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1.
The impact of xylem cavitation and embolism on leaf (K leaf) and stem (K stem) hydraulic conductance was measured in current-year shoots of Cercis siliquastrum L. (Judas tree) using the vacuum chamber technique. K stem decreased at leaf water potentials (ΨL) lower than ?1.0 MPa, while K leaf started to decrease only at ΨL 1.5 MPa. Leaf infiltration under vacuum with Phloxine B revealed that minor veins underwent extensive embolism and became non-functional at ΨL 1.5 MPa, thus indicating that leaf vein embolism was closely related to K leaf changes. Field measurements of leaf conductance to water vapour (g L) and ΨL showed that stomata closed when ΨL decreased below the ΨL threshold inducing loss of hydraulic conductance in the leaf. The partitioning of hydraulic resistances within shoots and leaves was measured using the high-pressure flow meter method. The ratio of leaf to shoot hydraulic resistance was about 0.8, suggesting that stem cavitation had a limited impact on whole shoot hydraulic conductance. We suggest that stomatal aperture may be regulated by the cavitation-induced reduction of hydraulic conductance of the soil-to-leaf water pathway which, in turn, strongly depends on the hydraulic architecture of the plant and, in particular, on leaf hydraulics. 相似文献
2.
The lignification of the leaf vein bundle sheath (BS) has been observed in many species and would reduce conductance from xylem to mesophyll. We hypothesized that lignification of the BS in lower‐order veins would provide benefits for water delivery through the vein hierarchy but that the lignification of higher‐order veins would limit transport capacity from xylem to mesophyll and leaf hydraulic conductance (Kleaf). We further hypothesized that BS lignification would mediate the relationship of Kleaf to vein length per area. We analysed the dependence of Kleaf, and its light response, on the lignification of the BS across vein orders for 11 angiosperm tree species. Eight of 11 species had lignin deposits in the BS of the midrib, and two species additionally only in their secondary veins, and for six species up to their minor veins. Species with lignification of minor veins had a lower hydraulic conductance of xylem and outside‐xylem pathways and lower Kleaf. Kleaf could be strongly predicted by vein length per area and highest lignified vein order (R2 = .69). The light‐response of Kleaf was statistically independent of BS lignification. The lignification of the BS is an important determinant of species variation in leaf and thus whole plant water transport. 相似文献
3.
Yael Grunwald Noa Wigoda Nir Sade Adi Yaaran Tanmayee Torne Sanbon Chaka Gosa Nava Moran Menachem Moshelion 《The Plant journal : for cell and molecular biology》2021,106(2):301-313
The leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSC proton pump, AHA2, we now test the hypothesis that it regulates the xylem sap pH and leaf radial water fluxes. We monitored the xylem sap pH in the veins of detached leaves of wild-type Arabidopsis, AHA mutants and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem sap pH and the leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf. Conversely, AHA2 knockdown, which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf, and elevating external pH to 7.5 decreased the BSCs Pf. All these showed a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance. 相似文献
4.
Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers 总被引:4,自引:0,他引:4
This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering to observe the recovery process. During both phases midday transpiration and leaf water potential (Ψleaf) were monitored. Stomatal responses to Ψleaf were established for each species and these relationships used to evaluate whether the recovery of gas exchange after drought was limited by postembolism hydraulic repair in leaves. Furthermore, the timing of gas-exchange recovery was used to determine the maximum survivable water stress for each species and this index compared with data for both leaf and stem vulnerability to water-stress-induced dysfunction measured for each species. Recovery of gas exchange after water stress took between 1 and >100 d and during this period all species showed strong 1:1 conformity to a combined hydraulic-stomatal limitation model (r2 = 0.70 across all plants). Gas-exchange recovery time showed two distinct phases, a rapid overnight recovery in plants stressed to <50% loss of leaf hydraulic conductance (Kleaf) and a highly Ψleaf-dependent phase in plants stressed to >50% loss of Kleaf. Maximum recoverable water stress (Ψmin) corresponded to a 95% loss of Kleaf. Thus, we conclude that xylem hydraulics represents a direct limit to the drought tolerance of these conifer species. 相似文献
5.
Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration1,2. Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (Ψleaf). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance3. Leaf hydraulic conductance (Kleaf = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. Kleaf is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, Kleaf responds strongly to the internal and external leaf environment3. Kleaf can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes4, and Kleaf declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation5-10. Because Kleaf can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity11-14.We present a simple method for simultaneous determination of Kleaf and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol • m-2 • s-1) is reached, gs is determined by dividing by vapor pressure deficit, and Kleaf by dividing by the water potential driving force determined using a pressure chamber (Kleaf= E /- Δψleaf, MPa)15.This method can be used to assess Kleaf responses to different irradiances and the vulnerability of Kleaf to dehydration14,16,17. 相似文献
6.
F. Raimondo P. Trifilò M. A. Lo Gullo R. Buffa A. Nardini S. Salleo 《Environmental and Experimental Botany》2009,66(2):249-256
The hydraulic architecture and water relations of two olive genotypes, ‘Leccino Dwarf’ (LD) and ‘Leccino Minerva’ (LM) growing at two irradiance levels i.e. full sunlight irradiance (HI) and 50% sunlight irradiance (LI) were studied. The two clones showed similar plant hydraulic conductances (Kplant) and similar conductance of roots and leaves (Kroot and Kleaf) when growing at equal irradiance levels. However, both Kplant and Kroot were significantly lower in LI plants than in HI ones. On the contrary, Kleaf was unaffected by the light regime. One-year-old twigs of LI plants produced longer xylem conduits but lower average diameter of conduits and less conduits per unit xylem cross-sectional area compared to HI plants. As a consequence total conductive cross-sectional area of twigs was computed to be about 16% smaller in LI individuals than in HI ones.The LM genotype resulted potentially more vulnerable to cavitation than the LD one, although shading did not influence this variable. Shading influenced root biomass negatively with stronger reduction in LM genotype than in LD one. Although transpiration rates were substantially lower in shaded than in HI plants minimum diurnal leaf water potential was about ?1.2 MPa for both clones regardless the irradiance regime. Our conclusion is that the hydraulic efficiency of both olive clones was adjusted to meet the evaporative demand imposed by the irradiance regime with consequently similar equal hydraulic sufficiency. 相似文献
7.
Déborah Corso Sylvain Delzon Laurent J. Lamarque Hervé Cochard José M. Torres-Ruiz Andrew King Timothy Brodribb 《Plant, cell & environment》2020,43(4):854-865
Identifying the drivers of stomatal closure and leaf damage during stress in grasses is a critical prerequisite for understanding crop resilience. Here, we investigated whether changes in stomatal conductance (gs) during dehydration were associated with changes in leaf hydraulic conductance (Kleaf), xylem cavitation, xylem collapse, and leaf cell turgor in wheat (Triticum aestivum). During soil dehydration, the decline of gs was concomitant with declining Kleaf under mild water stress. This early decline of leaf hydraulic conductance was not driven by cavitation, as the first cavitation events in leaf and stem were detected well after Kleaf had declined. Xylem vessel deformation could only account for <5% of the observed decline in leaf hydraulic conductance during dehydration. Thus, we concluded that changes in the hydraulic conductance of tissues outside the xylem were responsible for the majority of Kleaf decline during leaf dehydration in wheat. However, the contribution of leaf resistance to whole plant resistance was less than other tissues (<35% of whole plant resistance), and this proportion remained constant as plants dehydrated, indicating that Kleaf decline during water stress was not a major driver of stomatal closure. 相似文献
8.
Shatil-Cohen A Attia Z Moshelion M 《The Plant journal : for cell and molecular biology》2011,67(1):72-80
The hydraulic conductivity of the leaf vascular system (Kleaf) is dynamic and decreases rapidly under drought stress, possibly in response to the stress phytohormone ABA, which increases sharply in the xylem sap (ABAxyl) during periods of drought. Vascular bundle‐sheath cells (BSCs; a layer of parenchymatous cells tightly enwrapping the entire leaf vasculature) have been hypothesized to control Kleaf via the specific activity of BSC aquaporins (AQPs). We examined this hypothesis and provide evidence for drought‐induced ABAxyl diminishing BSC osmotic water permeability (Pf) via downregulated activity of their AQPs. ABA fed to the leaf via the xylem (petiole) both decreased Kleaf and led to stomatal closure, replicating the effect of drought. In contrast, smearing ABA on the leaf blade, while also closing stomata, did not decrease Kleaf within 2–3 h of application, demonstrating that Kleaf does not depend entirely on stomatal closure. GFP‐labeled BSCs showed decreased Pf in response to ‘drought’ and ABA treatment, and a reversible decrease with HgCl2 (an AQP blocker). These Pf responses, absent in mesophyll cells, suggest stress‐regulated AQP activity specific to BSCs, and imply a role for these cells in decreasing Kleaf via a reduction in Pf. Our results support the above hypothesis and highlight the BSCs as hitherto overlooked vasculature sensor compartments, extending throughout the leaf and functioning as ‘stress‐regulated valves’ converting vasculature chemical signals (possibly ABAxyl) into leaf hydraulic signals. 相似文献
9.
