Journal of Experimental Botany

Stomatal traits balance carbon gain with water loss, yet their breeding potential in wheat remains underexploited. This study investigated physiological and anatomical stomatal responses alongside yield across two years of large-scale field trials under water-limitation and delayed sowing-induced heat exposure. Across both seasons, stomatal conductance (gs) declined under stress, reflecting strong environmental constraint on gas-exchange (water-limitation: -26.9%; heat: -13.8%). Partitioning responses by leaf surface and genotype identified the adaxial surface as the dominant contributor to gs variation and the most stress responsive. Despite increases in theoretical anatomical gas-exchange capacity (gsmax), gs-efficiency declined, indicating partial decoupling between structural potential and realised conductance. Drought reduced stomatal size while increasing density whereas heat increased size, suggesting stress-specific anatomical plasticity. Moderate-to-high heritability was observed for anatomical traits (Water-limitation: 0.13-0.57; Heat: 0.42-0.71), contrasting with lower and less stable heritability for gs (water-limitation: 0.13-0.41; heat: 0.13-0.50). Genome-wide-association-mapping identified 169 putative QTLs, predominantly for anatomical traits, including stable and co-localised pleiotropic loci. Fourteen sets of closely positioned markers were detected across seasons or studies, with stable regions on chromosomes 2B, 3B and 7B emerging as key loci. Focusing on stable loci controlling adaxial stomatal anatomy offers a realistic strategy to enhance wheat photosynthetic efficiency and climate resilience. HighlightAdaxial stomatal traits dominate gas exchange responses to heat and drought in wheat, with stable anatomical QTL identified on chromosomes 2B, 3B and 7B. Their stability across environments supports their relevance for crop improvement in water-limited and high temperature systems.

Wheat (Triticum aestivum L.) production depends upon nitrogen fertilization and may be threatened by the climate conditions anticipated in the next few decades. The natural variation in the ability of wheat to assimilate carbon and different inorganic nitrogen forms, nitrate (NO3-) and ammonium (NH4+), into vegetative growth remains unexplored. Here, we evaluated growth under either NO3- or NH4+ as a sole nitrogen source for 875 spring hexaploid wheat accessions that represent the genetic diversity within the global germplasm. These accessions varied over 8-fold in vegetative biomass but grew similarly under moderate levels of either nitrogen form. At high, potentially toxic concentrations of NH4+, however, they lost approximately 20% of their biomass. We characterized the influence of changing CO2 levels in bi-parental Nested Association Mapping populations. Genetic backgrounds determined wheat biomass responses to CO2 enrichment and nitrogen form. Genome-Wide Association and linkage mapping identified certain loci as consistently associated with biomass accumulation under different nitrogen forms and CO2 levels. These results will assist breeding efforts to develop food crops that are resilient to the worlds climate changes.

Increasing global temperatures and the rising frequency of heat waves pose a significant threat to plant reproduction. The reproductive phase is particularly sensitive to heat stress, yet the underlying mechanisms regulating thermotolerance during this stage remain insufficiently understood, despite significant advcances in its understanding during vegetative growth. Heat stress responses are largely controlled by heat shock factors (HSFs) and their downstream targets, including heat shock proteins (HSPs). Among these, HSP101 is essential for acquired thermotolerance and recovery from stress, while HEAT SHOCK BINDING PROTEIN (HSBP) acts as a negative regulator of HSF activity, modulating the heat shock response. Here, we investigated the impact of elevated temperature regimes on the reproductive development of Arabidopsis thaliana, with a particular focus on pollen development and fertility. Our results show that heat stress negatively affects pollen development in a dose-dependent manner, leading to reduced reproductive success. We confirmed the critical role of HSP101 in reproductive thermotolerance using the hot1-3 mutant, deficient in HSP101. Furthermore, we provide evidence that the hot1-3 mutant is tetraploid. The origin of this event is unknown, but it is tempting to speculate that disruption of heat stress responses and interference with meiotic processes may lead to whole genome duplication. Overall, this study provides new insights into the regulation of plant reproductive development under heat stress and highlights the importance of HSP101 in maintaining fertility. These findings contribute to a better understanding of plant responses to rising temperatures and may inform strategies to enhance crop resilience under climate change. Main ConclusionFlowering Arabidopsis plants adapt to long-term high temperature by shortening the flowering period and reducing their fertility. The study also demonstrated that the commonly used hot1-3 mutant is tetraploid.

