21 results on '"Salleo, Sebastiano"'
Search Results
2. Ion-mediated enhancement of xylem hydraulic conductivity is not always suppressed by the presence of Ca 2+ in the sap
- Author
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Nardini, Andrea, Gascò, Antonio, Trifilò, Patrizia, Lo Gullo, Maria A., and Salleo, Sebastiano
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- 2007
3. Does short-term potassium fertilization improve recovery from drought stress in laurel?
- Author
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Oddo, Elisabetta, Inzerillo, Simone, Grisafi, Francesca, Sajeva, Maurizio, Salleo, Sebastiano, and Nardini, Andrea
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LAURUS nobilis ,XYLEM ,POTASSIUM fertilizers ,WATER vapor ,GAS exchange in plants ,HYDRAULIC conductivity ,EFFECT of drought on plants - Abstract
Xylem hydraulic conductance varies in response to changes in sap solute content, and in particular of potassium (K+) ion concentration. This phenomenon, known as the ‘ionic effect’, is enhanced in embolized stems, where it can compensate for cavitation-induced loss of hydraulic conductance. Previous studies have shown that in well-watered laurel plants (Laurus nobilis L.), potassium concentration of the xylem sap and plant hydraulic conductance increased 24 h after fertilization with KCl. The aim of this work was to test whether water-stressed laurel plants, grown under low potassium availability, could recover earlier from stress when irrigated with a KCl solution instead of potassium-free water. Two-year-old potted laurel seedlings were subjected to water stress by suspending irrigation until leaf conductance to water vapour (gL) dropped to ∼30% of its initial value and leaf water potential (ψL) reached the turgor loss point (ψTLP). Plants were then irrigated either with water or with 25 mM KCl and monitored for water status, gas exchange and plant hydraulics recovery at 3, 6 and 24 h after irrigation. No significant differences were found between the two experimental groups in terms of ψL, gL, plant transpiration, plant hydraulic conductance or leaf-specific shoot hydraulic conductivity. Analysis of xylem sap potassium concentration showed that there were no significant differences between treatments, and potassium levels were similar to those of potassium-starved but well-watered plants. In conclusion, potassium uptake from the soil solution and/or potassium release to the xylem appeared to be impaired in water-stressed plants, at least up to 24 h after relief from water stress, so that fertilization after the onset of stress did not result in any short-term advantage for recovery from drought. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
4. Do quantitative vessel and pit characters account for ion-mediated changes in the hydraulic conductance of angiosperm xylem?
- Author
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Jansen, Steven, Gortan, Emmanuelle, Lens, Frederic, Lo Gullo, Maria Assunta, Salleo, Sebastiano, Scholz, Alexander, Stein, Anke, Trifilò, Patrizia, and Nardini, Andrea
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ANGIOSPERMS ,XYLEM ,PLANT cells & tissues ,LAURACEAE ,PLANT species - Abstract
The hydraulic conductance of angiosperm xylem has been suggested to vary with changes in sap solute concentrations because of intervessel pit properties. The magnitude of the 'ionic effect' was linked with vessel and pit dimensions in 20 angiosperm species covering 13 families including six Lauraceae species. A positive correlation was found between ionic effect and vessel grouping parameters, especially the portion of vessel walls in contact with neighbouring vessels. Species with intervessel contact fraction (FC) values < 0.1 showed an ionic effect between 2% and 17%, while species with FC values > 0.1 exhibited a response between 10% and 32%. The ionic effect increased linearly with the mean fraction of the total vessel wall area occupied by intervessel pits as well as with the intervessel contact length. However, no significant correlation occurred between the ionic effect and total intervessel pit membrane area per vessel, vessel diameter, vessel length, vessel wall area, and intervessel pit membrane thickness. Quantitative vessel and pit characters are suggested to contribute to interspecific variation of the ionic effect, whereas chemical properties of intervessel pit membranes are likely to play an additional role. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
