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Wood formation is the Rosetta stone of tree physiology: a traceable, integrated record of physiological and morphological status. It also produces a large and persistent annual sink for terrestrial carbon, motivating predictive understanding. Xylogenesis studies have greatly expanded our knowledge of the intra-annual controls on wood formation, while dendroecology has quantified the environmental drivers of multi-annual variability. But these fields operate on different timescales, making it challenging to predict how short (e.g. turgor) and long timescale processes (e.g. disturbance) interactively influence wood formation. Toward this challenge, wood growth responses to natural climate events provide useful but incomplete explanations of tree growth variability. By contrast, direct manipulations of the tree vascular system have yielded unexpected insights, particularly outside of model species like boreal conifers, but they remain underutilized. To improve prediction of global wood formation, we argue for a new generation of experimental manipulations of wood growth across seasons, species, and ecosystems. Such manipulations should expand inference to diverse forests and capture inter- and intra-specific differences in wood growth. We summarize the endogenous and exogenous factors influencing wood formation to guide future experimental design and hypotheses. We highlight key opportunities for manipulative studies integrating measurements from xylogenesis, dendroanatomy, dendroecology, and ecophysiology., (© 2025 The Author(s). New Phytologist © 2025 New Phytologist Foundation.)

In temperate and boreal ecosystems, trees undergo dormancy to avoid cold temperatures during the unfavorable season. This phase includes changes in frost hardiness, which is minimal during the growing season and reaches its maximum in winter. Quantifying frost hardiness is important to assess the frost risk and shifts of species distribution under a changing climate. We investigate the effect of local conditions and intra-specific variation on frost hardiness in sugar maple (Acer saccharum Marsh.). Seedlings belonging to seven provenances from the northern area of the species' range were planted at two sites in Quebec, Canada. LT50, i.e. the lethal temperature for 50% of the cells, was measured monthly with the relative electrolyte leakage method on branches and buds from September 2021 to July 2022. LT50 varied between -4 °C in summer (July) and -68 °C in winter (February). Autumnal acclimation rates (September to early December) and mid-winter frost hardiness (December to early March) were similar in both sites. Samples in the southern site deacclimated faster than in the northern site between March and July because of a warmer and earlier spring. No difference in frost hardiness was detected between provenances. Our results suggest that the frost hardiness trait is similar within the northern part of the sugar maple distribution, with local weather conditions having a greater influence than provenance. We demonstrate that LT50 in sugar maple can exceed -55 °C, far below the minimum temperatures occurring in winter at the northern limit of the species. In order to minimize the risk of damage from extreme frost events exceeding tree frost hardiness, a careful evaluation of site characteristics is more important than provenance selection. Other factors should also be considered within the context of changing climate, in particular, the phenology of maple and avoidance of late frost in spring., (© The Author(s) 2025. Published by Oxford University Press.)

As major terrestrial carbon sinks, forests play an important role in mitigating climate change. The relationship between the seasonal uptake of carbon and its allocation to woody biomass remains poorly understood, leaving a significant gap in our capacity to predict carbon sequestration by forests. Here, we compare the intra-annual dynamics of carbon fluxes and wood formation across the Northern hemisphere, from carbon assimilation and the formation of non-structural carbon compounds to their incorporation in woody tissues. We show temporally coupled seasonal peaks of carbon assimilation (GPP) and wood cell differentiation, while the two processes are substantially decoupled during off-peak periods. Peaks of cambial activity occur substantially earlier compared to GPP, suggesting the buffer role of non-structural carbohydrates between the processes of carbon assimilation and allocation to wood. Our findings suggest that high-resolution seasonal data of ecosystem carbon fluxes, wood formation and the associated physiological processes may reduce uncertainties in carbon source-sink relationships at different spatial scales, from stand to ecosystem levels., (© 2024. The Author(s).)

