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International audience; Seed size and the growth environment are important variables that influence seed germination, growth and biomass of seedlings and future tree harvest and should thus be taken into account in agroforestry and reforestation programmes for endangered species like Pterocarpus erinaceus. In the present study, to assess seedling germination and vigour in P. erinaceus as a function of seed size in two environments, 1080 seeds and 360 seedlings were evaluated at two separate sites in Côte d'Ivoire. The results show that large seeds had very high germination rates (up to 100%) and produced more vigorous plants better able to adapt to climate change. The maternal environment and seed size had a significant influence on seed germination (P

Pterocarpus erinaceus est une espèce largement utilisée par les populations des zones sahéliennes et soudaniennes. Cependant, cette espèce est menacée par l’exploitation abusive des peuplements naturels. La présente étude vise à déterminer un idéotype de profondeur de semis des graines de Pterocarpus erinaceus pour relever le taux de germination de production des plantules dans le cadre de sa régénération. Pour ce faire, les graines ont été décortiquées et enfouies à différentes profondeurs (0,5 cm, 1 cm, 1,5 cm) sans traitement spécifique. L’évaluation de la vigueur des plantules a été basée sur des paramètres morphologiques qui sont : la hauteur (Ht), le diamètre au collet (Dcol), le nombre de feuille (Nf), la longueur des feuilles (Logfe) et la largeur des feuilles (Largfe). Les résultats ont montré que les meilleurs taux de germination (90,66 %) sont obtenus avec les semis enfouis à 0,5 cm du sol. Les faibles taux (41 %) de germinations ont été obtenus avec les semences enfouies à 1,5 cm. Cette expérimentation dénote que le semis superficiel des graines de Pterocarpus erinaceus est recommandé pour sa multiplication. Pterocarpus erinaceus is a species widely used by populations in the Sahelian and Sudanese zones. This species, however, is threatened by the abusive exploitation of natural stands. This paper focuses on determining a seedling depth ideotype of Pterocarpus erinaceus seeds in recording the germination rate of seedling production as part of its regeneration. In doing this, the seeds were shelled and buried at different depths (0,5 cm, 1 cm, 1,5 cm) without specific treatment. The evaluation of the sturdiness of the seedling was based on morphological parameters which are: height (Ht), neck diameter (Dcol), number of leaves (Nf), length of leaves (Logfe), and width of leaves (largfe). The results showed that the best germination rates (90,66 %) are obtained with seedlings buried at 0,5 cm from the ground. Low germination rates (41 %) were obtained with seeds buried at 1,5 cm. This experiment indicates that the superficial sowing of the seeds of Pterocarpus erinaceus is recommended for its multiplication.

Introduction Madagascar est un sanctuaire de caféiers sauvages. Sur les 124 espèces de caféiers inventoriées dans le monde, 61 sont présentes à Madagascar (Davis, 2010, 2011 ; Davis et al., 2006, 2011). Le genre Coffea est subdivisé en deux sous-genres : le sous-genre Coffea (à feuilles persistantes) et le sous-genre Baracoffea (à feuilles caduques) (Bridson et Verdcourt, 1988 ; Davis et al., 2006). Ce dernier regroupe neuf espèces endémiques xérophytiques ayant des caractéristiques morpholog...

Dans un monde confronté aux changements climatiques et à des pandémies en lien avec la destruction des milieux naturels, les enjeux liés à la préservation de la biodiversité sont dorénavant bien connus et ont donné lieu à des accords internationaux majeurs, comme le protocole de Nagoya. Dans ce contexte mondial, les recherches menées au Sud sont primordiales. Les contributions rédigées ici par des chercheurs dʼAfrique, de lʼocéan Indien, dʼAsie du Sud-Est et dʼEurope traduisent la vigueur de la recherche sur la biodiversité dans les pays intertropicaux francophones. Documenter la diversité des écosystèmes végétaux locaux, mieux connaître les savoirs traditionnels et les utilisations populaires des plantes ou des champignons, valoriser le rôle des collections botaniques, identifier des chaînes de valorisation économique responsables, gérer durablement les écosystèmes et leurs ressources, élaborer des outils stratégiques pour une gouvernance environnementale basée sur la science et, enfin, montrer la nécessité de lʼimplication citoyenne et de lʼensemble des acteurs concernés, tels sont les grands thèmes déclinés ici. Cet ouvrage collectif intéressera tous ceux qui travaillent sur la biodiversité des écosystèmes intertropicaux. Il souligne la nécessité dʼune science de lʼaction au service du développement durable.

