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Coste, S.; Baraloto, C.; Leroy, C.; Marcon, E.; Renaud, A.; Richardson, A.D.; Roggy, J.C.; Schimann, H.; Uddling, J.; Herault, B. |
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Title |
Assessing foliar chlorophyll contents with the SPAD-502 chlorophyll meter: a calibration test with thirteen tree species of tropical rainforest in French Guiana |
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Journal Article |
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Year |
2010 |
Publication |
Annals of Forest Science |
Abbreviated Journal |
Ann. For. Sci. |
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Volume |
67 |
Issue |
6 |
Pages  |
607 |
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Keywords |
chlorophyll estimate; model calibration; homographic functions; neotropical trees |
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Abstract |
Chlorophyll meters such as the SPAD-502 offer a simple, inexpensive and rapid method to estimate foliar chlorophyll content. However, values provided by SPAD-502 are unitless and require empirical calibrations between SPAD units and extracted chlorophyll values. Leaves of 13 tree species from the tropical rain forest in French Guiana were sampled to select the most appropriate calibration model among the often-used linear, polynomial and exponential models, in addition to a novel homographic model that has a natural asymptote. The homographic model best accurately predicted total chlorophyll content (mu g cm(-2)) from SPAD units (R-2 = 0.89). Interspecific differences in the homographic model parameters explain less than 7% of the variation in chlorophyll content in our data set. The utility of the general homographic model for a variety of research and management applications clearly outweighs the slight loss of model accuracy due to the abandon of the species' effect. |
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[Herault, Bruno] Univ Antilles Guyane, Unite Mixte Rech Ecol Forets Guyane, Kourou, France, Email: bruno.herault@ecofog.gf |
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EDP SCIENCES S A |
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1286-4560 |
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ISI:000282350300007 |
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EcoFoG @ eric.marcon @ |
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40 |
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Author |
Levionnois, S.; Ziegler, C.; Jansen, S.; Calvet, E.; Coste, S.; Stahl, C.; Salmon, C.; Delzon, S.; Guichard, C.; Heuret, P. |
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Title |
Vulnerability and hydraulic segmentations at the stem–leaf transition: coordination across Neotropical trees |
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Journal Article |
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Year |
2020 |
Publication |
New Phytologist |
Abbreviated Journal |
New Phytol. |
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Volume |
228 |
Issue |
2 |
Pages |
512-524 |
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Keywords |
drought-induced embolism resistance; hydraulic segmentation; leaf-specific conductivity; stem–leaf transition; tropical trees; vulnerability segmentation; air bubble; hydraulic conductivity; leaf; Neotropical Region; rainforest; tropical forest; vulnerability; xylem |
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Hydraulic segmentation at the stem–leaf transition predicts higher hydraulic resistance in leaves than in stems. Vulnerability segmentation, however, predicts lower embolism resistance in leaves. Both mechanisms should theoretically favour runaway embolism in leaves to preserve expensive organs such as stems, and should be tested for any potential coordination. We investigated the theoretical leaf-specific conductivity based on an anatomical approach to quantify the degree of hydraulic segmentation across 21 tropical rainforest tree species. Xylem resistance to embolism in stems (flow-centrifugation technique) and leaves (optical visualization method) was quantified to assess vulnerability segmentation. We found a pervasive hydraulic segmentation across species, but with a strong variability in the degree of segmentation. Despite a clear continuum in the degree of vulnerability segmentation, eight species showed a positive vulnerability segmentation (leaves less resistant to embolism than stems), whereas the remaining species studied exhibited a negative or no vulnerability segmentation. The degree of vulnerability segmentation was positively related to the degree of hydraulic segmentation, such that segmented species promote both mechanisms to hydraulically decouple leaf xylem from stem xylem. To what extent hydraulic and vulnerability segmentation determine drought resistance requires further integration of the leaf–stem transition at the whole-plant level, including both xylem and outer xylem tissue. © 2020 The Authors. New Phytologist © 2020 New Phytologist Trust |
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Univ. Bordeaux, INRAE, BIOGECO, Pessac, F-33615, France |
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Blackwell Publishing Ltd |
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0028646x (Issn) |
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EcoFoG @ webmaster @ |
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952 |
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Svensk, M.; Coste, S.; Gérard, B.; Gril, E.; Julien, F.; Maillard, P.; Stahl, C.; Leroy, C. |
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Title |
Drought effects on resource partition and conservation among leaf ontogenetic stages in epiphytic tank bromeliads |
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Journal Article |
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2020 |
Publication |
Physiologia Plantarum |
Abbreviated Journal |
Physiol. Plant. |
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170 |
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4 |
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488-507 |
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Keywords |
chlorophyll; nitrogen; water; Bromeliaceae; drought; metabolism; photosynthesis; plant leaf; Bromeliaceae; Chlorophyll; Droughts; Nitrogen; Photosynthesis; Plant Leaves; Water |
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Studying the response to drought stress of keystone epiphytes such as tank bromeliads is essential to better understand their resistance capacity to future climate change. The objective was to test whether there is any variation in the carbon, water and nutrient status among different leaf ontogenetic stages in a bromeliad rosette subjected to a gradient of drought stress. We used a semi-controlled experiment consisting in a gradient of water shortage in Aechmea aquilega and Lutheria splendens. For each bromeliad and drought treatment, three leaves were collected based on their position in the rosette and several functional traits related to water and nutrient status, and carbon metabolism were measured. We found that water status traits (relative water content, leaf succulence, osmotic and midday water potentials) and carbon metabolism traits (carbon assimilation, maximum quantum yield of photosystem II, chlorophyll and starch contents) decreased with increasing drought stress, while leaf soluble sugars and carbon, nitrogen and phosphorus contents remained unchanged. The different leaf ontogenetic stages showed only marginal variations when subjected to a gradient of drought. Resources were not reallocated between different leaf ontogenetic stages but we found a reallocation of soluble sugars from leaf starch reserves to the root system. Both species were capable of metabolic and physiological adjustments in response to drought. Overall, this study advances our understanding of the resistance of bromeliads faced with increasing drought stress and paves the way for in-depth reflection on their strategies to cope with water shortage. © 2020 Scandinavian Plant Physiology Society |
