Plant, Cell & Environment

Several tomato (Solanum lycopersicum) varieties are sensitive to heat stress, which compromises plant growth, development, and ultimately yield. Biostimulants represent a promising approach to improve crop performance, yet their widespread adoption is hindered by the incomplete understanding of their mechanisms of action. This study aimed to elucidate the physiological and molecular effects of a protein hydrolysate-based biostimulant (Leafamine(R)), in tomato, under both optimal and heat stress conditions. Leafamine(R) increased primary root length by 15 to 20% compared to the controls, independent of the tested conditions, through promotion of cell division and potentially expansion. Transcriptomic analyses revealed the upregulation of genes involved in cell division and expansion under both optimal and heat stress conditions and the downregulation of heat stress markers under heat stress conditions. Hormone and metabolite profiling showed elevated levels of jasmonic and salicylic acid, putrescine, citrulline, and GABA, after Leafamine(R) treatment, consistent with the activation of stress tolerance pathways. Leafamine(R) pre-treated seedlings exhibited reduced growth inhibition during heat exposure, suggesting a priming effect. These findings highlight Leafamine(R) as a promising biostimulant for enhancing tomato growth in the context of climate change and the potential of biostimulants generically.

Root hairs (RH) are excellent model systems for studying cell size and polarity since they elongate several hundred-fold their original size. Their tip growth is regulated by both intrinsic and environmental signals and is associated with the existence of a highly controlled cytoplasmic tip Ca{superscript 2} gradient, whose disruption impairs RH development. The molecular mechanisms underlying the Ca2+ homeostasis fine tuning and the Ca2+ organellar contributions to the cytoplasmic pool remain unclear. In the model plant Arabidopsis thaliana, many efflux routes are present, including those that employ Ca2+-pumps from the Autoinhibited Ca2+-ATPase (ACA) family. Here, we identified that the ER localized ACA2, and to a lower extent ACA7, are crucial ACAs required to control RH growth. By using genetically encoded Ca2+ biosensors we showed that Ca2+-dynamics are compromised in the aca2-2 mutant, having lower cytosolic Ca2+ concentration [Ca2+]cyt and growth rate, showing an altered homeostatic calcium setpoint compared to Col-0. Accordingly, the ACA2 mutation changed the dynamics of [Ca2+]cyt oscillations coupled to growth rate, inducing longer periods and more regular oscillations in the dominant high-frequency range (around 22 s), and slower oscillations (around 1 min) in the low-frequency range. Finally, expression of ACA2 with changes in four putative Ca2+ binding residues (ACA2{Delta}Ca2+) failed to rescue the RH growth phenotype in the aca2-2 mutant. Collectively, our findings indicate that ER-localized ACA2 and possibly ACA7 are crucial for modulating cytoplasmic Ca2+ signals, possibly composing a critical part of a negative feedback loop, and their absence leads to impairments in RH cell elongation.

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/741208v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@1238a49org.highwire.dtl.DTLVardef@4bc55corg.highwire.dtl.DTLVardef@8a277aorg.highwire.dtl.DTLVardef@25c625_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Legume-rhizobium symbiosis is constrained by carbon allocation and nutrient exchanges between the host plant and symbiotic bacteroids, emphasizing the necessity of biostimulant-based strategies to improve symbiotic efficiency. Studies suggest that plants provide carbon substrates (mainly TCA cycle intermediates) and nitrogen assimilation precursors to support bacteroid metabolism and nitrogen fixation. The GABA shunt represents a conserved bypass, linking the GS/GOGAT cycle, TCA cycle, and broader nitrogen metabolism. In the present study, the metabolic phenotypes upon rhizospheric application of exogenous {gamma}-aminobutyric acid (GABA) and succinate were investigated in pea. Application of exogenous GABA and succinate primarily altered the morpho-biochemical properties and root nodule establishment of the plant. While GABA supplementation reduced the root length and increased stomatal density, succinate treatment alone inhibited nodule organogenesis with disrupted symbiosome zoning. Metabolic rewirings associated with these phenotypic changes begin at the root nodule compartment, where exogenous GABA altered endogenous tricarboxylic acid (TCA) cycle pools, leading to higher turnover of TCA cycle intermediates, including succinate, fumarate, and malate, as well as elevated levels of sugars (sucrose, glucose, and fructose) and polyols (pinitol, mannitol, and myo-inositol). Concurrently, the plants accumulated substantially higher levels of asparagine (+3.9 log10-fold higher), accompanied by altered shoot protein content and enhanced elemental nitrogen content (+0.8-1%). Collectively, these findings demonstrate the potential of GABA as a biostimulant capable of altering the carbon-nitrogen dynamics and enhancing symbiotic functioning in pea root nodules, whereas succinate alters the process of nodule formation.