International audience; Parkia biglobosa is a much-loved and over-exploited African savannah species for its socio-economic importance. Knowing and taking into account its architectural unit, which is the basis for diagnosing phenology, productivity and tree health, could provide a new perspective on its sustainable management. The aim of this study is to establish the architectural development in Parkia biglobosa by retrospective analysis. To achieve this objective, 390 individuals of all sizes ranging from seedlings to senescent trees were observed and analysed under various soil and climatic conditions in Côte d’Ivoire. The results showed that Parkia biglobosa is a light plant but shading tolerant. It is a mixed vegetative axis plant, the stem is orthotropic* in its proximal part and plagiotropic* (collapsing) in its distal part in young stage. The tree then transitions to an adult and old stage into a tree with a plagiotropic* axis in the proximal and distal parts, the trunk is built up by superimposing collapsed relay axes that gradually straighten, branching is sympodial*, growth is defined and sexuality is terminal and lateral. The ontogeny takes place in three phases: initiation of development and establishment of the crown (young), then flowering and establishment of the architectural unity (adult) and finally the death of secondary axes in the crown, duplication of the architecture by a series of partial and total reiterations (old). The level of organisation is 5: the phytomere, the module or growth unit, the axis, the architectural unit and the reiterated complex. Retrospective analysis of the modules showed that the dimensions of the growth units are indicators of morphological variation and species adaptation to a changing climate (P < 0.05). However, the equations generated by the morphological and habitat dimension linkage models are not significant (R2 and r < 0.7) to be used as a guide for field data collection. This study represents an initiation into the architectural study of this species and the information provided will serve as a basis for further research into the architecture in relation to the sustainable use of this species.

International audience; L'analyse rétrospective permet d'accéder à des séries de croissance à long terme pour comprendre et interpréter le fonctionnement structurel des couronnes d'arbres nécessaire à leur gestion durable. L'objectif de cette étude était d'évaluer le développement et l'adaptation des pousses de la couronne chez Khaya senegalensis et Pterocarpus erinaceus à un environnement changeant en vue de l'établissement de parcelles permanentes. La morphologie des unités de croissance (UC) des axes de 420 individus jeunes, adultes et âgés a été analysée en plein soleil ou à l'ombre pendant la saison des pluies et la saison sèche dans sept endroits en Côte d'Ivoire. Les résultats ont montré que la morphologie des unités de croissance est un indicateur du choix des conditions de croissance. L'habitat hétérogène n'a pas eu d'effet significatif sur la morphologie des unités de croissance (P > 0,05) chez les deux espèces. La morphologie des unités de croissance varie d'un endroit (climat) à l'autre en raison de caractéristiques environnementales distinctes (P < 0,05). La partie sud du gradient (Toumodi et Bouaké dans la région centrale du pays) offre des zones favorables et donc prioritaires pour les programmes de reboisement basés sur les deux espèces. L'âge des individus a influencé le nombre de phytomères par unité de croissance (P < 0,05). Les jeunes individus (boutures) sont de bons idéotypes pour la sélection de génotypes résistants adaptés. Quelle que soit l'espèce, la saison des pluies augmente le taux de réussite de l'établissement des parcelles. Les unités de croissance des deux espèces sont pratiquement de la même taille (P > 0,05). Nos résultats pourraient constituer un guide de décision pour la sélection de milieux adaptés à la mise en œuvre de programmes de reboisement ou d'agroforesterie à base de Khaya senegalensis et Pterocarpus erinaceus, afin de conserver et de gérer durablement ces espèces dans le contexte actuel de changement climatique.

International audience; Pterocarpus erinaceus is over-exploited for its multiple uses. Its exploitation and trade are strictly prohibited in many countries, including Côte d'Ivoire, to prevent its extinction. It is nevertheless imperative to restore populations of this species, while accounting for its germinative capacities and its adaptation to changing climates. The aim of this study was to assess the seed germination and seedling development in Pterocarpus erinaceus in three different environments. A total of 2,160 seeds from different seed trees and 540 individuals germinated from seeds were selected and evaluated. The trials were conducted at three sites with distinct microclimates (two nurseries in Côte d’Ivoire and one greenhouse in France). The results showed that the environment had a significant influence on germination parameters (P < 0.05), whereas the seed trees did not (P > 0.05). The environment influenced the height and internodes length of the seedlings (P < 0.05). However, the diameter, number of leaves, and the length and width of the leaves of the seedlings were statistically identical from one site to another (P > 0.05). Seed trees influenced the number and length of seedlings leaves (P

International audience; Interpretation of primary growth markers (modules) is neglected in sustainable resource management processes, yet it opens up prospects for long time series on tree crown development, necessary for their characterization in the current context of climate change. This study aimed to assess the morphological variation of crown shoots in Parkia biglobosa in the face of a changing environment. Axis growth modules of 420 individuals of different ages were retrospectively analyzed in the presence or absence of shading during the wet and dry seasons in seven localities in Cote d’Ivoire. The results showed that the developmental environment of individuals did not influence the growth modules dimensions (P > 0.05). However, module size remained significantly different between locations (P < 0.05). The southern part of the gradient is still favourable and has priority for the establishment of permanent plots. The modules morphology differs from the youngest to the oldest individuals (P < 0.05). The rainy season remains the ideal period for the implementation of agroforestry reforestation programmes based on this species (P < 0.05). Parkia biglobosa is a monochasial sympod (Pseudo-monopod) with a relay axis that follows the Paul Champagnat architectural model in the young stage, and transits to the Wilhelm Troll model later in the adult and old stage. This information contributes to the understanding of the functioning of crown and the adaptation of this species to a varying environment. It could guide choice of suitable environment and ideal genotype for the implementation of a reforestation or agroforestry programme based on Parkia biglobosa.

