Tree Physiology

Bulk phloem flow is driven by pressure gradients generated by water drawn from the xylem, coupling source-sink transport with water status. Huanglongbing (HLB), a phloem-affecting bacterial disease of citrus, disrupts phloem transport, and causes canopy water deficit. Although improved water management can enhance HLB-affected tree health, the effects of HLB on water-driven source-sink relations are unknown. Fruits function as both carbon sink and water reservoir, but the role of fruit in regulating whole-tree water status remain poorly understood. We examined leaf-fruit water relations in HLB-affected citrus and evaluated how HLB exposure duration, fruit developmental stage, and source-sink manipulation shape these dynamics. Source-sink relations were manipulated in branches of symptomatic trees with long-term (four years) and recent (six months) HLB exposure. We girdled branches with a single fruit as the sink and defoliated at (0%, 50%, or 75%), and an ungirdled, non-defoliated branch served as control. We measured stomatal conductance, leaf hydraulic traits, leaf and fruit soluble sugars, diurnal fruit shrinkage (to estimate xylem backflow) and fruit water loss. Source-sink manipulation did not affect shoot total soluble sugar. HLB-exposure resulted in less negative osmotic potential, more negative turgor potential and reduced modulus of elasticity and relative water content at turgor loss point. HLB exposure also increased diurnal fruit shrinkage, with shrinkage responses to source-sink manipulation varying across fruit development stages. Collectively, these findings suggest that long-term HLB exposure promotes leaf acclimation to water deficits, however, high sink demand may diminish the leaf water status regulation at Stage II, when fruit sink carbon demand is highest.

Drought stress severely limits tree growth and survival, a problem intensifying under climate change due to the rising frequency of extreme weather events. Identifying genetic variants that modulate drought stress responses and enhance resilience is therefore of great interest for developing climate-adapted trees. While the MADS-box transcription factor AGL16 has been implicated in drought responses and stomatal regulation in herbaceous species, the function of its homolog in woody perennials remains largely unexplored. Here, we investigate the role of PtaAGL16 in the poplar hybrid Populus tremula x P. alba. We generated CRISPR/Cas9 knockout lines of PtaAGL16 in the poplar clone INRA 717-1B4. Plants were subjected to a severe drought stress regime followed by a re-watering recovery phase. Morphological and physiological traits, including growth, stomatal conductance, shoot vitality, and stomatal density, together with stress-associated metabolites and drought-responsive gene expression, were analyzed. All agl16 knockout lines exhibited significantly reduced drought-induced damage compared to the wild-type. While the wild-type suffered extensive defoliation and persistent stem necrosis, the knockout lines retained higher shoot vitality and resumed growth after re-watering, including the formation of new leaves. Consequently, vitality in the knockout lines reached up to 86%, compared to only 34% in the wild-type. This improved resilience was accompanied by reduced persistent oxidative membrane damage, as indicated by lower MDA levels after recovery. These findings indicate that the disruption of PtaAGL16 is associated with enhanced drought resilience in a woody perennial species and highlight its potential as a genetic target for improving climate adaptation in fast-growing forest trees.

The xylem safety-efficiency trade-off is a central paradigm in plant hydraulics, yet empirical support remains inconsistent. In this study, we highlight how this inconsistency may arise from variation in environmental and evolutionary constraints and from differences in observational scale. We analysed 38 diffuse-porous angiosperm and 24 conifer species grown in a common garden experiment to quantify the relationship between embolism resistance (P50) and specific hydraulic conductivity (Ks) across and within species, and its differences between three species groups differing in evolutionary ancestry and eco-hydrological strategy. When pooling over all species, we found evidence for a safety-efficiency trade-off both across and within species. However, this pattern was driven almost exclusively by the mesic broadleaved species. In contrast, the across-species pattern was suppressed in coniferous species due to the evolutionary constraints on efficiency posed by their tracheid-based wood anatomy, while there was no evidence for a trade-off on either level in hydrophilic broadleaved species, which evolved under conditions that pose reduced selective pressure on embolism resistance. Our results demonstrate that the safety-efficiency trade-off is not universal, but emerges only in specific ecological and evolutionary contexts, highlighting the importance of multi-scale analyses and constraint-based frameworks for interpreting plant hydraulic strategies.