The establishment of aphid-plant interaction involves the secretion of a salivary MIF protein. Morphological analyses revealed that aphid MpMIF1 prevents plant cell death, protects organelles from stress, and may promote plant cellular recovery. Co-expression of aphid MpMIF1 and the cell death inducer Npp1 revealed that MpMIF1 modulates autophagy-related genes ATG7/BECLIN1, impair plant senescence regulator ATAF1 and regulate apoptosis-like via Caspase-3-like activity. This effect on multiple-cell death pathways helps to maintain cellular homeostasis during aphid infection. Investigations on DNA Damage Response (DDR) signaling pathways demonstrated that aphid MpMIF1 reduces {gamma}H2A.X phosphorylation, maintains activity of the DNA repair protein RAD51 and stabilizes cell cycle checkpoint expression WEE1 under genotoxic stress. Therefore, MpMIF1 actively participates to the maintenance of a functional DDR. Finally, we showed that aphid MpMIF1 physically interacts with SOG1, a functional analog of animal p53 and central regulator of DDR, cell cycle arrest and programmed cell death in plants. These findings establish MpMIF1 as a key regulator of plant cell death during aphid-plant interactions and highlight its potential as a biotechnological tool for protecting major crops against aphid infection.

Drought is a major constraint on the productivity of durum wheat across Mediterranean and North African regions. To elucidate the mechanisms underlying drought resilience, we employed a combination of scenario-controlled phenomics and flag leaf transcriptomics across ten durum wheat genotypes. These included the Tunisian landraces Chili and Mahmoudi, seven breeding lines, and the reference cultivar Svevo. The plants were grown to maturity under well-watered or long-term drought conditions in pots and rhizotrons, enabling a comprehensive assessment of growth, yield components, root architecture, physiological traits, and reaction norm plasticity. Drought markedly reduced performance, yet Chili and Mahmoudi consistently maintained superior biomass, grain number and intrinsic water use efficiency (iWUE). This was supported by balanced C/N allocation, strong osmotic adjustment, and the ability to sustain robust root systems under stress, albeit through partly divergent physiological strategies. Transcriptomic profiling revealed highly genotype specific responses, with drought tolerance unrelated to the number of differentially expressed genes. Instead, the landraces displayed distinct regulatory programs involving mainly photosynthesis protection, ABA-related transporters, osmotic adjustment pathways, and stress-responsive transcription factors. These mechanistic insights identify actionable physiological and molecular determinants of drought plasticity and provide high value targets for accelerating the breeding of climate resilient durum wheat. HighlightsIntegrated phenomics and transcriptomics revealed landrace-specific physiological and molecular mechanisms enabling superior drought resilience and identifying actionable targets for durum wheat improvement.

Phenotypic plasticity is a key mechanism by which plants adjust their traits to environmental changes. These phenotypic adjustments are driven by plastic changes in gene expression regulated by gene regulatory networks. Drought, a major selective force in Mediterranean ecosystems, provides a powerful context to examine how genomic plasticity translates into phenotypic responses. Here, we used Dianthus inoxianus, a drought-tolerant Mediterranean carnation, in order to characterize the phenotypic and transcriptomic plasticity in response to drought stress combining ecophysiological measurements with RNA-seq, gene co-expression and gene regulatory network analyses. Most of the phenotypic traits exhibited low plasticity in response to drought, except water and osmotic potential. At transcriptome level, we identified 57 plastic genes, suggesting that drought tolerance in D. inoxianus relies predominantly on constitutive gene expression. These plastic genes were enriched in processes typically related to drought response, such as cell wall components and abscisic acid (ABA) signaling. Some plastic genes belonged to drought-responsive modules, while others were hubs in different modules acting as inter-modular connectors. Furthermore, the regulatory network revealed that these plastic genes were strongly regulated by multiple stress-responsive transcription factors, and that drought-associated modules were regulated through both ABA-dependent and ABA-independent pathways. In addition, we identified contrasting patterns of canalization and decanalization, with immune and post-transcriptional regulation remaining canalized under drought, whereas photosynthesis and amino acid metabolism became decanalized, potentially releasing cryptic genetic variation. Overall, our results emphasise that drought tolerance in D. inoxianus emerges from a strategy combining preadaptation with targeted plasticity in key molecular pathways.