Tropospheric ozone (O) is a major atmospheric pollutant that affects plant carbon metabolism, redox homeostasis, and secondary metabolism, including the biosynthesis and emission of biogenic volatile organic compounds (BVOCs). However, the contribution of BVOCs to O3 tolerance, particularly in tropical woody species, remains poorly understood. Here, we investigated whether acute O exposure (cumulative AOT40 of 3497.82 ppb h) induces alterations in photosynthetic performance, redox homeostasis, and BVOC partitioning in Eugenia uniflora. We evaluated gas exchange, photosynthetic pigments, ascorbate and glutathione pools, emitted BVOCs, modeled intercellular BVOC concentrations, and the relative carbon cost associated with BVOC emissions. O exposure significantly increased net CO2 assimilation without affecting stomatal conductance, transpiration, leaf water status, or chlorophyll concentrations, indicating maintenance of photosynthetic performance. Carotenoid concentrations and total glutathione decreased, whereas glutathione redox status was maintained. O induced marked compound-specific changes in BVOC composition and partitioning. Several monoterpenes appeared exclusively under O exposure, {gamma}-elemene emission increased significantly, and the relative distribution of individual BVOCs between the modeled intercellular and emitted pools was altered. These findings show that the response of E. uniflora to acute O exposure was characterized by interplay among carbon assimilation, glutathione redox regulation, and BVOC partitioning rather than by increased total volatile emission. Enhanced carbon assimilation occurred without additional carbon loss through BVOC release, while changes in the modeled intercellular pool indicate that part of the volatile response remained within the leaf. Our findings highlight BVOC partitioning as an important dimension of the plant response to oxidative stress and demonstrate that emission measurements alone may not fully capture the fate and potential physiological role of volatile carbon under O exposure. O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/743946v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@653af1org.highwire.dtl.DTLVardef@ca5forg.highwire.dtl.DTLVardef@1e641bforg.highwire.dtl.DTLVardef@1e68fae_HPS_FORMAT_FIGEXP M_FIG C_FIG BVOC Partitioning Contributes to Oxidative Stress Defence Under Acute O Exposure

Photorespiration significantly influences terrestrial carbon fluxes, yet empirical measurements of its variability across tree species and temperature conditions remain limited, constraining predictions of vegetation and climate models. We quantified apparent photorespiratory CO2 loss (Lapp) and its temperature response for seven temperate broadleaf tree species in northern Europe, using in situ O2-shift measurements in Uppsala, Sweden during peak summer. Apparent loss was derived as the difference between net CO2 assimilation under ambient (Anet) and O2-free conditions at three leaf temperatures (25, 30, and 35 {degrees}C), spanning typical and heat-wave scenarios. Apparent photorespiratory CO2 loss showed pronounced interspecific variation and increased with temperature, while net photosynthesis remained relatively stable. The ratio of apparent loss to net photosynthesis ({phi} = Lapp/Anet) rose sharply with temperature, reaching species-mean values up to 0.94 at 35 {degrees}C, indicating that photorespiration can represent nearly the entirety of net carbon gain under heat stress even when leaves remain net CO2 sinks. Suppression of photorespiration under N2 and associated changes in leaf temperature systematically reallocated photosynthetic electron transport: the fraction of ambient electron transport rate (ETR) allocated to net CO2 assimilation declined with temperature, whereas the complementary fraction allocated to apparent photorespiratory loss and other O2-dependent sinks increased, with ETR-based apparent loss and its proportional expression rising steeply across the 25-35 {degrees}C range. Together, these in situ flux and partitioning measurements reveal high variability and strong temperature sensitivity in apparent photorespiration among temperate trees. Compared to crop-based parameterisations, the {phi} values we report for temperate trees are substantially higher and more temperature-dependent, providing species-specific constraints that can improve Farquhar-von Caemmerer-Berry-type vegetation model representations of photorespiration in forest ecosystems.