Cellulose has long been viewed as the major load-bearing component in plant primary cell walls. Recent studies, however, suggest that pectin plays a significant role in cell wall mechanics despite a kPa-scaled modulus. Here we quantify the mechanical properties of centimeter-sized internodal cell walls of Chara corallina following treatments to remove calcium crosslinks or digest pectin. We also characterize the flow of water and gas through the cell wall as a function of pressure. We found that removal of calcium crosslinks did not affect wall strength and stress-relaxation behavior, yet it decreased the elastic modulus and increased permeability to water. In contrast, pectin removal had a dramatic impact on all measurements. Samples from which pectin had been removed exhibited lower strength and stiffness and had greater stress relaxation under constant strain. Pectin removal increased the permeability of the cell wall to water above that observed when calcium was removed and reduced the pressure at which gas "tunnels" through the cell wall ~ 2-fold. Our findings support the idea that pectin locally restricts the movement of cellulose microfibrils, with implications for understanding functional properties of primary cell walls in vascular plants and developing high-performance double-network materials.

Global change has a major impact on rivers and their associated terrestrial compartment, the riparian forest. The black poplar (Populus nigra L.), the dominant species of the European riparian forest, is considered an indicator of the biodiversity dynamics of these ecosystems, but is threatened with extinction in several parts of its range. The species is dioecious and shows wide variability in many traits, enabling it to adapt to a broad range of environmental conditions. A detailed characterization of this natural variability is therefore a key issue both for the conservation of natural populations and for biological engineering aimed at restoring riverbanks. Phenology is both an indicator of climate change and an adaptation lever for populations, particularly in perennial species such as trees. In this study, we characterized the spatial and temporal variability in flowering phenology by studying 13 natural black poplar populations along the Loire River, France. Flowering date and duration showed substantial variability both within and between populations, and males generally flowered earlier than females. Despite this variability, the ranking of individual trees' flowering dates was highly consistent across years. Most male-female pairs shared several days of overlapping flowering each year, and this overlap was moderately stable across years. Flowering dates advanced by about five to six days per degree Celsius during early spring, with no detectable difference in sensitivity between sexes. This work contributes to the characterization of flowering variability in an economically important tree species and may inform both the conservation of genetic resources and breeding.

Following a severe 2018 drought affecting much of Europe, European beech (Fagus sylvatica) exhibited patchy canopy dieback. To investigate the drivers of this mortality, we used a paired case-control design across Swiss forests, integrating phenotypic assessments and genomic analyses. Phenotypically, crown transparency and discoloration were used to classify tree damage state, while several other characteristics were measured to evaluate whether paired, neighboring damaged and undamaged trees were otherwise comparable, and to identify physiological stress signatures. Elevated leaf calcium content and red edge reflectance in dried leaves emerged as robust indicators of physiological stress. Genomic association models using reference-based SNP markers and reference-free k-mers were heavily confounded by micro-environmental variance and local population stratification even within our geographically limited study region. Our cross-validated genomic outliers showed no spatial overlap with predictive drought-associated loci previously identified in an independent German cohort. These findings indicate that drought survival in European beech is not governed by a universal set of major-effect alleles. Instead, tree performance appears highly context-dependent, likely shaped by micro-environmental heterogeneity and phenotypic condition. However, our results do not exclude polygenic drought responses involving multiple small-effect loci.