International audience; Organ biomass and leaf area are important parameters in plant physiology and production. They are used in structural and functional plant models to simulate tree architecture, but are difficult to determine quickly. Stem (length and internode diameter) and leaf (length and width) dimensions for their estimation provide a non-destructive and rapid field approach. This method has been applied on Khaya senegalensis, Pterocarpus erinaceus and Parkia biglobosa in Côte d'Ivoire. Internodes and leaves of the three species were sampled in 2019 and 2020 on three categories of axis in the architecture of individuals of different ages to maximise the variability of their size. All statistical relationships of the linear models found for the estimation of organ dry and fresh biomass and leaf area were significant for all three species (P = 0.001). A single equation was sufficient to estimate the dry (IDM) and fresh (IFM) biomass of the internodes, the dry (LDM) and fresh (LFM) biomass of the leaves and the leaf area (LA) from the dimensions of the internodes (Volume: VL) and leaves (Number of primary leaflets: NLt, length: LLtL and width: LLtW of the largest primary leaflet, number of secondary leaflets: NSeLt, length: LSeLtL and width: LSeLtW of the largest secondary leaflet). The relationship between the estimates and organ dimensions were defined by the following linear equations: IDM = 0.45 × VL + 0.02, LDM = 0.004 × NLt × LtL × LtW + 0.07 and LA = 0.83 × NLt × LtL × LtW for Khaya senegalensis; IDM = 0.33 × VL + 0.38, LDM = 0.4 × NLt × LtL × LtW − 0.64 and LA = 0.74 × NLt × LtL × LtW + 0.15 for Pterocarpus erinaceus then IDM = 0.47 × VL + 0.44, LDM = 0.44 × NSeLt × LSeLtL × LSeLtW × NLt + 0.94 and LA = 0.13 × NSeLt × LSeLtL × LSeLtW × NLt + 14.64 for Parkia biglobosa. This method can be applied to estimate the organ biomass and LA of species of the same family as the target species in an agroforestry system.

Introduction - The Guayule (Parthenium argentatum, Asteraceae), is a branched shrub native to northern Mexico showing a growing interest in research and agriculture (Ray, 1993). However, few studies have been done on the structure or functioning of the species and the production itineraries in relation to natural rubber production are still to assess. This study aims to propose a first FSPM of the species using the GreenLab model, calibrated with data issued from two varieties in different environmental conditions. The objective is to understand the interaction between the development of Guayule and natural rubber production. Materials and Methods - Experimental plots were conducted on two varieties (Fig. A), named CL1 (parent USDA 11591 triploid) and CLA1 (parent USDA AZ 101 tetraploid). The CL1 variety has small stem and leaf size compared to the CLA1 variety. These varieties were planted in the field under various environmental conditions related to density (9091 and 62500 plants/ha), and hydric pressure (100%, 66% and 33% of optimal supply). The measurements carried out to count number of phytomers per module as well as the number of relay axes. We also clustered the total dry weight of leaves and stems per module in order to build the axis organic series (Buis and Barthou, 1984) and to estimate the content of natural rubber from a NIRS analysis (Taurines et al., 2019). The field measurements from the series constituted a target to calibrate the GreenLab model functional parameters such as the organ sink functions (Kang et al, 2018).We chose such a cohort model, since the structure (here the module rank) can be analysed in the biomass production without detailed explicit geometrical computations. Results and Discussion - Experimental results. The Guayule shows a sympodial development composed of modules with a terminal inflorescence. Its architecture corresponds to the Leeuwenberg's model (F. Hallé et al. 1978) producing eight to nine modules per year. The number of internodes within the modules is almost stable regardless of variety and environmental conditions. The architecture of the two varieties CL1 and CLA1 is very similar, including the duration of the functioning of the organs (leaves and inflorescences). In the experiment, the biomass production per module (and thus per plant) was shown to be dependent on both density and water supply, according to the variety. Natural rubber content was found higher on young modules, and the water regime affected the natural rubber content of modules according to the variety (Fig. B). Modelling results. We have modelled the number of internodes per module with a constant binomial law. The number of relay axis per module was modelled with a damped binomial law, simulating the branching rate decreases on young modules. These laws allowed simulating the plant structure (Fig. C). We then retrieved the organ sinks parameters, fitting the target file, and found significant differences in the leaf sink functions, stronger for the variety CLA1. As a result, the simulation of the functional model allowed the module diameters and the total plant height of the two varieties to be recovered correctly (Fig. D.). We still need to validate the relation between the internode growth and natural rubber production from new field analysis. Acknowledgement - Authors thank the Agropolis Fondation supporting the “modelling guayule growth as an alternative source of natural rubber” project, referenced as PAI-10605-026.