Wood growth is key to understanding the feedback of forest ecosystems to the ongoing climate warming. An increase in spatial synchrony (i.e., coincident changes in distant populations) of spring phenology is one of the most prominent climate responses of forest trees. However, whether temperature variability contributes to an increase in the spatial synchrony of spring phenology and its underlying mechanisms remains largely unknown. Here, we analyzed an extensive dataset of xylem phenology observations of 20 conifer species from 75 sites over the Northern Hemisphere. Along the gradient of increase in temperature variability in the 75 sites, we observed a convergence in the onset of cell enlargement roughly toward the 5 th of June, with a convergence in the onset of cell wall thickening toward the summer solstice. The increase in rainfall since the 5 th of June is favorable for cell division and expansion, and as the most hours of sunlight are received around the summer solstice, it allows the optimization of carbon assimilation for cell wall thickening. Hence, the convergences can be considered as the result of matching xylem phenological activities to favorable conditions in regions with high temperature variability. Yet, forest trees relying on such consistent seasonal cues for xylem growth could constrain their ability to respond to climate warming, with consequences for the potential growing season length and, ultimately, forest productivity and survival in the future., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

A reliable assessment of forest carbon sequestration depends on our understanding of wood ecophysiology. Within a forest, trees exhibit different timings and rates of growth during wood formation. However, their relationships with wood anatomical traits remain partially unresolved. This study evaluated the intra-annual individual variability in growth traits in balsam fir [Abies balsamea (L.) Mill.]. We collected wood microcores weekly from April to October 2018 from 27 individuals in Quebec (Canada) and prepared anatomical sections to assess wood formation dynamics and their relationships with the anatomical traits of the wood cells. Xylem developed in a time window ranging from 44 to 118 days, producing between 8 and 79 cells. Trees with larger cell production experienced a longer growing season, with an earlier onset and later ending of wood formation. On average, each additional xylem cell lengthened the growing season by 1 day. Earlywood production explained 95% of the variability in xylem production. More productive individuals generated a higher proportion of earlywood and cells with larger sizes. Trees with a longer growing season produced more cells but not more biomass in the wood. Lengthening the growing season driven by climate change may not lead to enhanced carbon sequestration from wood production., (© 2023. The Author(s).)