Understanding how carbon-water coupling scales from leaves to ecosystems remains a major challenge because water-use efficiency (WUE) metrics integrate physiological, hydrological, and ecological processes. We integrated tree-ring width, triple stable isotopes ({delta}13C, {delta}18O and {delta}2H), eddy covariance (EC) observations, and a process-based model to investigate the drivers of intrinsic (iWUE) and ecosystem water-use efficiency (WUEeco) across biological scales in a mature Fagus sylvatica forest between 2004 and 2023. Modelled and isotope-derived iWUE were strongly correlated (r = 0.61, p < 0.05) and both indicated an approximately 20% long-term increase, consistent with increasing gross primary productivity. In contrast, WUEeco derived from EC was lower than model estimates and exhibited a positive trend not reproduced by the model. This divergence primarily reflected differences in biological representation and hydrological integration, as the single-species model underestimated ecosystem evapotranspiration by excluding co-occurring deciduous and evergreen species together with understory vegetation. Triple-isotope analyses showed that the long-term increase in iWUE was driven by enhanced photosynthetic assimilation rather than sustained stomatal closure, whereas {delta}18O and {delta}2H variability was mainly controlled by source-water dynamics. These findings provide a mechanistic framework for reconciling leaf- and ecosystem-scale WUE and improving predictions of forest carbon-water coupling under climate change.

Fire-dependent or fire-influenced ecosystems harbor species with diverse response strategies, such as smoke-stimulated germination and dormancy release through heat shocks. Although these cues influence germination in many fire-prone ecosystems, their effects on seeds of woody species from tropical dry forests (TDFs) remain poorly understood. We evaluated the germination response of twelve TDF woody species to three heat-shock temperatures (80, 120, and 160C), two exposure times (3 and 5 min), and two smoke conditions (with and without smoke water), plus dry and wet controls. We also assessed the relationship between germination and functional seed traits, including permeability, seed-coat thickness, mass, and shape index. Of the eleven species that germinated, four showed broad tolerance, with no significant reduction in germination even at 160C for 5 min, which was associated with lower permeability, thicker seed coats, and greater mass. Four other species showed restricted tolerance to heat, with significant declines in germination at higher temperatures or longer exposure times, and were associated with higher permeability, thinner seed coats, and lower seed mass. The remaining three species showed heat-stimulated germination between 80 and 120C and tended to have lower shape-index values. Smoke treatments significantly increased germination in three species, Ceiba pentandra, Guazuma ulmifolia, and Samanea saman. In the remaining species, significant differences were either absent or attributable to moisture or imbibition effects rather than to smoke itself. Overall, germination responses to heat were associated with variation in functional seed traits, whereas responses to smoke were less widespread and showed a less consistent functional pattern.

Background and aims: Perennial root systems develop over decades and exhibit continuous turnover of structural and absorptive components, yet most root architecture models treat woody roots as permanent and neglect root age structure. We developed an empirically constrained modelling framework that explicitly represents age-structured demography, growth regulation and dormancy in perennial root systems. Methods: We extended the functional-structural plant model CPlantBox to simulate perennial root development over decades by integrating age-dependent survival, secondary radial growth and climate-driven dormancy. The model was parameterised using unique three-dimensional root system data from young and mature grapevines, together with dendrochronological root age measurements, and coupled to root hydraulic properties. Key results: Empirical analyses revealed multi-cohort age distributions and substantial turnover of lignified structural roots, contradicting the assumption of a static woody scaffold. The model reproduced age distributions, order-specific survival probabilities and fine-to-structural root length ratios, and generated realistic, genotype-specific three-dimensional architectures. Simulated uptake profiles and hydraulic scenarios showed strong age- and architecture-driven effects. Conclusions: Explicitly representing woody root age distributions and age-dependent processes may fundamentally change predictions of perennial root system architecture and function. The framework advances root modelling beyond annual paradigms and provides a transferable tool for analysing long-term architectural and hydraulic consequences of genotype x climate interactions in perennial crops.

