Journal of Experimental Botany

All living organisms rely on the movement of ions across cell membranes as the fundamental physical basis of their internal energy and signaling, and plants are no exception. Plants perceive, integrate, and respond to environmental stimuli through electrical signals, classified as action, variation, and system potentials, that are coupled with calcium waves, reactive oxygen species, and hydraulic and hormonal changes to coordinate whole-organism responses despite the absence of a nervous system. Yet most studies characterize these signals using a single feature, such as amplitude or spike duration, in a single tissue, an approach that cannot establish how such signals correspond to the underlying ionic activity, mobility, and structural complexity of the signaling environment, or how this correspondence varies across organs. Here, we correlate plant bioelectrical signals with potential ionic energy flow using a multi-domain framework, combining discrete spike events, continuous waveform properties, spectral composition, and signal complexity applied to leaf, stem, and root recordings from tomato (Solanum lycopersicum) exposed to different stimulus. Electrical activity with increased stimulus strength, likely reflecting increased ionic flow, with the root showing the largest response. This suggests plant electrical signaling works as a distributed, ion-based information system, useful for stress monitoring and bio-inspired sensor design.

Starch granule initiation involves the extension of maltooligosaccharide primers by glucosyltransferases. STARCH SYNTHASE 4 (SS4) plays a central role in almost all examined plant species, while the plastidial PHOSPHORYLASE 1 (Pho1) also plays an important role in some species, including rice and wheat. In Arabidopsis, an additional enzymatically inactive homolog of SS4, STARCH SYNTHASE 5 (SS5) contributes to starch granule initiation. To elucidate the mechanism of starch granule initiation in potato tubers, we used CRISPR/Cas9 to generate ss4, ss5, and pho1a knockout mutants in the commercial tetraploid 'Clearwater Russet', to systematically investigate their contribution to granule initiation. In ss4 and ss5 tubers, starch granule size and morphology were unaltered relative to the wild type, suggesting that SS4 and SS5 are dispensable for normal granule initiation in potato tubers. In contrast, pho1a tubers had compound starch granules that arose from multiple initiations, greatly reduced granule size, and highly variable granule morphologies. Affinity pull-down to find Pho1a interaction partners identified LIKE EARLY STARVATION (LESV), although yeast 2-hybrid assays did not show direct protein-protein binding. When expressed alone in Nicotiana benthamiana leaves, Pho1a located to the chloroplast stroma, but when expressed alongside LESV, both proteins co-located on starch granules. This co-localisation, alongside the similar accumulation of small starch granules when LESV is knocked out in tubers, suggest a possible functional interaction in planta. These findings position Pho1a as the central glucosyltransferase in starch granule initiation in Clearwater Russet tubers, where it acts together with LESV.

O_LICereal grafting using embryonic tissues has recently become technically feasible; however, the physiological consequences of cereal grafting remain uncharacterized. C_LIO_LIWe systematically evaluate photosynthetic performance and stomatal dynamics across different graft combinations in two photosynthetically distinct species, rice (C3) and pearl millet (C4). We first assessed steady-state photosynthetic performance and dynamic stomatal responses in five-week-old rice and pearl millet grafts grown under a saturated water regime, to establish whether cereal grafting alters physiology at early stages. Next, we assessed same traits at the onset of optimal water regime, and after five days to determine whether any graft-induced effects on photosynthesis or growth persisted over time. C_LIO_LIWe observed that across contrasting water regimes and at different plant developmental stages, cereal grafting did not alter growth, photosynthesis or stomatal kinetics in either species, while revealing modest early stage C4-specific adjustments in stomatal dynamics without affecting photosynthetic capacity or biochemical parameters. C_LIO_LIWe demonstrate that cereal grafting does not alter core physiological traits in rice or pearl millet and can be deployed without long-term impact on photosynthesis. These findings establish cereal grafting as a tractable platform for mechanistic dissection of root-shoot signaling and trait combination across different C3 and C4 cereals. C_LI