The ability of seeds to survive until dormancy recedes and the germination requirements are met is an adaptive strategy. Proteomics improves our understanding of the mechanisms that control the adaptation to environmental heterogeneity. In this study, we investigated two European beech populations from different habitats that differed in dormancy and germination traits. We found that the populations exhibited different germination strategies, which were reflected in coordinated but quantitatively different proteomic reprogramming. The Miekinia population exhibited stronger accumulation of proteins involved in nucleotide sugar biosynthesis, S-adenosylmethionine metabolism, and flavonoid biosynthesis. Enhanced nucleotide sugar biosynthesis indicates more intensive cell wall remodelling and carbohydrate metabolism, which support embryo growth and faster germination. Increased S-adenosylmethionine metabolism suggests the epigenetic and hormonal regulation of germination differences between populations. Higher flavonoid biosynthesis indicates an enhanced antioxidant capacity associated with environmental protection. In contrast, the Wisa population showed stronger accumulation of proteins involved in RNA processing, suggesting tighter post-transcriptional regulation and proteome reorganization during germination. Consistent with its deeper dormancy and later germination, the Wisa population appears to rely more on RNA-level regulation, whereas the Miekinia population prioritizes metabolic activation. These contrasting proteomic profiles likely reflect population-specific physiological strategies associated with dormancy depth and adaptation to different climatic conditions. HighlightProteomic reprogramming reveals population-specific germination strategies in European beech, linking dormancy depth with contrasting metabolic activation and RNA-level regulation during the transition from dormancy to germination.

Legumes establish mutualistic symbiosis with nitrogen (N)-fixing bacteria, which allows them to utilize atmospheric N2. Because the maintenance of symbiosis requires abundant carbon (C) sources, legumes regulate the balance between carbon consumption and nitrogen acquisition by systemically controlling the nodule number through CLAVATA1 (CLV1)-like receptors. In Lotus japonicus, the CLV1-like receptor HYPERNODULATION ABERRANT ROOT FORMATION1 (HAR1) acts in shoots to regulate root nodulation and contributes to symbiotic C/N coordination. This raises the possibility that HAR1 may also influence plant growth and nitrogen utilization beyond symbiotic nodulation. In this study, we showed that HAR1 plays a critical role in regulating nitrogen use to enhance growth under conditions of high nitrate availability, even in non-symbiotic environments. Unlike the wild-type, the har1 mutant failed to increase its growth in response to higher nitrate availability. This lack of growth response was associated with a lower rate of net biomass production per unit leaf area and a reduced capacity for biomass production per unit plant nitrogen. We further found that nitrate-responsive TCA cycle-related organic acids were higher in har1 leaves than in wild-type leaves even under low nitrate conditions. Because the HAR1 mutation did not affect photosynthetic traits, we propose that HAR1 promotes growth under non-symbiotic conditions by coordinating nitrogen utilization with primary metabolism. One-sentence summaryLotus japonicus CLV1-like receptor HAR1 improves nitrogen utilization and growth at high nitrate conditions by regulating organic acid metabolism, independent of root nodule symbiosis.

O_LIC4 photosynthesis and the crassulacean acid metabolism (CAM) rarely co-evolved in a single lineage, but Portulaca can switch from C4 to CAM under drought stress. Little is known about CAM responses to nutrient availability, hence the goal of this work was to assess the influence of macronutrients over C4-CAM. C_LIO_LIP. oleracea was grown hydroponically and subjected to treatments (+/- PEG) for: nitrate deficiency (-NO3-), ammonium (NH4+), NO3- + NH4+, magnesium (-Mg), phosphorus (-P), calcium (-Ca), potassium (-K), and sulphur (-S) deficiencies, and salt stress. Samples were monitored for diurnal titratable acidity ({Delta}H+), osmotic potential, and gene relative expression for core C4/CAM and signaling genes. C_LIO_LI-NO3- induced CAM even without PEG, a process probably without the mediation of abscisic acid (ABA). Notably, -P showed a trend to induce CAM without PEG and -Ca prevented CAM induction even with PEG. Salt stress induced CAM, and NH4+ was not toxic for P. oleracea. Other treatments showed less conspicuous responses. C_LIO_LIThis work brings an unprecedented overview of the nutrition of C4 and CAM, suggesting perspectives for deepening the study of C4-CAM. Understanding the molecular mechanisms and environmental signaling of C4-CAM is essential for realizing the evolution of two CCMs in a single plant. C_LI