Introduction - Functional structural modelling of shrubs, especially aromatic plants, confronts with a fine consideration of their structures, often complex and with many reiterations, especially for sympodial plants. The models and their simulations are therefore complex and costly to use for the selection and definition of crop routes. Here we propose alternative solutions suitable for sympodial plants that do not show neoformations, by reducing the structural complexity to that of a monocaul plant. Material and methods - The conceptual framework used is that of GreenLab, in its most extensive formalism, applicable in particular to the stochastic modelling of rhythmically growing trees (Wang et al., 2012). In our case, sympodial plants erect axes composed of modules. First, in the absence of neoformations, the succession of phytomers per module is replaced by a meta-phytomer (Jaeger et al. 2016), each module materializing a development cycle. We extend this work to the functional properties that inherit from those of the phytomers: we substitute the binomial probabilities at the phytomer scale by distributions reflecting mean and variance at the module scale. In a second step, we linearize the representation of the structure as follows: we represent an axis of theoretical development including the succession of meta-phytomers, from the initial module (unique, it is the oldest) to the last (the youngest). This representation is thus similar to that of a monocaul plant, except that we substitute a cohort of metaphytomers instead of each phytomer. Under these conditions, we can use a simple version of the model dedicated to single-stemmed plants, StemGL (Ribeyre et al. 2018), after taking into account several phytomers per age along the trunk, with particular impact on the distribution of secondary growth biomass. The approach is applied to the Guayule, a plant of increasing interest for latex production (Snoeck et al., 2015). Results and discussion - In our application on the Guayule, stochastic structures were generated by the explicit phytomer approach and the meta-phytomer approach where we show that the number of organs generated is reduced by a factor close to (N-1)∙ba where N represents the mean number of phytomers per module, b the mean branching factor and a the age. Similarly, the linearization of the structure allows a substantial reduction of time (by a factor of 7 for age 4 and up to more than 1000 for age 8) while obtaining the same biomass distributions in simulation and the same values in the estimation of the model functional structural parameters. The lack of geometric instantiation is open to discussion. In our implementation under StemGL, the visualization of simulated plants is based on functional representation [Jaeger et al. 2018]. It does not take into account geometrical features such as height, but allows the materialization of biomass variations and the number of meta-phytomers per cohort (C and D in the figure). Conclusion - An approach well adapted to a context requiring numerous simulations and experiments. The gain in complexity brought is major and becomes the only possible alternative for important ages (the complexity remaining linear in age and not polynomial). It is exploitable on stochastic models and on a large number of species showing sympodial growth, with a single physiological age. Acknowledgement - Authors thank the Agropolis Fondation supporting the “modelling guayule growth as an alternative source of natural rubber” project, referenced as PAI-10605-026.

RATIONALE - Two coffee species are mainly cultivated: Arabica and Robusta. Beside these species, the 139 wild coffee species/taxa belong to the Coffea genus are largely unknown to coffee scientists although these species may be crucial for future coffee crop development to face climate changes. These wild coffee species conserved in living collection revealed large morphological variations, but also growth habitats and adaptation. In addition to morphology, large variations were observed in terms of seed biochemical compounds involved in the quality of coffee such as caffeine, trigonelline, sucrose and mangiferin contents into others. However, this diversity was reported so far in any publicly available database. METHODS A database has been built using Pl@ntNet Publish. It is an IT platform dedicated to the dissemination of botanical data focused on taxa or specimen levels. It is based on Symfony (PHP) and MongoDB and allows users to manage data publication spaces. RESULTS - In this study, we developed the Wild Coffee Species (WCS) database: http://publish.plantnet-project. org/project/wildcofdb_en. It presents: (i) each species held in collection on the sites of La Reunion island and Kianjavato (Madagascar) with a photo gallery (597 images); (ii) different detailed information such as synonymy, natural distributions, habitats, architectural, morphological, phenological, biochemistry, genetic/genomic data (chloroplast genomes, whole genome sequencing and GBS), trait of interest retrieved from the literature and personal observations on living collection; (iii) a general geographical map of the species distribution. CONCLUSIONS & PERSPECTIVES - The WCS database represents the first comprehensive information about wild coffees species, to help researchers working in the preservation of coffee species, geneticists and breeders working with trait or genes of interest and improvement of cultivated species or breeders motivated to re-cultivate forgotten species adapted to climate changes or adapted to specific habitats.

International audience; Khaya senegalensis is one of the largest and most majestic trees in Africa. Overexploited for its precious wood and medicinal values, the natural stands of this species are in danger of extinction in Cote d'Ivoire. Its sustainable management through regeneration techniques and assessment of its degree of adaptation to the changing climate is necessary. The aim of this study is to evaluate the effect of different environments on seedling germination and development in Khaya senegalensis. A total of 2160 seeds from different mother plants and 540 individuals from seed germination were selected and evaluated. The trials were conducted on three sites that were distinct by their microclimate (two nurseries in Cote d'Ivoire and one greenhouse in France). Analysis of variance showed that germination and morphology parameters were not influenced by the characteristics of the mother plants used (p > 0.05), but rather by the study sites (P < 0.05). The stable and controlled greenhouse climate was more advantageous for latency time (12.66 ± 0.80 days), germination delay (16.96 96 ± 0.54 days), germination speed (19.66 ± 2.95 days), germination duration (10.83 ± 2.27 days) and germination rate (88.88 ± 7.97) with more vigorous sowing than the other two sites. The results showed in general that the higher the height of the seedlings, the thicker the diameter of the seedlings (r = 0.796) and the higher the number of leaves (r = 0.946). This savannah species is native to the arid zones of Africa, but this study highlighted its adaptive potential to changing and different climates. These results are decision support tools for the regeneration of native pioneer forest species with high agroforestry potential and socio-economic importance such as Khaya senegalensis. This study could be extended to other species in order to restore disturbed ecosystems.