Diurnal patterns of hydraulic conductance of the leaf lamina (Kleaf) were monitored in a field‐grown tropical tree species in an attempt to ascertain whether the dynamics of stomatal conductance (gs) and CO2 uptake (Aleaf) were associated with short‐term changes in Kleaf. On days of high evaporative demand mid‐day depression of Kleaf to between 40 and 50% of pre‐dawn values was followed by a rapid recovery after 1500 h. Leaf water potential during the recovery stage was less than ?1 MPa implying a refilling mechanism, or that loss of Kleaf was not linked to cavitation. Laboratory measurement of the response of Kleaf to Ψleaf confirmed that leaves in the field were operating at water potentials within the depressed region of the leaf ‘vulnerability curve’. Diurnal courses of Kleaf and Ψleaf predicted from measured transpiration, xylem water potential and the Kleaf vulnerability function, yielded good agreement with observed trends in both leaf parameters. Close correlation between depression of Kleaf, gs and Aleaf suggests that xylem dysfunction in the leaf may lead to mid‐day depression of gas exchange in this species. 相似文献
10.
11.
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
12.
ALICIA POU HIPOLITO MEDRANO JAUME FLEXAS STEPHEN D. TYERMAN 《Plant, cell & environment》2013,36(4):828-843
We examined the role of aquaporins (AQPs) in regulating leaf hydraulic conductance (Kleaf) in Vitis vinifera L. (cv Chardonnay) by studying effects of AQP inhibitors, and AQP gene expression during water stress (WS) and recovery (REC). Kleaf was measured after 3 h of petiole perfusion with different solutions and to introduce inhibitors. The addition of 0.1 mm HgCl2 to 15 mm KCl reduced Kleaf compared with perfusion in 15 mM KNO3 or KCl, and these solutions were used for leaves from control, WS and REC plants. Perfusion for 3 h did not significantly alter stomatal conductance (gs) though expression of VvTIP1;1 was increased. WS decreased Kleaf by about 30% and was correlated with gs. The expression of VvTIP2;1 and VvPIP2;1 correlated with Kleaf, and VvTIP2;1 was highly correlated with gs. There was no association between the expression of particular AQPs during WS and REC and inhibition of Kleaf by HgCl2; however, HgCl2 treatment itself increased expression of VvPIP2;3 and decreased expression of VvPIP2;1 . Inhibition by HgCl2 of Kleaf only at early stages of WS and then after REC suggested that apoplasmic pathways become more important during WS. This was confirmed using fluorescent dyes confined to apoplasm or preferentially accumulated in symplasm. 相似文献
13.
Muhammad Adnan Tabassum Yuhui Ye Tingting Yu Guanglong Zhu Muhammad Shahid Rizwan Muhammad Atif Wahid Shaobing Peng Yong Li 《Acta Physiologiae Plantarum》2016,38(4):92
Higher plant hydraulic conductivity (K plant) is vital for plant growth, especially under PEG-induced water deficit stress (PEG-IWDS). Leaf venation architecture is a key determinant of leaf hydraulic conductivity (K leaf) and K leaf is a major component of K plant across different plant species. However, there is little information about (1) varietal difference in leaf vein development in cereal crops, such as rice plants; (2) the effects of PEG-IWDS on leaf vein development; (3) the coordination between leaf venation architecture and K plant as well as K leaf under PEG-IWDS. In the present study, widely cultivated eight rice cultivars were grown hydroponically under well-watered condition (WWC) and PEG-IWDS, simulated by adding 15 % (w/v) PEG6000. Leaf venation architecture, including total longitudinal leaf vein number, leaf vein numbers per unit width (LVNW), vein thickness and leaf mass per area, as well as K plant and K leaf were measured to address above-mentioned questions. The results showed that leaf venation architecture exhibited significant varietal differences and PEG-IWDS significantly increased LVNW while decreased vein thickness. PEG-IWDS suppressed both K plant and K leaf but the decrease was much higher in K plant than K leaf. There was a significant and positive correlation observed between LVNW and K leaf under both WWC and PEG-IWDS but the correlation between LVNW and K plant was only significant under WWC. K leaf was significantly and positively correlated with K plant under WWC but not under PEG-IWDS. It is concluded that K leaf is a major determinant for K plant under WWC but not under PEG-IWDS; therefore, breeding or selecting rice cultivars with high LVNW can improve shoot water supplement under WWC but not under PEG-IWDS condition. 相似文献
14.
