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Eero Nikinmaa - One of the best experts on this subject based on the ideXlab platform.

  • Gradients and dynamics of inner bark and needle osmotic Potentials in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst)
    Plant cell & environment, 2017
    Co-Authors: Teemu Paljakka, Eero Nikinmaa, Tuula Jyske, Anna Lintunen, Heidi Aaltonen, Teemu Holtta
    Abstract:

    Preconditions of phloem transport in conifers are relatively unknown. We studied the variation of needle and inner bark axial osmotic gradients and Xylem Water Potential in Scots pine and Norway spruce by measuring needle and inner bark osmolality in saplings and mature trees over several periods within a growing season. The needle and inner bark osmolality was strongly related to Xylem Water Potential in all studied trees. Sugar concentrations were measured in Scots pine, and they had similar dynamics to inner bark osmolality. The sucrose quantity remained fairly constant over time and position, whereas the other sugars exhibited a larger change with time and position. A small osmotic gradient existed from branch to stem base under pre-dawn conditions, and the osmotic gradient between upper stem and stem base was close to zero. The turgor in branches was significantly driven by Xylem Water Potential, and the turgor loss point in branches was relatively close to daily minimum needle Water Potentials typically reported for Scots pine. Our results imply that Xylem Water Potential considerably impacts the turgor pressure gradient driving phloem transport and that gravitation has a relatively large role in phloem transport in the stems of mature Scots pine trees.

  • diurnal patterns in scots pine stem oleoresin pressure in a boreal forest
    Plant Cell and Environment, 2016
    Co-Authors: Kaisa Rissanen, Teemu Holtta, Eero Nikinmaa, Anni Vanhatalo, Juho Aalto, Hannu Rita, Jaana Back
    Abstract:

    Coniferous tree stems contain large amounts of oleoresin under positive pressure in the resin ducts. Studies in North-American pines indicated that the stem oleoresin exudation pressure (OEP) correlates negatively with transpiration rate and soil Water content. However, it is not known how the OEP changes affect the emissions of volatile vapours from the trees. We measured the OEP, Xylem diameter changes indicating changes in Xylem Water Potential and monoterpene emissions under field conditions in mature Scots pine (Pinus sylvestris L.) trees in southern Finland. Contrary to earlier reports, the diurnal OEP changes were positively correlated with temperature and transpiration rate. OEP was lowest at the top part of the stem, where Water Potentials were also more negative, and often closely linked to ambient temperature and stem monoterpene emissions. However, occasionally OEP was affected by sudden changes in vapour pressure deficit (VPD), indicating the importance of Xylem Water Potential on OEP as well. We conclude that the oleoresin storage pools in tree stems are in a dynamic relationship with ambient temperature and Xylem Water Potential, and that the canopy monoterpene emission rates may therefore be also regulated by whole tree processes and not only by the conditions prevailing in the upper canopy.

  • linking phloem function to structure analysis with a coupled Xylem phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

  • Linking phloem function to structure: Analysis with a coupled Xylem-phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Münch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and .

  • Linking phloem function to structure: Analysis with a coupled Xylem–phloem transport model
    Journal of theoretical biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

Teemu Holtta - One of the best experts on this subject based on the ideXlab platform.

  • Gradients and dynamics of inner bark and needle osmotic Potentials in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst)
    Plant cell & environment, 2017
    Co-Authors: Teemu Paljakka, Eero Nikinmaa, Tuula Jyske, Anna Lintunen, Heidi Aaltonen, Teemu Holtta
    Abstract:

    Preconditions of phloem transport in conifers are relatively unknown. We studied the variation of needle and inner bark axial osmotic gradients and Xylem Water Potential in Scots pine and Norway spruce by measuring needle and inner bark osmolality in saplings and mature trees over several periods within a growing season. The needle and inner bark osmolality was strongly related to Xylem Water Potential in all studied trees. Sugar concentrations were measured in Scots pine, and they had similar dynamics to inner bark osmolality. The sucrose quantity remained fairly constant over time and position, whereas the other sugars exhibited a larger change with time and position. A small osmotic gradient existed from branch to stem base under pre-dawn conditions, and the osmotic gradient between upper stem and stem base was close to zero. The turgor in branches was significantly driven by Xylem Water Potential, and the turgor loss point in branches was relatively close to daily minimum needle Water Potentials typically reported for Scots pine. Our results imply that Xylem Water Potential considerably impacts the turgor pressure gradient driving phloem transport and that gravitation has a relatively large role in phloem transport in the stems of mature Scots pine trees.

