Photosynthesis Research

Photosynthetic electron transport is tightly regulated to balance ATP and NADPH production and prevent over-reduction of the photosynthetic machinery. How this balance is maintained under severe ATP limitation, particularly under anoxia, is not fully resolved. Here, we used several deletion mutants of chloroplast ATP synthase subunits from Chlamydomonas reinhardtii to examine how electron flow is reorganized under anoxic conditions through the interplay between linear electron flow, cyclic electron flow, and alternative electron sinks. Using a combination of optical spectroscopy methods and membrane inlet mass spectrometry, we characterized changes in photosynthetic electron transport, proton motive force relaxation and gas exchange. Under oxic conditions, the {Delta}atpH mutant (lacking the c-subunit) showed strong acceptor-side limitation at photosystem I (PSI), whereas atpC1-2 (lacking the {gamma}-subunit) resembled the wild type. Under anoxia, this limitation was partially relieved, coinciding with sustained electron transport and prolonged hydrogen production. In particular, the {Delta}atpH mutant exhibited increased cyclic electron flow under oxic conditions and maintained PSI activity under anoxia despite impaired ATP synthesis. Prolonged hydrogen production was also observed in atpC1-2, which did not share the increased respiration of {Delta}atpH. Hydrogenase activity under anoxia is consistent with a role as an electron sink that may help alleviate PSI acceptor-side limitation and rebalance the redox state of the electron transport chain. These findings show that ATP synthase deficiency reorganizes photosynthetic electron flow and promotes prolonged hydrogen production, and point to hydrogenase as a candidate electron sink under energy-constrained conditions.

Pigment composition and regulation are critical for efficient photosynthesis in the ocean, where light intensity decreases and the spectrum narrows with depth. Fucoxanthin (Fx), the main carotenoid of several microalgal lineages, harvests the blue-green light prevailing in the deep euphotic zone. In pelagophytes, the acylated derivative 19'-butanoyloxyfucoxanthin (19'-BFx) is abundant, yet its function and regulation remain unclear. Here, we investigated how irradiance and spectral quality shape photoacclimation in Pelagomonas calceolata, an abundant and cosmopolitan low-light pelagophyte. Cultures were grown under blue or white light across 2-60 umol photons m^-2 s^-1. We analysed growth, PSII photophysiology, pigment composition, gene expression levels, and the impact of spectral shifts on the 19'-BFx/Fx ratio. Pelagomonas calceolata grew optimally under dim blue light and displayed low non-photochemical quenching (NPQ) under assay conditions. Transcriptomes revealed broad remodelling driven mainly by irradiance and modulated by light colour, including carotenoid-related processes. Dim blue light progressively increased the 19'-BFx/Fx ratio, whereas white light kept it low and reversed the response after a blue-to-white shift. These results identify reversible, spectrum-dependent 19'-BFx accumulation as a key component of photoacclimation in P. calceolata and separate irradiance-driven from spectrum-dependent cellular responses. This plasticity may explain the ecological success of P. calceolata in low-light oceans.

Chlorophyll fluorescence imaging is a powerful tool used to characterize abiotic and biotic stress response of photosynthesis in plants. However, extracting metrics such as Fv/Fm (maximum quantum yield of photosystem II) from chlorophyll fluorescence images remains a substantial bottleneck in large measurement campaigns, often requiring significant manual effort. To resolve this issue, we developed fvfmPy, a user-friendly program which enables rapid analysis of chlorophyll fluorescence images of arrays of leaf discs. fvfmPy uses algorithmic image segmentation to identify regions of interest and extract fluorescence metrics from tens or hundreds of leaf samples per image with little to no manual input. fvfmPy is developed in Python and includes a graphical user interface enabling intuitive parameter adjustment and real-time quality control checking. We additionally developed fvfmR, an R wrapper package for fvfmPy. Fv/Fm values extracted with fvfmPy were indistinguishable from those obtained using manual methods (r2 > 0.99) but required 94% less time to complete (13 s vs. 200 s per 100 measurements). fvfmPy and fvfmR were built to directly integrate with existing fluorescence software packages and can greatly increase throughput of fluorescence measurements to help address key challenges in agriculture and ecology.