The resurgent frequency of extreme weather events and their strongly distinctive spatial patterns lead to a growing interest in phenology as an indicator of tree susceptibility. Using a long-term chronology of observations collected in situ, we predicted and investigated the spatial patterns and environmental drivers of spring leaf phenology across maple stand polygons dominated by Acer saccharum Marsh. and/or Acer rubra L. in eastern North America for 2000-2018. Model' calibration was based on Bayesian ordinal regressions relating the timing of the phenological events' observations to the MODIS vegetation indices EVI, NDVI and LAI. DAYMET data have been extracted to compute temperature and precipitation during spring phenology. Model accuracy increased as the season progressed, with prediction uncertainty spanning from 9 days for bud swelling to 4 days for leaf unfolding. NDVI and LAI were the best predictors for the onset and ending of spring phenology, respectively. Bud swelling occurred at the end of March in the early stands and at the onset of May in the late stands, while leaf unfolding was completed at the beginning of April for the early and in mid-June for the late stands. Early and late stands polarized towards a south-west-north-east gradient. In the south-western regions, which are also the driest, total precipitation and minimum temperature explained respectively 73 % and 25 % of the duration of spring phenology. In the north-eastern regions, precipitation and minimum temperature explained 62 % and 26 % of the duration of spring phenology. Our results suggest high vulnerability to extreme weather events in stands located in the south-west of the species distribution. The increasing incidence of drought in these locations might affect spring phenology, decreasing net primary production in these stands. Warmer nights might expose the buds to late frosts, events that are expected to become more frequent in the coming years., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objective: Alternatives to conventional acute hospitalizations have been particularly useful during the COVID-19 pandemic. However, little is known on the management and outcomes of COVID-19 in older patient admitted to non-acute settings. The main aim of this study was to determine the effect of geriatrics syndromes on functional outcomes in older COVID-19 patients cared in sub-acute units., Methods: Prospective multicenter observational cohort study of patients aged 65 years and older with COVID-19, admitted to sub-acute units in Italy and Spain. Multivariable logistic regression models were used to test the association between geriatric syndromes and other clinical variables, and the functional status at discharge, defined by a Barthel Index >  = 80., Results: A total of 158 patients were included in the study with a median age of 82 [Interquartile Range 81, 83]; of these 102 (65%) patients had a Barthel Index ≥ 80 at discharge. In the main multivariable logistic regression model a higher severity of frailty-measured with the Clinical Frailty Scale-(OR 0.30; CI 0.18-0.47), and the presence of delirium (OR 0.04; CI 0.00-0.35) at admission were associated with lower odds of a higher functional status at discharge. Other variables associated with lower functional status were female gender (OR 0.36; CI 0.13-0.96), and a higher number of comorbidities (OR 0.48; CI 0.26-0.82)., Conclusion: The study reports a relatively high prevalence of functional recovery for older COVID-19 patients admitted to sub-acute units. Additionally, it underlines the importance of targeting geriatrics syndromes, in particular frailty and delirium, for their possible effects on functional recovery., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background and Aims: Upscaling carbon allocation requires knowledge of the variability at the scales at which data are collected and applied. Trees exhibit different growth rates and timings of wood formation. However, the factors explaining these differences remain undetermined, making samplings and estimations of the growth dynamics a complicated task, habitually based on technical rather than statistical reasons. This study explored the variability in xylem phenology among 159 balsam firs [Abies balsamea (L.) Mill.]., Methods: Wood microcores were collected weekly from April to October 2018 in a natural stand in Quebec, Canada, to detect cambial activity and wood formation timings. We tested spatial autocorrelation, tree size and cell production rates as explanatory variables of xylem phenology. We assessed sample size and margin of error for wood phenology assessment at different confidence levels., Key Results: Xylem formation lasted between 40 and 110 d, producing between 12 and 93 cells. No effect of spatial proximity or size of individuals was detected on the timings of xylem phenology. Trees with larger cell production rates showed a longer growing season, starting xylem differentiation earlier and ending later. A sample size of 23 trees produced estimates of xylem phenology at a confidence level of 95 % with a margin of error of 1 week., Conclusions: This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size when assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Under climate change, the increasing occurrence of late frost combined with advancing spring phenology can increase the risk of frost damage in trees. In this study, we tested the link between intra-specific variability in bud phenology and frost exposure and damages. We analysed the effects of the 2021 late frost event in a black spruce (Picea mariana (Mill.) BSP) common garden in Québec, Canada. We hypothesised that the timing of budbreak drives the exposure of vulnerable tissues and explains differences in frost damage. Budbreak was monitored from 2015 to 2021 in 371 trees from five provenances originating between 48° and 53° N and planted in a common garden at 48° N. Frost damages were assessed on the same trees through the proportion of damaged buds per tree and related to the phenological phases by ordinal regressions. After an unusually warm spring, minimum temperatures fell to -1.9°C on May 28 and 29, 2021. At this moment, trees from the northern provenances were more advanced in their phenology and showed more frost damage. Provenances with earlier budbreak had a higher probability of damage occurrence according to ordinal regression. Our study highlights the importance of intra-specific variability of phenological traits on the risk of frost exposure. We provide evidence that the timings of bud phenology affect sensitivity to frost, leading to damages at temperatures of -1.9°C. Under the same conditions, the earlier growth reactivation observed in the northern provenances increases the risks of late frost damage on the developing buds., (© 2022 Scandinavian Plant Physiology Society.)