Introduction The Guayule (Parthenium argentatum, Asteraceae), is a small ramified tree native to the northern Mexico and south western United States. The guayule shows a growing interest in research and agriculture (Ray, 1993). Howe-ver, the production itineraries in relation to latex production are still not assessed, and so far little studies were done on the plant structure and functioning. This study aims to propose a first FSPM of the species using the Green-Lab model, calibrated from data issued from two varieties in different environmental conditions. Materials and Methods The studying methodology is first based on a qualitative architectural analysis (Barthelemy and al., 2007). Second, on the various axis typologies, the development and branching stochastic rules can then be retrieved from field internode distributions collections. Finally, the organ source and sink relations parameters can be fitted from dedi-cated dry weight measurements (Kang et al., 2018).Experimental plots were hold south of France, close to Montpellier on two varieties CL1 and CLA1, with four envi-ronmental conditions related to density and hydric pressure (no stress, low stress and high stress).. The sampling was optimized to the plant structure and to quantify the polyisoprene and resins contents.Results and Discussion The guayule shows a sympodial development is composed of modules with terminal inflorescence. Its architecture corresponds to the Leeuwenberg's model (Hallé et al., 1978). The axes are constituted of successive modules. Stu-dying the plant structure, we found out that the number of relay axis per module follows a binomial distribution. The modules are ordered from the plant base to the top. And these modules are composed of internodes whose number also follows a binomial law, which parameters are quite stable from one order to another. In the further modelling process, we thus did consider that the plant elementary unit was the module, called as a meta­phytomer. Under this assumption, we summarized the total dry weight of leaves and internodes per module to build the axis organic series (Buis and Barthou, 1984). Field measurements issued from these two series constituted then a target to be adjusted by the structural functional GreenLab model (Kang et al, 2018) in order to calibrate the organ source parameters. An initial analysis calculated the strength sink of leaves and internodes in a context of free growth and analysed the differences between the two varieties. We are currently applying the methodology to assess the impact on the parameters of development and growth, the effects of planting density and irrigation. Conclusions This first modelling study hold on two varieties on the Guayule tree shows that the plant structure can be effi-ciently modelled using a simple module approach. The development parameters, defining the module number of phytomers and branching rules are nearly stable and close for both varieties under the various environmental conditions. First functioning parameters were also retrieved from the measurements. These parameters make it possible to obtain the first stochastic 3D simulations of the Guayule's growth and architecture for both varieties.

Knowledge of plant architecture allows retrospective study of plant development, hence provides powerful tools, through modelling and simulation, to link this development with environmental constraints, and then predict its response to global change. The present study aims to determine some of the main endogenous and exogenous variables driving the architectural development of three North American conifers. We measured architectural traits retrospectively on the trunk, branches and twigs of whole tree crowns for each species: annual shoot length (ASL), needle length, branching patterns and reproduction organs (male and female). We fitted a partial least square (PLS) regression to explain each architectural trait with respect to topological, ontogenic and climatic variables. Results showed a significant weight of these three groups of variables for previous and current year, corresponding, respectively, to organogenesis and elongation. Topological and ontogenic variables had the greatest weight in models. Particularly, all architectural traits were strongly correlated with ASL. We highlighted a negative architectural response of two species to higher than average temperatures, whereas the third one took advantage of these higher temperatures to some degree. Tree architectural development weekly but significantly improved with higher precipitation. Our study underlines the strong weight of topology and ontogeny in tree growth patterns at twig and branch scales. The correlation between ASL and other tree architectural traits should be integrated into architectural development models. Climate variables are secondary in importance at the twig scale. However, interannual climate variations influence all axis categories and branching orders and therefore significantly impact crown development as a whole. This latter impact may increase with climate change, especially as climate affects architectural traits over at least 2 years, through organogenesis and elongation., This study proposes an original insight into tree architectural development, by combining in a simultaneous analysis three sets of explanatory variables: ontogenic, topological and climatic factors. It targets three common North American conifers (Picea mariana; Pinus banksiana; Pinus strobus), the detailed architecture of which is poorly known. Thus it brings new knowledge about these species and their response to environmental constraints. Our results may help improve the assessment of the future of these species in the context of climate change, particularly through the knowledge of interactions between exogenous (climate and site conditions) and endogenous factors (ontogeny, topology).

The study aimed to identify the ontogenetic, environmental and phyllotactic growth components, observed in Eucalyptus grandis. The trees grown in Itatinga Experimental station near Sao Paulo (Brazil) were affected by two treatments: addition of Potassium and rainfall partial exclusion. Tree growth data correspond to the retrospective measurement of the length of successive internodes along the main stem. The growth of eucalyptus main stem was decomposed into three components: (i) an ontogenetic component structured as a succession of roughly stationary phases at coarse scale (ii) growth fluctuations corresponding to the impact of the changing climatic conditions at an intermediate scale and (iii) a more or less systematic alternation of long and short internodes at _ne scale. The ontogenetic component shows three main growth phases: an establishment phase, a maximum growth phase and a drift phase. The Potassium addition and the rainfall partial exclusion do not affect the succession of growth phases but only, for the Potassium addition, the growth level within the phases. The alternating pattern was a direct consequence of phyllotaxis and strongly depends on the mean internode length. We show that this alternating pattern can be disrupted in case of meristem death.