Drought during reproductive development and grain filling is a major constraint to bread wheat productivity in rainfed environments. In the present study, we employed genome-wide association analysis in an untapped diversity panel of wheat genotypes relevant to natural dryland conditions. A total of 186 genotypes were evaluated for drought-related physiological, biomass, and architectural traits under terminal rainfed stress in Azerbaijan. Relative water content, plant height, fresh weight, dry weight, flag leaf length, and flag leaf width were assessed at the milk ripening stage. These data were subjected to genome-wide association analysis using 19,737 SNP markers to identify loci and epistatic interactions involved in the determination of these traits. The panel showed broad phenotypic variation and significant genotypic effects for all traits, with broad-sense heritability ranging from 0.991 for plant height to 0.385 for flag leaf width. GWAS identified a major locus for relative water content on chromosome 2D at SNP marker AX-86184518, which explained 11.94% of the genotypic variation. Candidate-gene analysis highlighted the proximal WEB-family-like gene TraesCS2D03G1001000 as the main candidate gene. Plant height showed strong additive loci, mainly on chromosomes 2A and 4A, whereas biomass and flag leaf traits showed suggestive additive loci and epistatic interactions. These findings provide candidate loci and interaction patterns in the genetic make-up of essential traits, which may facilitate indirect selection in breeding new varieties.

Plant roots exhibit remarkable developmental plasticity, resulting in the adaptation of growth direction and architecture upon environmental changes. Previously, we demonstrated that inorganic phosphate (Pi) triggers Arabidopsis roots to skew to the left when grown on tilted agar plates. This so-called 'phosphate-dependent skewing' (PDS) is caused by a right-handed (clockwise, CW) circumnutation of the root tip, which is driven by a left-handed (counterclockwise, CCW) cell file rotation (CFR) of epidermal cells in the root elongation zone, and involves the cortical microtubule cytoskeleton (Sheng et al., 2024). In the present study, we demonstrate that NaCl triggers a skewing response in the opposite direction and that all other helical movements are also reversed. Thus, 'Salt-Induced Rightward Skewing' (SIRS) is accompanied by a right-handed (CW) epidermal CFR, a left-handed (CCW) circumnutation of the root tip, and hence, a left-handed (CCW) helical root growth. Comparing different Na+- and Cl- salts revealed that SIRS is predominantly caused by cations, and can be induced by K+ and osmotic stress as well, although Na+ is most efficient. To get further insight into the mechanism underlying this response, we tested candidate genes from an earlier GWAS on root responses to salt stress (Deolu-Ajayi et al., 2019) for their potential involvement. This identified GLT1 and DOB1 as being involved in the root skewing response to Pi and NaCl, respectively. Our findings reveal that Pi and salinity elicit opposing effects on root circumnutation, and hence root skewing and growth direction. Understanding the molecular machinery driving this helical behaviour may help explain adaptive mechanisms, including changes in the spatial architecture of roots, and may facilitate the optimization of crop yield under abiotic stress conditions through breeding or crop management strategies. Our results also shed new light on halotropism, which is typically measured as a change in root growth direction to the right, which in the present study has been identified to represent SIRS.

Barley yellow dwarf virus (BYDV), transmitted by the bird cherry-oat aphid (Rhopalosiphum padi L.), is among the most damaging viral diseases of barley, but the mechanisms underlying resistance to both the virus and its vector remain poorly understood. Here, we investigated resistance associated with the Hordeum bulbosum-derived Ryd4 introgression in the barley hybrid SY Kestrel by integrating behavioural, electrophysiological, physiological and multi-omics analyses with functional validation of defence metabolites. SY Kestrel exhibited constitutive volatile-mediated antixenosis together with strong post-settlement antibiosis characterised by impaired phloem feeding, reduced aphid fitness and suppression of BYDV gene expression 10 days after transmission. Integrated transcriptomic, metabolomic and small RNA analyses revealed coordinated immune activation, chloroplast remodelling and defence metabolism associated with the resistance introgression. Candidate immune regulators were identified both within the refined Ryd4 interval and the surrounding introgressed region. Maintenance of photosystem II function was accompanied by reprogramming of -linolenic acid-derived oxylipin metabolism, while phenylpropanoid and branched-chain amino acid/lysine pathways generated metabolites that directly reduced aphid survival. We demonstrate that the Ryd4 introgression coordinates constitutive vector deterrence with host defence reprogramming to restrict aphid colonisation and suppress BYDV establishment. These results provide a mechanistic framework for improving durable resistance to aphid-transmitted viruses in cereals.

