Physiologia Plantarum

Ensuring food security is one of the main challenges related to a growing global population under climate change conditions. The increasing soil salinity levels, drought, heatwaves, and late chilling severely threaten crops and often co-occur in field conditions. This work aims to provide deeper insight into the impact of single vs combined abiotic stresses at the growth, biochemical and photosynthetic levels in Arabidopsis thaliana L. By studying single and combined stresses, stress interactions and synergic effects have been highlighted. Lower photosynthetic efficiency was recorded from the beginning in all the conditions that included salinity. Consistently, membrane stability and ROS production, combined with a targeted metabolomic quantification of glycine, GABA, proline, and glycine-betaine molecular markers, highlighted the hierarchically stronger impact of salinity and its combinations on plant biochemistry. Untargeted metabolomics coupled with multivariate statistics pointed out distinct metabolic reprogramming triggered by the different stress conditions, either alone or in combination, differentiating the impact of salinity, drought, and their combination with cold and heat. These results contribute to delving into the impact of various stress combinations, hierarchically highlighting the stress-specific effects and pointing out different interactions. HIGHLIGHTSCombined stresses highlighted synergic and stronger impact on Arabidopsis secondary metabolism, redox imbalance and photosynthetic performance compared to individual stresses. Overall, salinity and its combination were the most impactful.

Molecular adaptations are prevalent in carnivorous plants in response to habitat and environmental stress. We used the chloroplast genome and characterized the specific adaptations in the photosystem genes and their interacting partners in Nepenthes khasiana, a carnivorous pitcher plant. When compared with the carnivorous and non-carnivorous groups across Caryophyllales, Lamiales, Poales, Ericales, and Oxalidales, we found Nepenthes-specific changes in psaA, psaB, psaC and psaH. Of these, only a single amino acid change each, G147 in the protein psaA and R40 in the protein ndhD, impacted the three-dimensional structural conformation of the corresponding proteins. Modeling the interaction between the psaA and the ndhD proteins identified group-specific changes between the models between Nepentheceae versus others. The least distance between the structure-impacting residues of psaA and ndhD was 25.9 [A] for Nepenthes and 19.4 [A] for non-Nepenthes models. Given that the chloroplast ndh and photosystem I subunits form a large super-complex with the light-harvesting carrier proteins from the nucleus to mediate cyclic electron transport, our observations may indicate specific adaptations in the cyclic electron transport arm of the photosynthetic machinery in the Nepenthes species.

More than 70% of lands cultivated area is affected by alkaline salinity stress. As 98% of plants are glycophytes - unable to successfully reproduce under salinity - our previous research focused on comparative studies of Arabidopsis thaliana demes with differential performance under neutral and alkaline salinity (neuSAL and alkSAL) due to local adaptation processes. Here, an integrated analysis on leaf tissue was performed, including physiological indicators, nutritional status, endogenous phytohormonal concentration and transcriptome profiling, to further understand differences in molecular mechanisms underlying neuSAL and alkSAL responses. The results support that alkSAL is more detrimental to plant performance than neuSAL and indicate higher sensitivity to alkSAL in demes locally adapted to coastal siliceous soils. A decreased internal Fe use efficiency in coastal demes under alkSAL is proposed to be the driver of their enhanced sensitivity, and sequence variation at {beta}-CA1 and -CA1 locus is hypothesized to contribute to the imbalance of Fe homeostasis. Dissection on the down-regulated transcripts shared by neuSAL and alkSAL confirmed enhanced inhibition of central features on primary and secondary metabolism in coastal individuals under alkSAL. The cell wall and vacuolar {beta}-galactosidase BGAL4 was revealed as a candidate for conferring tolerance to neuSAL by favoring stress-regulated cell wall rearrangement, but not to alkSAL, probably due to pH-restricted enzymatic activity. In addition, differential modulation of endogenous phytohormonal cues was reported among salinity types and demes, by which higher alteration of the auxinic, ethylene and jasmonic acid signaling pathways was exerted by alkSAL but sustained ABA biosynthesis was detected only in coastal plants under neuSAL. Weighted correlation network analysis (WGCNA) confirmed the involvement of the identified candidate genes in co-expression modules significantly correlating with favorable responses to neuSAL and alkSAL. Overall, the present study provides useful insights into key targets for breeding improvement in alkaline saline soils.

