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Moreno Vertovec - One of the best experts on this subject based on the ideXlab platform.
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influence of the ectomycorrhizas formed by tuber melanosporum vitt on hydraulic conductance and water relations of Quercus Ilex l seedlings
Annals of Forest Science, 2000Co-Authors: Andrea Nardini, Sebastiano Salleo, Melvin T Tyree, Moreno VertovecAbstract:The physiological impact of ectomycorrhizal infection was investigated in the association between Tuber melanosporum Vitt. and Quercus Ilex L. A number of physiological parameters were investigated on 2-year-old seedlings inoculated for 22 months (I-seedlings) compared to non-inoculated plants (NI-seedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NI-seedlings. I-seedlings had higher values of net assimilation and stomatal conductance than NI - seedlings. Root hydraulic conductance per unit root surface area of I-seedlings was much reduced to 0.44 〈 that of NI-seedlings but had 2.5〈 more fine root surface area than NI-seedlings. When root conductance was scaled by leaf area, the I-seedlings had 1.27 〈 the root conductance per unit leaf area compared to NI-seedlings. I-seedlings also had significantly higher hydraulic conductances of shoots with leaves, of shoots without leaves and lower leaf blade hydraulic resistances. hydraulic conductance / water relations / ectomycorrhiza / Quercus Ilex L. / HPFM
Loretta Gratani - One of the best experts on this subject based on the ideXlab platform.
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Responses of Quercus Ilex from different provenances to experimentally imposed water stress
Biologia plantarum, 2003Co-Authors: P. Pesoli, Loretta Gratani, Walter LarcherAbstract:Responses of Quercus Ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψpd) and midday (Ψm) leaf water potential of stressed seedlings decreased on an average until −4.0 and −4.2 MPa, respectively, in the severe water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 – 83.6 % and the photosynthetic rates (PN) near zero. The critical threshold value of Ψpd for complete stomatal closure was from −4.0 to −4.5 MPa. The leaf damage after the severe water stress was significantly greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves).
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Shoot growth efficiency and production of Quercus Ilex L. in different climates
Flora - Morphology Distribution Functional Ecology of Plants, 2002Co-Authors: M. F. Crescente, Loretta Gratani, Walter LarcherAbstract:Summary Structural and functional traits of Quercus Ilex L. were monitored in plants growing in the climax area (Castelporziano, Rome; site A) and at the northern distribution limit (Nago, Trento; site B) in Italy. The most distinctive climatic differences between the two sites were duration and frequency of drought, heat spells in summer at site A, and the occurrence of frost and sub-zero temperatures in winter at site B. The potential productivity of Quercus Ilex lies in its tendency to be slow growing with maximum vegetative activity from the end of April to the end of June at Castelporziano, and from the middle of May to the middle of July at Nago, when air temperatures favoured the highest photosynthetic rates (90‐100%). The lower shoot biomass production at site B was due to the lower relative growth rates in shoot length (RGRl < 20%) and in shoot dry mass (RGRm
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Leaf temperature effects on gas exchange in Quercus Ilex L. growing under field conditions
Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology, 2000Co-Authors: Loretta GrataniAbstract:ABSTRACT Gas exchange temperature dependence in Quercus Ilex shrubs growing in the Mediterranean maquis was analysed. The gas exchange trend was monitored during the year: photosynthetic activity (A net) reached the highest average rates in early spring and autumn (12.5 µmol m-2s-1 was the absolute maximum A net measured) and the lowest rates were monitored in the middle of June. There was a good correlation (r = 0.72) between A net and g s (A net = 4.1246 ln g s + 4316; P < 0.01), indicating that stomatal control of CO2 diffusion plays an important role in controlling photosynthetic activity. Leaf temperature allowing the highest photosynthetic and stomatal conductance rates of Quercus Ilex were in the range 17.5 – 29°C. A net and gs dropped below half its maximum value when leaf temperatures were below 11.5°C and above 35.7°C. Transpiration rates (E) were strongly related to leaf temperature; E increased as leaf temperature increased and the highest E rates were monitored in June, despite a 46% decrease...
