The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
T A Mansfield - One of the best experts on this subject based on the ideXlab platform.
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Where does all the calcium go ? Evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
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where does all the calcium go evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
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the stomatal physiology of Calcicoles in relation to calcium delivered in the xylem sap
Proceedings of The Royal Society B: Biological Sciences, 1994Co-Authors: D L R De Silva, T A MansfieldAbstract:Physiological mechanisms in Calcicoles in simulated highly calcareous habitats have been investigated using Campanula glomerata, Centaurea scabiosa and Leontodon hispidus. Diffusion resistance of the leaves was unaffected by high concentrations (15 mol m$^{-3}$) of rhizospheric calcium in all three species, and in C. scabiosa and L. hispidus there was no inhibition of leaf extension even at 20 mol m$^{-3}$. Free calcium concentrations in samples of xylem sap taken from the roots were found to be very close to those in the rhizosphere. However, stomata on isolated epidermis of C. scabiosa and L. hispidus closed in response to elevated free calcium in the same manner as those of Commelina communis, a calcium-neutral plant. It is concluded that the Calcicoles must possess an efficient mechanism to remove high concentrations of free calcium delivered into the leaf's apoplast by the transpiration stream. If the xylem sap reached the apoplast around the stomata containing even 5-10% of its free calcium, stomatal function would be disturbed. If these species are representative of Calcicoles in general, the leaf's mechanism for preventing excess calcium from reaching the stomatal guard cells may be indispensable. The capacity to remove or sequester most of the calcium delivered in the xylem may be a key factor in determining whether a plant is a calcicole or not.
D L R De Silva - One of the best experts on this subject based on the ideXlab platform.
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The regulation of apoplastic calcium in relation to intracellular signalling in stomatal guard cells
Journal of Plant Nutrition and Soil Science, 1998Co-Authors: D L R De Silva, A M Hetherington, Terry A. MansfieldAbstract:It is now well established that calcium has a substantive role in intracellular signalling in stomatal guard cells. Much less attention has, however, been paid to the importance of maintaining an apoplastic calcium concentration which permits this mechanism to operate. Data are presented for the calcicole Leontodon hispidus, in which the xylem sap may contain over 16 mM free calcium, showing that the concentration of calcium in the guard cell apoplast may be as low as 0.10 mM. This appears to be achieved by the deposition of considerable amounts of calcium oxalate in the mesophyll, particularly in the palisade tissue. Of the calcium delivered directly into the epidermis by the transpiration stream, a large proportion is diverted into the trichomes. It seems unlikely that stomatal regulation over long distances (e.g. from root to shoot) is accomplished via apoplastic calcium, but over shorter distances (the span of a few cells in the epidermis) signalling via calcium in the apoplast is entirely feasible and it is worthy of further investigation. Die Regulierung des apoplastischen Calciums im Hinblick auf die intrazellulare Signalubertragung in stomataren Schlieszellen Die bedeutende Rolle des Calciums in der intrazellularen Signalubertragung in stomataren Schlieszellen ist gut belegt. Wie wichtig die Aufrechterhaltung einer apoplastischen Calciumkonzentration ist, die diesen Mechanismus uberhaupt erst ermoglicht, hat jedoch viel weniger Aufmerksamkeit gefunden. Die hier vorgestellten Ergebnisse fur die calcicole Art Leontodon hispidus, in der der Xylemsaft mehr als 16 mM freies Calcium enthalten kann, zeigen, das die Calciumkonzentration im Schlieszellenapoplasten Werte von nur 0.10 mM erreichen kann. Es scheint, das dies durch die Ablagerung betrachtlicher Mengen Calciumoxalat im Mesophyll, besonders im Palisadengewebe, erreicht wird. Ein groser Teil des Calciums, das mit dem Transpirationsstrom direkt in die Epidermis gelangt, wird in die Trichome abgeleitet. Es erscheint unwahrscheinlich, das die stomatare Regulation uber lange Strecken (z. B. von der Wurzel zum Spros) mittels apoplastischen Calciums erreicht wird, aber uber kurzere Strecken (uber wenige Epidermiszellen hinweg) ist die Signalubertragung durch Calcium im Apoplasten durchaus moglich und weiterer Untersuchung wert.