O_LITranspiration plays a central role in plant water relations and strongly influences plant growth. Continuous monitoring is essential for understanding responses to environmental conditions and improving water management in both natural and agricultural systems. Gas-exchange techniques such as infrared gas analysers (IRGAs) and porometers are widely used but are challenging for long-term or large-scale monitoring. On the other hand, the FylloClip is a low-cost, leaf-mounted capacitance sensor developed previously to monitor transpiration by detecting condensation of water vapour near the leaf surface. Here, we evaluated the potential of the FylloClip for monitoring transpiration dynamics and assessed environmental conditions that may affect its performance. C_LIO_LIThe FylloClip was tested under growth chamber, greenhouse, and tropical field conditions. We evaluated how its capacitance measurements respond to rainfall, temperature and humidity, and compared FylloClip measurements with transpiration measured with an IRGA. C_LIO_LIThere was a strong correlation (r = 0.85) between FylloClip and IRGA data. Both systems captured similar diurnal transpiration patterns, with transpiration declining simultaneously under water deficit. Rainfall and very high relative humidity produced FylloClip signals that could be misinterpreted as high transpiration, although transpiration is negligible under these conditions. C_LIO_LIOur results revealed that FylloClips capture temporal patterns of transpiration with high accuracy and resolution, providing a reliable tool for long-term, large-scale monitoring of transpiration dynamics in ecophysiological studies and precision agriculture. C_LI

Biuret, a nitrogen-rich by-product of urea and a common contaminant of urea-based fertilisers, has long been considered a passive phytotoxin, affecting plant performances. Yet its effects on root development and the existence of endogenous mechanisms of perception or tolerance remain largely uncharacterised. Here we combined physiological, developmental, genetic and transcriptomic approaches to investigate the response of Arabidopsis thaliana to biuret. Biuret inhibited primary root growth in a dose-dependent manner by reducing meristematic cell division rather than cell elongation, and concomitantly impaired shoot growth by limiting leaf expansion. This root inhibition was reversible upon biuret removal and was accompanied by increased auxin-responsive (DR5) and decreased cytokinin-responsive (TCS) outputs at the root apex, consistent with a regulated remodelling of meristem activity rather than purely cumulative damage. A forward genetic screen identified the biuret-resistant mutant bir29, which sustained root and inflorescence development under inhibitory concentrations. Using {superscript 1}N-labelled biuret, we showed that resistance occurred without any change in biuret influx or accumulation, uncoupling sensitivity from exposure. Whole-genome transcriptomics revealed that bir29 fails to execute the wild-type response, neither repressing the cell-cycle machinery nor deploying the stress-associated programme induced by biuret. Genetic characterisation linked resistance to multiple genomic loci required for full resistance. Together, the results indicate that biuret triggers an active, reversible and genetically tractable developmental response, suggesting that this xenobiotic compound is integrated into endogenous signalling networks. Significance StatementBiuret, a poorly metabolised contaminant of urea fertilisers, is generally regarded as a passive phytotoxin, yet we show that it inhibits Arabidopsis root growth through a reversible and genetically tractable developmental response, accompanied by reorganised auxin and cytokinin signalling, rather than through cumulative chemical injury. The isolation of the resistant mutant bir29 suggests that plants integrate this xenobiotic molecule into endogenous signalling networks, reframing biuret as an informative probe of root developmental regulation.

RationaleDeveloping climate-resilient crops requires understanding the developmental and physiological mechanisms governing responses to unpredictable environmental stresses. While agricultural selection historically favored phenotypic uniformity, highly volatile conditions can favor risk-spreading "bet-hedging". However, because standard genetic mapping relies on shifting plot-level averages, loci controlling population-level variance remain cryptic. MethodsWe investigated the pleiotropic effects of the Dry2.2 quantitative trait locus (candidate gene HvCEN) using an allelic series of wild barley (Hordeum vulgare ssp. spontaneum) introgressions housed in distinct cultivated backgrounds, evaluated via high-resolution single-plant physiological phenotyping and mini-plot field trials. ResultsSpecific wild alleles confer robust developmental canalization under water limitation, maintain harvest traits, stabilize vascular lignification, and drive a uniform senescence escape strategy. Conversely, carriers of cultivated alleles deploy a bet-hedging strategy under stress, more than doubling inter-plant developmental variation (volume, maturity timing). This variance-driven strategy relies on epistatic interactions, rendering Dry2.2 invisible to traditional mean-centric GWAS plots. ConclusionImproving crop resilience in volatile climates requires expanding selection focus beyond static, plot-level averages to include the active genetic design of population-level variance strategies.

