Resource manipulation through experimental defoliation has legacy effects on allocation to reproductive and vegetative organs in Quercus ilex

International audienceAbstract Background and Aims In plants, high costs of reproduction during some years can induce trade-offs in resource allocation with other functions such as growth, survival and resistance against herbivores or extreme abiotic conditions, but also with subsequent reproduction. Such trade-offs might also occur following resource shortage at particular moments of the reproductive cycle. Because plants are modular organisms, strategies for resource allocation to reproduction can also vary among hierarchical levels. Using a defoliation experiment, our aim was to test how allocation to reproduction was impacted by resource limitation. Methods We applied three levels of defoliation (control, moderate and intense) to branches of eight Quercus ilex trees shortly after fruit initiation and measured the effects of resource limitation induced by leaf removal on fruit development (survival, growth and germination potential) and on the production of vegetative and reproductive organs the year following defoliation. Key Results We found that defoliation had little impact on fruit development. Fruit survival was not affected by the intense defoliation treatment, but was reduced by moderate defoliation, and this result could not be explained by an upregulation of photosynthesis. Mature fruit mass was not affected by defoliation, nor was seed germination success. However, in the following spring defoliated branches produced fewer shoots and compensated for leaf loss by overproducing leaves at the expense of flowers. Therefore, resource shortage decreased resource allocation to reproduction the following season but did not affect sex ratio. Conclusions Our results support the idea of a regulation of resource allocation to reproduction beyond the shoot scale. Defoliation had larger legacy effects than immediate effects

Resource manipulation through experimental defoliation has legacy effects on allocation to reproductive and vegetative organs in Quercus ilex

International audienceBackground and Aims In plants, high costs of reproduction during some years can induce trade-offs in resourceallocation with other functions such as growth, survival and resistance against herbivores or extreme abioticconditions, but also with subsequent reproduction. Such trade-offs might also occur following resource shortageat particular moments of the reproductive cycle. Because plants are modular organisms, strategies for resource allocationto reproduction can also vary among hierarchical levels. Using a defoliation experiment, our aim was totest how allocation to reproduction was impacted by resource limitation.• Methods We applied three levels of defoliation (control, moderate and intense) to branches of eight Quercusilex trees shortly after fruit initiation and measured the effects of resource limitation induced by leaf removal onfruit development (survival, growth and germination potential) and on the production of vegetative and reproductiveorgans the year following defoliation.• Key Results We found that defoliation had little impact on fruit development. Fruit survival was not affected bythe intense defoliation treatment, but was reduced by moderate defoliation, and this result could not be explainedby an upregulation of photosynthesis. Mature fruit mass was not affected by defoliation, nor was seed germinationsuccess. However, in the following spring defoliated branches produced fewer shoots and compensated for leafloss by overproducing leaves at the expense of flowers. Therefore, resource shortage decreased resource allocationto reproduction the following season but did not affect sex ratio.• Conclusions Our results support the idea of a regulation of resource allocation to reproduction beyond theshoot scale. Defoliation had larger legacy effects than immediate effects

Reproduction alternation in trees: testing the resource depletion hypothesis using experimental fruit removal in Quercus ilex

International audienceThe keystones of resource budget models to explain mast seeding are that fruit production depletes tree stored resources, which become subsequently limiting to flower production the following year. These two hypotheses have, however, rarely been tested in forest trees. Using a fruit removal experiment, we tested whether preventing fruit development would increase nutrient and carbohydrates storage and modify allocation to reproduction and vegetative growth the following year. We removed all the fruits from nine adult Quercus ilex L. trees shortly after fruit set and compared, with nine control trees, the concentrations of nitrogen (N), phosphorus (P), zinc (Zn), potassium (K) and starch in leaves, twigs and trunk before, during and after the development of female flowers and fruits. The following year, we measured the production of vegetative and reproductive organs as well as their location on the new spring shoots. Fruit removal prevented the depletion of N and Zn in leaves during fruit growth. It also modified the seasonal dynamics in Zn, K and starch in twigs, but had no effect on reserves stored in the trunk. Fruit removal increased the production of female flowers and leaves the following year, and decreased the production of male flowers. Our results show that resource depletion operates differently for male and female flowering, because the timing of organ formation and the positioning of flowers in shoot architecture differ between male and female flowers. Our results suggest that N and Zn availability constrain flower production in Q. ilex, but also that other regulatory pathways might be involved. They strongly encourage further experiments manipulating fruit development over multiple years to describe the causal relationships between variations in resource storage and/or uptake, and male and female flower production in masting species

Postprandial Stimulation of Muscle Protein Synthesis in Old Rats Can Be Restored by a Leucine-Supplemented Meal

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Climate anomalies and neighbourhood crowding interact in shaping tree growth in old‐growth and selectively logged tropical forests