Soil salinization threatens global agriculture reducing yields, yet the metabolic signals controlling salt-sensitive root plasticity in alfalfa remain unclear. We hypothesize that salinity transiently uncouples the sucrose-trehalose-6-P (Tre6P)- Sucrose non-fermenting kinase 1 (SnRK1) nexus, aligning with a biphasic root metabolic response and altered root architecture. Alfalfa seedlings were grown in a hydroponic system and exposed to 200 mM NaCl, with root samples collected from 1 h to 7 d. While primary root growth and biomass remained unchanged, lateral root development was enhanced under salinity. Early response (1 h-1 d) was characterized by reduced carbon metabolites, low Tre6P, increased malondialdehyde, and SnRK1 activation, with a decline in glycolytic and TCA intermediates. During this phase, sucrose was negatively correlated with both Tre6P and SnRK1. Late response (3-7 d) showed a SnRK1 reactivation, Tre6P recovery, and osmoprotectant accumulation, including increased antioxidant capacity (+75% at 3dpt), proline (+178%), and sucrose (+18%) and starch depletion (-57%) at 7dpt respect to control. These metabolic changes coincided with the enhanced lateral root emergence. These findings indicate a two-phase response: early metabolic downscaling with transient Suc-Tre6P-SnRK1 disruption, followed by recovery with Tre6P restoration, SnRK1 reactivation, osmoprotection, and sustained root plasticity under salinity. HighlightSalinity triggers a temporary metabolic shift in alfalfa roots: plants first conserve energy, then adapt to stress, maintaining lateral root growth and flexible root architecture.

Malate and fumarate constitute a significant transient carbon stock that is dynamically synthesized during the photoperiod. These organic acids are diurnally stored and remobilised from the vacuole, and they have a key role in the cellular metabolic regulation. This function is well known in C4 and CAM plants. However, in C3 species that are the majority of terrestrial plants, the importance of the vacuolar accumulation/release and its influence on plant growth is still an open question. In Here we addressed this issue generating multiple knockout mutants in Arabidopsis thaliana lacking vacuolar anion channels of the Aluminium-Activated Malate Transporter (ALMT) family, to impair malate and fumarate transport to the vacuole. We show that in these mutants reducing vacuolar transport of malate and fumarate in mesophyll cells leads to a dramatic growth impairment. Metabolic and fluxomic analysis revealed that vacuolar malate and fumarate transport influences plant carbon and nitrogen metabolism as well as cellular pH and ionic homeostasis. In conclusion, our results show that the transport organic acids like malate and fumarate across the vacuolar membrane is essential for plant growth in a C3 plant too. These results establish the importance of the vacuolar pools of malate and fumarate in plant metabolism.