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Where does all the calcium go ? Evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
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where does all the calcium go evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
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the stomatal physiology of Calcicoles in relation to calcium delivered in the xylem sap
Proceedings of The Royal Society B: Biological Sciences, 1994Co-Authors: D L R De Silva, T A MansfieldAbstract:Physiological mechanisms in Calcicoles in simulated highly calcareous habitats have been investigated using Campanula glomerata, Centaurea scabiosa and Leontodon hispidus. Diffusion resistance of the leaves was unaffected by high concentrations (15 mol m$^{-3}$) of rhizospheric calcium in all three species, and in C. scabiosa and L. hispidus there was no inhibition of leaf extension even at 20 mol m$^{-3}$. Free calcium concentrations in samples of xylem sap taken from the roots were found to be very close to those in the rhizosphere. However, stomata on isolated epidermis of C. scabiosa and L. hispidus closed in response to elevated free calcium in the same manner as those of Commelina communis, a calcium-neutral plant. It is concluded that the Calcicoles must possess an efficient mechanism to remove high concentrations of free calcium delivered into the leaf's apoplast by the transpiration stream. If the xylem sap reached the apoplast around the stomata containing even 5-10% of its free calcium, stomatal function would be disturbed. If these species are representative of Calcicoles in general, the leaf's mechanism for preventing excess calcium from reaching the stomatal guard cells may be indispensable. The capacity to remove or sequester most of the calcium delivered in the xylem may be a key factor in determining whether a plant is a calcicole or not.
Luc Barbaro - One of the best experts on this subject based on the ideXlab platform.
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reponses fonctionnelles des communautes de pelouses Calcicoles aux facteurs agro ecologiques dans les prealpes francaises
Botany, 2000Co-Authors: Luc Barbaro, Thierry Dutoit, Emmanuel Corcket, Jeanpaul PeltierAbstract:The identification of functional groups in calcareous grasslands of southern Vercors (Rhone-Alpes, France) is investigated through relationships between biological traits of the species and agro-ecological factors. Community patterns are determined by (i) the level of edaphic stress (oligotrophy and xericity) and (ii) the regime and the intensity of agropastoral management (grazing and mechanical cutting). In such grasslands submitted to regular disturbance, life traits related to dispersal and regeneration processes have greater importance for the differentiation of species than morphological traits, and Grime's adaptative strategies are the best predictors of species ordination on agro-ecological gradients (e.g., stress and disturbance). A classification of species in functional groups based on the same life traits and similar responses to disturbances is proposed, and its role in defining adequate conservation management of calcareous grassland by low-intensity livestock farming is discussed. The funct...