Photosynthetic organisms protect themselves from excess light through non-photochemical quenching (NPQ), a process that safely dissipates excess light energy as heat. Current understanding of NPQ is largely drawn from a few model systems, leaving it unclear how universal NPQ mechanisms are across the green lineage. We characterize the slow, sustained NPQ of the green alga, Auxenochlorella protothecoides x symbiontica (UTEX 250-A). The Auxenochlorella genome lacks Light-Harvesting Complex Stress Related (LHCSR), one of the two proteins required for the fast energy-dependent quenching (qE) component of NPQ. Mutants lacking the Photosystem II Subunit S (PSBS)-like gene (psbsl1) in Auxenochlorella had no effect on NPQ, indicating this alga lacks canonical qE. We identified two candidate enzymes associated with zeaxanthin-dependent quenching (qZ), which has slower kinetics: a plant-type Violaxanthin De-Epoxidase (VDE) and an algal-type Chlorophycean Violaxanthin De-Epoxidase (CVDE). High light did not trigger the expected conversion of violaxanthin to zeaxanthin, a pigment change that is a hallmark of qZ. Mutants lacking VDE (vde1), CVDE (cvde1), or both enzymes (vde1 cvde1) still displayed slow, reversible NPQ. However, when the Auxenochlorella VDE1 and CVDE1 were expressed in a VDE-deficient mutant of Nicotiana benthamiana, both enzymes restored zeaxanthin production and NPQ, confirming they are catalytically functional de-epoxidases. Together, these results reveal an alga that retains two functional, evolutionarily distinct xanthophyll-cycle enzymes yet does not rely on typical xanthophyll pigment dynamics for photoprotection. This points to a biological function that is decoupled from de-epoxidase activity, highlighting unexplored diversity in green algal photoprotection.

Lipid droplets (LDs) play a central role in cellular carbon and energy homeostasis, in particular through the roles played by numerous LD-associated proteins. A long-standing question concerns how these proteins are molecularly organized at the seemingly overcrowded LD surface. Delayed in TAG Hydrolysis 1 (DTH1) has been identified as a key protein for efficient LD degradation in Chlamydomonas reinhardtii, however the underlying molecular mechanism remains unknown. DTH1 contains several structural features including a coiled-coil domain, a phosphatidylethanolamine (PE) specific lipid-binding domain, intrinsically disordered regions, and an alpha-helical C-terminal domain, that make it a compelling candidate for acting as a molecular scaffold in protein recruitment and/or organelle tethering. In this study, we used the Chlamydomonas knock-out mutant dth1 as an entry point to begin dissecting the molecular organization of proteins at the LD surface. Comparative lipidomic and proteomic analyses of isolated LDs from both WT and dth1 mutants revealed several key features associated with LD degradation during nutrient recovery. First, PE emerged as an important lipid species involved in LD degradation. Second, active communication occurs among multiple subcellular organelles particularly between LDs, peroxisomes and mitochondria. Third, DTH1 was found to play a critical role in remodeling both the LD proteome and lipidome. Furthermore, detailed analyses of LD degradation during nitrogen recovery uncovered the formation of micro-LDs, a phenomenon not yet reported in microalgae. Collectively, these results highlight the tight coordination of metabolic activities across subcellular compartments and emphasize the importance of intracellular carbon trafficking during stress recovery.

Carbon allocation governs how plants partition assimilates among leaves, roots, stems, and reproductive organs, directly shaping growth and yield. Most crop models represent this partitioning using fixed or empirically derived coefficients, which limits their ability to predict how allocation responds to genotype, environment, or their interaction. Eco-evolutionary optimality theory offers an alternative where the allocation strategy is allowed to emerge from the marginal costs and benefits of investing carbon in each organ. While this approach has been applied successfully to trees, it has not previously been developed for herbaceous plants. Here, we present DAESIM2-Plant, a mechanistic plant growth model that couples physiological processes including photosynthesis, stomatal conductance, plant hydraulics, and canopy radiative transfer, with an eco-evolutionary optimal allocation scheme for leaves and roots. This is applied to wheat by coupling it to a source-sink grain production module. Using a series of idealized sensitivity experiments, we show that the model reproduces well-documented patterns of plasticity in carbon allocation: diminishing returns on leaf investment as canopy closure and water limitation are approached, a shift in allocation toward roots under drier conditions, and a root:shoot response that depends jointly on soil moisture and the plant's existing root:leaf balance. Simulating a full growing season across a gradient of soil moisture levels reveals a threshold-like response in canopy development, biomass accumulation, and grain yield, with yield constrained by the same assimilate supply that governs vegetative growth during the critical period and grain filling. This provides a promising basis for generalizing model behaviour across a wide range of environmental conditions. Evaluating these results against experimental and field trial data remains an important next step.