5. Ion-mediated enhancement of xylem hydraulic conductivity is not always suppressed by the presence of Ca2+ in the sap.
- Author
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Nardini, Andrea, Gascò, Antonio, Trifilò, Patrizia, Lo Gullo, Maria A., and Salleo, Sebastiano
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XYLEM ,PLANT physiology ,PERFUSION ,IONIZATION (Atomic physics) ,WOODY plants - Abstract
The physiological significance of ion-mediated enhancement of xylem hydraulic conductivity (Kh) in planta has recently been questioned. The phenomenon has been suggested to be an artefact caused by the use of deionized water as a reference fluid during measurements of the impact of different ions on Kh. In the present study, ion-mediated changes in Kh were measured in twigs of five woody species during perfusion with 25 mM KCl compared with different reference fluids like deionized water, a commercial mineral water containing different ions (including 0.5 mM Ca2+), and a 1 mM CaCl2 solution. Both fully hydrated twigs and twigs with about 50% loss of hydraulic conductivity due to cavitation-induced embolism were tested. Adding 25 mM KCl to the three reference fluids caused Kh to increase by about 20%. The KCl-mediated increase of Kh was even larger (up to 100%) in embolized twigs. The presence of Ca2+ in the reference solution decreased, but not suppressed, the KCl-mediated enhancement of Kh in fully hydrated twigs of three species, but not in the other two species tested. Ca2+ did not affect the Kh response to KCl in embolized twigs. These data suggest that the recently reported suppression of the ‘ionic effect’ by the presence of calcium in the xylem sap is not a general phenomenon and that ion-mediated changes of Kh may play a role in planta partially to compensate for cavitation-induced loss of xylem hydraulic conductivity. [ABSTRACT FROM PUBLISHER]
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- 2007
- Full Text
- View/download PDF
6. Effects of reduced irradiance on hydraulic architecture and water relations of two olive clones with different growth potentials
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Sebastiano Salleo, Andrea Nardini, M. A. Lo Gullo, Patrizia Trifilò, Rosalia Buffa, Fabio Raimondo, Raimondo, F, Trifilo', P, LO GULLO, Ma, Buffa, R, Nardini, Andrea, and Salleo, Sebastiano
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Sunlight ,Chemistry ,Diurnal temperature variation ,transpiration rate ,Irradiance ,Xylem ,Plant Science ,olive ,shading ,hydraulic architecture ,xylem features ,Horticulture ,Light intensity ,Hydraulic conductivity ,Botany ,Shading ,Agronomy and Crop Science ,Ecology, Evolution, Behavior and Systematics ,Transpiration - Abstract
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.
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- 2009
7. The hydraulic conductance of Fraxinus ornus leaves is constrained by soil water availability and coordinated with gas exchange rates
- Author
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Sebastiano Salleo, Emmanuelle Gortan, Antonio Gascó, Andrea Nardini, Gortan, E, Nardini, Andrea, Gasco', A, and Salleo, Sebastiano
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biology ,Physiology ,Water stress ,Rain ,Fraxinus ornus ,Water ,Biological Transport ,Plant Transpiration ,Plant Science ,Leaf water potential ,Carbon Dioxide ,biology.organism_classification ,Photosynthesis ,Hydraulic conductance ,Arid ,Plant Leaves ,Leaf ,Soil ,Fraxinus ,Agronomy ,Hydraulic conductivity ,Soil water ,Environmental science ,Precipitation ,Water vapor - Abstract
Leaf hydraulic conductance (K leaf ) is known to be an important determinant of plant gas exchange and photosynthesis. Little is known about the long-term impact of different environmental factors on the hydraulic construction of leaves and its eventual consequences on leaf gas exchange. In this study, we investigate the impact of soil water availability on K leaf of Fraxinus ornus L. as well as the influence of K leaf on gas exchange rates and plant water status. With this aim, K leaf , leaf conductance to water vapour (g L ), leaf water potential (Ψ leaf ) and leaf mass per area (LMA) were measured in F. ornus trees, growing in 21 different sites with contrasting water availability. Plants growing in arid sites had lower K leaf , g L and Ψ leaf than those growing in sites with higher water availability. On the contrary, LMA was similar in the two groups. The K leaf values recorded in sites with two different levels of soil water availability were constantly different from each other regardless of the amount of precipitation recorded over 20 days before measurements. Moreover, K leaf was correlated with g L values. Our data suggest that down-regulation of K leaf is a component of adaptation of plants to drought-prone habitats. Low K leaf implies reduced gas exchange which may, in turn, influence the climatic conditions on a local/regional scale. It is concluded that leaf hydraulics and its changes in response to resource availability should receive greater attention in studies aimed at modelling biosphere-atmosphere interactions.