  • diurnal patterns in scots pine stem oleoresin pressure in a boreal forest
    Plant Cell and Environment, 2016
    Co-Authors: Kaisa Rissanen, Teemu Holtta, Eero Nikinmaa, Anni Vanhatalo, Juho Aalto, Hannu Rita, Jaana Back
    Abstract:

    Coniferous tree stems contain large amounts of oleoresin under positive pressure in the resin ducts. Studies in North-American pines indicated that the stem oleoresin exudation pressure (OEP) correlates negatively with transpiration rate and soil Water content. However, it is not known how the OEP changes affect the emissions of volatile vapours from the trees. We measured the OEP, Xylem diameter changes indicating changes in Xylem Water Potential and monoterpene emissions under field conditions in mature Scots pine (Pinus sylvestris L.) trees in southern Finland. Contrary to earlier reports, the diurnal OEP changes were positively correlated with temperature and transpiration rate. OEP was lowest at the top part of the stem, where Water Potentials were also more negative, and often closely linked to ambient temperature and stem monoterpene emissions. However, occasionally OEP was affected by sudden changes in vapour pressure deficit (VPD), indicating the importance of Xylem Water Potential on OEP as well. We conclude that the oleoresin storage pools in tree stems are in a dynamic relationship with ambient temperature and Xylem Water Potential, and that the canopy monoterpene emission rates may therefore be also regulated by whole tree processes and not only by the conditions prevailing in the upper canopy.

  • linking phloem function to structure analysis with a coupled Xylem phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

  • Linking phloem function to structure: Analysis with a coupled Xylem-phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Münch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and .

  • Linking phloem function to structure: Analysis with a coupled Xylem–phloem transport model
    Journal of theoretical biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

Maurizio Mencuccini - One of the best experts on this subject based on the ideXlab platform.

  • linking phloem function to structure analysis with a coupled Xylem phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

  • Linking phloem function to structure: Analysis with a coupled Xylem-phloem transport model
    Journal of Theoretical Biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Münch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and .

  • Linking phloem function to structure: Analysis with a coupled Xylem–phloem transport model
    Journal of theoretical biology, 2009
    Co-Authors: Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa
    Abstract:

    We carried out a theoretical analysis of phloem transport based on Munch hypothesis by developing a coupled Xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing Xylem Water Potential. The minimum number of Xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because Xylem Water Potential affected both Xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the Xylem reduced the need for investment in the phloem and vice versa.

  • Capacitive effect of cavitation in Xylem conduits: results from a dynamic model
    Plant Cell and Environment, 2009
    Co-Authors: Teemu Holtta, HervÉ Cochard, Eero Nikinmaa, Maurizio Mencuccini
    Abstract:

    Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the Xylem to transport Water to leaves provided that embolized conduits are not refilled. However, as a Xylem conduit is filled with gas during cavitation, Water is freed to the transpiration stream and this transiently increases Xylem Water Potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models Xylem Water Potential, Xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the Water release effect of Xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of Water in Xylem conduits. This ratio is typically large in large trees and during drought.

  • Capacitive effect of cavitation in Xylem conduits: results from a dynamic model
    Plant Cell and Environment, 2009
    Co-Authors: Teemu Holtta, HervÉ Cochard, Eero Nikinmaa, Maurizio Mencuccini
    Abstract:

    Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the Xylem to transport Water to leaves provided that embolized conduits are not refilled. However, as a Xylem conduit is filled with gas during cavitation, Water is freed to the transpiration stream and this transiently increases Xylem Water Potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models Xylem Water Potential, Xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the Water release effect of Xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of Water in Xylem conduits. This ratio is typically large in large trees and during drought.

HervÉ Cochard - One of the best experts on this subject based on the ideXlab platform.