Leaf hydraulic conductance and the vulnerability to water deficits have profound effects on plant distribution and mortality. In this study, we compiled a leaf hydraulic trait dataset with 311 species-at-site combinations from biomes worldwide. These traits included maximum leaf hydraulic conductance (Kleaf), water potential at 50% loss of Kleaf (P50leaf), and minimum leaf water potential (Ψmin). Leaf hydraulic safety margin (HSMleaf) was calculated as the difference between Ψmin and P50leaf. Our results indicated that 70% of the studied species had a narrow HSMleaf (less than 1 MPa), which was consistent with the global pattern of stem hydraulic safety margin. There was a positive relationship between HSMleaf and aridity index (the ratio of mean annual precipitation to potential evapotranspiration), as species from humid sites tended to have larger HSMleaf. We found a significant relationship between Kleaf and P50leaf across global angiosperm woody species and within each of the different plant groups. This global analysis of leaf hydraulic traits improves our understanding of plant hydraulic response to environmental change. 相似文献
15.
Are leaves ‘freewheelin'? Testing for a Wheeler‐type effect in leaf xylem hydraulic decline
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A recent study found that cutting shoots under water while xylem was under tension (which has been the standard protocol for the past few decades) could produce artefactual embolisms inside the xylem, overestimating hydraulic vulnerability relative to shoots cut under water after relaxing xylem tension (Wheeler et al. 2013). That study also raised the possibility that such a ‘Wheeler effect’ might occur in studies of leaf hydraulic vulnerability. We tested for such an effect for four species by applying a modified vacuum pump method to leaves with minor veins severed, to construct leaf xylem hydraulic vulnerability curves. We tested for an impact on leaf xylem hydraulic conductance (Kx) of cutting the petiole and minor veins under water for dehydrated leaves with xylem under tension compared with dehydrated leaves after previously relaxing xylem tension. Our results showed no significant ‘cutting artefact’ for leaf xylem. The lack of an effect for leaves could not be explained by narrower or shorter xylem conduits, and may be due to lesser mechanical stress imposed when cutting leaf petioles, and/or to rapid refilling of emboli in petioles. These findings provide the first validation of previous measurements of leaf hydraulic vulnerability against this potential artefact. 相似文献
16.
Plasticity of vulnerability to leaf hydraulic dysfunction during acclimation to drought in grapevines: an osmotic‐mediated process
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Sebastian Martorell Hipolito Medrano Magdalena Tomàs José M. Escalona Jaume Flexas Antonio Diaz‐Espejo 《Physiologia plantarum》2015,153(3):381-391
Previous studies have reported correlation of leaf hydraulic vulnerability with pressure–volume parameters related to cell turgor. This link has been explained on the basis of the effects of turgor on connectivity among cells and tissue structural integrity, which affect leaf water transport. In this study, we tested the hypothesis that osmotic adjustment to water stress would shift the leaf vulnerability curve toward more negative water potential (Ψleaf) by increasing turgor at low Ψleaf. We measured leaf hydraulic conductance (Kleaf), Kleaf vulnerability [50 and 80% loss of Kleaf (P50 and P80); |Ψleaf| at 50 and 80% loss of Kleaf, respectively), bulk leaf water relations, leaf gas exchange and sap flow in two Vitis vinifera cultivars (Tempranillo and Grenache), under two water treatments. We found that P50, P80 and maximum Kleaf decreased seasonally by more than 20% in both cultivars and watering treatments. However, Kleaf at ?2 MPa increased threefold, while osmotic potential at full turgor and turgor loss point decreased. Our results indicate that leaf resistance to hydraulic dysfunction is seasonally plastic, and this plasticity may be mediated by osmotic adjustment. 相似文献
17.
Yong-Qiang Wang Ming-Yuan Ni Wen-Hao Zeng Dong-Liu Huang Wei Xiang Peng-Cheng He Qing Ye Kun-Fang Cao Shi-Dan Zhu 《Annals of botany》2021,128(2):183
Background and AimsLeaf 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.MethodsWe 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 ResultsWe 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.ConclusionsThe findings of this study reveal leaf biomechanical–hydraulic safety correlation in sub-tropical woody species. 相似文献
18.