Forest canopy height is sensitive to shifts in demography (which affect tree size distributions and abundances of short-vs. tall-statured species) and allometry. Demographic and allometric effects on canopy height have not previously been studied across a large region. We analyzed more than two million individual tree measurements from about 60,000 remeasured inventory plots in non-plantation forests across 19 ecoregions of the conterminous United States to quantify changes in aboveground live tree biomass (AGB), canopy height, and its demographic and allometric components from ~2003-2025. We tested the hydraulic limitation hypothesis, which predicts decreasing tree height with increasing hydraulic stress. AGB was strongly correlated with canopy height across ecoregions, and AGB change was strongly correlated with canopy height change over time. Canopy height change was positive in nearly all eastern ecoregions but varied in sign across western ecoregions. Demographic shifts led to increased canopy height in most eastern ecoregions but decreased canopy height in most western ecoregions. In contrast, allometric shifts, averaged across species, caused either positive or no significant change in ecoregion-mean canopy height. Our results were consistent with several predictions of the hydraulic limitation hypothesis: (i) intraspecific allometric shifts were more positive for understory than for canopy trees, (ii) across ecoregions, canopy height was positively correlated with precipitation and negatively correlated with vapor pressure deficit, and (iii) canopy height change over time was positively correlated with precipitation change. However, our results suggest modifications to the hydraulic limitation hypothesis, because allometric shifts tended to be positive, even in ecoregions with decreasing precipitation and increasing vapor pressure deficits. Such allometric shifts, which seem counter to the hydraulic limitation hypothesis, may be caused by CO2-driven increases in water-use efficiency. Whatever their cause, allometric shifts should be accounted for to avoid biased estimates of canopy height change and biomass change.

Forests are threatened by a multitude of stressors, including anthropogenic disturbances and climate change. Assessing how forests will respond to these stressors requires a comprehensive understanding of net primary productivity (Npp), environmental constraints on growth, and adaptive capacity. A parameter of significant uncertainty is belowground Npp (bNpp), which can account for up to 80% of total Npp but is poorly estimated and rarely measured directly. We used a cross-biome dataset of direct, field-based measurements of aboveground and belowground primary productivity and 21 climatic and soil variables to identify potential constraints on bNpp and belowground carbon allocation in boreal and cold temperate forests. Soil variables, rather than climate variables, were the main drivers of bNpp and belowground allocation across biomes. The importance of soil variables suggests that soil nutrient dynamics, especially soil nutrient pool and flux variables, must be explicitly modeled to more accurately predict feedbacks between climate, productivity, and within-tree carbon allocation. Within biomes, environmental drivers of belowground allocation varied between low versus high allocation forests, indicating that environmental drivers are site-specific and the development of within-biome, site-scale classifications for forest ecosystems could be useful. Changes in soil variables, such as increasing soil nitrogen pools, caused abrupt and large decreases in bNpp for boreal, but not cold temperate forests. Threshold-like shifts indicate that boreal forests might have lower adaptive capacity and higher sensitivity to disturbances than cold temperate forests. With 70% of boreal forests characterized by low bNpp, disturbances such as anthropogenic nitrogen deposition could cause large-scale decreases in bNpp that could push these forests beyond their adaptive capacity.

Premise of the study. Phenotypic plasticity is advantageous for many plants that experience environmental fluctuations, but strong selection pressures can establish limits to plasticity. In deciduous trees, the ability to time leaf elongation in response to spring temperatures can extend the length of the growing season for a given year's climate. However, emergence timing may have undergone strong selection by factors like cold temperatures, limiting the capacity of locally adapted populations to adjust via plasticity to new conditions. Methods. Using a nine-year dataset of 659 families of Quercus lobata in two common gardens, we tested how climate of origin and annual temperatures at the gardens affected variation in phenology. We then examined whether leaf emergence timing was under selection in the gardens by testing its effects on growth. Finally, we tested whether among-year plasticity in leaf emergence timing conferred a growth benefit. Key results. Year-to-year environmental variation explained more phenological variation than genetic differences associated with climate of origin, yet trees from cooler climates were more constrained in their ability to track temperature than trees from warmer climates. We found evidence of weak stabilizing and directional selection on phenology, suggesting that strong selection in favor of earlier phenology is unlikely. Finally, we found no evidence that selection has favored increased plasticity in Q. lobata. Conclusions. Phenological plasticity remains a key driver of plants' response to changing temperatures, but it is constrained by natural selection. As temperatures rise, these processes may disproportionately limit the ability of trees adapted to cooler climates to shift their phenology to match spring temperatures.