  • Capacitive effect of cavitation in Xylem conduits: results from a dynamic model
    Plant Cell and Environment, 2009
    Co-Authors: Teemu Holtta, HervÉ Cochard, Eero Nikinmaa, Maurizio Mencuccini
    Abstract:

    Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the Xylem to transport Water to leaves provided that embolized conduits are not refilled. However, as a Xylem conduit is filled with gas during cavitation, Water is freed to the transpiration stream and this transiently increases Xylem Water Potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models Xylem Water Potential, Xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the Water release effect of Xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of Water in Xylem conduits. This ratio is typically large in large trees and during drought.

  • Capacitive effect of cavitation in Xylem conduits: results from a dynamic model
    Plant Cell and Environment, 2009
    Co-Authors: Teemu Holtta, HervÉ Cochard, Eero Nikinmaa, Maurizio Mencuccini
    Abstract:

    Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the Xylem to transport Water to leaves provided that embolized conduits are not refilled. However, as a Xylem conduit is filled with gas during cavitation, Water is freed to the transpiration stream and this transiently increases Xylem Water Potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models Xylem Water Potential, Xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the Water release effect of Xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of Water in Xylem conduits. This ratio is typically large in large trees and during drought.

  • Within crown variation in hydraulic architecture in beech (Fagus sylvatica L): evidence for a stomatal control of Xylem embolism
    Annals of Forest Science, 2002
    Co-Authors: Damien Lemoine, HervÉ Cochard, André Granier
    Abstract:

    The stomatal control of embolism in Fagus sylvatica L. was analysed in response to crown position and experimental changes of trunk hydraulic resistance. On one mature beech tree deep cuts were made in the trunk to increase the resistance to Water transfert. We followed the changes in leaf and Xylem Water Potential and stomatal conductance after the cuts at three levels within the canopy. We characterised vulnerability to cavitation for branches taken from two levels of irradiance (sun-exposed branches and shaded ones). Some differences appeared between shade and sun-exposed branches. When the leaf Water Potential dropped, stomatal conductances decreased earlier and faster in the shade branches. These results are well correlated with vulnerability to cavitation, shade branches being more vulnerable than sun-acclimated branches. Xylem Water Potential levels producing fifty percent loss of hydraulic conductivity were lower in sun-exposed branches than in shade grown ones (-3.1 MPa vs. -2.5 MPa on average). Xylem Water Potentials that induced stomatal closure were above the threshold-value inducing cavitation both for shade and sun-exposed branches. We confirmed that vulnerability to cavitation in Fagus sylvatica can acclimate to contrasting ambient light conditions, and we conclued that stomatal response to Water stress occured early and sufficiently fast to protect Xylem from dysfunction.

  • Within crown variation in hydraulic architecture in beech (Fagus sylvatica) L): evidence for a stomatal control of Xylem embolism
    Annals of Forest Science, 2002
    Co-Authors: Damien Lemoine, HervÉ Cochard, André Granier
    Abstract:

    The stomatal control of embolism in Fagus sylvaticaL. was analysed in response to crown position and experimental chan- ges of trunk hydraulic resistance. On one mature beech tree deep cuts were made in the trunk to increase the resistance to Water transfert. We followed the changes in leaf and Xylem Water Potential and stomatal conductance after the cuts at three levels within the canopy. We characterised vulnerability to cavitation for branches taken from two levels of irradiance (sun-exposed branches and shaded ones). Some differences appeared between shade and sun-exposed branches. When the leaf Water Potential dropped, stomatal conductances decrea- sed earlier and faster in the shade branches. These results are well correlated with vulnerability to cavitation, shade branches being more vulnerable than sun-acclimated branches. Xylem Water Potential levels producing fifty percent loss of hydraulic conductivity were lower in sun-exposed branches than in shade grown ones (-3.1 MPa vs. -2.5 MPa on average). Xylem Water Potentials that induced stomatal closure were above the threshold-value inducing cavitation both for shade and sun-exposed branches. We confirmed that vulnerability to cavitation in Fagus sylvatica can acclimate to contrasting ambient light conditions, and we conclued that stomatal response to Water stress occured early and sufficiently fast to protect Xylem from dysfunction. beech (Fagus sylvatica L.) / Xylem embolism / stomatal regulation / irradiance / acclimation