Background and Aims
Leaf hydraulic properties are strongly linked with transpiration and photosynthesis in many species. However, it is not known if gas exchange and hydraulics will have co-ordinated responses to climate change. The objective of this study was to investigate the responses of leaf hydraulic conductance (Kleaf) in Glycine max (soybean) to growth at elevated [CO2] and increased temperature compared with the responses of leaf gas exchange and leaf water status.Methods
Two controlled-environment growth chamber experiments were conducted with soybean to measure Kleaf, stomatal conductance (gs) and photosynthesis (A) during growth at elevated [CO2] and temperature relative to ambient levels. These results were validated with field experiments on soybean grown under free-air elevated [CO2] (FACE) and canopy warming.Key results
In chamber studies, Kleaf did not acclimate to growth at elevated [CO2], even though stomatal conductance decreased and photosynthesis increased. Growth at elevated temperature also did not affect Kleaf, although gs and A showed significant but inconsistent decreases. The lack of response of Kleaf to growth at increased [CO2] and temperature in chamber-grown plants was confirmed with field-grown soybean at a FACE facility.Conclusions
Leaf hydraulic and leaf gas exchange responses to these two climate change factors were not strongly linked in soybean, although gs responded to [CO2] and increased temperature as previously reported. This differential behaviour could lead to an imbalance between hydraulic supply and transpiration demand under extreme environmental conditions likely to become more common as global climate continues to change. 相似文献19.
Differential coordination of stomatal conductance,mesophyll conductance,and leaf hydraulic conductance in response to changing light across species
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Stomatal conductance (gs) and mesophyll conductance (gm) represent major constraints to photosynthetic rate (A), and these traits are expected to coordinate with leaf hydraulic conductance (Kleaf) across species, under both steady‐state and dynamic conditions. However, empirical information about their coordination is scarce. In this study, Kleaf, gas exchange, stomatal kinetics, and leaf anatomy in 10 species including ferns, gymnosperms, and angiosperms were investigated to elucidate the correlation of H2O and CO2 diffusion inside leaves under varying light conditions. Gas exchange, Kleaf, and anatomical traits varied widely across species. Under light‐saturated conditions, the A, gs, gm, and Kleaf were strongly correlated across species. However, the response patterns of A, gs, gm, and Kleaf to varying light intensities were highly species dependent. Moreover, stomatal opening upon light exposure of dark‐adapted leaves in the studied ferns and gymnosperms was generally faster than in the angiosperms; however, stomatal closing in light‐adapted leaves after darkening was faster in angiosperms. The present results show that there is a large variability in the coordination of leaf hydraulic and gas exchange parameters across terrestrial plant species, as well as in their responses to changing light. 相似文献
20.
Roles of Morphology, Anatomy, and Aquaporins in Determining Contrasting Hydraulic Behavior of Roots
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Helen Bramley Neil C. Turner David W. Turner Stephen D. Tyerman 《Plant physiology》2009,150(1):348-364
The contrasting hydraulic properties of wheat (Triticum aestivum), narrow-leafed lupin (Lupinus angustifolius), and yellow lupin (Lupinus luteus) roots were identified by integrating measurements of water flow across different structural levels of organization with anatomy and modeling. Anatomy played a major role in root hydraulics, influencing axial conductance (Lax) and the distribution of water uptake along the root, with a more localized role for aquaporins (AQPs). Lupin roots had greater Lax than wheat roots, due to greater xylem development. Lax and root hydraulic conductance (Lr) were related to each other, such that both variables increased with distance from the root tip in lupin roots. Lax and Lr were constant with distance from the tip in wheat roots. Despite these contrasting behaviors, the hydraulic conductivity of root cells (Lpc) was similar for all species and increased from the root surface toward the endodermis. Lpc was largely controlled by AQPs, as demonstrated by dramatic reductions in Lpc by the AQP blocker mercury. Modeling the root as a series of concentric, cylindrical membranes, and the inhibition of AQP activity at the root level, indicated that water flow in lupin roots occurred primarily through the apoplast, without crossing membranes and without the involvement of AQPs. In contrast, water flow across wheat roots crossed mercury-sensitive AQPs in the endodermis, which significantly influenced Lr. This study demonstrates the importance of examining root morphology and anatomy in assessing the role of AQPs in root hydraulics. 相似文献