International audienceClimate extremes and biotic interactions at the neighbourhood scale affect tropical forest dynamics with long‐term consequences for biodiversity, global carbon cycling and climate change mitigation. However, forest disturbance may change crowding intensity, and thus the relative contribution of climate extremes and neighbourhood interactions on tree growth, thereby influencing tropical forest resistance and resilience to climate change. Here, we aim to evaluate the separate and interactive effects of climate and neighbours on tree growth in old‐growth and disturbed tropical forests. We used 30 years of growth measurements for over 300 tropical tree species from 15 forest plots in French Guiana to investigate the separate and interactive effects of climate anomalies (in solar radiation, maximum temperature, vapour pressure deficit and climatic water deficit) and neighbourhood crowding on individual tree growth. Contrasting old‐growth and selectively logged forests, we also examined how disturbance history affects tree growth sensitivity to climate and neighbours. Finally, for the most abundant 100 species, we evaluated the role of 12 functional traits pertaining to water relations, light and carbon use in mediating tree growth sensitivity to climate anomalies, neighbourhood crowding and their interactions. Climate anomalies tied to heat and drought stress and neighbourhood crowding independently reduced tree growth, and showed positive interactive effects which attenuated their separate effects on tree growth. Their separate and interactive effects were stronger in disturbed than undisturbed forests. Fast‐growing species (i.e. higher intrinsic growth rates) were more abundant in disturbed forests and more sensitive to climate anomalies and neighbourhood crowding. Traits related to water relations, light and carbon use captured species sensitivities to different climate anomalies and neighbourhood crowding levels but were weak predictors of their interactions. Synthesis : Our results demonstrate that climate anomalies and neighbourhood crowding can interact to shape tropical tree growth, suggesting that considering the biotic context may improve predictions of tropical forest dynamics facing altered climate regimes. Furthermore, species traits can capture tree growth sensitivity to the separate effects of climate and neighbours, suggesting that better representing leading functional dimensions in tropical tree strategies offers a promising way towards a better understanding of the underlying ecological mechanisms that govern tropical forest dynamics.Les extrêmes climatiques ainsi que les interactions biotiques à l'échelle du voisinage, affectent la dynamique des forêts tropicales, avec des conséquences à long terme pour la biodiversité, le cycle global du carbone et l'atténuation du changement climatique. Cependant, les perturbations forestières peuvent faire varier localement les voisinages, et ainsi modifier la contribution relative des extrêmes climatiques et des interactions de voisinage sur la croissance des arbres, ce qui peut impacter la résistance et la résilience des forêts tropicales au changement climatique. Nos travaux visent à évaluer les effets individuels et interactifs du climat et des voisins sur la croissance des arbres dans les forêts tropicales non‐pertubées et perturbées. Nous avons utilisé 30 ans de mesures de croissance pour plus de 300 espèces d'arbres tropicaux provenant de 15 parcelles forestières en Guyane française pour étudier les effets individuels et interactifs des anomalies climatiques (en termes de rayonnement solaire, de température maximale, de déficit de pression de vapeur, et de déficit hydrique climatique) et des interactions de voisinage sur la croissance individuelle des arbres. En comparant les forêts exploitées sélectivement aux forêtsnon‐pertubées, nous avons également examiné comment l'historique des perturbations peut influencer la sensibilité de la croissance des arbres au climat et aux voisins. Enfin, pour les 100 espèces les plus abondantes, nous avons évalué le rôle de 12 traits fonctionnels reflétant les relations hydriques, l'utilisation de la lumière et du carbone sur la réponse de la croissance des arbres aux anomalies climatiques, aux interactions de voisinage et à leurs interactions. Les anomalies climatiques liées aux stress thermique et hydrique, ainsi que les interactions de voisinage, réduisent la croissance des arbres. De plus, elles peuvent interagir positivement, ce qui atténue leurs effets individuels sur la croissance des arbres. Leurs effets individuels et interactifs sont plus forts dans les forêts perturbées que dans les forêts non‐perturbées. Les espèces à croissance rapide (c'est‐à‐dire à taux de croissance intrinsèque plus élevé) sont plus abondantes dans les forêts perturbées, et aussi plus sensibles aux anomalies climatiques et aux interactions de voisinage. Les traits liées aux relations hydriques, à la lumière et à l'utilisation du carbone captent la sensibilité des espèces aux différentes anomalies climatiques et aux différents niveaux d'interactions de voisinage, mais ne prédisent pas leurs interactions. Synthèse : Nos résultats montrent que les anomalies climatiques et les interactions de voisinage peuvent interagir pour façonner la croissance des arbres tropicaux, ce qui suggère que prendre en compte le contexte biotique peut améliorer les prévisions de la dynamique des forêts tropicales face aux changements climatiques. En outre, les traits des espèces peuvent capter la sensibilité de la croissance des arbres aux effets individuels du climat et des voisins, ce qui suggère que mieux représenter les principales dimensions des stratégies fonctionnelles des arbres tropicaux ouvre sur une meilleure compréhension des mécanismes écologiques qui régissent la dynamique des forêts tropicales

Sarcopenia: its assessment, etiology, pathogenesis, consequences and future

Sarcopenia is a loss of muscle protein mass and loss of muscle function. It occurs with increasing age, being a major component in the development of frailty. Current knowledge on its assessment, etiology, pathogenesis, consequences and future perspectives are reported in the present review. On-going and future clinical trials on sarcopenia may radically change our preventive and therapeutic approaches of mobility disability in older peopleY. Rolland, S. Czerwinski, G. Abellan Van Kan, J.E. Morley, M. Cesari, G. Onder, J. Woo, R. Baumgartner, F. Pillard, Y. Boirie, W.M.C. Chumlea, B. Vella