To adapt to the change of intertidal environment, intertidal macroalgae have evolved complicated Ci utilization mechanism. However, our knowledge regarding the CO2 concentrating mechanism (CCM) of macroalgae is limited. Carbonic anhydrase (CA), a key component of CCM, plays important roles in many physiological reactions in various organisms. While there are a large number of genes encoding CA in the Pyropia yezoensis genome, the exact function of specific CA in P. yezoensis remains elusive. To explore the specific function of chloroplast CA in intertidal macroalgae, we produced chloroplast-localized {beta}CA1 knockdown mutants of P. yezoensis through RNA interference, and Pyca1i mutants showed a notable decrease in leaf area and overall biomass, as well as decreased soluble protein and unsaturated fatty acid content under different DIC conditions. However, Pyca1i mutants showed relatively higher starch content compared to the wild-type. The activity of enzymes involved in Calvin cycle, photorespiration, Pentose-phosphate pathway and floridean starch synthesis of P.yezoensis indicated an effective starch accumulation pathway after interference of {beta}CA1. All results suggest that the decreased activity of Py{beta}CA1 impaired the CCM and development of thalli of P.yezoensis, but stimulated starch accumulation in the cytoplasm through feedback to the photorespiration pathway and PP pathway to replenish intermediates for the Calvin cycle. This study is the first to explore the specific function of chloroplast CA in intertidal macroalgae using genomic technology. The results provide valuable insights into the adaption mechanisms of intertidal macroalgae to their environment.

To increase the nutritional value of forage, transgenic ryegrass known as High Metabolizable Energy (HME) were previously generated that co-express cysteine-oleosin and diacylglycerol O-acyltransferase. HME not only accumulate lipids in the leaf but also has elevated CO2 assimilation and increased biomass. Shading is one of the most influencing factors for ryegrass growth environments particularly in swards. The aim of this study, therefore, was to determine the influence of irradiance levels on photosynthesis and gene expression in the HME leaves when compared with their corresponding non-transformant (NT). Under low light (150-250 {micro}mol m-2 s-1) and standard light (600-1000 {micro}mol m-2 s-1), the HME accumulated more lipid than NT. The previously reported elevated photosynthesis and increased biomass was observed when the HME were grown under standard light but not under low light. Under both light conditions, compared to NT, the HME had upregulated a number of transcripts involved in lipid metabolism, light capturing, photosynthesis, and sugar signalling network while downregulated genes participated in sugar and fructan biosynthesis. We further discuss how the HME differentially manipulated several genes other metabolic pathways including maintenance of redox homeostasis. Combined, the data suggests that the increased photosynthesis capacity in the HME likely corresponds to an increase of micro-lipid sink strength; these are influenced by available light energy and may be related to diffusional and biochemical activities of stomata. Overall, this work provides a clearly understanding of the changes in molecular and biochemical mechanisms underlying the carbon storing as leaf lipid sink of the HME ryegrass. One sentence summaryShading led to increase leaf lipid accumulation but limit the greater photosynthesis trait of high lipid ryegrass which may be related to limitation of biochemical activities of stomata.

Vitis vinifera, also known as grapevine, is widely cultivated and commercialized, particularly to produce wine. As wine quality is directly linked to fruit quality, studying grapevine metabolism is important to understand the processes underlying grape composition. Genome-scale metabolic models (GSMMs) have been used for the study of plant metabolism and advances have been made, allowing the integration of omics datasets with GSMMs. On the other hand, Machine learning (ML) has been used to analyze omics data, and while the combination of ML with GSMMs has shown promising results, it is still scarcely used to study plants. Here, the first GSSM of V. vinifera was reconstructed and validated, comprising 7199 genes, 5399 reactions, and 5141 metabolites across 8 compartments. Tissue-specific models for stem, leaf, and berry of the Cabernet Sauvignon cultivar were generated from the original model, through the integration of RNA-Seq data. These models have been merged into diel multi-tissue models to study the interactions between tissues at light and dark phases. The potential of combining ML with GSMMs was explored by using ML to analyze the fluxomics data generated by green and mature grape GSMMs, helping to understand the factors influencing grape quality at different developmental stages.