- Published
- 2009
8. Reduced Content of Homogalacturonan Does Not Alter the Ion-Mediated Increase in Xylem Hydraulic Conductivity in Tobacco
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Andrea Nardini, Sebastiano Salleo, Antonio Gascó, Felice Cervone, Nardini, Andrea, Gasco', A, Cervone, F, and Salleo, Sebastiano
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food.ingredient ,Pectin ,Physiology ,Nicotiana tabacum ,ionis effect ,Plant Science ,Polysaccharide ,xylem hydraulic conductivity ,Ion ,food ,Hydraulic conductivity ,Xylem ,Tobacco ,Botany ,pi membrane ,pectins ,Genetics ,pectin ,Ions ,chemistry.chemical_classification ,biology ,fungi ,Aspergillus niger ,Water ,food and beverages ,biology.organism_classification ,Membrane ,chemistry ,Biophysics ,Pectins ,Research Article - Abstract
Xylem hydraulic conductivity (K s) in stems of tobacco (Nicotiana tabacum) wild-type SR1 was compared to that of PG7 and PG16, two transgenic lines with increased levels of expression of the gene encoding the Aspergillus niger endopolygalacturonase (AnPGII). Activity of AnPGII removes in planta blocks of homogalacturonan (HG) with deesterified carboxyls, thus increasing the degree of neutrality of pectins. The effect of K+ was tested in increasing stem K s using model plants with more neutral polysaccharides in primary walls and, hence, in intervessel pit membranes. K s measured with deionized water was compared to that with KCl solutions at increasing concentrations (ΔK s, %). Plants transformed for HG degree of neutrality showed a dwarfed phenotype, but ΔK s did not differ among the three experimental groups. The ion-mediated hydraulic effect saturated at a KCl concentration of 25 mm in SR1 plants. All the three tobacco lines showed ΔK s of around +12.5% and +17.0% when perfused with 10 and 25 mm KCl, respectively. Because modification of HG content did not influence ion-mediated hydraulic enhancement, we suggest that pectin components other than HG, like rhamnogalacturonan-I and/or rhamnogalacturonan-II, might play important roles in the hydrogel behavior of pit membranes.
- Published
- 2007
9. Does short-term potassium fertilization improve recovery from drought stress in laurel?
- Author
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Sebastiano Salleo, Andrea Nardini, Simone Inzerillo, Francesca Grisafi, Maurizio Sajeva, Elisabetta Oddo, E., Oddo, S., Inzerillo, F., Grisafi, M., Sajeva, Salleo, Sebastiano, Nardini, Andrea, Oddo, E, Inzerillo, S, Grisafi, F, Sajeva, M, Salleo, S, and Nardini, A
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Irrigation ,hydraulic conductance ,hydraulic conductance, ionic effect, Laurus nobilis L., xylem sap ,Physiology ,Potassium ,Turgor pressure ,chemistry.chemical_element ,Plant Science ,Laurus ,xylem sap ,Laurus nobilis ,food ,Hydraulic conductivity ,Stress, Physiological ,Xylem ,Settore BIO/04 - Fisiologia Vegetale ,Fertilizers ,Transpiration ,fungi ,food and beverages ,Water ,Plant Transpiration ,food.food ,Droughts ,ions ,Plant Leaves ,Horticulture ,Agronomy ,chemistry ,Shoot ,ion - Abstract
Xylem hydraulic conductance varies in response to changes in sap solute content, and in particular of potassium (K(+)) ion concentration. This phenomenon, known as the 'ionic effect', is enhanced in embolized stems, where it can compensate for cavitation-induced loss of hydraulic conductance. Previous studies have shown that in well-watered laurel plants (Laurus nobilis L.), potassium concentration of the xylem sap and plant hydraulic conductance increased 24 h after fertilization with KCl. The aim of this work was to test whether water-stressed laurel plants, grown under low potassium availability, could recover earlier from stress when irrigated with a KCl solution instead of potassium-free water. Two-year-old potted laurel seedlings were subjected to water stress by suspending irrigation until leaf conductance to water vapour (g(L)) dropped to ∼30% of its initial value and leaf water potential (ψ(L)) reached the turgor loss point (ψ(TLP)). Plants were then irrigated either with water or with 25 mM KCl and monitored for water status, gas exchange and plant hydraulics recovery at 3, 6 and 24 h after irrigation. No significant differences were found between the two experimental groups in terms of ψ(L), g(L), plant transpiration, plant hydraulic conductance or leaf-specific shoot hydraulic conductivity. Analysis of xylem sap potassium concentration showed that there were no significant differences between treatments, and potassium levels were similar to those of potassium-starved but well-watered plants. In conclusion, potassium uptake from the soil solution and/or potassium release to the xylem appeared to be impaired in water-stressed plants, at least up to 24 h after relief from water stress, so that fertilization after the onset of stress did not result in any short-term advantage for recovery from drought.