Flowering time and monocarpic senescence are tightly environmentally and genetically controlled. Typically, early flowering and staygreen traits are associated with opposing life-history strategies; stress avoidance versus adaptation; with flowering time an overarching regulator of crop cycle length. We developed RIL populations segregating for Ppd-1 and NAM-1 variation, which are otherwise isogenic. Multi-year field experiments enabled exploration and uncoupling of the relationship between heading and staygreen traits. Heading date manipulation enabled introduction of staygreen traits to their target breeding environments, characterised by a hot-finish. Under moderate stress, we report a 2.9% and 1.9% increase in grain width (P<0.0001), and 5.8% and 3.7% increase in TGW (P<0.0001), plus significantly greater yield (P<0.1) for late heading staygreen RILs homozygous for NAM-A1, and NAM-D1 missense variants, respectively. Grain yield increases were proportionate to the delay in senescence, being greater for the NAM-A1 than the NAM-D1 variant. For RIL populations segregating for both traits, senescence variation was observed relative to heading-date. Regarding grain yield, the staygreen trait-associated increase in source size could not compensate for the Ppd-1a associated pleiotropic reduction in sink size, even under hypothesised continental target breeding environments, with trait competition identified. Therefore, to maximise the benefits associated with staygreen traits, especially in early-heading favouring environments required targeted manipulation of source-sink dynamics, and we propose multiple strategies. HighlightStaygreen traits were associated with extending grain fill duration, increasing grain width, TGW and grain yield. There appears an antagonist relationship between earlier heading and staygreen traits.

Salinity is a major crop production constraint in dry pea (Pisum sativum L.), making the development of salt-tolerant varieties essential to improve crop productivity and land-use efficiency. The genetic mechanisms of salt tolerance in dry pea is largely unknown, and research on salt-tolerant genes is limited. In this study, we established comprehensive genomic and transcriptomic resources, along with a robust screening protocol, to dissect the genetic basis of salinity tolerance using two germplasm sets: the USDA pea diversity panel, consisting of approximately 200 globally sourced accessions, and a set of 300 modern elite lines from the NDSU Pulse Crops Breeding Program. Genetic variation for the salinity response was assessed based on ten phenotypic traits, with root dry weight, shoot dry weight, and specific root length identified as key indicators based on their heritability. Genome-wide association mapping uncovered significant genomic regions and several candidate genes linked to salt stress, with the strongest association found on chromosome 6. Overlapping QTL signals across traits suggest a shared genetic architecture underlying salinity tolerance. Field-based transcriptomic analysis further identified five putative genes involved in salinity response conserved across multiple crop species. Notably, Psat5g000800, encoding a glycosyl hydrolase gene, was markedly upregulated under salinity stress. These findings highlight the complex, multi-gene regulatory nature of salinity tolerance in dry pea and underscore the importance of functional validation of candidate genes. This study provides key insights and practical tools to support breeding efforts aimed at improving salt tolerance in dry pea.

O_LIHydroxycinnamic acid amides (HCAAs) are phenylpropanoid-derived metabolites with known antimicrobial and structural roles in plant defence against pathogens. However, their contribution to mechanical wound responses remains unclear, especially in terms of tissue regeneration and signalling. C_LIO_LIHere, we used tomato transgenic plants overexpressing the tyramine hydroxycinnamoyl transferase (THT), the key biosynthetic enzyme for HCAA production, to investigate the role of HCAAs in wound-induced responses, combining targeted metabolite profiling, gene expression, confocal microscopy, antioxidant assays, and volatile analyses. C_LIO_LIWe show that THT overexpression enhances wound-induced accumulation of HCAAs, promoting vascular lignification, suberization, callose deposition, and increased regeneration capacity. Additionally, 35S::THT plants display a distinct VOC profile that modulates defence gene expression in neighbouring wild-type plants, even in the absence of injury. C_LIO_LIThese results identify THT as a key regulator of structural reinforcement and defence priming after mechanical damage. Our findings highlight a novel role for HCAAs in wound healing and interplant signalling, with potential applications for improving crop resilience to mechanical stress. C_LI