Low CO2 condition was considered a preconditioning or selection pressure for C4 evolution. However, it remains elucidated how low CO2 condition contribute to the evolutionary assembly of the C4 pathway. We conducted a systematic transcriptomics and metabolomics analysis under short-term low CO2 condition and found that Arabidopsis grown under this condition showed increased expression of most genes encoding C4- related enzymes and transporters. Low CO2 condition increased NH4+ content in leaves; as expected, photorespiratory and ammonia refixing pathways were enhanced. Furthermore, we found that compared to low CO2 condition, in vitro treatment with NH4+ induced a similar pattern of changes in C4 related genes and genes involved in ammonia refixation. This supports that increased expression of C4 genes induced by low CO2 condition can supply carbon skeleton for ammonia recycling. This study provides new insight into the regulatory preconditioning which may have facilitated the evolution of C4 photosynthesis under low atmospheric CO2 environments.

WITHDRAWAL STATEMENTThe authors have withdrawn their manuscript because of the necessary revisions to the manuscript that may reorient the study findings. Its publication will be possible only after the peer review process in a scientific journal. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author

Understanding comprehensive mechanisms of the downregulation of photosynthesis induced by accumulation of non-structural carbohydrates (NSCs) is essential for the future food security.x Despite numerous studies, whether NSCs accumulation directly affects steady-state maximum photosynthesis and photosynthetic induction, as well as underlying gene expression profiles, remains unknown so far. We evaluated the relationship between photosynthetic capacity and NSCs accumulation induced by cold-girdling, sucrose feeding, and low nitrogen treatment in Glycine max and Phaseolus vulgaris. In G. max, changes in transcriptome profiles were further investigated focusing on physiological processes of photosynthesis and NSCs accumulation. NSCs accumulation decreased maximum photosynthetic capacity and delayed photosynthetic induction in both species. In G. max, such photosynthetic downregulation was explained by coordinated downregulation of photosynthetic genes involved in Calvin cycle, Rubisco activase, photochemical reactions, and stomatal opening. Furthermore, sink-source imbalance may have triggered a change in the balance of sugar-phosphate translocators in chloroplast membranes, which may have promoted starch accumulation in chloroplasts. Our findings provided an overall picture of the photosynthetic downregulation and NSCs accumulation in G. max, demonstrating that the photosynthetic downregulation is triggered by NSCs accumulation and cannot be explained simply by N deficiency. One Sentence SummaryAccumulation of nonstructural carbohydrates directly induced both downregulation and delayed induction of photosynthesis by coordinated transcriptomic changes in photosynthetic genes in Glycine max.

O_LINitrous oxide (N2O) substantially contributes to climate change and stratospheric ozone degradation, yet large uncertainties in its global budget indicate unknown or overlooked sources. Increasing evidence suggests that plants may also produce N2O, though the underlying mechanisms and pathways remain poorly constrained. C_LIO_LITo examine whether plants can form N2O under sterile conditions and to assess the contribution of different plant parts, we applied a novel 15N stable isotope labelling approach using sterile Cichorium intybus root and shoot cultures incubated separately under light and dark conditions. C_LIO_LIAll root/shoot cultures showed N2O formation under dark conditions, whereas shoots under light showed reduced or even uptake of N2O, indicating photosynthetically driven suppression of formation pathways or simultaneous internal degradation of N2O. C_LIO_LIIsotopic analyses revealed distinct formation pathways: roots supplemented with 15NO3- showed position-specific 15N enrichment consistent with N2O formation via nitric oxide as an intermediate, linking root-derived N2O to NO3- reduction. In contrast, root/shoot incubations with 15N-NH4+ supplementation and shoots in darkness emitted N O without clear 15N enrichment suggesting alternative formation pathways independent of these compounds. Our isotopic labelling approach powerfully disentangled N2O formation mechanisms yet highlights necessary further exploration of plant N2O cycling to improve global budgets and enable potential mitigation strategies. C_LI