- Published
- 2014
10. Competitive strategies for water availability in two Mediterranean Quercus species
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M. A. Lo Gullo, Andrea Nardini, Sebastiano Salleo, Nardini, Andrea, LO GULLO, Ma, and Salleo, Sebastiano
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Absorption of water ,biology ,Physiology ,media_common.quotation_subject ,Quercus cerris ,Plant Science ,Quercus suber ,Interspecific competition ,biology.organism_classification ,Competition (biology) ,Fagaceae ,Horticulture ,Hydraulic conductivity ,Botany ,Environmental science ,Water content ,media_common - Abstract
Competition for water availability was studied in a mixed natural stand of Quercus suber L. and Quercus cerris L. growing in Sicily by measuring diurnal changes of leaf conductance to water vapour (g L ), water potential (Ψ L ) and relative water content (RWC) in April, July and October 1997 as well as the seasonal changes in root hydraulic conductance per unit leaf surface area (K RL ). Quercus cerris behaved as a drought-tolerant species, with strong reductions of K RL , Ψ L , and RWC in the summer. By contrast, Q. suber appeared to withstand summer drought by an avoidance strategy based on reducing g L , maintaining Ψ L and RWC high and K RL at the same level as that measured in the spring. A 'conductance ratio' (CR) was calculated in terms of the ratio of g L to K RL . Seasonal changes of this ratio contrasted in the two species, thus suggesting that Q. suber and Q. cerris did not really compete for available water. In the summer, when Q. suber was extracting water from the soil to maintain high leaf hydration, Q. cerris had restricted water absorption, thus suffering drought but tolerating its effects. The possibility that cohabitation of drought-tolerant with drought-avoiding species can be generalized is also discussed.
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- 1999
11. Effects of NaCl addition to the growing medium on plant hydraulics and water relations of tomato
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Andrea Nardini, Patrizia Trifil, Sebastiano Salleo, Maria A. Lo Gullo, Fabio Raimondo, P., Trifilò, M. A., Lo Gullo, F., Raimondo, Salleo, Sebastiano, and Nardini, Andrea
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Sodium ,Potassium ,chemistry.chemical_element ,Plant Science ,Biology ,xylem sap ,xylem hydraulic conductance ,Hydraulic conductivity ,Botany ,Hoagland solution ,salt stress ,xylem feature ,Water transport ,ionic effect ,ionic effect - salt stress - xylem features - xylem hydraulic conductance- xylem sap - tomato ,fungi ,food and beverages ,Xylem ,biology.organism_classification ,Salinity ,xylem features ,chemistry ,salt stre ,Solanum ,Agronomy and Crop Science - Abstract
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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- 2013
12. Do quantitative vessel and pit characters account for ion-mediated changes in the hydraulic conductance of angiosperm xylem?
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Patrizia Trifilò, Emmanuelle Gortan, Anke Stein, Steven Jansen, Andrea Nardini, Maria A. Lo Gullo, Sebastiano Salleo, Frederic Lens, Alexander Scholz, Jansen, S., Gortan, E., Lens, F., Lo Gullo, M. A., Salleo, Sebastiano, Scholz, A., Stein, A., Trifilo', P., Nardini, Andrea, and Staff publications
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Physiology ,Plant Science ,Biology ,Positive correlation ,Ion ,Potassium Chloride ,Lauraceae ,Magnoliopsida ,Hydraulic conductivity ,Xylem ,Botany ,wood anatomy ,intervessel pit membrane ,angiosperms ,hydraulic conductivity ,ionic effect ,vessel grouping ,angiosperm ,Ions ,Water ,Biological Transport ,Hydraulic conductance ,Vessel diameter ,Membrane ,cardiovascular system ,Ionic effect ,Pectins - Abstract
• The hydraulic conductance of angiosperm xylem has been suggested to vary with changes in sap solute concentrations because of intervessel pit properties. • The magnitude of the ‘ionic effect’ was linked with vessel and pit dimensions in 20 angiosperm species covering 13 families including six Lauraceae species. • A positive correlation was found between ionic effect and vessel grouping parameters, especially the portion of vessel walls in contact with neighbouring vessels. Species with intervessel contact fraction (FC) values < 0.1 showed an ionic effect between 2% and 17%, while species with FC values > 0.1 exhibited a response between 10% and 32%. The ionic effect increased linearly with the mean fraction of the total vessel wall area occupied by intervessel pits as well as with the intervessel contact length. However, no significant correlation occurred between the ionic effect and total intervessel pit membrane area per vessel, vessel diameter, vessel length, vessel wall area, and intervessel pit membrane thickness. • Quantitative vessel and pit characters are suggested to contribute to interspecific variation of the ionic effect, whereas chemical properties of intervessel pit membranes are likely to play an additional role.