Auxin is involved in various developmental processes of plants, including cell division in cambium and xylem differentiation. However, most studies linking auxin and xylem cell production are performed in environments with a strong seasonality (i.e., temperate and boreal climates). The temporal dynamics of auxin and cambial activity of subtropical trees remain basically unknown. In this study, we sampled four microcores weekly in three individuals of Chinese red pine (Pinus massoniana Lamb.) from February to December 2015-16 to compare xylem formation with auxin concentration in subtropical China. During the entire period of sampling, the number of cambial cells varied from 2 to 7, while the number of cells in the enlarging zone ranged from 1 to 4 and from 1 to 5 in the wall-thickening zone. In 2015, the average auxin concentration was 3.46 ng g-1, with 33 xylem cells being produced at the end of the year. In 2016, a lower auxin concentration (2.59 ng g-1) corresponded to a reduced annual xylem production (13.7 cells). No significant relationship between auxin concentration and number of xylem cells in differentiation was found at the weekly scale. Unlike in boreal and temperate forests, the lack of wood formation seasonality in subtropical forests makes it more difficult to reveal the relationship between auxin concentration and number of xylem cells in differentiation at the intra-annual scale. The frequent and repeated samplings might have reduced auxin concentration in the developing cambium and xylem, resulting in a lower xylem cell production., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

Wood density is the product of carbon allocation for structural growth and reflects the trade-off between mechanical support and water conductivity. We tested a conceptual framework based on the assumption that micro-density depends on direct and indirect relationships with endogenous and exogenous factors. The dynamics of wood formation, including timings and rates of cell division, cell enlargement, and secondary wall deposition, were assessed from microcores collected weekly between 2002 and 2016 from five black spruce stands located along a latitudinal gradient in Quebec, Canada. Cell anatomy and micro-density were recorded by anatomical analyses and X-ray measurements. Our structural equation model explained 80% of micro-density variation within the tree-ring with direct effects of wall thickness (σ = 0.61), cell diameter (σ = -0.51), and photoperiod (σ = -0.26). Wood formation dynamics had an indirect effect on micro-density. Micro-density increased under longer periods of cell-wall deposition and shorter durations of enlargement. Our results fill a critical gap in understanding the relationships underlying micro-density variation in conifers. We demonstrated that short-term responses to environmental variations could be overridden by plastic responses that modulate cell differentiation. Our results point to wood formation dynamics as a reliable predictor of carbon allocation in trees., (© 2021 The Authors New Phytologist © 2021 New Phytologist Foundation.)

Background and Aims: Understanding how plant allometry, plant architecture and phenology contribute to fruit production can identify those plant traits that maximize fruit yield. In this study, we compared these variables and fruit yield for two shrub species, Vaccinium angustifolium and Vaccinium myrtilloides, to test the hypothesis that phenology is linked to the plants' allometric traits, which are predictors of fruit production., Methods: We measured leaf and flower phenology and the above-ground biomass of both Vaccinium species in a commercial wild lowbush blueberry field (Quebec, Canada) over a 2-year crop cycle; 1 year of pruning followed by 1 year of harvest. Leaf and flower phenology were measured, and the allometric traits of shoots and buds were monitored over the crop cycle. We hand-collected the fruits of each plant to determine fruit attributes and biomass., Key Results: During the harvesting year, the leafing and flowering of V. angustifolium occurred earlier than that of V. myrtilloides. This difference was related to the allometric characteristics of the buds due to differences in carbon partitioning by the plants during the pruning year. Through structural equation modelling, we identified that the earlier leafing in V. angustifolium was related to a lower leaf bud number, while earlier flowering was linked to a lower number of flowers per bud. Despite differences in reproductive allometric traits, vegetative biomass still determined reproductive biomass in a log-log scale model., Conclusions: Growing buds are competing sinks for non-structural carbohydrates. Their differences in both number and characteristics (e.g. number of flowers per bud) influence levels of fruit production and explain some of the phenological differences observed between the two Vaccinium species. For similar above-ground biomass, both Vaccinium species had similar reproductive outputs in terms of fruit biomass, despite differences in reproductive traits such as fruit size and number., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