Transgenerational plasticity can shape plant phenotype and influence plant response to environmental changes in interaction with the current conditions. While how past stress interact with either current optimal or stress conditions is increasingly documented within a single plant, transgenerational plasticity remains particularly poorly understood especially at the metabolome level. In our study, we investigated whether heat stress induces transgenerational metabolic and phenotypic modifications along two successive clonal ramet generations of the sub-Antarctic aquatic plant Limosella australis. We performed untargeted metabolomic approaches and measured morphologic and performance traits, to assess both transgenerational plasticity of the metabolome and the phenotype. We found that heat stress remodelled the metabolic profile and influenced the foraging strategy of our clonal plant, and that some of these metabolic changes persisted into the first clonal generation. This one therefore adopted an intermediate growth strategy, even though culture conditions were optimal. By comparing differentially accumulated features between daughter ramets from heat stressed mother ramets and from unstressed mother ramets, we identified common and specific metabolites accumulation to heat stress response, belonging to diverse compound families. However, we did not observe any adaptative advantage and any metabolic imprint during another heat stress applied on the second clonal generation. This work provides especially new clues into how plant metabolome integrates and transfers previous stressed clonal generation's information.

Heatwaves during flowering and grain development threaten global wheat production, yet the extent to which developmental stage shapes molecular and phenotypic responses remains unclear. Here, we investigated whether heat stress (36/29{degrees}C for 48 h) imposed at closely spaced developmental stages surrounding anthesis generates stage-specific molecular responses that are associated with subsequent effects on grain properties. Heat exposure increased floret abortion most strongly when it was imposed at the trinucleate stage (TN; [~]48%) compared with the binucleate (BN) and early post-anthesis stages. Methylation levels were largely unaffected by prior heat treatments; however, heat induced stage- and locus-specific methylation changes, particularly at BN. Spatial RNA-seq revealed tissue-specific heat responses that were distinctively different in BN and TN. Integrated metabolomic analyses revealed stage-dependent metabolic reprogramming, including shifts towards stress-associated pathways. Despite heat stress at BN generating broader molecular reprogramming in developing grain, exposure at TN produced stronger effects on grain set and composition, revealing a decoupling between the magnitude of responses and phenotypic outcomes. Together, these findings demonstrate that subtle differences in developmental stage influence the complex molecular responses to heat and subsequent grain properties.

As extreme heat events increase in frequency and intensity worldwide, understanding how woody perennial crops respond to higher maximum temperatures is critical. Perennials face distinct challenges, persisting across many seasons under increasingly variable and extreme conditions, and heat waves threaten the viability of wine grape cultivars through impacts on yield, wine quality, and long-term vine health. To test whether irrigation practices before and during heat waves affect grapevine carbon (C) storage and health, we experimentally manipulated irrigation regimes surrounding heat waves from 2019-2021 in a commercial Cabernet Sauvignon vineyard in the Lodi AVA of Californias Central Valley. Vine physiological traits and yield were measured throughout, and whole-vine nonstructural carbohydrate (NSC) concentrations were quantified after three growing seasons. Although lower supplemental irrigation reduced photosynthesis, stomatal conductance, and fruit yield, whole-vine NSCs did not differ significantly in any perennial organ by the experiments end, indicating that reproductive output and final NSC status responded to irrigation on different timescales. These results suggest that moderate supplemental irrigation during heat events is sufficient to mitigate negative impacts on yield and quality while supporting recovery of NSC reserves, though longer-term monitoring is needed to confirm that this short-term resilience persists.

Far-red light (FR; 700-750 nm) is increasingly incorporated into controlled-environment lighting because it can improve photosynthetic efficiency when combined with comparatively shorter wavelengths. In long-day leafy crops such as spinach, however, FR may also promote the transition from vegetative to reproductive growth and thereby reduce marketable yield. Most studies have evaluated FR fraction, intensity or end-of-day exposure, whereas the developmental timing of FR has rarely been tested, particularly in spinach. Here, we evaluated six commercial spinach cultivars (Amador, Harp, Renegade, Responder, Rubino and Santa Cruz) in an indoor vertical farm under a common red-green-blue background (PPFD 260-264 {micro}mol m-{superscript 2} s-{superscript 1}, 12 h photoperiod, 24 {degrees}C) and four FR timing treatments: no FR (Control), FR throughout production (FullFR), FR during early development only (EarlyFR), and FR during late development only (LateFR). LateFR increased marketable fresh weight relative to Control (244 vs 224 g) and reduced flowering incidence, whereas far-red supplied during early development reduced fresh weight (158 g) and increased flowering. The magnitude of the timing response differed among cultivars: switching from EarlyFR to LateFR recovered 0 % fresh weight in Amador but 107 % in Renegade and Rubino, with the largest penalties occurring in otherwise bolt-resistant cultivars. EarlyFR also increased total chlorophyll and reduced the chlorophyll a:b ratio. These results show that FR response in spinach is strongly conditioned by developmental stage and cultivar. Although LateFR received more total far-red than EarlyFR, it behaved like the Control, indicating that the penalty was set by far-red timing rather than dose. Treatment differences in bolting and yield tracked an estimated phytochrome photostationary-state deficit during early development: a phytochrome-deficit model markedly outperformed a cumulative-dose model ({Delta}AIC = 441), and the deficit x cultivar interaction was strong (p < 0.001), with bolt-resistant cultivars losing most yield when far-red coincided with the early developmental window. We therefore propose that FR should be treated as a genotype-dependent management variable rather than as a fixed spectral input, with late application and bolt-resistant cultivars offering the most favourable combination for vertical-farm spinach production. Framed within the breeders equation, the close match between the trial and production environment and the scope for shorter breeding cycles indoors suggest that genotype and far-red timing can be optimised jointly to accelerate genetic gain.