Huda Techno Enclave - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of Xylem Water Potential in Ten Native Plants of North-eastern Mexico
    International journal of Bio-resource and Stress Management, 2010
    Co-Authors: Humberto González-rodríguez, Israel Cantú-silva, Roque Gonzalo Ramírez-lozano, Marco Vinicio Gómez-meza, J. I. Uvalle Sauceda, Ratikanta Maiti, Huda Techno Enclave
    Abstract:

    Since Water stress is the most limiting factor in north-eastern Mexico, the present study focused to characterize the Xylem Water Potentials (Ψ, MPa) of ten native tree and shrub species such as Acacia rigidula (Leguminosae; shrub), Bumelia celastrina (Sapotaceae; tree), Castela texana (Verbenaceae; shrub), Celtis pallida (Ulmaceae; shrub), Forestiera angustifolia (Oleaceae; tree), Karwinskia humboldtiana (Rhamnaceae; shrub), Lantana macropoda (Simaroubaceae; shrub), Leucophyllum frutescens (Scrophulariaceae; shrub), Prosopis laevigata (Leguminosae; tree) and Zanthoxylum fagara (Rutaceae; tree) under drought and high soil Water content. Under drought conditions, P. laevigata, A. rigidula and C. texana achieved higher Ψ at pre-dawn with values of -2.72, -2.78 and -3.42 MPa, respectively, while minimum value of -6.82 MPa was observed in Z. fagara. Similarly, higher Ψ at mid-day was registered in C. texana, B. celastrina and P. laevigata with values around -4.15 MPa, while lower values (

  • characterization of Xylem Water Potential in ten native plants of north eastern mexico
    International journal of Bio-resource and Stress Management, 2010
    Co-Authors: Humberto Gonzalezrodriguez, J. I. Uvalle Sauceda, Ratikanta Maiti, Israel Cantusilva, Roque Gonzalo Ramirezlozano, Marco Vinicio Gomezmeza, Huda Techno Enclave
    Abstract:

    Since Water stress is the most limiting factor in north-eastern Mexico, the present study focused to characterize the Xylem Water Potentials (Ψ, MPa) of ten native tree and shrub species such as Acacia rigidula (Leguminosae; shrub), Bumelia celastrina (Sapotaceae; tree), Castela texana (Verbenaceae; shrub), Celtis pallida (Ulmaceae; shrub), Forestiera angustifolia (Oleaceae; tree), Karwinskia humboldtiana (Rhamnaceae; shrub), Lantana macropoda (Simaroubaceae; shrub), Leucophyllum frutescens (Scrophulariaceae; shrub), Prosopis laevigata (Leguminosae; tree) and Zanthoxylum fagara (Rutaceae; tree) under drought and high soil Water content. Under drought conditions, P. laevigata, A. rigidula and C. texana achieved higher Ψ at pre-dawn with values of -2.72, -2.78 and -3.42 MPa, respectively, while minimum value of -6.82 MPa was observed in Z. fagara. Similarly, higher Ψ at mid-day was registered in C. texana, B. celastrina and P. laevigata with values around -4.15 MPa, while lower values (<-7.0 MPa) were acquired by L. macropoda, K. humboldtiana and Z. fagara. In contrast, under high soil Water content, pre-dawn Ψ varied from -0.52 MPa (K. humboldtiana) to -1.63 MPa (C. texana). With respect to mid-day Ψ data, Ψ values ranged from -1.43 MPa (L. macropoda) to -2.28 MPa (C. texana). Since the plant species A. rigidula, B. celastrina, C. texana and P. laevigata achieved higher pre-dawn and mid-day Ψ values under drought conditions, the results indicated that these species could be considered as drought adapted species while, L. macropoda, K. humboldtiana and Z. fagara which acquired lower Water Potentials, may not be suitable to drought and thus, may be in a physiological disadvantage under limited Water conditions. The study suggests that the first four species may serve as a pertinent model to study the strategies of adapta tion to drought at high tissue Water Potential while the later may serve as an adequate model to study plant adaptation to drought at low tissue Water Potential. The implications of this study suggest that the species respond differently to drought through the employment of different strategies and there is scope for forest and range management practices in the selection of drought tolerant species for planting and reforestation of drought prone areas.