- Published
- 2011
13. Ion-mediated compensation for drought-induced loss of xylem hydraulic conductivity in field-growing plants of Laurus nobilis
- Author
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Patrizia Trifil, Andrea Nardini, Fabio Raimondo, Sebastiano Salleo, Maria A. Lo Gullo, Trifilo', P, Nardini, Andrea, Raimondo, F, Lo Gullo, Ma, and Salleo, Sebastiano
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Ecophysiology ,Irrigation ,Potassium ,chemistry.chemical_element ,cavitation ,gas exchange ,hydraulic conductivity ,laurel ,potassium ,water stress ,xylem ,Plant Science ,Biology ,Photosynthesis ,Laurus nobilis ,food ,Hydraulic conductivity ,Water transport ,fungi ,food and beverages ,Xylem ,water stre ,food.food ,Agronomy ,chemistry ,Agronomy and Crop Science - Abstract
Xylem cavitation is a common occurrence in drought-stressed plants. Cavitation-induced embolism reduces xylem hydraulic conductivity (kxylem) and may lead to stomatal closure and reduction of photosynthetic rates. Recent studies have suggested that plants may compensate for kxylem loss through ion-mediated enhancement of the residual water transport capacity of functioning conduits. To test this hypothesis, field-grown laurel (Laurus nobilis L.) plants were subjected to mild drought stress by suspending irrigation. Drought treatment induced a significant increase in xylem embolism compared with control (well watered) plants. Xylem sap potassium concentration ([K+]) increased during the day both in control and water stressed plants. Midday values of sap [K+] were significantly higher in water stressed plants. The recorded increase in sap potassium concentration induced significant enhancement of residual kxylem when solutions with different [K+] were perfused through excised stems sampled in the field and measured in the laboratory. In planta measurements of stem hydraulic conductance revealed no change between water stressed plants and controls. Our data suggest that ion-mediated enhancement of residual kxylem buffered the actual loss of hydraulic conductance suffered by plants during the warmest hours of the day as well as under mild drought stress conditions.
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- 2010
14. Heterogeneity of gas exchange rates over the leaf surface in tobacco: an effect of hydraulic architecture?
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Andrea Nardini, Sebastiano Salleo, Emmanuelle Gortan, Matteo Ramani, Nardini, Andrea, Gortan, E, Ramani, M, and Salleo, Sebastiano
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Pressure-volume curves ,Hygrometer ,biology ,Physiology ,Chemistry ,Hedera ,Nicotiana tabacum ,fungi ,Turgor pressure ,food and beverages ,Water ,Plant Transpiration ,Plant Science ,biology.organism_classification ,Spatial heterogeneity ,Apex (geometry) ,Plant Leaves ,Horticulture ,Hydraulic conductivity ,Botany ,Tobacco ,Osmotic pressure - Abstract
Spatial heterogeneity of gas exchange rates in the leaves of Nicotiana tabacum L. (tobacco) was investigated. Leaf conductance to water vapour was higher (by about 18%) at the apical regions of leaves than at the basal ones. Local, small-scale measurements of pressure-volume (PV) parameters and water status (performed with a dewpoint hygrometer) revealed that bulk leaf water potential, osmotic potential, turgor pressure and bulk modulus of elasticity were not significantly different in the leaf apex or base. Hydraulic measurements showed that the apical regions of the leaf blade were about 30% more conductive than the basal regions. Such differences were explained by analogous differences in terms of venation patterns. In fact, vein density turned out to be higher (by about 13%) near the leaf apex with respect to the leaf base. On the contrary, stomatal density was the same both in the apical and basal leaf portions. Our data suggest that spatial stomatal heterogeneity may arise from heterogenous distribution of local hydraulic resistances and would be addressed to maintaining local water potential above critical values, possibly triggering vein cavitation.