Temperate forests increasingly face extreme air temperature, but plant physiological responses, particularly alterations in carbon allocation or protection via volatile organic compound (VOC) emissions, remain poorly understood. We pulse-labelled well-watered saplings of Fagus sylvatica and Pseudotsuga menziesii in a controlled heat stress experiment with 13CO2 to quantify heat-induced shifts in CO2, VOC and C pool exchange, specifically analyzing compound-specific {delta}13C of terpenoids, water-soluble organic matter (WSOM) and dark respiration. Under heat stress, up to 50% of fresh assimilates were directed to maintenance respiration and 1-2% to VOC emissions, while net assimilation and water use efficiency decreased by 50-75% in both species. Heat directly affected metabolic processes and reduced turnover rates of fresh assimilates in F. sylvatica, but accelerated them in P. menziesii. Strong 13C labelling of some compounds, particularly acyclic ones, suggested increased de novo synthesis of specific terpenoids for heat stress protection. By tracing the fate of recently assimilated 13CO2 we demonstrate that heat stress reduces net carbon uptake and water use efficiency, disrupts turnover of C pools and increases carbon loss via respiration and de novo synthesis of specific VOCs, potentially diminishing net carbon uptake of forests under future heat extremes.

The root meristem is essential for stem cell maintenance and root development in plants. In Arabidopsis, Root meristem Growth Factor (RGF) peptides and their receptors regulate root meristem size through reactive oxygen species (ROS)-dependent signalling. RGF1-mediated ROS redistribution post-translationally stabilises the root meristem master regulator PLETHORA2 (PLT2). Although genomic studies suggest that RGF-receptor modules are evolutionarily conserved across land plants, their functional characterisation has remained largely limited to Arabidopsis. Here, we show that Oryza sativa RGF1-1 (OsRGF1-1) functions as a rice homologue of Arabidopsis RGF1 (AtRGF1). CRISPR/Cas9-generated Osrgf1-1 mutants exhibited shorter seminal roots, reduced root meristem size, and decreased superoxide (O2*-) accumulation. EdU staining further confirmed that cell proliferation activity was reduced in the Osrgf1-1 mutants. The Osrgf1-1 mutants were sensitive to low concentrations of chemically synthesised mature OsRGF1-1 peptide. This low dose of OsRGF1-1 peptide restored seminal root growth and O2*- accumulation in the Osrgf1-1 mutants but had no detectable effect on the wild type. Functional analyses using Arabidopsis rgfr receptor mutants further demonstrated that OsRGF1-1 is perceived through conserved RGF receptor machinery. Together, our findings provide the first functional evidence that the RGF1-receptor-ROS signalling module is evolutionarily conserved between dicots and monocots in the regulation of root meristem development.

O_LIThe heat tolerance of tree species has recently received increased attention, as it is critical for the response of forest ecosystems to climate change. Most studies rely on laboratory experiments with detached leaves, where the thermostability of photosystem II (PS II) is analyzed using chlorophyll fluorescence analysis. The temperature at which the maximum quantum yield (Fv/Fm) of PS II is reduced by 50% (T50) is often used as key measure of heat tolerance despite of weak mechanistic corroboration and inconsistent definitions. We propose a new metric consisting of a critical temperature (TIP) and a corresponding fluorescence value (FIP). C_LIO_LIWe analyzed the effect of incubation time and temperature on different versions of T50. C_LIO_LIT50 was strongly dependent on the duration of heat exposure, decreasing exponentially with incubation time. T50 and TIP values derived from short-term treatments of different incubation times <1 h are not comparable, but stabilize after longer intervals of heat exposure. C_LIO_LIT50 of Fv/Fm specified without considering incubation time is a meaningless metric. Specifications derived from short-term heat treatments should be avoided, because the result is highly influenced by the experimental setup. Different calculation methods for T50 influence the result and elucidate different aspects of the heat response. C_LI