Euglena longa is a heterotrophic model euglenid, of significant research interest as a unicellular eukaryote. To provide broad insight into the localisation of its proteome we used subcellular spatial proteomics (SSP), based on a label-free version of LOPIT-DC (Localisation of Organelle Proteins by Isotope Tagging after Differential Centrifugation), in which organelles are separated by differential centrifugation and each protein is assigned to a compartment from its abundance profile across the fractions. We detected 5,909 proteins, using protein abundance profiles across fractions to resolve 16 different subcellular compartments, such as the plastid, pellicle, and peroxisomes, and assigned high-confidence localisations to 2,955 of them. This study serves as a proteomic dataset to resolve protein compartmentalisation for this euglenid, enabling evolutionary, biological and functional insight and analysis. We are drafting manuscripts concerning the metabolic nature of the plastid, the evolutionary origins of the pellicle, and the functions of the peroxisome. Investigators interested in using this data prior to publication are encouraged to contact us to avoid overlap and to facilitate coordinated and collaborative use of this resource.

- C2 photosynthesis reduces photorespiratory carbon loss by shuttling glycine from mesophyll (M) to bundle sheath (BS) tissues, where glycine decarboxylase (GDC) releases CO2 that accumulates around rubisco. C2 photosynthesis has been considered a constitutive character, but as a metabolic trait, it may acclimate to the rate of photorespiratory glycine production. - We grew eleven species from two eudicot and two grass lineages spanning C3 to C2 phenotypes at 32 {degrees}C days and 200 or 800 {micro}mol mol-1 CO2. Acclimation was assessed using leaf gas exchange, GDC P-protein immunolocalization, M and BS ultrastructure, photosynthetic enzyme activity, and photosynthesis modelling. - Low relative to high growth CO2 enhanced C2-related phenotypes in sub-C2 and C2 species but not C3 or proto-Kranz species. Sub-C2 species positioned chloroplasts closer to mitochondria and had lower modelled BS conductance. C2 species increased rubisco capacity and GDC allocation to the BS. Aspartate aminotransferase activity increased in both sub-C2 and C2 species. - Acclimation to greater photorespiratory conditions strengthens C2 photosynthesis, but only in species whose BS has crossed a threshold of organelle and GDC investment. We hypothesize that acclimation could expose C2-related traits to selection and facilitate the origin of C4 photosynthesis.

Plankton plays a fundamental role in aquatic ecosystems, influencing biogeochemical cycles and serving as a key food source for many organisms. Recent high-throughput imaging technologies enable the rapid acquisition of large volumes of microscopic images, creating new opportunities for monitoring planktonic ecosystems. However, the manual processing and annotation of the vast amounts of data generated by these devices remain time-consuming tasks. In this context, machine learning-based classification models offer a promising solution. In this data paper, we introduce a new labeled freshwater plankton dataset comprising approximately 88,000 images distributed across 43 taxa. We also present the labeling assistance method we used to facilitate dataset annotation. Finally, we present a baseline based on a convolutional neural network (CNN), which achieves a classification accuracy of 93% on our dataset.

The core antenna of the photosystem I (PSI) complex of oxygenic photosynthesis operates at near perfect quantum efficiency, making it one of the most efficient energy conversation devices in nature. The presence of low energy or red chlorophylls (chls) is nearly universal in this core antenna, and these red chls are known to extend the light harvesting capacity and control the rate of energy migration in PSI. Surprisingly, the significance of the structural position of the red chls in PSI remains unknown. In this study, we introduced mutations that generate specific red sites in the PSI core antenna, consistent with those observed in natural species. Using CryoEM, we characterized the structural changes at these red sites. Using transient absorption spectroscopy, we measured the effects of red chlorophyll at specific sites on energy transfer and trapping in PSI to identify their functional significance. While one site funneled energy to the reaction center, the other slowed equilibration in the antenna. These opposing effects indicate different functions are associated with the different red chlorophyll location, reconciling previous seemingly incompatible suggestions as to their functional role.