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- 2008
15. Xylem embolism alleviated by ion-mediated increase in hydraulic conductivity of functional xylem: insights from field measurements
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Patrizia Trifilò, Sebastiano Salleo, Andrea Nardini, Maria A. Lo Gullo, Katia Callea, Trifilo', P, LO GULLO, Ma, Salleo, Sebastiano, Callea, K, and Nardini, Andrea
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Physiology ,Potassium ,pits ,Phytolacca dioica ,chemistry.chemical_element ,drought ,gas exchange ,Plant Science ,Phloem ,Trees ,food ,cavitation ,Hydraulic conductivity ,Xylem ,Cations ,Botany ,hydrogels ,Phytolacca ,Water transport ,Platanus orientalis ,biology ,Chemistry ,Water ,Biological Transport ,Fabaceae ,Evergreen ,biology.organism_classification ,food.food ,Horticulture ,Ceratonia siliqua ,cations ,potassium ,Seasons - Abstract
Recent studies have shown that, in some species, xylem hydraulic conductivity (K(h)) increases with increasing cation concentration of xylem sap. Evidence indicates that K(h) increases as a result of the de-swelling of pit membrane pectins caused by cation neutralization of polygalacturonanes. We tested whether this ionic effect partly compensates for the embolism-induced loss of stem hydraulic conductivity (PLC) by increasing K(h) of functioning conduits. We report changes in PLC, leaf water status and potassium concentration ([K(+)]) of xylem sap measured in April and July in two evergreens (Ceratonia siliqua L. and Phytolacca dioica L.) and one deciduous tree (Platanus orientalis L.) growing in the field in Sicily. In summer, Ceratonia siliqua and Phytolacca dioica showed similar native embolism (PLC = 30-40%) and [K(+)] of xylem sap (14 to 17 mM), and K(h) of stems perfused with 10 to 25 mM KCl increased by 15 to 18% compared with K(h) of stems perfused with a low concentration of a multi-ionic solution. In contrast, native [K(+)] of sap of Platanus orientalis was 50% of that in the two evergreens in summer, with a parallel lack of detectable changes in PLC that was below 10% in both spring and summer. The ionic effect was PLC-dependent: the enhancement of K(h) induced by 10 to 25 mM KCl changed from 15% for fully hydrated stems to 50-75% for stems with PLC = 50%. In Ceratonia siliqua, PLC was less than 10% in spring and about 40% in summer; concurrently, xylem sap [K(+)] increased from 3 to about 15 mM. This [K(+)] at the recorded PLC would cause an increase in residual K(h) of about 30%. Hence, the actual reduction in water transport capacity of Ceratonia siliqua stems in summer is about 20%. Similar calculations for Phytolacca dioica suggest that the actual loss of hydraulic conductivity in stems of this species in summer would be only about 10%, and not 30% as suggested by hydraulic measurements performed in the laboratory. We conclude that an increase in [K(+)] of xylem sap might be involved in the up-regulation of residual K(h), thus substantially alleviating the embolism-induced reduction in leaf water supply.
- Published
- 2008
16. Ion-mediated enhancement of xylem hydraulic conductivity is not always suppressed by the presence of Ca2+ in the sap
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Antonio Gascó, Sebastiano Salleo, Andrea Nardini, Patrizia Trifilò, Maria A. Lo Gullo, Nardini, Andrea, Gasco', A, Trifilo', P, LO GULLO, Ma, and Salleo, Sebastiano
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Ions ,Physiological significance ,ionic effect ,Physiology ,Chemistry ,Analytical chemistry ,chemistry.chemical_element ,Xylem ,Water ,Biological Transport ,Plant Science ,Calcium ,calcium ,hydraulic conductivity ,pectins ,xylem ,Plants ,Ion ,Potassium Chloride ,Mineral water ,Hydraulic conductivity ,Botany ,Ionic effect - Abstract
The physiological significance of ion-mediated enhancement of xylem hydraulic conductivity (K h ) in planta has recently been questioned. The phenomenon has been suggested to be an artefact caused by the use of deionized water as a reference fluid during measurements of the impact of different ions on K h . In the present study, ion-mediated changes in K h were measured in twigs of five woody species during perfusion with 25 mM KCl compared with different reference fluids like deionized water, a commercial mineral water containing different ions (including 0.5 mM Ca 2+ ), and a 1 mM CaCl 2 solution. Both fully hydrated twigs and twigs with about 50% loss of hydraulic conductivity due to cavitation-induced embolism were tested. Adding 25 mM KCl to the three reference fluids caused K h to increase by about 20%. The KCl-mediated increase of K h was even larger (up to 100%) in embolized twigs. The presence of Ca 2+ in the reference solution decreased, but not suppressed, the KCl-mediated enhancement of K h in fully hydrated twigs of three species, but not in the other two species tested. Ca 2+ did not affect the K h response to KCl in embolized twigs. These data suggest that the recently reported suppression of the ‘ionic effect’ by the presence of calcium in the xylem sap is not a general phenomenon and that ion-mediated changes of K h may play a role in planta partially to compensate for cavitation-induced loss of xylem hydraulic conductivity.
- Published
- 2007
17. Seasonal changes in the ion-mediated increase of xylem hydraulic conductivity in stems of three evergreens: any functional role?