The increasing frequency and intensity of heatwaves under climate change highlight the need to understand how biodiversity regulates forest canopy thermal dynamics. Although tree diversity can buffer the microclimate, its effects on canopy temperature and the role of mycorrhizal symbioses remain unclear. We addressed this question in the MyDiv tree diversity experiment in Germany, where tree species richness (1-, 2-, and 4-species mixtures) and mycorrhizal types (arbuscular, ectomycorrhizal, and mixed) are factorially manipulated. During the 2024 growing season, we conducted nine uncrewed aerial vehicle (UAV) surveys using integrated thermal and LiDAR sensors to quantify canopy temperature and structural complexity, together with measurements of leaf water content, specific leaf area, soil moisture, and vapour pressure deficit (VPD). Increasing tree diversity generally reduced canopy temperature, although the strength of this relationship varied seasonally and among mycorrhizal types. Cooling effects were strongest during peak summer heat and were more pronounced in arbuscular mycorrhizal (AM) communities than in ectomycorrhizal (EM) and mixed (AM+EM) communities. In contrast, EM communities exhibited greater canopy structural complexity, whereas AM communities maintained higher soil and leaf water content. Structural complexity increased with tree diversity but did not necessarily result in greater canopy cooling. Structural equation modelling revealed that forest thermal buffering emerged through complementary structural and hydraulic pathways, whose relative importance shifted seasonally, with hydraulic regulation becoming increasingly important under hotter and drier conditions. By linking canopy temperature, canopy structure, and plant water relations, our study provides mechanistic insights for understanding how multiple facets of biodiversity regulate forest thermal buffering under climate warming.

In a warmer and drier climate, forest productivity will depend on trees' ability to maintain carbon uptake and hydraulic function. Whether fast-growing genotypes of boreal conifers are more vulnerable to combined climatic stress remains uncertain. Using a full-factorial field experiment, we investigated how progressive soil drying combined with extended warming affects growth, xylem development, and photosynthesis in two Picea glauca families with contrasting growth strategies. Rainout structures first reduced soil moisture from 25% to 18%, followed by a +5{degrees}C warming treatment applied using infrared heaters. During the warmest and driest period in August, air temperature reached 34.5{degrees}C in the warmed plots, while soil moisture declined to a low of 15% in the combined rainout and warming treatment. Contrary to expectations, both fast- and slow-growing white spruce families exhibited similar resilience to concurrent warming and soil drying. This finding challenges the prevailing theory that faster growth increases vulnerability to climatic stress. Despite an approximately 50% reduction in rainfall, pre-dawn water potential remained above -0.5 MPa across treatments, reflecting that seedlings were able to avoid hydraulic stress. Although the fast-growing family maintained greater height and diameter growth compared to the slow-growing family, both exhibited similar physiological and anatomical responses to warming. Warming decreased stomatal conductance, which increased intrinsic water-use efficiency. Latewood xylem traits related to hydraulic efficiency were also reduced under warming. Together, these coordinated stomatal and xylem adjustments decreased water loss and protected hydraulic function, enabling both families to maintain high photosynthesis and growth under simulated climate conditions. Overall, white spruce exhibits strong phenotypic plasticity, supporting intraspecific resilience to moderate warming and soil drying representative of projected 21st-century summer conditions for central and eastern Canada.

Poisonous plants frequently deploy toxic metabolites in an organ- and ontogenetic-specific manner, yet the developmental dynamics of these plant specialised metabolites remain poorly understood. In the Solanaceae, steroidal glycosides (SGs), including steroidal glycoalkaloids (SGAs) and steroidal saponin glycosides (SSGs), are major defence metabolites with potent ecological and pharmacological activities. Here, we investigated how their metabolic profiles are reorganised during flower and fruit development in Solanum dulcamara using untargeted metabolomics and chemometric molecular networking. Non-metric multidimensional scaling (NMDS) using classified metabolite features recovered clear organ-specific and chemotype-specific segregation of samples, which was further strengthened when analyses were restricted to metabolomic features annotated as SGs. In flowers, orthogonal projections to latent structures discriminant analysis (OPLS-DA) separated both floral developmental stage and chemotype, demonstrating that developmental stage and inherited SG polymorphism represent independent axes of chemodiversity in flowers. Chemometric molecular networks showed pronounced diversification of hydroxycinnamate metabolism towards anthesis, including accumulation of caffeoylputrescine in flower buds and progressive acylation of spermidine conjugates across flower development. Upon anthesis, glycosylated hydroxycinnamates and flavonoids, and hydroxycinnamoyl-acylated flavonoid glycosides are accumulated. Fruit ripening followed a contrasting trajectory, in which SGAs were associated with unripe fruit pericarp, whereas ripe pericarp accumulated N- and O-acetylated SGA derivatives, oxidative deamination products, and predicted steroid degradation products, indicating stepwise detoxification of toxic steroidal glycosides during seed maturation. Together, these findings show that the poisonous chemistry in S. dulcamara is highly dynamic and developmentally orchestrated. Flowers accumulate structurally complex metabolites toward anthesis, including conjugates of hydroxycinnamates, whereas fruits metabolise toxic SGAs into less toxic SGs during ripening, linking metabolic remodelling to reproduction and seed dispersal.