O_LIPhotoperiod is a stable seasonal signal. Although the photoperiodic flowering is well understood in short-day (SD) and long-day (LD) annual plants, regulatory mechanisms in perennials remain elusive. In a perennial woodland strawberry (Fragaria vesca L.), flowering is induced in SDs in autumn and plants flower following spring, while in plants with mutated FvTERMINAL FLOWER1 (FvTFL1), LDs induce flowering. C_LIO_LIWe investigated photoperiodic flowering of F. vesca through phenotypic and molecular characterization of transgenic lines and their crosses. We studied natural variation in flowering time and gene expression in European accessions, and explored their correlations with climatic, geographical and genetic origins. C_LIO_LIWe showed that FvGIGANTEA (FvGI) and FvCONSTANS (FvCO) activate FvFLOWERING LOCUS T1 (FvFT1) in LDs resulting in early flowering in fvtfl1 mutant, while in SD F. vesca, activation of FvTFL1 by FvFT1 reverses the photoperiodic requirement of flowering. In natural accessions, decreasing expression of FvFT1 and FvTFL1 towards colder climates in the east and north correlated with earlier flowering. C_LIO_LIWe define a photoperiodic flowering mechanism controlling floral transition of perennial F. vesca in autumn that differs from known mechanisms in annual and perennial plants. Our findings open new avenues to understand how perennial plants cope with changing seasons across climatic and geographical ranges. C_LI

Processing of ribosomal RNA (rRNA) is essential for ribosome biogenesis, translation, plant development, and stress adaptation. Ribosome processing factor-2 (RPF2), which plays a role in the later stages of rRNA maturation, interacts with ribosomal protein L10A (RPL10A). RPF2 overexpression in Arabidopsis and Nicotiana benthamiana showed enhanced plant growth and trichome development due to increased gibberellic acid (GA) levels. Conversely, RPF2-silenced and mutant plants had a dwarf phenotype, reduced stomatal apertures, and decreased glucosinolate accumulation. RPF2 silenced and mutant plants also showed compromised nonhost disease resistance, whereas RPF2 overexpression lines exhibited enhanced disease resistance to both host and nonhost pathogens. RPL10A and RPF2 overexpression lines were sensitive to abscisic acid (ABA) and tolerant to drought, which is attributed to their unique roles in translation regulation. Despite having larger stomatal apertures, RPF2 overexpression plants displayed low pathogen multiplication rates and reduced water loss, indicating independent resistance mechanisms associated with ribosomal functions in translation regulation. Although both RPL10A and RPF2 proteins interact with each other and are involved in translation regulation, proteomic analysis suggests that they regulate the translation of distinct sets of genes during pathogen or drought stress. These findings indicate that RPF2 and RPL10A play independent roles in the regulation of unique protein translation.

High-temperature stress poses a major threat to wheat productivity, particularly during early developmental stages. Root system architecture (RSA) plays a key role in stress adaptation; however, its variation under high-temperature stress remains insufficiently characterized, especially in genetically diverse populations. In this study, we evaluated RSA responses of representative genotypes from a Multiple Synthetic Derivatives (MSD) wheat population under control and high-temperature conditions using a time-resolved two-dimensional phenotyping platform. High-temperature stress significantly affected most root traits, with lateral root-related parameters, including second pair seminal root length (SPSRL), root system width (RSW), and convex hull area (CHA), showing relatively greater responsiveness than vertical traits. Integrative analyses combining stress indices and multivariate approaches revealed distinct genotypic response patterns. MSD417 and MSD034 maintained higher root performance under stress, indicating greater tolerance, whereas MSD392 exhibited pronounced sensitivity, and MSD054 showed limited responsiveness. These findings suggest the importance of distinguishing between active stress tolerance and apparent stability and indicate that lateral root-related traits may represent useful targets for selection. Overall, the findings of this study validate the practical usefulness of the RSA screening approach and identify MSD genetic resources harboring RSA traits relevant to breeding heat-resilient wheat.