New insights into the intra-annual dynamics of tree-ring formation can improve our understanding of tree-growth response to environmental conditions at high-resolution time scales. Obtaining this information requires, however, a weekly monitoring of wood formation, sampling that is extremely time-intensive and scarcely feasible over vast areas. Estimating the timing of cambial and xylem differentiation by modeling thus represents an interesting alternative for obtaining this important information by other means. Temporal dynamics of cambial divisions can be extracted from the daily tree-ring growth rate computed by the Vaganov-Shashkin (VS) simulation model, assuming that cell production is tightly linked to tree-ring growth. Nonetheless, these predictions have yet to be compared with direct observations of wood development, i.e., via microcoring, over a long time span. We tested the performance of the VS model by comparing the observed and predicted timing of wood formation in black spruce [ Picea mariana (Mill.)]. We obtained microcores over 15 years at 5 sites along a latitudinal gradient in Quebec (Canada). The measured variables included cell size and the timing of cell production and differentiation. We calibrated the VS model using daily temperature and precipitation recorded by weather stations located on each site. The predicted and observed timing of cambial and enlarging cells were highly correlated ( R 2 = 0.8); nonetheless, we detected a systematic overestimation in the predicted timing of cambial cells, with predictions delayed by 1-20 days compared with observations. The growth rate of cell diameter was correlated with the predicted growth rate assigned to each cambial cell, confirming that cell diameter developmental dynamics have the potential to be inferred by the tree-ring growth curve of the VS model. Model performances decrease substantially in estimating the end of wood formation. The systematic errors suggest that the actual relationships implemented in the model are unable to explain the phenological events in autumn. The mismatch between the observed and predicted timing of wood formation in black spruce within our study area can be reduced by better adapting the VS model to wet sites, a context for which this model has been rarely used., (Copyright © 2020 Buttò, Shishov, Tychkov, Popkova, He, Rossi, Deslauriers and Morin.)

Background and Aims: Secondary growth is a process related to the formation of new cells that increase in size and wall thickness during xylogenesis. Temporal dynamics of wood formation influence cell traits, in turn affecting cell patterns across the tree ring. We verified the hypothesis that cell diameter and cell wall thickness are positively correlated with the duration of their differentiation phases., Methods: Histological sections were produced by microcores to assess the periods of cell differentiation in black spruce [Picea mariana (Mill.) B.S.P.]. Samples were collected weekly between 2002 and 2016 from a total of 50 trees in five sites along a latitudinal gradient in Quebec (Canada). The intra-annual temporal dynamics of cell differentiation were estimated at a daily scale, and the relationships between cell traits and duration of differentiation were fitted using a modified von Bertalanffy growth equation., Key Results: At all sites, larger cell diameters and cell wall thicknesses were observed in cells that experienced a longer period of differentiation. The relationship was a non-linear, decreasing trend that occasionally resulted in a clear asymptote. Overall, secondary wall deposition lasted longer than cell enlargement. Earlywood cells underwent an enlargement phase that lasted for 12 d on average, while secondary wall thickness lasted 15 d. Enlargement in latewood cells averaged 7 d and secondary wall deposition occurred over an average of 27 d., Conclusions: Cell size across the tree ring is closely connected to the temporal dynamics of cell formation. Similar relationships were observed among the five study sites, indicating shared xylem formation dynamics across the entire latitudinal distribution of the species.The duration of cell differentiation is a key factor involved in cell growth and wall thickening of xylem, thereby determining the spatial variation of cell traits across the tree ring., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The decline in functional capacity is a heterogeneous phenomenon in the elderly. An accelerated ageing determines a frail status. It results in an increased vulnerability to stressors for decreased physiological reserves. The early identification of a frail status is essential for preventing loss of functional capacity, and its clinical consequences. Frailty and mobility limitation result from an interplay of different pathways including multiple anabolic deficiency, inflammation, oxidative stress, and a poor nutritional status. However, the age-related decline in insulin-like growth factor 1 (IGF-1) bioactivity deserves special attention as it could represent the ideal crossroad of endocrine, inflammatory, and nutritional pathways to frailty. Several minerals, namely magnesium, selenium, and zinc, appear to be important determinants of IGF-1 bioactivity. This review aims to provide an overview of the potential usefulness of nutrients modulating IGF-1 as potential therapeutic targets in the prevention of mobility limitation occurring in frail older subjects.

