electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water
potentials to drop from predawn values to values corresponding to 50% loss of K
leaf or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The
results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their
ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted
for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in
savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits. 相似文献
10.
Stem hydraulic capacitance decreases with drought stress: implications for modelling tree hydraulics in the Mediterranean oak Quercus ilex
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Roberto L Salomón Jean‐Marc Limousin Jean‐Marc Ourcival Jesús Rodríguez‐Calcerrada Kathy Steppe 《Plant, cell & environment》2017,40(8):1379-1391
Hydraulic modelling is a primary tool to predict plant performance in future drier scenarios. However, as most tree models are validated under non‐stress conditions, they may fail when water becomes limiting. To simulate tree hydraulic functioning under moist and dry conditions, the current version of a water flow and storage mechanistic model was further developed by implementing equations that describe variation in xylem hydraulic resistance (RX) and stem hydraulic capacitance (CS) with predawn water potential (ΨPD). The model was applied in a Mediterranean forest experiencing intense summer drought, where six Quercus ilex trees were instrumented to monitor stem diameter variations and sap flow, concurrently with measurements of predawn and midday leaf water potential. Best model performance was observed when CS was allowed to decrease with decreasing ΨPD. Hydraulic capacitance decreased from 62 to 25 kg m?3 MPa?1 across the growing season. In parallel, tree transpiration decreased to a greater extent than the capacitive water release and the contribution of stored water to transpiration increased from 2.0 to 5.1%. Our results demonstrate the importance of stored water and seasonality in CS for tree hydraulic functioning, and they suggest that CS should be considered to predict the drought response of trees with models. 相似文献
11.
SANDRA J. BUCCI FABIAN G. SCHOLZ MARIA LAURA PESCHIUTTA NADIA S. ARIAS FREDERICK C. MEINZER GUILLERMO GOLDSTEIN 《Plant, cell & environment》2013,36(12):2163-2174
Hydraulic architecture was studied in shrub species differing in rooting depth in a cold desert in Southern Argentina. All species exhibited strong hydraulic segmentation between leaves, stems and roots with leaves being the most vulnerable part of the hydraulic pathway. Two types of safety margins describing the degree of conservation of the hydraulic integrity were used: the difference between minimum stem or leaf water potential (Ψ) and the Ψ at which stem or leaf hydraulic function was reduced by 50% (Ψ – Ψ50), and the difference between leaf and stem Ψ50. Leaf Ψ50 – stem Ψ50 increased with decreasing rooting depth. Large diurnal decreases in root‐specific hydraulic conductivity suggested high root vulnerability to embolism across all species. Although stem Ψ50 became more negative with decreasing species‐specific Ψsoil and minimum stem Ψ, leaf Ψ50 was independent of Ψ and minimum leaf Ψ. Species with embolism‐resistant stems also had higher maximum stem hydraulic conductivity. Safety margins for stems were >2.1 MPa, whereas those for leaves were negative or only slightly positive. Leaves acted as safety valves to protect the integrity of the upstream hydraulic pathway, whereas embolism in lateral roots may help to decouple portions of the plant from the impact of drier soil layers. 相似文献
12.
Photosynthetic pathway alters xylem structure and hydraulic function in herbaceous plants 总被引:2,自引:0,他引:2
Plants using the C4 photosynthetic pathway have greater water use efficiency (WUE) than C3 plants of similar ecological function. Consequently, for equivalent rates of photosynthesis in identical climates, C4 plants do not need to acquire and transport as much water as C3 species. Because the structure of xylem tissue reflects hydraulic demand by the leaf canopy, a reduction in water transport requirements due to C4 photosynthesis should affect the evolution of xylem characteristics in C4 plants. In a comparison of stem hydraulic conductivity and vascular anatomy between eight C3 and eight C4 herbaceous species, C4 plants had lower hydraulic conductivity per unit leaf area (KL) than C3 species of similar life form. When averages from all the species were pooled together, the mean KL for the C4 species was 1.60 × 10?4 kg m?1 s?1 MPa?1, which was only one‐third of the mean KL of 4.65 × 10?4 kg m?1 s?1 MPa?1 determined for the C3 species. The differences in KL between C3 and C4 species corresponded to the two‐ to three‐fold differences in WUE observed between C3 and C4 plants. In the C4 species from arid regions, the difference in KL was associated with a lower hydraulic conductivity per xylem area, smaller and shorter vessels, and less vulnerable xylem to cavitation, indicating the C4 species had evolved safer xylem than the C3 species. In the plants from resource‐rich areas, such as the C4 weed Amaranthus retroflexus, hydraulic conductivity per xylem area and xylem anatomy were similar to that of the C3 species, but the C4 plants had greater leaf area per xylem area. The results indicate the WUE advantage of C4 photosynthesis allows for greater flexibility in hydraulic design and potential fitness. In resource‐rich environments in which competition is high, an existing hydraulic design can support greater leaf area, allowing for higher carbon gain, growth and competitive potential. In arid regions, C4 plants evolved safer xylem, which can increase survival and performance during drought events. 相似文献
13.
