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Calcicoles

The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform

T A Mansfield – 1st expert on this subject based on the ideXlab platform

  • Where does all the calcium go ? Evidence of an important regulatory role for trichomes in two Calcicoles
    Plant Cell and Environment, 1996
    Co-Authors: D L R De Silva, A M Hetherington, T A Mansfield

    Abstract:

    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.

  • where does all the calcium go evidence of an important regulatory role for trichomes in two Calcicoles
    Plant Cell and Environment, 1996
    Co-Authors: D L R De Silva, A M Hetherington, T A Mansfield

    Abstract:

    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.

  • the stomatal physiology of Calcicoles in relation to calcium delivered in the xylem sap
    Proceedings of The Royal Society B: Biological Sciences, 1994
    Co-Authors: D L R De Silva, T A Mansfield

    Abstract:

    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 – 2nd expert on this subject based on the ideXlab platform

  • The regulation of apoplastic calcium in relation to intracellular signalling in stomatal guard cells
    Journal of Plant Nutrition and Soil Science, 1998
    Co-Authors: D L R De Silva, A M Hetherington, Terry A. Mansfield

    Abstract:

    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.

  • Where does all the calcium go ? Evidence of an important regulatory role for trichomes in two Calcicoles
    Plant Cell and Environment, 1996
    Co-Authors: D L R De Silva, A M Hetherington, T A Mansfield

    Abstract:

    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.

  • where does all the calcium go evidence of an important regulatory role for trichomes in two Calcicoles
    Plant Cell and Environment, 1996
    Co-Authors: D L R De Silva, A M Hetherington, T A Mansfield

    Abstract:

    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.

Luc Barbaro – 3rd expert on this subject based on the ideXlab platform

  • reponses fonctionnelles des communautes de pelouses Calcicoles aux facteurs agro ecologiques dans les prealpes francaises
    Botany, 2000
    Co-Authors: Luc Barbaro, Thierry Dutoit, Emmanuel Corcket, Jeanpaul Peltier

    Abstract:

    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…

  • dynamique agro ecologique des communautes de pelouses seches Calcicoles du vercors meridional application a la gestion conservatoire de la biodiversite par le pastoralisme
    , 1999
    Co-Authors: Luc Barbaro

    Abstract:

    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.