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Levionnois, S.; Coste, S.; Nicolini, E.; Stahl, C.; Morel, H.; Heuret, P. |
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Title |
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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Year |
2020 |
Publication |
Tree physiology |
Abbreviated Journal |
Tree Physiol. |
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Volume |
40 |
Issue |
2 |
Pages |
245-258 |
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Keywords |
allometry; leaf size; petiole anatomy; scaling; theoretical hydraulic conductivity; vessel widening; xylem |
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Abstract  |
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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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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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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Levionnois, S.; Jansen, S.; Wandji, R.T.; Beauchêne, J.; Ziegler, C.; Coste, S.; Stahl, C.; Delzon, S.; Authier, L.; Heuret, P. |
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Title |
Linking drought-induced xylem embolism resistance to wood anatomical traits in Neotropical trees |
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Journal Article |
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Year |
2021 |
Publication |
New Phytologist |
Abbreviated Journal |
New Phytol. |
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Volume |
229 |
Issue |
3 |
Pages |
1453-1466 |
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Keywords |
bordered pits; drought-induced embolism; pit membrane; transmission electron microscopy; tropical trees; vessel grouping; xylem anatomy |
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Drought-induced xylem embolism is considered to be one of the main factors driving mortality in woody plants worldwide. Although several structure–functional mechanisms have been tested to understand the anatomical determinants of embolism resistance, there is a need to study this topic by integrating anatomical data for many species. We combined optical, laser, and transmission electron microscopy to investigate vessel diameter, vessel grouping, and pit membrane ultrastructure for 26 tropical rainforest tree species across three major clades (magnoliids, rosiids, and asteriids). We then related these anatomical observations to previously published data on drought-induced embolism resistance, with phylogenetic analyses. Vessel diameter, vessel grouping, and pit membrane ultrastructure were all predictive of xylem embolism resistance, but with weak predictive power. While pit membrane thickness was a predictive trait when vestured pits were taken into account, the pit membrane diameter-to-thickness ratio suggests a strong importance of the deflection resistance of the pit membrane. However, phylogenetic analyses weakly support adaptive coevolution. Our results emphasize the functional significance of pit membranes for air-seeding in tropical rainforest trees, highlighting also the need to study their mechanical properties due to the link between embolism resistance and pit membrane diameter-to-thickness ratio. Finding support for adaptive coevolution also remains challenging. © 2020 The Authors New Phytologist © 2020 New Phytologist Foundation |
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UMR BIOGECO, INRAE, Université de Bordeaux, Pessac, 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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997 |
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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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2020 |
Publication |
New Phytologist |
Abbreviated Journal |
New Phytol. |
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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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Author |
Cochard, H.; Coste, S.; Chanson, B.; Guehl, J.M.; Nicolini, E. |
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Title |
Hydraulic architecture correlates with bud organogenesis and primary shoot growth in beech (Fagus sylvatica) |
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Journal Article |
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2005 |
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Tree Physiology |
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Tree Physiol. |
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25 |
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12 |
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1545-1552 |
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Keywords |
development; hydraulic conductance; leaf primordia; meristem; xylem |
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Abstract |
In beech (Fagus sylvatica L.), the number of leaf primordia preformed in the buds determines the length and the type (long versus short) of annual growth units, and thus, branch growth and architecture. We analyzed the correlation between the number of leaf primordia and the hydraulic conductance of the vascular system connected to the buds. Terminal buds of short growth units and axillary buds of long growth units on lower branches of mature trees were examined. Buds with less than four and more than five leaf primordia formed short and long growth units, respectively. Irrespective of the type of growth unit the bud was formed on, the occurrence of a large number of leaf primordia was associated with high xylem hydraulic conductance. Xylem conductance was correlated to the area of the outermost annual ring. These results suggest that organogenesis and primary growth in buds correlates with secondary growth of the growth units and thus with their hydraulic architecture. Possible causal relationships between the variables are discussed. |
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INRA UBP, UMR PIAF, F-63039 Clermont Ferrand, France, Email: cochard@clermont.inra.fr |
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HERON PUBLISHING |
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0829-318X |
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ISI:000234019900008 |
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EcoFoG @ webmaster @ |
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281 |
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