Protein import across the chloroplast outer membrane is mediated by the TOC complex and regulated by GTP hydrolysis at two receptor GTPases, large and small. The former are the {beta}-barrel-containing Toc159 family of proteins (Sun and Jarvis 2023; H. Li and Chiu 2010; Shi and Theg 2013a; Kessler and Schnell 2009). The smallest member of this family in higher plants is Toc90, which has long been regarded as functionally unimportant due to the absence of obvious phenotypes in early mutant studies (Kubis et al. 2004; Infanger et al. 2011a). It was hypothesised that Toc90 is a relic of an ancestral Toc159 protein from early green lineage organisms (Hofmann and Theg 2003; Reumann et al. 2005). Here, we challenge this view by combining genetic, biochemical, phylogenetic, and in silico structural analyses to show that Toc90 is not an ancient remnant, but rather a neofunctionalised derivative of Toc159, and likely the most recently evolved member of the family. We show that Toc90 physically associates with Toc33 as a part of a photosynthetic TOC complex. Furthermore, we identify Toc90 as a regulator of chloroplast ageing. Our findings redefine Toc90 as an active and specialised component of the chloroplast protein import machinery, playing a pivotal role in senescence, especially in reducing photosynthetic protein abundance. Together, these results highlight Toc90 as a promising target for manipulating chloroplast longevity and plant senescence, with potential to improve crop productivity and yield.

Cyanobacteria are unique among prokaryotes in possessing photosynthetic thylakoid membranes enclosing an internal lumen, where superoxide production is expected to be substantial. Thylakoid-associated superoxide dismutases (SODs) would seem the obvious first line of defense, yet many cyanobacteria rely instead on a single soluble cytoplasmic enzyme, raising the question of what role thylakoid-associated SOD isoforms actually play. Using Cyanothece sp. PCC 7425, which encodes both a cytoplasmic FeSOD and a thylakoid-associated MnSOD, we combined sequence analysis, structural, genetics, and biochemical approaches to characterise FeSOD and MnSOD cellular localisation and assess each enzyme's contribution to superoxide defense. Cyanobacterial MnSODs display diverse N-terminal architectures, consistent with soluble, transmembrane, or lipid-anchored forms, yet contribute only modestly to superoxide defense in Cyanothece PCC 7425 and, very likely, across cyanobacteria broadly. Soluble FeSOD instead provides the major line of defense, showing that thylakoid association does not guarantee physiological importance. This predominance of a cytoplasmic enzyme highlights the central role of cytoplasmic superoxide detoxification, consistent with superoxide being generated mainly at the PSI acceptor side, and extends to the chloroplast stroma of plants. Our findings support a model in which SOD distribution reflects metal availability, enzyme properties, and subcellular organisation : FeSOD protects the compartment harbouring the main targets of PSI-associated superoxide, whereas MnSOD is retained where thylakoid association offers additional local protection, but becomes dispensable when the local ROS burden is limited. Spatial matching between superoxide production, antioxidant localisation, and target vulnerability may thus shape the diversification and maintenance of antioxidant systems across cyanobacteria and chloroplasts.

Sporadically, all plastids produce dynamic tubular extensions in response to myriad stresses. Although the use of fluorescent proteins revealed these transient tubules to be stroma-filled and led to their being called stromules, the mechanism underlying tubule extension from a spheroidal plastid remained unknown. As plastids in viridiplantae have two bounding membranes the fluid stroma remains confined within the inner envelope membrane (IEM) while the outer envelope membrane (OEM) around the IEM forms the interface with the rest of the cytoplasm. Here, using a sucrose treatment for inducing tubules in the dark in transgenic Arabidopsis plants expressing different stroma and OEM-targeted fluorescent proteins we carried out comparative molecular-genetic and lipidomics analyses. Our data strongly suggest that plastid tubule formation occurs due to increase in bilayer-forming galactolipids such as digalactosyldiacylglycerol (DGDG) on the OEM. While the dynamic behaviour of stromules occurs within an external encasing OEM, stresses such as phosphate starvation and high light intensity cause the galactolipid-rich OEM-tubule projecting beyond the stromule to be shed into the cytoplasm. OEM shedding from long tubules with extended plastid outreach into the cell suggests their important role in dispersing plastid-derived, membrane-stabilizing, galactolipids to the rest of the cell to augment its resilience to stress.