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Sebastiano Salleo, Emmanuelle Gortan, Antonio Gascó, Andrea Nardini, Gasco', A, Salleo, Sebastiano, Gortan, E, and Nardini, Andrea
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Winter rest ,Water transport ,Physiology ,Chemistry ,Xylem ,Cell Biology ,Plant Science ,General Medicine ,Evergreen ,food.food ,Horticulture ,Phillyrea latifolia ,Laurus nobilis ,food ,Hydraulic conductivity ,Botany ,Genetics ,Saturation (chemistry) - Abstract
Changes in hydraulic conductivity (K h ) were measured monthly in stems of Laurus nobilis between July 2005 and June 2006 and in March and June 2006 in stems of Prunus laurocerasus and Phillyrea latifolia. Percent enhancement of K h (ΔK h ) was recorded as KCI injected into stems compared with deionized water. Stems of L. nobilis perfused with increasing [KCl] saturated the hydraulic effect at 50 mM KCI, while P. laurocerasus and Ph. latifolia showed saturation at 17 and less than 5 mM KCI, respectively. Impressive seasonal changes in ΔK h were recorded in L. nobilis, from +120% in February to +20% during the growth period. ΔK h was negatively correlated to minimum air temperatures and was highest during winter frost. Negative correlation also existed between ΔK h and conduit lengths as detected during transition of plants from activity to winter rest and from winter to spring. In the winter, the thermal effect was prevailing. High cavitation-induced K h loss coincided with high ΔK h . Similar but much smaller seasonal effects on ΔK h were recorded in the other two species where, however, also smaller seasonal changes in conduit lengths were recorded. We conclude that (1) the K + -induced effect on K h was because of interference of the cation with pectins of intervessel pit membranes (increasingly crossed by the ionic solution in stems with shorter conduits); (2) winter frost might have an effect on ΔK h and (3) seasonal changes in ΔK h because of possible change in pectic composition may represent a mechanism to regulate water flows in planta.
- Published
- 2007
18. Ion-mediated increase in the xylem hydraulic conductivity of Laurel stems: role of pits and consequences for the impact of cavitation on water transport
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Andrea Nardini, Emmanuelle Gortan, Sebastiano Salleo, Antonio Gascó, Gasco', A, Nardini, Andrea, Gortan, E, and Salleo, Sebastiano
- Subjects
Physiology ,Kinetics ,Analytical chemistry ,Mineralogy ,Plant Science ,Conductivity ,Laurus nobili ,Ion ,pectins ,Hydraulic conductivity ,hydraulic method ,xylem cavitation ,Ions ,Laurus nobilis ,pit membranes ,pectin ,Water transport ,Plant Stems ,Chemistry ,Water ,Xylem ,Biological Transport ,Membrane ,Cavitation ,pit membrane - Abstract
Changes in hydraulic conductivity (K(h)) were measured in stems of Laurus nobilis L. during perfusion with KCl, NaCl or sucrose solutions. Ionic solutes induced marked increase of K(h) with respect to deionized water but sucrose had no effect. The kinetics of KCl-induced K(h) increase was measured together with changes in [K(+)] of the perfused solution. K(h) increases were paralleled by increases in the [K(+)](out)/[K(+)](in) ratio. Samples of different lengths or with increasing percentage loss of conductivity (PLC) due to xylem cavitation were tested, with the aim of increasing radial flow through intervessel pits. KCl solutions enhanced the K(h) of 12-cm-long samples with a concentration-dependent effect up to 100 mm KCl. DeltaK(h) increased from 3 to 30% in 1.5- and 12-cm-long samples, respectively and remained constant for longer samples. Increasing PLC induced an exponential increase in DeltaK(h). PLC measured with KCl solutions was significantly less than that measured with deionized water, suggesting that measurements of PLC can be affected by the composition of the perfused solution. Experiments support the hypothesis that the 'ionic effect' is mediated by physico-chemical changes of pectins of the pit membranes and raise the possibility that plants might alter the ionic composition of the xylem sap to alleviate the hydraulic impact of cavitation.