Hydraulic adjustments in aspen (Populus tremuloides) seedlings following defoliation involve root and leaf aquaporins 总被引:1,自引:0,他引:1
Juan Liu María A. Equiza Alfonso Navarro-Rodenas Seong H. Lee Janusz J. Zwiazek 《Planta》2014,240(3):553-564
Main conclusion
Changes in root and leaf hydraulic properties and stimulation of transpiration rates that were initially triggered by defoliation were accompanied by corresponding changes in leaf and root aquaporin expression. Aspen (Populus tremuloides) seedlings were subjected to defoliation treatments by removing 50, 75 % or all of the leaves. Root hydraulic conductivity (Lpr) was sharply reduced in plants defoliated for 1 day and 1 week. The decrease in L pr could not be prevented by stem girdling and it was accompanied in one-day-defoliated plants by a large decrease in the root expression of PIP1,2 aquaporin and an over twofold decrease in hydraulic conductivity of root cortical cells (L pc). Contrary to L pr and L pc, 50 and 75 % defoliation treatments profoundly increased leaf lamina conductance (K lam) after 1 day and this increase was similar in magnitude for both defoliation treatments. Transpiration rates (E) rapidly declined after the removal of 75 % of leaves. However, E increased by over twofold in defoliated plants after 1 day and the increases in E and K lam were accompanied by five- and tenfold increases in the leaf expression of PIP2;4 in 50 and 75 % defoliation treatments, respectively. Defoliation treatments also stimulated net photosynthesis after 1 day and 3 weeks, although the increase was not as high as E. Leaf water potentials remained relatively stable following defoliation with the exception of a small decrease 1 day after defoliation which suggests that root water transport did not initially keep pace with the increased transpirational water loss. The results demonstrate the importance of root and leaf hydraulic properties in plant responses to defoliation and point to the involvement of PIP aquaporins in the early events following the loss of leaves. 相似文献14.
《Journal of biological education》2012,46(3):137-141
We present a practical for university-level students aimed at measuring and comparing xylem hydraulic properties of co-existing plant species. After sampling branches of several woody species in the field, their main hydraulic properties were measured using a simple set-up. Hydraulic conductivity (Kh ) was calculated as the ratio between water flow through a plant segment and the pressure gradient driving the flow. The percent reduction in conductivity due to xylem embolism (i.e. air-filled conduits) was estimated by comparing Kh before and after flushing the measure segments to remove all native embolism. Raw hydraulic conductivity was standardised by cross-sectional wood area or supported leaf area to obtain more meaningful measures of conducting capacity. The results showed differences among study species, particularly between conifers and angiosperms. These differences are briefly discussed in terms of wood anatomy and the general biology of the species. Overall the practical provides a good opportunity for students to appreciate the main aspects of xylem water transport and the constraints it imposes on plant water relations. 相似文献
15.
Wheat plants (Triticum aestivum var. INTA x2018;Cinco Cerros’) were grown in pots with fine sand under a rain-out shelter to assess their response to a water
shortage spanning most of the growth cycle. Three watering treatments, based on different thresholds of plant-available water,
were started 8 weeks after sowing and maintained for 10 weeks. After allowing recovery from any short-term embolism, stem-segment
and root-system hydraulic conductances were then measured by standard low-pressure methods. Stress treatments reduced, as
compared to controls, tiller number (by 31% and 41% for moderate and intense drought, respectively), total plant biomass (by
21% and 52%) and total plant leaf area (43% and 68%). The capacity of stems to transport water was reduced only by the most
intense treatment (and then by no more than 50%), but root-system hydraulic conductance (k
R) was strongly reduced by both treatments (37% and 80%, respectively). The transport capacity of belowground structures decreased
not only on an absolute basis (k
R), but also per unit root mass (K
RS: 51% and 83%) and per unit of leaf area (K
RL: 23% and 73%). Simulation of maximum transpiration under different soil and plant water conditions indicate that these changes
in plant hydraulics had a significant impact on either transpiration at the leaf level or leaf water status for a given transpiration
rate. 相似文献
16.
Stem and leaf hydraulic properties are finely coordinated in three tropical rain forest tree species 总被引:2,自引:0,他引:2
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Markus Nolf Danielle Creek Remko Duursma Joseph Holtum Stefan Mayr Brendan Choat 《Plant, cell & environment》2015,38(12):2652-2661
Coordination of stem and leaf hydraulic traits allows terrestrial plants to maintain safe water status under limited water supply. Tropical rain forests, 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 rain forest tree species by analyses of hydraulic vulnerability [hydraulic methods and ultrasonic emission (UE) analysis], pressure‐volume relations and in situ pre‐dawn and midday water potentials (Ψ). 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 at ?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. 相似文献
17.