Rising atmospheric CO2 concentrations consistently reduce mineral concentrations in C crops, yet the mechanisms driving this decline - dilution, reduced transpiration-driven mass flow, and altered root nutrient acquisition capacity - have rarely been tested simultaneously under field conditions. Here, we grew two soybean (Glycine max Merr.) varieties with contrasting yield responses to elevated [CO2] (Loda and HS93-4118) at the Soybean Free Air CO2 Enrichment (SoyFACE) facility and quantified the independent contributions of dilution, transpiration, and root uptake to observed changes in tissue mineral concentration and nutrient yield. Elevated [CO2] increased grain yield by 21% and 6% in Loda and HS, respectively, and reduced transpiration by 13-14% across both varieties. A decomposition analysis revealed that while dilution and reduced transpiration each exerted negative effects on tissue nutrient concentrations, with their combined effect representing a 31-40% potential reduction in whole-plant concentration, active root uptake responses were positive for nearly all nutrients, largely offsetting these losses and resulting in observed concentration declines substantially smaller than either mechanism alone would predict. Consequently, whole-plant nutrient yield increased under elevated CO2 for all elements measured, and grain nutrient yield increased for most. The relationship between seasonal transpiration and nutrient yield was steeper under elevated CO2 for most macronutrients, indicating that plants acquired more nutrients per unit water transpired, not less, under elevated CO2. These results demonstrate that root uptake is the dominant compensatory response to elevated [CO2] driven dilution and reduced mass flow in soybean, that nutrient yield is maintained or increased for most elements under elevated [CO2], and that Fe represents a physiologically and nutritionally significant vulnerability in future CO2 environments.

Flower color has primarily been studied in the context of pollinator attraction, although effects on thermal energy balance are also important, especially in the context of global climate change. We used infrared imaging to compare petal temperatures of white versus pigmented cultivars of ten angiosperm taxa under controlled environmental conditions. Excised sets of flowers (n= 6 sets per species) exhibiting white, light, and/or dark anthocyanin (red to purple) coloration were mounted perpendicularly to the sun at mid-day, under clear sky, low wind (<1 m s-1) conditions. Sunlight was filtered through either UV-transparent or UV-opaque film, and petal temperatures were measured using an infrared camera after one minute equilibration. In all species, pigmented flowers were significantly warmer than lighter-colored conspecifics. Mean differences averaged +5.3{degrees}C for darker-colored versus white morphs, +2.9{degrees}C for lighter-colored versus white. Most warming was associated with visible wavelengths, but additional warming under UV-inclusion was also observed in some species. In situ observations of intact landscape plants under low-wind, high-light conditions corroborated experimental results, with differences exceeding 10{degrees}C observed in some taxa. Temperature differences >7{degrees}C were also recorded for purple versus white sections of the same flower in multicolored Viola and Petunia cultivars. Follow-up experiments using dark-pink and white varieties of Impatiens x hybrida corroborated well-known effects of sunlight intensity and wind speed on floral temperatures, helping to explain inconsistent reports in the literature. Our results clearly demonstrate that anthocyanin pigments can have significant and dramatic impacts on floral temperatures, which could be an important factor driving evolution of flower color. In the context of climate change, floral pigments could amplify the effects of rising global temperatures, negatively impacting plant reproduction and crop yields, especially on the warmer end of species ranges. Changes in flower color could also potentially induce shifts in pollinator communities, which could have community-scale effects.