La relance de la caféiculture ivoirienne nécessite la prise en compte de l'architecture des plantes. En effet, de nombreuses composantes architecturales sont des facteurs de productivité chez le caféier. Certains modèles génériques permettent de faire une analyse fine de l'architecture des plantes. Le modèle structure-fonction GreenLab a été utilisé pour déterminer, par une méthode non destructive, les paramètres de développement et de croissance architecturaux de six espèces de caféiers d'origine africaine dont la principale espèce cultivée en Côte d'Ivoire. A savoir : C. canephora (GREECAN), C. stenophylla (STE), C. racemosa (RAC), C. pseudozanguebariae (PSE), C. liberica var liberica (LIB) et C. liberica var dewevrei (DEW). L'espèce CAN a montré des feuilles et des entre-noeuds de taille moyenne, intermédiaire entre ceux de DEW et LIB qui ont de grandes feuilles et de longs entre-noeuds et ceux de STE et RAC qui ont de petits organes. Le fonctionnement des méristèmes défini par les probabilités de croissance des tiges (P), des branches (B) et de ramification, ont faiblement varié d'une espèce à l'autre. Mais, RAC et STE ont présenté un développement plus rapide que les autres espèces. L'ajustement des séries organiques par le modèle a permis d'estimer les paramètres sources-puits, moteurs de la croissance des plantes, et de simuler l'architecture des caféiers. Ces paramètres ont varié d'une espèce à une autre en fonction de la taille des organes. La calibration du modèle GreenLab a permis de comprendre le fonctionnement et la variabilité interspécifique de l'architecture des caféiers. Chaque espèce présente son propre schéma de développement et de croissance.

Potassium and water availability are limiting factors for tree growth. Their influence on anatomical and morphological traits is well known but their combined effects on tree growth remain uncertain. Eucalyptus grandis trees (Itatinga, SP states -Brazil) were analysed in a split-plot experimental design of one clone (ADD clone name) growing under different water regimes (37% rainfall exclusion and no rainfall exclusion) and fertilization treatments (increased potassium supply and control potassium supply). Eight trees per plot were sampled representing a total of 32 trees. Wood anatomy traits (vessel frequency, diameter and lumen area, theoretical hydraulic conductivity, ray frequency and fibre lumen/wall dimensions), morphological traits (tree height, DBH and slenderness) and wood mechanical properties (longitudinal elastic modulus and specific modulus) were studied in order to investigate how water availability and potassium fertilization influenced these traits. Fertilized trees were both taller and had wider diameters than non-fertilized trees. Vessel diameter and theoretical hydraulic conductivity were also notably higher in fertilized trees. By contrast rainfall exclusion had no significant effect on tree growth and measured traits. Mechanical properties were similar across treatments and showed relatively high values compared to values known previously for Eucalyptus. In addition to the effects of potassium, anatomical traits showed strong relationships with morphological traits of trees. But all expected wood anatomical traits modifications in response to rainfall exclusion, as vessel diameter decreased, were not observed. The results suggest that potassium has a markedly positive effect on tree growth promoting taller and larger trees and that trees, at least of this clone, have developed mechanisms that mitigate against limited water availability. Potassium supply seems to indirectly impacts anatomical traits. Indeed, results show that modification of anatomical traits is primary linked to tree height and DBH witch are driven here by K fertilization.

International audience; Accurate expertise on plant development in space and time is fundamental to underpin conservation and management practices. Considering that trees are long-life organisms with a complex structure, understanding the rules of tree development, from seedlings to adult trees and for a given environment, is a steep task. Compared to field monitoring, retrospective analysis of plant incremental development (RAPID), based on the observation of morpho-anatomical markers allows accessing the past dynamics of plant architecture on many varied plants. However, it is clear that besides this very general approach, works based on axis thickening (mainly trunk) and growth rings structure (GR) remain a broad majority and they are recognized as a full-fledged discipline called dendrochronology. Etymologically, dendrochronology is the science (-logia) of reading the time (khronos) in trees (dendron). Nevertheless, it is clear that this definition applies equally to the crown expansion and to the understanding of the primary growth, branching or flowering processes through the study of morphological or macro-anatomical markers. Moreover, it is important to note that theses approaches can be applied not only in trees, but also in perennial herbaceous herbs or mosses that conduce some authors to propose the term herbchronology. Without trying to change the term of dendrochronology, etymologically limited, but widely used and deeply rooted in the scientific landscape, we support the idea that it should be extended to all approaches concerning the RAPID. In this presentation, we’ll depict a summary of methods that allow accessing the past development of plants considering four major processes, growth I and II, branching, and flowering whatever the biological life-form. We’ll discuss the close connection amongst the nature of theses processes, their phenology and the resulting morpho-anatomical structure. Considering that plant form integrates multiple environmental factors but, also, internal trade-offs among functions, we argue that integrative studies considering jointly morpho-anatomical markers in a RAPID approach offers powerful insights for diverse fields including plant biology, ecology, conservation