- Published
- 2006
19. Water stress-induced modifications of leaf hydraulic architecture in sunflower: co-ordination with gas exchange
- Author
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Sebastiano Salleo, Andrea Nardini, Nardini, Andrea, and Salleo, Sebastiano
- Subjects
Physiology ,Water stress ,Water ,Biological Transport ,Plant Transpiration ,Plant Science ,Biology ,Sunflower ,Polyethylene Glycols ,Plant Leaves ,Agronomy ,Tap water ,Hydraulic conductivity ,Osmotic Pressure ,Helianthus annuus ,Helianthus ,Osmotic pressure ,Ordination ,Water vapor - Abstract
The hydraulic architecture, water relationships, and gas exchange of leaves of sunflower plants, grown under different levels of water stress, were measured. Plants were either irrigated with tap water (controls) or with PEG600 solutions with osmotic potential of -0.4 and -0.8 MPa (PEG04 and PEG08 plants, respectively). Mature leaves were measured for hydraulic resistance (R(leaf)) before and after making several cuts across minor veins, thus getting the hydraulic resistance of the venation system (R(venation)). R(leaf) was nearly the same in controls and PEG04 plants but it was reduced by about 30% in PEG08 plants. On the contrary, R(venation) was lowest in controls and increased in PEG04 and PEG08 plants as a likely result of reduction in the diameter of the veins' conduits. As a consequence, the contribution of R(venation) to the overall R(leaf) markedly increased from controls to PEG08 plants. Leaf conductance to water vapour (g(L)) was highest in controls and significantly lower in PEG04 and PEG08 plants. Moreover, g(L) was correlated to R(venation) and to leaf water potential (psi(leaf)) with highly significant linear relationships. It is concluded that water stress has an important effect on the hydraulic construction of leaves. This, in turn, might prove to be a crucial factor in plant-water relationships and gas exchange under water stress conditions.
- Published
- 2005
20. Xylem cavitation and hydraulic control of stomatal conductance in Laurel (Laurus nobilis L.)
- Author
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Maria A. Lo Gullo, Franco Pitt, Andrea Nardini, Sebastiano Salleo, Salleo, Sebastiano, Nardini, Andrea, Pitt, F., and LO GULLO, M. A.
- Subjects
Stomatal conductance ,Physiology ,Xylem ,Plant Science ,Lauraceae ,Biology ,biology.organism_classification ,food.food ,Laurus nobilis ,food ,Hydraulic conductivity ,Cavitation ,Botany ,Shoot ,Woody plant - Abstract
The possible link between stomatal conductance (gL), leaf water potential (ΨL) and xylem cavitation was studied in leaves and shoots of detached branches as well as of whole plants of Laurus nobilis L. (Laurel). Shoot cavitation induced complete stomatal closure in air-dehydrated detached branches in less than 10 min. By contrast, a fine regulation of gL in whole plants was the consequence of ΨL reaching the cavitation threshold (ΨCAV) for shoots. A pulse of xylem cavitation in the shoots was paralleled by a decrease in gL of about 50%, while ΨL stabilized at values preventing further xylem cavitation. In these experiments, no root signals were likely to be sent to the leaves from the roots in response to soil dryness because branches were either detached or whole plants were growing in constantly wet soil. The stomatal response to increasing evaporative demand appeared therefore to be the result of hydraulic signals generated during shoot cavitation. A negative feedback link is proposed between gL and ΨCAV rather than with ΨL itself.
- Published
- 2000
21. Limitation of stomatal conductance by hydraulic traits: sensing or preventing xylem cavitation?
- Author
-
Sebastiano Salleo, Andrea Nardini, Nardini, Andrea, and Salleo, Sebastiano
- Subjects
Stomatal conductance ,Water transport ,Ecology ,Physiology ,fungi ,food and beverages ,Xylem ,Forestry ,Plant Science ,Biology ,Evergreen ,Horticulture ,Hydraulic conductivity ,Shoot ,Botany ,Woody plant ,Transpiration - Abstract
We tested the hypothesis that hydraulic conductance per unit leaf surface area of plant shoots (KSL) determines the maximum diurnal stomatal conductance (gL) that can be reached by plants growing in the field. A second hypothesis was tested that some xylem cavitation cannot be avoided by transpiring plants and might act as a signal for regulating gL. Eleven woody species were studied, differing from each other with respect to taxonomy, wood anatomy and leaf habit. Maximum diurnal gL, transpiration rate (EL), pre-dawn and minimum diurnal leaf water potential (Ψpd and Ψmin, respectively) were measured in the field. The critical Ψ level at which stem cavitation was triggered (Ψcav) was measured on detached branches, using the acoustic method. A high-pressure flow meter was used to measure maximum KSL of 1-year-old shoots. Both gL and EL were positively related to KSL. The whole-plant hydraulic conductance per unit leaf area (KWL) of all the species studied, calculated as the ratio of EL to ΔΨ (=Ψpd-Ψmin) was closely related to KSL. In every case, Ψmin (ranging between –0.85 and –1.35 MPa in the different species) dropped to the Ψcav range or was
- Published
- 2000
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