Crop models are essential for predicting climate change impacts on agriculture, yet their validation under multi-stress conditions remains limited. This study evaluated two widely-used wheat models, APSIM and STICS, using data from three Free-Air CO2 Enrichment (FACE) experiments (USA, Germany, Australia) combining elevated CO2 (eCO2), water deficit, and warming. Environmental characterisation using simulation-based stress indices revealed that intended "controls" frequently experienced hidden heat and water stress, meaning models were calibrated on crops already undergoing physiological adjustments. Evaluation of simulated yield and components revealed a clear hierarchy in prediction errors (RRMSE): unlimited conditions (3-9%) < single stress (4-27%, with a need to improve response to heat stress) < combined stress (17-123%). Elevated CO2 generally increased prediction uncertainty for crops experiencing water stress. Our results suggest that current stress functions from the models fail to capture the synergistic coupling between drought and heat stress. This highlights the urgent need for more mechanistic modelling to improve the reliability of climate change impact assessments.

Photosynthesis is acknowledged as a potential target to increase crop yield. Improved photosynthesis may be achieved by conventional breeding, exploiting the available natural genetic variation for photosynthesis traits. This approach is challenging for crops due to limitations in high-throughput photosynthesis phenotyping, the highly polygenic nature of photosynthesis, and its strongly dynamic response to environmental changes. Recent advancements in phenomics make accurate and detailed photosynthesis phenotyping more feasible, with the model species Arabidopsis thaliana paving the way for applications in crops. In this study, we examined photosynthesis parameters over time in the global Arabidopsis HapMap diversity panel exposed to three conditions: optimal nutrient supply, low phosphorus supply and low nitrogen supply. Combined with two previous studies on photosynthesis in response to low temperature, and to a one-step change in irradiance from low light to high light, five high-quality datasets were systematically analysed using the same approach (with one million-maker set, uni- and multi-variate analyses). Our findings emphasize the genetic complexity of photosynthesis, detecting hundreds of significant quantitative trait loci, only a small number of which are robust, and of which most are condition specific. Robust loci, found in multiple conditions, exemplify those suited for conferring higher all-round photosynthesis, and targets for marker-assisted selection, contributing to environmental resilience, while the multitude of small-effect conditional loci suggest that genomic selection approaches may be more suited to improve crop photosynthesis.

Plant cold acclimation emerges from coordinated adjustments in photosynthesis, primary metabolism, and intracellular carbon allocation. Yet, the regulatory role of subcellular metabolite compartmentation in natural variation of cold acclimation remains insufficiently understood. Here, we investigated four Arabidopsis thaliana accessions grown either individually or in bulk to determine how growth configuration and genotype shape the metabolism of sugars and organic acids during cold exposure. Using non-aqueous fractionation, we quantified plastidial, cytosolic, and vacuolar sugar pools alongside whole-cell carbohydrates, organic acids, enzyme activities, photosynthetic parameters, and stress markers. A neural-network classifier revealed that subcellular sugar distribution together with sugar amounts and organic acids provided the strongest discriminatory power among accessions, surpassing photosynthetic traits and enzyme activities. Our findings demonstrate that natural variation in cold acclimation is strongly determined by genotype-specific subcellular metabolite architectures, and that the cultivation strategy modulates these intracellular signatures. We conclude that subcellular compartmentation of metabolites represents a cellular control layer for natural variation of cold acclimation and resilience in Arabidopsis thaliana.