Forests regulate climate and sustain biodiversity, but their resilience is increasingly threatened by drought-induced hydraulic failure, when xylem water transport is impaired by embolism. A critical but poorly constrained determinant of this risk largely due to limited observations of deep root water uptake is the amount of root-accessible (sub)soil water storage (SR), which governs land-atmosphere exchanges during prolonged dry periods. While ecohydrological theory has long suggested a balance between soil water storage in the rooting zone, vegetation growth and drought tolerance, this concept has not yet been integrated into predictive models of hydraulic failure. Here we propose a novel, process-based inversion framework that integrates ecohydrological optimality theory with principles of plant hydraulic to infer SR. Using the SurEau plant hydraulic model, we estimate the SR value that balances the costs of soil exploration with the avoidance of drought-induced hydraulic damage. Applied first to a well-instrumented Mediterranean Quercus ilex forest, the inferred SR closely matched independent neutron probe and eddy covariance measurements and accurately reproduced observed drought responses, including leaf water potential and sap flow dynamics. We then scaled the approach across European forests remotely-sensed data, to assess spatially explicit SR estimates and associated hydraulic failure risk. Across more than 20 species and sites, inferred SR and drought stress metrics aligned with field observations and outperformed estimates based on conventional soil databases or remote-sensing-only approaches. By linking plant physiology and ecohydrological theory within a scalable inversion framework, this approach improves predictions of forest drought risk under climate change.

Stemflow transports water and biological material from forest canopies to the stem base, yet fungal studies of this flux have largely relied on microscopy of conidia. We used ITS2 metabarcoding to characterize fungal environmental DNA (eDNA) in stemflow from 15 trees - five each of American beech (Fagus grandifolia), sugar maple (Acer saccharum), and tulip poplar (Liriodendron tulipifera) in a closed-canopy forest in northeastern Ohio, USA. Stemflow was sampled during eight rain events in the leafless season (November 2024-May 2025), along with simulated bark and gutter washes to assess near-collar and collector signals. Natural stemflow communities were compositionally distinct from both controls and occupied greater ordination space. Ascomycota dominated across all samples, with Parafenestella, Cytospora, Microcera, Nectria, and Aureobasidium among the most abundant resolved genera and 13 of the 25 most abundant taxa differed significantly among host species. Woody-plant-associated endophytes, canker fungi, and saprobes dominated ecological guild composition. Storm event explained 28.6% of taxonomic variation, host tree species 24.1%, and their interaction 10.0%. Guild composition was more strongly structured by host species (35.4%) than storm event (20.4%). Lichenized fungi and lichen-associated fungi were detected. Thus, leafless-season stemflow integrates broad bark-associated fungal eDNA, including recurrent lichen-derived material, beyond the morphologically distinctive conidia captured by traditional methods. Stemflow eDNA therefore offers a minimally invasive means of monitoring canopy fungal diversity and the strong host and temporal filtering of DNA exported from woody surfaces.

Background and aims Alpine ecosystems are highly sensitive to climate change, with rising temperatures threatening ecosystem structure and function. This study examined the short-term responses of alpine grassland ecosystems (Mont Blanc, Italy) to projected climate scenarios using an Ecotron mesocosm experiment. Methods Ecosystem monoliths were exposed to current (~420 ppm CO2) and future CO2; concentrations (~550 and ~800 ppm) under RCP 4.5 and RCP 8.5 scenarios, incorporating changes in temperature, precipitation, humidity, and radiation. CO2; fluxes (NEP, GPP, Reco), soil chemistry, vegetation coverage, above- and belowground biomass, and plant functional traits were assessed throughout the experiment. Results Alpine grassland ecosystems withstood moderate warming (RCP 4.5), while under severe warming (RCP 8.5), GPP, vegetation cover and biomass increased with a shift toward aboveground allocation, although daytime NEP remained stable as gains were offset by higher Reco, with no detectable water and nutrients limitations. On a diel basis, higher GPP was offset by enhanced Reco, indicating a potential towards net C loss. Salix herbacea exhibited functional trait adjustments-higher LMA and Na, and elevated delta15N-reflecting greater leaf longevity, water-use efficiency, and altered nitrogen metabolism, suggesting potential community reorganization. Conclusion Over a single growing season, alpine ecosystems appeared relatively stable under moderate warming. However, under the more severe RCP 8.5 scenario, biomass allocation shifted toward greater aboveground and reduced belowground investment, leading to altered C fluxes that, if sustained over the long-term, could drive the ecosystem C balance from a sink to a source. Responses were plant species-specific, indicating uneven acclimation within the community.