In rhythmic growth tree species, the activity of shoot apical meristem shows an active period of phytomer production followed of a rest period. The number of organs produced varies with the annual seasonality and among the individuals of a population measured at a given time. Teak architecture is compound of 4 categories of axis, each corresponding to one physiological age of the meristems. This approach has been integrated in functional-structural tree model, GreenLab, based on the source –sink relationships at organ level. The originality of the presented research is the integration of the dynamics of tree development in the biomass production modeling over the time. The analyzed teaks have from one-year-old to seven-year-old. The stochastic aspect of phytomer production, resulting from meristem activity is based on the Bernoulli process. Light interception, biomass production and biomass partitioning among competing organs, including secondary growth, is performed according to the GreenLab model hypothesis. The annual growth pattern included the processes of shoot polycyclism and pre- and neoformation. Phytomer distributions inside growth units are analyzed according to their physiological and chronological ages. The branching pattern of growth units is detailed by taking account of the branching rate for each type of axillary axis (main branches, long shoot and short shoot. Data assimilation of the measurements is based on organic series which correspond to the organ weights according to their rank from the basis to the top of growth units. Parameter identification of development and growth is done by fitting the observed organic series with the theoretical ones, using the nonlinear least square method. Using the computed parameters and adding geometrical traits, enables the full 3D simulation of young Teak tree architecture including the secondary growth. The integration of the wood density as a parameter of the model is discussed. The using of this model can provide quantitative key insights in order to develop teak ideotypes. (Texte intégral)

International audience

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Global climate models agree in predicting a warmer climate on most continental areas, with more frequent extreme events such as heat waves and repeated or exceptional droughts. By increasing drought stress, global warming is a direct threat to forest health and survival in all types of forest ecosystems around the world. Two physiological mechanisms can be involved, separately or simultaneously, in tree decline or mortality during these stressing events: hydraulic failure and carbon starvation. Study goals: We present a study performed as an international effort to understand the influence of climate change and extreme events on the architectural development of forest trees, mainly conifers, in several countries. We discuss its potential contribution to forest decline and die-back. Fourteen conifers and one broadleaved species from Europe, USA and Canada were studied with the same protocol. In 47 sites as a whole, nearly 11000 twigs, from 2300 branches of 470 trees were sampled between 2005 and 2014, some of them repeatedly every year or few years. Branch and trunk length growth, architectural development (branching and polycyclism rates) and reproduction were retrospectively measured from morphological markers over a period of 10 to 45 years according to species. Needle or leaf number per growth unit, size and life span were measured on a subsample of twigs. Study sites include four experimental designs with climate manipulation in controlled conditions: rain exclusion, irrigation or heating and combinations of heat and drought on one of them. A phenological survey was performed on three of them to monitor monthly tree architectural development. Study sites cover conditions going from the limit of the desert to the tree line in mountains. We developed a generic architectural model for conifer trunks or branches, based on the relationships between climate and all measured parameters of tree architecture and needles. It aims at simulating the immediate consequences and after-effects of climate stresses on tree architecture and leaf area, for 10-year periods. In both Europe and Northern America, repeated or extreme droughts, heat waves and other stresses considerably reduced tree and branch vigour for all species at all sites, leading to reduced branch length and tree height growth, low polycyclism and branching rates, shorter and narrower than normal needles or leaves, and small number of needles or leaves per growth unit. A strong reduction of the life span of leaves and needles for evergreen species was also measured. Thus a significant leaf area deficit was observed and modelled during or just after but also several years after severe stresses. Two mechanisms explained the long lasting legacies of these stresses: (i) the slow recovery of the number of active twigs, due to the twig deficit induced by a low branching rate during and after the stress, limiting the number of leaves and needles, and (ii) the persistence, for many years on some species, of the cohorts of small leaves and needles formed in the bad years. The long lasting reduction of tree leaf area may contribute to carbon shortage and, in extreme cases, to delayed die-off by carbon starvation.

Togo implements a policy of intensive teak (Tectona grandis) plantations to supplement the supply of wood products from natural forests.. These plantations are the most important because of the breadth of areas planted and of the exceptional quality of teak wood. The main objective of our study is to better understand the relationship between stand management and wood quality for different teak origins. For this purpose, a non-destructive approach is proposed based on architectural analyses in order to find indicators, of the variability of wood physical properties. This method was tested on teak plantations located in South-East Togo in the village of Agbavé (0045->6°43.J. Four plots of initial density 2500 stems/ha and tree age between 10 and 11 years were chosen in order to investigate the effect of thinning for two different oteak populations. The first provenance was introduced in Togo during the beginning of the last century. The second comes from Tanzania via Benin Republic and was introduced in Togo some years ago.. The links between developmental stages (provided by an architectural analysis) and the radial variability of wood specific density were investigated on 20 trees sampled on each studied plot (80 trees in total). The architectural analysis is a global, multileve1 and dynamic approach to plant development and allows to identify the endogenous processes of growth and to separate them from the plasticity of their expression resulting from external constraints (Barthelemy and Caraglio 2007). The analysis of radial growth was achieved on 5cm thick slice samples taken from the studied trees and located on the 1st, 2nd and 4th growth units of the trunk. The study of the variability of wood radial properties, in particular the specific density, was carried out by direct and indirect measures using the near infrared spectrometry (Bertrand and Dufour 2000). First results show how the expression .of morphological events (e.g. branching, flowering,Jorking, etc..) is related to the radial variation of wood properties and how these links are impacted by sylvicultural practices. These correlations will be used to implement a model of wood quality in a structural-functional tree model.