Soil salinity is a rapidly intensifying abiotic stress that significantly limits wheat productivity, particularly in coastal and irrigated agroecosystems. Although sodium (Na+) ion exclusion has been recognized as a key tolerance mechanism, the integration of physiological performance with Nax1-mediated molecular regulation among regionally adapted wheat genotypes remains insufficiently characterized. The present study aimed to dissect salinity tolerance by combining hydroponic phenotyping, multivariate trait analysis, molecular marker profiling, and quantitative expression analysis of the Na+ ion transporter gene Nax1. Seventeen spring wheat genotypes were evaluated under four salinity levels (0.0, 10, 12, and 14 dS m-{superscript 1}). Germination and survival rate, shoot and root growth, and biomass accumulation were measured. Principal component analysis (PCA) and hierarchical clustering were performed to classify genotypes, while SSR (simple sequence repeat) and Nax-linked markers assessed genetic diversity. Relative Nax1 expression was quantified using qRT-PCR (quantitative real-time polymerase chain reaction). Salinity significantly reduced germination, survival, elongation, and biomass, with strong genotype-dependent variation. Multivariate analyses clearly separated tolerant and sensitive genotypes, with biomass retention and survival contributing most to total variation. Marker analysis revealed moderate genetic polymorphism. Notably, tolerant genotypes exhibited 3-6-fold induction of Nax1 under severe salinity, positively correlating with biomass maintenance. These findings demonstrate that salinity tolerance in wheat is associated with coordinated physiological resilience and enhanced Nax1-mediated Na ion exclusion, thereby advancing mechanistic understanding and supporting molecular-assisted breeding for salt-affected environments.

Previously, the chitin receptor-interacting protein kinase LIK1 (LysM receptor kinase 1/CERK1-interacting kinase) was shown to play an important role in regulating chitin signaling and plant defense. A limited proteolysis proteomics study revealed several LIK1-derived peptides that showed differential abundance between ATP-treated and mock-treated Arabidopsis samples, suggesting a possible involvement of LIK1 in extracellular ATP (eATP) signaling. To explore this possibility, LIK1 mutants were obtained and examined for their response to ATP. The results showed that mutations in LIK1 significantly reduced the expression of eATP-responsive genes. In addition, LIK1 was found to interact with the eATP receptor P2K1 and to be phosphorylated by it. The LIK1 protein was localized to the plasma membrane and its gene expression appeared to be ubiquitous. Collectively, these findings indicate that LIK1 not only contributes to chitin signaling but also participates in eATP signaling, highlighting its potential role as a shared component in multiple signaling pathways to regulate plant responses to diverse internal and external cues.

RAP2.6, an AP2/ERF transcription factor (TF), regulates plant stress responses; however, its role in floral transition remains unexplored. Here, we evaluated RAP2.6s role in flowering and the associated transcriptional changes in Arabidopsis thaliana under long-day conditions. RAP2.6-overexpressing line showed early flowering with fewer rosette leaves, whereas rap2.6-1 mutant flowered later, had more rosette leaves, and higher expression of the floral repressor FLOWERING LOCUS C (FLC). Early flowering in the overexpressing line was accompanied by transcriptional activation of the floral integrators GIGANTEA (GI), FLOWERING LOCUS T (FT), and COSTANS (CO), potentially through RAP2.6 interaction with GCC/DRE cis-regulatory elements. RAP2.6-mediated floral transition depended on nitric oxide (NO), with flowering time largely varying based on NO bioactivity. RAP2.6 was found to be a downstream regulator of Arabidopsis S-NITROSOGLUTATHIONE REDUCTASE 1 (GSNOR1) in controlling S-nitrosothiol (SNO) levels, flowering time, and silique formation. The NITRIC OXIDE-ASSOCIATED 1 (NOA1)-dependent reduction in NO levels abolished early flowering in 35S::RAP2.6 plants without affecting silique formation. Furthermore, enhanced cytokinin sensitivity and upregulation of cytokinin biosynthetic genes suggest cytokinin involvement in RAP2.6-mediated flowering. Together, these findings highlight the crucial role of RAP2.6 in regulating flowering time by integrating redox and hormonal signaling to coordinate reproductive development in A. thaliana.