Hydraulic and photosynthetic co-ordination in seasonally dry tropical forest trees 总被引:25,自引:3,他引:22
In the present study the linkage between hydraulic, photosynthetic and phenological properties of tropical dry forest trees were investigated. Seasonal patterns of stem‐specific conductivity (KSP) described from 12 species, including deciduous, brevi‐deciduous and evergreen species, indicated that only evergreen species were consistent in their response to a dry‐to‐wet season transition. In contrast, KSP in deciduous and brevi‐deciduous species encompassed a range of responses, from an insignificant increase in KSP following rains in some species, to a nine‐fold increase in others. Amongst deciduous species, the minimum KSP during the dry season ranged from 6 to 56% of wet season KSP, indicating in the latter case that a significant portion of the xylem remained functional during the dry season. In all species and all seasons, leaf‐specific stem conductivity (KL) was strongly related to the photosynthetic capacity of the supported foliage, although leaf photosynthesis became saturated in species with high KL. The strength of this correlation was surprising given that much of the whole‐plant resistance appears to be in the leaves. Hydraulic capacity, defined as the product of KL and the soil–leaf water potential difference, was strongly correlated with the photosynthetic rate of foliage in the dry season, but only weakly correlated in the wet season. 相似文献
18.
Hydraulic lift among native plant species in the Mojave Desert 总被引:9,自引:1,他引:8
Hydraulic lift was investigated among native plants in the Mojave Desert using in situ thermocouple psychrometers. Night lighting
and day shading experiments were used to verify the phenomenon. Hydraulic lift was detected for all species examined: five
shrub species with different rooting depths and leaf phenologies and one perennial grass species. This study was the first
to document hydraulic lift for a CAM species, Yucca schidigera. The pattern of diel flux in soil water potential for the CAM
species was temporally opposite to that of C3 species: for the CAM plant, soil water potential increased in shallow soils during the day when the plant was not transpiring
and decreased at night when transpiration began. Because CAM plants transport water to shallow soils during the day when surrounding
C3 and C4 plants transpire, CAM species that hydraulically lift water may influence water relations of surrounding species to a greater
extent than hydraulically lifting C3 or C4 species. A strong, negative relationship between the percent sand in the study site soils at the 0.35 m soil depth and the
frequency that hydraulic lift was observed at that depth suggests that the occurrence of hydraulic lift is negatively influenced
by coarse-textured soils, perhaps due to less root–soil contact in sandy soils relative to finer-textured soils. Differences
in soil texture among study sites may explain, in part, differences in the frequency that hydraulic lift was detected among
these species. Further investigations are needed to elucidate species versus soil texture effects on hydraulic lift.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
Water resource partitioning,stem xylem hydraulic properties,and plant water use strategies in a seasonally dry riparian tropical rainforest 总被引:7,自引:0,他引:7
This study investigated seasonal variation in the origin of water used by plants in a riparian tropical rainforest community and explored linkages between plant water source, plant xylem hydraulic conductivity and response to the onset of dry conditions. The study focused on five co-dominant canopy species, comprising three tree species (Doryphora aromatica, Argyrodendron trifoliolatum, Castanospora alphandii) and two climbing palms (Calamus australis and Calamus caryotoides). Stable isotope ratios of oxygen in water (18O) from soil, groundwater, stream water and plant xylem measured in the wet season and the subsequent dry season revealed water resource partitioning between species in the dry season. Measurement of stem-area-specific hydraulic conductivity (KS) in the wet season and subsequent dry season showed a significant dry-season loss of KS in three of the five species (Castanospora alphandii, Calamus australis and C. caryotoides) and a decrease in mean KS for all species. This loss of hydraulic conductivity was positively correlated with the difference between wet-season and dry-season midday leaf water potentials and with leaf carbon isotope discrimination, indicating that plants that were less susceptible to loss of conductivity had greater control over transpiration rate and were more water-use efficient. 相似文献
20.
YONG‐JIANG ZHANG FREDERICK C. MEINZER JIN‐HUA QI GUILLERMO GOLDSTEIN KUN‐FANG CAO 《Plant, cell & environment》2013,36(1):149-158
Midday depressions in stomatal conductance (gs) and photosynthesis are common in plants. The aim of this study was to understand the hydraulic determinants of midday gs, the coordination between leaf and stem hydraulics and whether regulation of midday gs differed between deciduous and evergreen broadleaf tree species in a subtropical cloud forest of Southwest (SW) China. We investigated leaf and stem hydraulics, midday leaf and stem water potentials, as well as midday gs of co‐occurring deciduous and evergreen tree species. Midday gs was correlated positively with midday stem water potential across both groups of species, but not with midday leaf water potential. Species with higher stem hydraulic conductivity and greater daily reliance on stem hydraulic capacitance were able to maintain higher stem water potential and higher gs at midday. Deciduous species exhibited significantly higher stem hydraulic conductivity, greater reliance on stem capacitance, higher stem water potential and gs at midday than evergreen species. Our results suggest that midday gs is more associated with midday stem than with leaf water status, and that the functional significance of stomatal regulation in these broadleaf tree species is probably for preventing stem xylem dysfunction. 相似文献