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Stomatal conductance correlates with photosynthetic activity in Quercus Ilex L. during the year
Ecologia mediterranea, 1999Co-Authors: Loretta Gratani, Roberto BassaniAbstract:La conductance stomatique en correlation avec la photosynthese nette au cours de l’annee chez Quercus Ilex L. La photosynthese nette (Anet) et la conductance stomatique (gs) ont ete mesurees sur des individus de Quercus Ilex, au sein d’un maquis present sur une dune sablonneuse le long de la cote du Lazio, aux alentours de Rome. Les mesures ont ete effectuees par beau temps, de fevrier a novembre 1996. Des temperatures de feuille (Tleaf) comprises entre 17°C et 29°C permettent la realisation de 90 a 100 % du taux maximum de photosynthese nette. De meme, la photosynthese nette diminue de plus de 50 % quand Tleaf est inferieur a 11°C ou au-dessus de 36°C, indiquant un declin marque de l’activite des mesophylles. Les taux de transpiration (E) les plus eleves ont ete observes pendant l'ete, bien que la conductance stomatique soit la plus basse. En ete, l’effet combine de la reduction de l’assimilation et de la perte d’eau elevee (transpiration) provoque une baisse d’efficacite d'utilisation de l’eau (WUE). Toutefois, la fermeture stomatique n’est jamais longue apres les periodes chaudes et seches et, quand les conditions deviennent plus favorables, un accroissement de gs et Anet est possible. Quercus Ilex est donc capable d’assimiler le carbone a un taux plus eleve pendant les periodes d'evaporation reduite, et de minimiser la perte d’eau estivale grâce a la diminution de la conductance stomatique en ete.
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Leaf and shoot growth dynamics of Quercus Ilex L.
Acta Oecologica-international Journal of Ecology, 1996Co-Authors: Loretta GrataniAbstract:L'activite vegetative de Quercus Ilex L. a lieu pendant la periode de faible stress hydrique directement consecutive aux abondantes precipitations de la fin de l'hiver. La faible temperature de l'air est le facteur limitant l'eclosion des bourgeons, alors qu'une temperature de l'air elevee agit sur la surface foliaire specifique (SLA) au cours de la periode de croissance. La photosynthese nette et la conductance stomatale augmentent avec une elevation de la temperature des feuilles jusqu'a 25°C; mais elles decroissent lorsque la temperature des feuilles avoisine 30°C (a la fin du mois de mai) ou est inferieure a 18°C (en novembre). La surface foliaire specifique va en s'accroissant du maquis bas a la strate arbustive forestiere en reponse a une irradiation decroissante. Le patron de SLA presente des valeurs maximales apres l'eclosion des bourgeons qui decroissent ensuite pour atteindre une valeur constante. Les arbustes de la foret sempervirente presentent une SLA elevee en mai en raison d'un double accroissement de la surface foliaire, alors que le poids sec foliaire ne change que legerement au cours de la premiere expansion. Le taux de croissance relative maximum (RGR) en mai-juin amene les feuilles a atteindre 90% de leur taille et de leur structure definitives avant la periode de secheresse, ce qui permet a l'expansion foliaire (la periode de plus grande demande nutritionnelle) de ne pas etre defavorablement affectee. Les temperatures estivales de l'air reduisent le taux de croissance relative mais ne bloquent pas completement l'expansion foliaire jusqu'a septembre-octobre. La variation intraspecifique de la SLA reflete la plasticite phenotyque de Quercus Ilex dans les habitats differents et demontre son aptitude a repondre adequatement a des facteurs de l'environnement en modifiant la morphologie des feuilles.
Andrea Nardini - One of the best experts on this subject based on the ideXlab platform.
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influence of the ectomycorrhizas formed by tuber melanosporum vitt on hydraulic conductance and water relations of Quercus Ilex l seedlings
Annals of Forest Science, 2000Co-Authors: Andrea Nardini, Sebastiano Salleo, Melvin T Tyree, Moreno VertovecAbstract:The physiological impact of ectomycorrhizal infection was investigated in the association between Tuber melanosporum Vitt. and Quercus Ilex L. A number of physiological parameters were investigated on 2-year-old seedlings inoculated for 22 months (I-seedlings) compared to non-inoculated plants (NI-seedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NI-seedlings. I-seedlings had higher values of net assimilation and stomatal conductance than NI - seedlings. Root hydraulic conductance per unit root surface area of I-seedlings was much reduced to 0.44 〈 that of NI-seedlings but had 2.5〈 more fine root surface area than NI-seedlings. When root conductance was scaled by leaf area, the I-seedlings had 1.27 〈 the root conductance per unit leaf area compared to NI-seedlings. I-seedlings also had significantly higher hydraulic conductances of shoots with leaves, of shoots without leaves and lower leaf blade hydraulic resistances. hydraulic conductance / water relations / ectomycorrhiza / Quercus Ilex L. / HPFM
Walter Larcher - One of the best experts on this subject based on the ideXlab platform.