Boreal forested streams receive substantial inputs of terrestrial carbon (C) from riparian vegetation in the form of leaf litter, which is processed by litter-associated microorganisms. In addition to these leaf-litter C inputs, boreal streams also receive significant concentrations of dissolved organic carbon (DOC), which may represent an alternative major resource pool for litter-associated microorganisms. As leaf litter quality decreases over the process of decomposition, DOC may increasingly become a more suitable C source for the microbial communities. We investigated how DOC availability, litter type, and microbial succession influenced respiration and decomposition. Alder, birch, and spruce litter were incubated for 65 days in 12 outdoor experimental channels supplied with natural boreal stream water. Higher time-adjusted DOC concentrations were associated with higher respiration and lower relative mass remaining, whereas DOC flux received less support. Respiration and mass loss followed litter-specific trajectories, with birch showing a respiration peak that was not matched by proportional mass loss. Prokaryotic and eukaryotic communities differed among litter types and changed through time but explained process variation only for specific litter types and responses. Our results suggest that DOC can sustain litter-associated microbial activity and partly decouple respiration from litter decomposition, thereby affecting boreal stream C processing.

Plants frequently experience recurrent drought events separated by periods of rehydration. Although drought imposes strong constraints on plant physiology, prior exposure may alter subsequent stress responsiveness through memory-based mechanisms. Here, we investigated whether recurrent drought at distinct developmental stages establishes stress memory in sugarcane and whether this response persists across vegetative propagation. Two genotypes contrasting in drought tolerance and productivity (IACCTC07-8008 and IACSP95-5000, respectively) were grown under greenhouse conditions and subjected to three drought cycles imposed either at tillering or maturation stage. Gas exchange, photochemical performance, leaf water status, primary metabolite profile, and growth traits were assessed across cycles, and vegetative propagules were subsequently evaluated under renewed drought. The first drought cycle imposed strong limitations on carbon assimilation and photochemistry in both genotypes and developmental stages. However, subsequent cycles resulted in attenuated reductions in A and g, improved intrinsic water use efficiency, and partial stabilization of PSII performance, indicating a modified stress-response trajectory. Young plants displayed earlier improvements (from the second cycle), whereas in mature plants this shift was evident mainly during the third cycle. Recurrent drought promoted sustained reorganization of amino acid, carbohydrate, organic acid and polyol metabolism alongside increased root biomass and higher relative water content during later cycles. Importantly, propagules derived from drought-conditioned plants exhibited faster recovery of photosynthetic performance and reduced cumulative physiological impairment under renewed drought, despite showing similar stress sensitivity at maximum water deficit. This persistence of enhanced recovery capacity across vegetative propagation indicates that drought-induced memory was maintained beyond the initially stressed plants. Together, our findings demonstrate that recurrent drought establishes a metabolically imprinted state in clonal sugarcane, integrating physiological adjustment, metabolic reprogramming, and whole-plant acclimation. These results highlight the potential of stress memory as a mechanism supporting resilience in perennial crops exposed to increasingly recurrent drought events.