Process-based tree growth models provide a mechanistic framework for investigating how climate conditions regulate tree growth across daily to annual time scales. Yet, their broader application across species and environments is constrained by the limited accessibility in open-source environments and the difficulty of estimating physiological parameters that are rarely measured directly. Here, we present virtualRings, a new R package integrating the Vaganov-Shashkin model (VSM) and the RINGS3 models, and focus on the implementation and calibration of VSM. Using tree-ring width observations from seven Northern Hemisphere sites across various environmental conditions, we compared the traditional bootstrap-based calibration approach with the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). CMA-ES improved agreement between simulated and observed radial tree growth and provided an efficient approach for model parameter estimation. We further evaluated practical CMA-ES settings to balance computational cost and performance and discussed its potential limitations. The virtualRings package provides an open and reproducible platform for tree growth simulation, facilitating the application of important process-based models across species and environments and the investigation of how temperature and moisture constraints regulate daily tree-ring formation across spatial and temporal scales.

Understanding how root phenotypic plasticity enhances resource-use efficiency can help understand the outcomes of plant competition and identify suitable genotypes for medium- to low-input agricultural systems. Auxin regulates multiple root growth processes, including the root architectural responses to nitrogen (N). We explored the extent to which auxin-mediated local and systemic responses to external and internal N influences plant N uptake and use, using a functional-structural-plant (FSP) modelling approach. A simplified auxin module was developed at the level of the organ and integrated into an FSP model to represent physiological plastic root responses to N. Model performance was evaluated against experimental data. We then ran simulations under various N conditions with local or systemic responses enabled or disabled, to quantify their contribution to N uptake and use. Simulations showed that local auxin responses enhanced N uptake by distributing more roots towards deeper soil layers and increased N forage, thereby avoiding N stress. Systemic auxin responses reduced N uptake by distributing more roots near the top soil layers, which reduced plant size and N demand, thereby enhancing stress tolerance. This points to a trade-off in N uptake between the tolerance and avoidance strategies, which can be traced back to biomass and N investment resulting from source-sink relationships in the plant. Representing hormone-mediated root plasticity in an FSP model provides mechanistic insights into plant strategies for resource capture.

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.

Plant root cellular architecture and cell wall composition influence plant productivity, stress resilience, biotic interactions, and potentially soil carbon accumulation. This study establishes comprehensive compositional parameters for roots of a lowland switchgrass genotype, DVR3. Root traits were analyzed in 12.5 cm depth segments, from Zone 1 near the surface to Zone 4 down to 50 cm. Mean abundance ({micro}g/mg) for major cell wall components included cellulose 470 {+/-} 20, xylose 250 {+/-} 20, lignin 170 {+/-} 15, and total suberin 35 {+/-} 5. Composition and cellular anatomy varied with depth, in a partially coordinated manner. Cross sections showed extensive aerenchyma in mature root regions despite greater root mass density, corresponding to abundant lignin and cellulose. Deep roots were enriched for pectin-associated traits, including arabinogalactan II, homogalacturonan, and arabinose-associated linkages. Suberin content did not vary significantly, though Casparian strip formation, endoderm and exoderm thickening, and suberin surface staining progressed with development. Similar trends in root lignin and specific root length were observed for another lowland switchgrass genotype, AP13. These results suggest that it may be possible to genetically enhance native switchgrass root chemistry to promote soil penetration and below-ground carbon accumulation by reducing variability with development, potentially via cell-type specific adjustments. HighlightOlder, shallower switchgrass crown roots are enriched in lignin and cellulose, and deeper, younger roots are pectin-rich with juvenile cellular anatomy. A more uniform compositional distribution might enhance below-ground traits. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/744798v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@159de98org.highwire.dtl.DTLVardef@124d714org.highwire.dtl.DTLVardef@1a49c14org.highwire.dtl.DTLVardef@2fa67_HPS_FORMAT_FIGEXP M_FIG C_FIG Schematic summary of switchgrass root anatomy and composition across four 12.5-cm depth zones of a 50-cm root system. Zone 1 represents older, shallow roots and Zone 4 includes younger roots and root tips. Representative cross-sections show greater aerenchyma development in older roots than in young root tips. The compositional heatmap shows higher cellulose, lignin, and xylose in Zone 1, higher pectin and nitrogen in Zone 4, and relatively little variation in suberin across zones.