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dynamique agro ecologique des communautes de pelouses seches Calcicoles du vercors meridional application a la gestion conservatoire de la biodiversite par le pastoralisme
1999Co-Authors: Luc BarbaroAbstract:Les pelouses seches Calcicoles du parc naturel regional du vercors representent un enjeu de conservation majeur dans les prealpes du sud, en raison d'une diminution de leur utilisation traditionnelle par les systemes d'elevage extensif. Le principal objectif de ce travail est la construction d'un modele multivarie de leur dynamique sous l'influence des conditions d'habitat (stress) et des modes de gestion (perturbations). La premiere partie analyse leurs influences respectives, combinees, et leurs interactions sur la composition floristique, par analyse canonique des correspondances (acc). L'effet separe de la lithologie est le plus determinant, expliquant 12% de la variabilite floristique, tandis que le meilleur modele est obtenu avec l'effet cumule des perturbations (frequence d'entretien mecanique x intensite de paturage) et de la lithologie (24%). Des groupes fonctionnels d'especes avec les memes traits biologiques et les memes reponses aux facteurs agro-ecologiques sont identifies par une analyse d'ordination a 3 tableaux (analyse rlq). La seconde partie traite de l'utilisation du modele multivarie pour evaluer les effets de la gestion conservatoire et de la restauration experimentale sur la richesse specifique, la rarete des especes et leur amplitude de niche sur les gradients agro-ecologiques. Les assemblages d'orchidees, especes cibles pour la gestion conservatoire, montrent des reponses complexes aux modes de gestion, dependant des traits biologiques des especes. Enfin, les resultats d'une experience de 6 ans de restauration de 4 pelouses par debroussaillement et paturage montrent que la richesse specifique et le nombre d'annuelles et d'especes rares ont augmente, avec des maxima atteints 3 a 4 ans apres debroussaillement. Le maintien ou la restauration de pratiques agro-pastorales extensives (combinaison de paturage et d'entretien mecanique pluri-annuel), parait donc indispensable pour conserver a long terme les pelouses Calcicoles du vercors.
L Barbaro - One of the best experts on this subject based on the ideXlab platform.
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organisation agro ecologique des pelouses et landes Calcicoles du parc naturel regional du vercors rhone alpes france
Ecologie, 1998Co-Authors: L Barbaro, P CozicAbstract:In the Vercors Regional Natural Park (Rhone-Alpes, France), we study the respective influence ofabiotic (i.e. soil and moisture conditions) and biotic factors (i.e. shrub dynamics and agricultural practices) on the agro-ecological organization of the vegetation, according to a synchronic sample of the floristic composition of calcareous grasslands and shrublands. We use the hierarchical properties of multivariate analysis (Correspondence Analysis) to determine the main factors of organization of these communities. These main factors are trophic level (i.e. stress) and successional dynamics (i.e. disturbance). We search for correlations between sample ordinations obtained by CA and values of environment and management variables, for predictive modelling of species turnover along gradients. Above-ground phytomass of grasslands for axis 1, and percentage cover of shrub layer for axis 2 are the best correlated variables with floristic ordinations. Agro-ecological classification of both grassland communities and species have been performed with cluster analysis. Finally, we use life forms and life strategies of species to characterize functional groups occurring at every stage of trophic and successional gradients.
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typologie agro ecologique des pelouses landes et fruticees Calcicoles pâturees des prealpes calcaires parc naturel regional du vercors france
1997Co-Authors: L BarbaroAbstract:/ Parallelement aux travaux sur l'inventaire et la dynamique des vegetations des espaces supraforestiers (alpages menes par l'equipe agro-ecologie pastorale du Cemagref (division AMM), cette etude realisee au sein de cette equipe de recherche s'interesse a des espaces situes plus bas en altitude soumis a de fortes mutations de pratiques et objet de preoccupations agri-environnementales importantes. Dans l'optique de formuler a terme des recommandations de gestion de ces espaces, l'etude porte sur la dynamique de milieux agro-pastoraux du Vercors plus ou moins enfriches, dans un contexte d'evolution de pratiques sur ce massif. La premiere phase consiste en l'elaboration d'une typologie agro-ecologique de pelouses et landes Calcicoles pâturees du Vercors soumises a des niveaux divers de pression pastorale (allegement, abandon, reprise ). La methode retenue s'appuie sur les points majeurs suivants : - echantillonnage synchronique d'une centaine de stations de pelouses Calcicoles de moyenne montagne du Vercors en voie d'enfrichement ; - caracterisation de ces pelouses par releves phyto-ecologiques quantifies et releves des conditions d'utilisation ; - ordination et classification (typologie) des communautes de pelouses Calcicoles prealpines (AFC,CAH) selon les principaux facteurs agro-ecologiques, - analyse des principaux facteurs d'organisation de ces communautes vegetales. L'echantillonnage synchronique de la centaines de pelouses Calcicoles de moyenne montagne du Vercors en voie d'enfrichement suite au processus historique de deprise agro-pastorale, a permis de mettre en evidence les principaux facteurs d'organisation de ces communautes vegetales a forte valeur biologique et patrimoniale. L'ordination optimale des stations et des especes dans un espace agro-ecologique plurifactoriel, grâce aux methodes d'analyse statistique multivariee, permet de porter un diagnostic sur le degre d'organisation ou de desorganisation des peuplements de pelouses, suite aux modifications de pratiques pastorales. L'utilisation conjointe d'une methode de classification hierarchique permet d'elaborer une typologie agro-ecologique de ces groupements, prenant en compte differents objectifs de gestion concernant la ressource pastorale ou differents aspects de la biodiversite. Une presentation detaillee de chacun des types de vegetation est realisee : une typologie des especes est egalement proposee.