Reforestation is a leading natural climate solution, but bulk soil organic carbon (C) often responds slowly, obscuring early belowground change. We tested whether soil aggregates reveal early structural reorganization that affects C retention pathways at a three-year-old experimental reforestation planting established on former pasture in Oregon, USA. We sampled soils at 0-20 and 20-40 cm beneath incense cedar (Calocedrus decurrens; arbuscular mycorrhizal [AM]), black cottonwood (Populus trichocarpa; AM and ectomycorrhizal [EcM]), ponderosa pine (Pinus ponderosa; EcM), and treeless controls. We measured bulk soil C concentration and C:N, aggregate size distribution and mean weight diameter (MWD), fraction-associated C, and, in a subset of surface aggregate fractions, natural-abundance {delta}13C to evaluate soil C pools, physical structure, C distribution, and C processing. After three years, reforestation did not produce significant differences in bulk soil C between planted trees and treeless controls. In surface soil, MWD averaged 36% higher under incense cedar and 58% higher under black cottonwood than under controls, whereas ponderosa pine remained similar to controls. The clearest treatment differences in C distribution occurred in macroaggregates. Incense cedar and black cottonwood had higher large (>2000 m) macroaggregate-associated C than controls, while black cottonwood combined a greater proportion of large macroaggregates with lower C concentrations, indicating that structural development and C accumulation were partly decoupled. Species patterns were broadly consistent with stronger early aggregate responses under AM-compatible species in former-pasture legacy conditions; by contrast, the EcM-associated ponderosa pine remained closer to treeless controls across multiple aggregate measures. Treatment effects weakened with depth and were limited in microaggregates (250-53 m) and silt-and-clay (<53 m) fractions. Smaller aggregate fractions were progressively enriched in {delta}13C, consistent with greater C processing in protected fractions, but treatment-level isotope differences had not yet emerged. Soil aggregates showed species-associated belowground reorganization, revealing how tree identity and former-pasture legacy may shape early soil C organization before consistent differences emerged in bulk soil C. Aggregate measures can complement bulk soil C measurements in restoration monitoring as early indicators of belowground soil C trajectories shaped by tree species identity and land-use legacy.

Understanding the genetic architecture of ecophysiological traits related to carbon gain and water loss is crucial to develop cultivars tolerant to abiotic stresses and that maintain productivity in the context of climate change. This can be achieved both through experiments in the greenhouse on potted plants under controlled conditions and in the field. However, the stability of genetic determinism of ecophysiological traits across environmental conditions has rarely been evaluated. We studied a grapevine diversity panel grown both in a greenhouse and in the field, to investigate the impact of growing conditions on leaf ecophysiological traits related to leaf morphology, fluorescence, gas exchange and water use efficiency. The correlation structure between traits was conserved within each environment even though, for most traits, cultivars ranking was not conserved between both environments. However, a set of cultivars, sharing the same functioning pattern in terms of gas exchange and fluorescence in both environments, was identified. Single- and multi-environment Genome-Wide Association Studies (GWAS), based on a dense genotyping matrix, were used to dissect the genetic architecture of leaf traits. The Quantitative Trait Loci (QTLs) identified through single-environment analyses differed substantially from those detected using multi-environment ones. Multi-environment approaches highlighted shared QTLs across environments for gas exchange and fluorescence traits. Candidate genes associated with carbon- and water-related functions were further identified in these genomic regions. Despite the weak correlation between greenhouse and field trait values, combining both environments enabled the identification of robust genetic regions associated with ecophysiological traits of interest.

Seed ecophysiology is essential for understanding plant regeneration and developing effective conservation and ecological restoration strategies, yet knowledge remains scarce for most threatened Cerrado species. We characterised the germination niche, desiccation tolerance and storage behaviour of Xyris paradisiaca (Xyridaceae), an Endangered species endemic to Central Brazil, to assess whether its restricted distribution is associated with narrow germination requirements and to inform seed-based conservation. Germination was tested across light regimes, constant temperatures, decreasing water potentials and short-duration heat shocks, while thermal- and hydro-time models were used to quantify thermal and hydric thresholds. Seeds exhibited an absolute light requirement but broad abiotic tolerances. Germination remained >87% between 15 and 40 {degrees}C, with estimated cardinal temperatures of Tb = 8.94 {degrees}C, To = 33.13 {degrees}C and Tc = 45.53 {degrees}C. Germination remained similar to the control down to -0.6 MPa and exceeded 40% at -1.0 MPa, with a median base water potential of {Psi}b = -1.03 MPa. Germination also remained high after 1-min heat shocks up to 200 {degrees}C. Seeds were desiccation tolerant, with 100% germination after drying and a viability loss index of -0.04, and germination remained >90% after 24 months of ambient storage. Thus, the highly restricted distribution of X. paradisiaca is not driven by a narrow physiological germination niche. Its broad environmental tolerances, desiccation tolerance and favourable storage behaviour also highlight its unexplored potential for seed-based restoration, propagation and ex situ conservation.