Background: Endothelial dysfunction is predictor of cardiovascular diseases that have different prevalence in men and women before menopause. Sex hormones and sex hormone binding globulin (SHBG), novel risk factors for diabetes and cardiovascular diseases even in older individuals, might explain this difference. However, the relationship between these hormones and endothelial function has never been addressed in the elderly., Methods and Results: 430 men and,424 women 70 years older of Prospective Study of the Vasculature in Uppsala Seniors study, with complete data on SHBG, testosterone(T), estradiol(E2), endothelium-independent vasodilation (EIDV), endothelium-dependent vasodilation(EDV), flow-mediated vasodilation (FMD) and the pulse wave analysis (reflection index, RI) were evaluated. Multivariate regression analysis adjusted for confounders was used to assess the relationship between T, E2, SHBG and endothelial function. In men we found a positive relationship between SHBG and EDV (β ± SE 3.60 ± 0.83, p<0.0001), EIDV (2.42 ± 0.58, p<0.0001) but not with FMD. The relationship between SHBG and EDV and EIDV was maintained after adjustment for sex (1.64 ± 0.47, p<0.001 and 1.79 ± 0.35, p<0.0006, respectively). After adjustment for confounders, the relationship between SHBG and EDV and EIDV was still statistically significant (2.63 ± 0.90 and 1.86 ± 0.63, p = 0.004 for both). In women SHBG and EIDV were positively associated (1.58 ± 0.46; p = 0.0007), and this relationship was independent of sex (1.79 ± 0.35; p<0.001). No significant interaction SHBG * SEX was found for EIDV (p = 0.72). In a combined analysis in two sexes, SHBG and EIDV were positively associated (1.13 ± 0.45; p = 0.01). SHBG was not associated with EDV, FMD and RI. No significant relationship was found between T or E2 and EDV, EIDV, FMD or RI in both sexes., Conclusions: In older men SHBG, but not T and E2, is positively and independently associated with EDV in resistance arteries. In both sexes, SHBG was positively and independently associated with EIDV., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Importance: The use of proton pump inhibitors (PPIs) has rapidly increased during the past several years. However, concern remains about risks associated with their long-term use in older populations., Objective: To investigate the relationship between the use of PPIs and the risk of death or the combined end point of death or rehospitalization in older patients discharged from acute care hospitals., Design: We investigated the relationship between PPI use and study outcomes using time-dependent Cox proportional hazards regression in patients 65 years or older discharged from acute care medical wards from April 1 to June 30, 2007., Setting: Eleven acute care medical wards., Participants: Four hundred ninety-one patients (mean [SD] age, 80.0 [5.9] years)., Main Outcome Measures: Mortality and the combined end point of death or rehospitalization. RESULTS The use of PPIs was independently associated with mortality (hazard ratio, 1.51 [95% CI, 1.03-2.77]) but not with the combined end point (1.49 [0.98-2.17]). An increased risk of mortality was observed among patients exposed to high-dose PPIs vs none (hazard ratio, 2.59 [95% CI, 1.22-7.16])., Conclusions and Relevance: In older patients discharged from acute care hospitals, the use of high-dose PPIs is associated with increased 1-year mortality. Randomized controlled studies including older frail patients are needed. In the meantime, physicians need to use caution and balance benefits and harms in long-term prescription of high-dose PPIs.