{beta}-Cyclocitral ({beta}-cc), a {beta}-carotene oxidation product, has been proposed as an early retrograde signal that primes protection against photooxidative stress. Its temporal relationship with photosynthetic acclimation, however, remains unresolved. Exogenous {beta}-cc elicited cytosolic calcium changes within minutes and induced the {beta}-cc-responsive pAER::LUC detoxification reporter within 40 min. We exposed Arabidopsis thaliana plants to 1500 mol photons m-2 s-1 under ventilation creating a high-irradiance regime without concomitant heat stress and with a relatively mild photooxidative outcome (RT-EL). Non-photochemical quenching increased, whereas PSII maximum quantum yield progressively decreased during RT-EL, with both responses approaching a plateau by 16 h. Volatile {beta}-cc pretreatment did not improve photosynthetic performance or NPQ dynamics, whereas endogenous {beta}-cc and {beta}-cyclocitric acid accumulated only after prolonged RT-EL exposure (16 h). By contrast, hormone profiling and RNA-seq revealed extensive {beta}-cc-dependent reprogramming that was largely opposite to the RT-EL transcriptional response. Together, these results reveal a kinetic separation between rapid {beta}-cc signaling and its endogenous production. Under RT-EL major photosynthetic adjustments precede detectable {beta}-cc accumulation, whereas {beta}-cc triggers cellular responses within minutes once present. We therefore propose that the timing of {beta}-cc action during excess light is determined primarily by the onset of substantial {beta}-carotene oxidation.

Structural model building and refinement need many decisions between different programs. These decisions often depend on an experienced researcher who knows how the programs work together and how to read experimental data. We used Claude Code with Claude Opus 5.5 to supervise this work for 24 cryo-EM and X-ray cases. The work finished in about 36 hours on one workstation. The agent prepared the inputs, ran established programs, read the validation results, compared candidate models and chose the next step. For 15 deposited cryo-EM models with weak starting geometry, the median MolProbity score improved from 2.62 to 1.76. For three crystal structures, the agent models came close to the published Rfree values. Chemical information such as ligands, ions and modifications must be provided by the researcher, in the same way as the sequence. With this information, the agent can place and check these components. These results show that agent supervision is acceptable when every decision can be inspected. The researcher makes the final scientific judgment. We suggest practical requirements for this kind of use. Future AI agents may help researchers obtain high quality and reliable structures of biological macromolecules.

To reduce health risks for human space exploration, it is important to model the effects of deep-space radiation on biological systems. The budding yeast Saccharomyces cerevisiae is a common model organism in space radiobiology, but little is known about how radiation damage to individual cells translates into the population-level effects that experiments measure. The Agent-Based Model for Microbial Populations Exposed to Radiation (AMMPER) is a spatially explicit agent-based model that simulates the effects of ionizing radiation on S. cerevisiae cells and produces population-level results. Its goal is to improve experiment design and data interpretation. AMMPER-1 demonstrated that agent-based simulations can qualitatively reproduce the effects of proton radiation on the growth rate of wild-type and DNA-repair mutant yeast. Here, we present AMMPER-2, which addresses limitations of the first model and expands its capabilities. AMMPER-2 incorporates the dynamics of the redox dye alamarBlue, a data type commonly generated in spaceflight microbiology experiments, and models the fate of reactive oxygen species in more detail. It also adds an improved graphical interface and runs faster. AMMPER-2 remains easy to execute in Python on a standard personal laptop, providing space biologists a tool to explore experimental conditions, generate hypotheses, and interpret data from microbial space radiation experiments.

With a sub-3-micrometer cell and a 27-Mbp diploid genome, the small but mighty Picochlorum celeri doubles within three hours and exceeds 30 g m-2 d-1 outdoors with CO2 supplied. In climate-simulating photobioreactors, productivity declined from 39 g m-2 d-1 under 2.25% CO2 to near zero in air and resumed within hours of CO2 restoration with photosystem II photochemistry largely retained. We profiled the transcriptome, proteome, phosphoproteome, ubiquitinome, acetylome, metabolome and lipidome, including the first site-resolved green-algal ubiquitinome. In air, the Rubisco large subunit tripled to 7.6% of protein while its two small-subunit isoforms, 70% identical, exchanged near-reciprocally, a novel CO2-dependent switch that we propose retunes Rubisco to low CO2. Photorespiratory enzymes increased in abundance whereas proteins involved in external nitrogen assimilation decreased, consistent with increased reliance on internal nitrogen recycling as carbon fixation became limiting. Transcript and protein responses were nearly uncoupled, with cytosolic ribosomal proteins declining despite increased transcripts and plastid ribosomal proteins spared. Phosphorylation was extensively remodeled, as were the lysine modifications ubiquitination, acetylation and CO2-dependent carbamylation, where a CO2-competition assay identified 86 bicarbonate-protected lysines, including RbcL K252. CO2 limitation therefore imposes a reversible growth arrest that reduces cytosolic translational investment while preserving photosynthetic capacity for rapid recovery.