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Laboratoire Ecologie Fonctionnelle et Environnement, Université de Toulouse, CNRS, Toulouse, 31062, France |
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Blackwell Publishing Ltd |
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00319317 (Issn) |
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PDF trop gros voir la documentaliste – merci |
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EcoFoG @ webmaster @ |
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943 |
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Coste, S.; Roggy, J.C.; Sonnier, G.; Dreyer, E. |
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Title |
Similar irradiance-elicited plasticity of leaf traits in saplings of 12 tropical rainforest tree species with highly different leaf mass to area ratio |
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Journal Article |
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2010 |
Publication |
Functional Plant Biology |
Abbreviated Journal |
Funct. Plant Biol. |
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37 |
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4 |
Pages |
342-355 |
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Keywords |
functional diversity; light availability; photosynthetic nitrogen use efficiency; photosynthetic capacity; tropical rainforest |
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Leaf traits of tropical tree species display an important inter-specific diversity, as detected for instance in the large range of values of leaf mass : area ratio (LMA). They also demonstrate a large irradiance-elicited plasticity, but there is still debate whether this plasticity differs among species. To address this question, leaf traits were recorded on saplings from 12 rainforest tree species in French Guiana, grown under approximately 5, 10 and 20% relative irradiance. Fifteen structural and physiological leaf traits related to photosynthesis were measured. The irradiance-elicited plasticity was quantified using a relative distance plasticity index. A large inter-specific diversity was detected for all leaf traits. A principal component analysis opposed species with a large mass-based photosynthesis, respiration, N content and photosynthetic nitrogen use efficiency, to species with a large leaf mass : area ratio, LMA. The two pioneer species used in this study displayed the largest photosynthetic capacity (and lowest LMA) and ranked at one end of the species continuum. Relative irradiance affected almost all traits with the exception of mass-based photosynthesis. A weak interaction was found between species and relative irradiance and the species ranking was maintained among relative irradiance treatments for the majority of the traits. A principal component analysis of the values of relative-distance plasticity index failed to reveal any consistent patterns of traits or species. We concluded that irradiance-elicited plasticity of leaf traits was similar among species irrespective of LMA and successional status, despite the occurrence of a large inter-specific diversity for the investigated traits. |
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[Dreyer, Erwin] Nancy Univ, INRA, UMR Ecol & Ecophysiol Forestieres 1137, IFR Ecosyst Forestiers Agroressources Biomol & Al, F-54280 Champenoux, France, Email: dreyer@nancy.inra.fr |
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CSIRO PUBLISHING |
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1445-4408 |
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ISI:000275979100009 |
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EcoFoG @ eric.marcon @ |
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63 |
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Levionnois, S.; Coste, S.; Nicolini, E.; Stahl, C.; Morel, H.; Heuret, P. |
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Scaling of petiole anatomies, mechanics and vasculatures with leaf size in the widespread Neotropical pioneer tree species Cecropia obtusa Trécul (Urticaceae) |
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Journal Article |
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2020 |
Publication |
Tree physiology |
Abbreviated Journal |
Tree Physiol. |
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40 |
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2 |
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245-258 |
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allometry; leaf size; petiole anatomy; scaling; theoretical hydraulic conductivity; vessel widening; xylem |
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Although the leaf economic spectrum has deepened our understanding of leaf trait variability, little is known about how leaf traits scale with leaf area. This uncertainty has resulted in the assumption that leaf traits should vary by keeping the same pace of variation with increases in leaf area across the leaf size range. We evaluated the scaling of morphological, tissue-surface and vascular traits with overall leaf area, and the functional significance of such scaling. We examined 1,271 leaves for morphological traits, and 124 leaves for anatomical and hydraulic traits, from 38 trees of Cecropia obtusa Trécul (Urticaceae) in French Guiana. Cecropia is a Neotropical genus of pioneer trees that can exhibit large laminas (0.4 m2 for C. obtusa), with leaf size ranging by two orders of magnitude. We measured (i) tissue fractions within petioles and their second moment of area, (ii) theoretical xylem hydraulic efficiency of petioles and (iii) the extent of leaf vessel widening within the hydraulic path. We found that different scaling of morphological trait variability allows for optimisation of lamina display among larger leaves, especially the positive allometric relationship between lamina area and petiole cross-sectional area. Increasing the fraction of pith is a key factor that increases the geometrical effect of supportive tissues on mechanical rigidity and thereby increases carbon-use efficiency. We found that increasing xylem hydraulic efficiency with vessel size results in lower leaf lamina area: xylem ratios, which also results in potential carbon savings for large leaves. We found that the vessel widening is consistent with hydraulic optimisation models. Leaf size variability modifies scaling of leaf traits in this large-leaved species. © The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permission@oup.com. |
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UMR AMAP, CIRAD, CNRS, IRD, Université de Montpellier, Montpellier, 34398, France |
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NLM (Medline) |
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17584469 (Issn) |
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Export Date: 16 March 2020 |
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EcoFoG @ webmaster @ |
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921 |
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