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Responses of Quercus Ilex from different provenances to experimentally imposed water stress
Biologia plantarum, 2003Co-Authors: P. Pesoli, Loretta Gratani, Walter LarcherAbstract:Responses of Quercus Ilex L. seedlings from three different localities in Italy to experimentally imposed drought stress were analysed. Predawn (Ψpd) and midday (Ψm) leaf water potential of stressed seedlings decreased on an average until −4.0 and −4.2 MPa, respectively, in the severe water stress. At the end of the severe water stress the relative water content (RWC) was 72.5 – 83.6 % and the photosynthetic rates (PN) near zero. The critical threshold value of Ψpd for complete stomatal closure was from −4.0 to −4.5 MPa. The leaf damage after the severe water stress was significantly greater in seedlings originated from the acorns of climax area (45 % total leaf injured area and 40 % fallen leaves) than in the other seedlings (on an average 20.5 % total leaf injured area and 21 % fallen leaves).
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Shoot growth efficiency and production of Quercus Ilex L. in different climates
Flora - Morphology Distribution Functional Ecology of Plants, 2002Co-Authors: M. F. Crescente, Loretta Gratani, Walter LarcherAbstract:Summary Structural and functional traits of Quercus Ilex L. were monitored in plants growing in the climax area (Castelporziano, Rome; site A) and at the northern distribution limit (Nago, Trento; site B) in Italy. The most distinctive climatic differences between the two sites were duration and frequency of drought, heat spells in summer at site A, and the occurrence of frost and sub-zero temperatures in winter at site B. The potential productivity of Quercus Ilex lies in its tendency to be slow growing with maximum vegetative activity from the end of April to the end of June at Castelporziano, and from the middle of May to the middle of July at Nago, when air temperatures favoured the highest photosynthetic rates (90‐100%). The lower shoot biomass production at site B was due to the lower relative growth rates in shoot length (RGRl < 20%) and in shoot dry mass (RGRm
Corrado Tani - One of the best experts on this subject based on the ideXlab platform.
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Structural and functional traits of Quercus Ilex in response to water availability
Environmental and Experimental Botany, 2002Co-Authors: Filippo Bussotti, Davide Bettini, Paolo Grossoni, Silvia Mansuino, Renzo Nibbi, Costanza Soda, Corrado TaniAbstract:Abstract Water potential and morpho-anatomical parameters were measured, during the course of 1 year, on leaves of Quercus Ilex trees growing in two coastal stands in Tuscany (Central Italy) with different conditions of water availability: Colognole (CL, mesic site) and Cala Violina (CV, xeric site). Morpho-anatomical measurements included: general leaf features and sclerophylly indices (surface area, thickness, mass per area and density), leaf moisture indices (water content, relative water content, succulence) and histochemical analysis (detection and localization of cutine and tannins in the leaves and starch reserves in the twigs). During the warmest and driest period (August) pre-dawn water potential ( ψ pd ) in Holm-oak leaves reached −2.7 MPa at CV and −0.6 MPa at CL. Leaf surface was lower (−34%) and total leaf thickness (+10%), as well as spongy-palisade parenchyma ratio (+20%) were higher at CV. The sclerophylly parameters (leaf mass per area and leaf tissue density) were higher at CV than at CL (+24% leaf mass per area and +19% leaf tissue density). Among the moisture parameters, water content was higher at CL (+8%) and succulence was higher at CV (+13%). No differences in relative water content were observed between the two sites. All the parameters considered were substantially stable during the study period, with the exception of relative water content at CL, that fluctuated within the year. Histochemical analysis revealed a greater thickness of the upper cuticular layer at CV, whereas there were no differences in tannin distribution and content between the two sites. Differences in starch storage were detected in branchlets: it was abundant in CV but very scarce at CL. The strategies of Quercus Ilex to cope with water stress were discussed at morpho-structural level.