Hundreds of proteins in the cell require iron (Fe) or Fe-containing cofactors to function. However, how Fe2+ or Fe3+ are specifically allocated to each of these proteins in plant cells remains largely unknown. It has been proposed that Fe metalation could be driven by specific interactions with Fe-shuttling proteins known as Fe-chaperones. Here, we present the first family of plant Fe2+-chaperones (ICHAPs) with orthologues in dicots and monocots. The role of these proteins in Fe distribution to Fe-dependent metabolic processes has been illustrated using symbiotic nitrogen fixation in Medicago truncatula root nodules. ICHAP1 is a soluble Fe2+-binding protein that interacts with plasma membrane Fe2+ transporter NRAMP1, but not with symbiosome Fe2+-transporters. ICHAP1 mutants present altered Fe distribution in cells and they cannot fix nitrogen. A second family member, ICHAP2 is required to target Fe2+ to symbiosomes, as it accepts Fe2+ from ICHAP1 and interacts with symbiosome Fe2+-importer VTL8, but not with NRAMP1. These results indicate a path for Fe2+ allocation from the plasma membrane to the symbiosome through specific protein-protein interactions and Fe2+ exchange from NRAMP1 to ICHAP1, to ICHAP2, and to VTL8.

Bread wheat (Triticum aestivum) is a staple food crucial for global caloric intake and food security. The current climate emergency demands the development of sustainable agricultural practices, particularly in the context of drought-induced yield reductions in bread wheat. Microalgae-based biostimulants have emerged as promising tools to enhance crop tolerance to drought stress while concurrently mitigating atmospheric CO2 accumulation. This study characterizes the transcriptomic responses to the foliar application of the microalgae-based biostimulant LRMTM in drought-stressed and fully irrigated wheat plants unveiling its mode of action. Drought stress at the tillering stage significantly altered gene expression activating key pathways related to phosphate starvation response (PSR), inositol phosphate signaling, and tocopherol biosynthesis. The application of the microalgae-based biostimulant LRMTM in drought-stressed plants further enhanced the expression of drought-responsive genes, particularly those involved in PSR and carbon fixation. Specific responses to LRMTM treatment in drought-stressed plants were also found related to abscisic acid (ABA) signaling activating genes involved in stomata closure, which plays a critical role in drought tolerance. In fully irrigated plants, LRMTM treatment was also beneficial modulating circadian rhythms, shade avoidance and attenuating stress responses. Phenotypic analysis showed that LRMTM-treated plants exhibited enhanced drought tolerance, increased height and spike length even under fully irrigated conditions. These results indicate that the microalgae-based biostimulant LRMTM not only enhances wheat response to drought but also promotes growth and productivity in both stressed and non-stressed conditions which could contribute to the development of sustainable agriculture in the face of the current climate challenges.

The chloroplast NADH dehydrogenase-like (NDH) complex mediates cyclic electron transport (CET) around photosystem I (PSI) and contributes to photosynthetic regulation and photoprotection under various environmental stresses. Although NDH function has been extensively characterized under controlled conditions, NDH-deficient mutants often show only subtle phenotypes in such environments, leaving its physiological importance under naturally fluctuating field conditions poorly understood. Here, we evaluated growth, yield, and photosynthetic performance of NDH-deficient rice cultivated under field conditions. Mutant plants exhibited reduced biomass accumulation and grain yield compared with wild type. Detailed physiological analyses revealed that NDH deficiency markedly decreased PSI electron transport and CO2 assimilation, particularly under low temperature and sub-saturating irradiance. At moderate and high temperatures, reductions in carbon fixation were largely confined to low-light conditions, whereas at low temperatures, impairment extended across nearly the entire light response range. Under repetitive fluctuating light regimes, NDH-deficient plants showed progressive declines in photosynthesis accompanied by a selective decrease in PSI photochemical capacity without changes in PSII maximum efficiency, indicating PSI-specific photoinhibition. These findings demonstrate that NDH-dependent CET plays a crucial role in sustaining photosynthetic efficiency and crop productivity in dynamic field environments by stabilizing PSI redox balance and maintaining long-term carbon gain. Summary StatementNDH-dependent cyclic electron transport supports photosynthesis and yield in field-grown rice by maintaining PSI function under fluctuating light, low temperature, and sub-saturating irradiance.