The endonuclear symbiont Holospora obtusa invades the macronucleus of Paramecium caudatum using an infectious-form invasion-tip containing a major 89-kDa periplasmic protein implicated in escape from the host digestive vacuole and macronuclear invasion. Sequence-based analyses placed this protein within a Holospora-specific family and predicted an N-terminal membrane-anchoring module and a long alpha-helical C-terminal region. AlphaFold2 modeling followed by molecular dynamics indicated that the C-terminal region forms an antiparallel, spectrin-repeat-like helical solenoid containing a localized three-helix coiled-coil. The protein exhibits a large pH-dependent charge difference, becoming 55 units more positive at pH 4 than at pH 7. Independent simulations at these pH values differed mainly in the relative orientation of the N-terminal core and C-terminal rod, described by DynDom as an approximately 35 degrees rigid-body rotation about a hinge centered on Gly291. However, none of the nearby glutamates (Glu273, Glu275, and Glu302) formed a pH-dependent salt bridge, and no specific protonation-dependent interaction responsible for the conformational difference was identified. We nonetheless propose, as a testable hypothesis, that acidification of the digestive vacuole may promote this reorientation, thereby repositioning the N-terminal membrane-anchoring module at the bacterial surface as an early step toward escape from the vacuole.

Blooms of the toxic dinoflagellate Ostreopsis cf. ovata can cause respiratory irritation in beach users, yet their environmental drivers and temporal dynamics remain poorly understood. Here, we use a dynamical-systems approach to investigate how environmental conditions shape bloom dynamics from long-term time series of algal abundance and abiotic variables. Using the global modelling framework GPoM, we reconstruct nonlinear ordinary differential equation systems and identify candidate models capable of reproducing key features of the observed dynamics, including chaotic behaviour. Topological and statistical analyses reduce the candidate models to two systems that best capture the observed distributions and dynamical patterns. These models reveal distinct combinations of environmental conditions associated with bloom occurrence and amplitude, providing a framework for interpreting bloom trajectories and a potential basis for short-term prediction.

Drought stress significantly reduces tomato (Solanum lycopersicum L.) productivity, and early detection is critical to minimize yield losses through timely interventions. In this study, we developed Drought-Spec-Net, a hybrid 1D convolutional neural network that integrates local and global spectral feature extraction to detect early drought stress from visible and near infrared (Vis NIR) spectra data of tomato seedlings. The model was trained on 378 samples using an 80:20 train test split, with 20% of the training set reserved for validation. DroughtSpecNet outperformed the evaluated baseline and state of the art models, achieving 97% accuracy, 95% precision, 98% recall, and an F1 score of 97%. To improve the agronomic interpretation of the model outputs, predicted drought probabilities were converted into a literature-informed potential yield impact indicator using a maximum impact level of 60%. On the test set (76 samples), mapped potential yield-impact values ranged from 0% to 60%, with an average reduction of 12.97%. We also conducted an initial experiment using our greenhouse RGB dataset, collected daily from drought treated and well-watered tomato plants at West Virginia State University (WVSU). From this dataset, 44 images were selected for ilastik-based canopy segmentation, producing plant-level drought severity indices (DSI) with a mean of 0.28, median of 0.14, and range of 0.01 to 0.91. Additionally, we trained and fine-tuned a large language model (LLM) based on PLLaMA7BInstruct, called AgriLLaMA, for automated agronomic report generation from Drought-Spec-Net outputs. The generated reports summarize predicted stress levels, mapped potential yield impacts, and preliminary management considerations. This integrated approach not only improves early drought stress detection but also delivers quantitative and interpretable estimates of potential productivity losses, providing a complete framework connecting physiological stress detection to actionable agricultural outcomes.