A M Hetherington - One of the best experts on this subject based on the ideXlab platform.
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The regulation of apoplastic calcium in relation to intracellular signalling in stomatal guard cells
Journal of Plant Nutrition and Soil Science, 1998Co-Authors: D L R De Silva, A M Hetherington, Terry A. MansfieldAbstract:It is now well established that calcium has a substantive role in intracellular signalling in stomatal guard cells. Much less attention has, however, been paid to the importance of maintaining an apoplastic calcium concentration which permits this mechanism to operate. Data are presented for the calcicole Leontodon hispidus, in which the xylem sap may contain over 16 mM free calcium, showing that the concentration of calcium in the guard cell apoplast may be as low as 0.10 mM. This appears to be achieved by the deposition of considerable amounts of calcium oxalate in the mesophyll, particularly in the palisade tissue. Of the calcium delivered directly into the epidermis by the transpiration stream, a large proportion is diverted into the trichomes. It seems unlikely that stomatal regulation over long distances (e.g. from root to shoot) is accomplished via apoplastic calcium, but over shorter distances (the span of a few cells in the epidermis) signalling via calcium in the apoplast is entirely feasible and it is worthy of further investigation. Die Regulierung des apoplastischen Calciums im Hinblick auf die intrazellulare Signalubertragung in stomataren Schlieszellen Die bedeutende Rolle des Calciums in der intrazellularen Signalubertragung in stomataren Schlieszellen ist gut belegt. Wie wichtig die Aufrechterhaltung einer apoplastischen Calciumkonzentration ist, die diesen Mechanismus uberhaupt erst ermoglicht, hat jedoch viel weniger Aufmerksamkeit gefunden. Die hier vorgestellten Ergebnisse fur die calcicole Art Leontodon hispidus, in der der Xylemsaft mehr als 16 mM freies Calcium enthalten kann, zeigen, das die Calciumkonzentration im Schlieszellenapoplasten Werte von nur 0.10 mM erreichen kann. Es scheint, das dies durch die Ablagerung betrachtlicher Mengen Calciumoxalat im Mesophyll, besonders im Palisadengewebe, erreicht wird. Ein groser Teil des Calciums, das mit dem Transpirationsstrom direkt in die Epidermis gelangt, wird in die Trichome abgeleitet. Es erscheint unwahrscheinlich, das die stomatare Regulation uber lange Strecken (z. B. von der Wurzel zum Spros) mittels apoplastischen Calciums erreicht wird, aber uber kurzere Strecken (uber wenige Epidermiszellen hinweg) ist die Signalubertragung durch Calcium im Apoplasten durchaus moglich und weiterer Untersuchung wert.
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where does all the calcium go evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
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Where does all the calcium go ? Evidence of an important regulatory role for trichomes in two Calcicoles
Plant Cell and Environment, 1996Co-Authors: D L R De Silva, A M Hetherington, T A MansfieldAbstract:In previous studies of the Calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m−3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for 'protecting' stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca2+ in intra-cellular signalling in guard cells can continue to be performed without disturbance.