The evolutionary significance of somatic mosaicism created within plants by random epigenetic drift or localized responses to the environment will rest on its transgenerational implications. This paper tests whether the epigenetic mosaicism exhibited by individuals of a long-lived tree leaves some discernible "imprint" in the next gametophytic generation. Paired samples of leaves and pollen from five distinct branches within each of five wild-growing Pistacia terebinthus (Anacardiaceae) trees were characterized epigenetically using genome-wide DNA cytosine methylation level and multivariate epigenetic fingerprinting. Pollen grains were also characterized phenotypically by size and shape. Individual trees were somatically heterogeneous with regard to both cytosine methylation level and multilocus epigenetic fingerprints of leaf tissue, and within-tree variance in leaf epigenetic features exceeded among-tree variance. Phenotypic and epigenetic features of pollen differed significantly among branches of individual trees, and intraplant variation in phenotype and epigenetic fingerprints of pollen was predicted by intraplant variation in epigenetic features of leaves. Results provide evidence that intraindividual epigenetic heterogeneity arising in long-lived plants can leave its imprint into subsequent sporophyte generations via the production of epigenetically and phenotypically heterogeneous haploid gametophytes. Testable hypotheses for future epigenetic research on wild populations of non-model plants are suggested.

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 xerophyte argan (Sideroxylon spinosum) has great ecological and socioeconomic importance for Morocco. However, it is endangered due to climate change and human overexploitation. We assess drought resistance traits of argan and test the potential of arbuscular mycorrhizal (AM) symbiosis to promote its growth and mitigate the consequences of drought. We compare ten endemic Moroccan mycorrhizal inocula with the model AM fungus Rhizophagus irregularis and with the drought-adapted isolate Diversispora omaniana. We integrated physiological phenotyping and RNA sequencing to investigate the stress resistance mechanisms of argan against drought. We show that AM symbiosis significantly mitigates drought effects on plant growth, mainly by improving water relations and photosynthetic efficiency, resulting in increased growth rates. Taken together, physiological and transcriptomic analyses show that stress markers were moderatly induced during severe drought stress irrespective of mycorrhizal status, suggesting that argan adopts a drought-coping strategy that involves both, stress avoidance and stress tolerance. Argan is highly AM-responsive, both at the phenotypic and transcriptomic level, suggesting that AM has great potential to promote argan growth under drought stress.

Peptide hormone signaling coordinates plant growth and osmotic stress responses, yet how the transition between these responses is regulated remains poorly understood. Here, we investigated the function of the rice PLANT PEPTIDES CONTAINING SULFATED TYROSINE 8 (OsPSY8) peptide in osmotic stress responses. OsPSY8 was predominantly expressed in root tissues under non-stress conditions, with preferential expression in lateral roots where it promoted root growth. Osmotic stress rapidly reduced OsPSY8 expression in roots through the OsWRKY24 transcription factor. Loss-of-function ospsy8 mutants exhibited enhanced osmotic stress tolerance, whereas OsPSY8 overexpression increased osmotic stress susceptibility. Transcriptomic analyses revealed that disruption of OsPSY8 activated stress-responsive pathways, including those associated with lignin biosynthesis, compatible solute production, cell wall remodeling, and reactive oxygen species (ROS) scavenging, and was accompanied by increased lignin accumulation in roots. In contrast, overexpression of OsPSY8 resulted in maintenance of growth-associated transcriptional programs while suppressing stress-responsive pathways under osmotic stress. Together, these findings identify OsPSY8 as an important regulator of the transition from growth to stress adaptation in rice and suggest that stress-induced repression of PSY signaling is required to disengage growth programs and activate adaptive responses during osmotic stress. Significance StatementCrop survival during drought depends on the ability to transition from growth to stress adaptation. Plant peptide hormones have emerged as important regulators of this critical transition, highlighting the importance of investigating their roles and potential for improving crop resilience. We show that a rice peptide hormone regulates this transition. Under non-stress conditions, this peptide hormone, predominantly expressed in rice roots, promotes root growth while suppressing stress responses. During osmotic stress, expression of the peptide hormone decreases, resulting in activation of stress-responsive pathways, such as lignin biosynthesis and reactive oxygen species scavenging. These findings demonstrate that a peptide hormone coordinates the balance between growth and stress adaptation in rice, with broader implications for understanding and improving crop resilience.