En région méditerranéenne, le sapin pectiné se trouve dans la limIte sud de son aire de répartition et depuis 2003, des dépérissements sont observés dans le département de l'Aude et dans la région Provence-Alpes-Côte d'Azur. Ce constat preoccupe les forestiers et pose de façon cruciale la question du diagnostic de l'état de santé des arbres. Comment ne pas confondre vieillissement et dépérissement? Quel est l'état normal, ou arbre de référence, d'un sapin? Peut-on pronostiquer le caractère passager ou inéluctable d'un dépérissement? La méthode d'analyse architecturale des arbres (ou méthode ARC HI) appliquée au sapin répond à ces interrogations. En reconstituant la dynamique de développement depuis la plantule jusqu'à la sénescence, elle nous renseigne sur l'ontogénèse du sapin. C'est en se référant à cette séquence que la méthode ARCHI peut prendre en compte les deux composantes d'un dépérissement, à savoir: les symptômes de dégradation des houppiers, c'est-à-dire les écarts à la normale, et les processus de résilience, c'est-à-dire les retours à la normale (ou à un état proche de la normale). Cinq états sont ainsi définis: l'état normal (arbre sain), les écarts à la normale (arbres stressés), les retours à la normale (arbres résilients et descentes de cimes) et les points de non-retour à la normale (arbres en dépérissement irréversible). Après simplification du protocole d'observation sur le terrain, une clef de détermination des types architecturaux est proposée aux gestionnaires forestiers. Les perspectives offertes par la méthode ARCHI sont passées en revue, de même que ses limites.

The Coffea genus includes 103 species with 53 endemic to Madagascar (namely Mascarocoffea).The three main centres of species diversity for coffee trees are Madagascar (naturally low-caffeine species), Cameroon and Tanzania. However, Madagascar has the higher Coffea diversity in terms of total number of species due to the great variety of forest types including littoral, evergreen, gallery, mixed deciduous, dry, xerophytic and high-altitude. During these last 20 years, deforestation in Madagascar has become dramatic and has drastically reduced the distribution area of Coffea species. The collection maintained at the Kianjavato Research Station is unique since no living material is authorized to be conserved out of Madagascar. Conservation strategies based on scientific data are needed and become urgent in terms of biodiversity preservation and sustainable development. Recent studies in Coffea trees showed that their phenotypic plasticity could be explain the restricted distribution of Coffea species. Our recent preliminary results showed a high architectural diversity (i.e. architectural model, growth process, branching degree, branch location) between Coffea species and an interspecific variability of functional traits (Leaf Area Mass, wood density). The functional-structural model GreenLab is a dynamic model taking into account architectural plasticity of the plants and biomass allocation to organ level. Potentials of GreenLab model to represent environment x genotype interactions, in particular through its stable endogenous parameter as such the organ sink functions have been demonstrated in some species and they will be tested for Coffea species. The present study focuses on 5 species endemic to Madagascar with different phenotypic traits and forest habitats. For each species, architecture and genetic comparative analyses between individuals growing in situ (natural forest) and ex situ (common garden test) will be performed. In addition, we have set up two experimental stands to analyse the site effect. These whole results will be used to introduce genetic factors into the GreenLab model. The global aim of our approach is to analyse the adaptive capacity and phenotypic plasticity at the individual level within Coffea populations. (Texte intégral)

Silver fir presents a great hierarchised architecture with a strict monopodial development (Massart's architectural model). Moreover silver fir presents neither polycyclism nor immediate branching (often involved in the plastic response of primary growth). Despite these limitations, silver firs present a large range of distribution: from Central Europe to Mediterranean mountains. The aim of this poster is to test the hypothesis that silver firs offset this limitation with a strong plasticity at the annual shoot scale and on needle morphology. The study was done in Mont Ventoux, a French Mediterranean mountain which provides contrasted forest environments in terms of elevation and with a marked summer drought. Quantitative traits of annual shoots of 2 years old branches (length, diameter and number of needles, dry mass) and needles (surface and dry mass) where recorded on 80 saplings growing in different light environments. Effects of tree size and architectural position of annual shoot within tree crown on measured traits were higher than any environmental fluctuation. These morphogenetic gradients are consistent with the concept of physiological age of meristems (Barthélémy & Caraglio 2007): huge effect of tree development, branching order and position. All studied traits present a significant plasticity which may be implies in the success of silver firs in the studied site. No clear hierarchy was found between the phenotypic plasticity of annual shoot plasticity and the one of needles. We can suggest that all measured traits act simultaneously during tree development and in response to environmental fluctuations ('a variational module' sensu Wagner et al 2007). (Texte intégral)