Elevated CO2 (E[CO2]) improves the biomass and yield when combined with water-stress in C4 plants. Although several studies described the molecular response of the C4 plant Sorghum bicolor during drought exposure, none reported its combinatorial effect with E[CO2] in the roots. We decided to perform a molecular analysis using green prop roots, the portion of the radicular system photosynthetically active and more sensible to drought. Whole-transcriptome analysis identified 394 up- and 1,471 down-regulated genes. Among the E[CO2] induced pathways, photosynthesis stood out. Carbon fixation, phenylpropanoid, phenolic compounds, and fatty acid biosynthesis-related pathways were repressed. Protein family analysis showed induction of chlorophyll a-b binding protein family, and repression of glutathione-related enzymes. Protein-protein interaction networks exhibited well-defined clusters, including genes related to cell organization and biogenesis, oxi-reduction process, and photosynthesis being induced. The findings suggest that the E[CO2] mitigates the water deficit by antioxidant and osmoregulation activity, as well as by accumulation of sugar-alcohols in the green prop roots, which may be responsible by the increase in biomass together with the cell proliferation. The higher carbon uptake explains the increase in photosynthetic and primary metabolism activities. Our data revealed that green prop roots present an intriguing metabolism under water deficit and E[CO2], showing its crucial role in the drought tolerance acquisition in a predicted future global atmosphere.

Calcium is the most common secondary messenger of the plant signal transduction mechanism. The Calcium-dependent protein kinases (CDPKs), a plant multi-gene family protein, act as sensors of calcium ion concentration inside plant cells. CDPKs convert variations in calcium concentration into a signal and phosphorylate various proteins that translate calcium signals into physiological reactions. Aquilaria agallocha is an aromatically important crop due to the production of valuable fragrant resinous agarwood in their heartwood. The trees produce agarwood when wounded and exposed to biotic and abiotic stresses. CDPKs are essential in plant development and growth, biotic and abiotic stress responses, and phytohormone-mediated signalling pathways. A comprehensive investigation of the stress-combating gene family (CDPK) in the A. agallocha genome is currently lacking. In this work, we used a bioinformatics approach to examine the entire genome of A. agallocha and identified 24 CDPK genes. According to the molecular phylogenetic relationships, the putative AaCDPKs are grouped into four groups. Synteny analysis identified a few conserved segments (orthologous genes) between A. agallocha and Arabidopsis thaliana (eight pairs), A. sinensis (twenty pairs), Glycine max (sixteen pairs), Solanum tuberosum (five pairs), and Vitis vinifera (ten pairs). Duplication analysis of AaCDPK genes indicated that dispersed duplications significantly contributed to the expansion of the CDPK gene family of A. agallocha. The observed AaCDPK-RBOH interaction within the protein interaction network suggests that this interaction may be crucial in integrating Ca2+ and ROS signaling pathways. RNA-seq data analysis shows differential expression of seven putative AaCDPK genes in agarwood tissue. qRT-PCR analysis revealed that six out of ten selected AaCDPK genes exhibited altered expression levels in response to MeJA, H2O2, and CaCl2 treatments. Integrated promoter analysis, PPI data, and in silico gene expression validated with qRT-PCR-analysis collectively suggest the role of CDPK-RBOH as a signalling molecule in initiating phytohormone-mediated agarwood resin formation. This study provides a strong foundation for future investigations into the study of functional roles and regulatory mechanisms of AaCDPK genes in sesquiterpene biosynthesis and agarwood formation.

The response of photosynthetic CO2 assimilation to changes of illumination affects plant growth and crop productivity under natural fluctuating light conditions. However, the effects of nitrogen (N) supply on photosynthetic physiology after transition from low to high light are seldom studied. To elucidate this, we measured gas exchange and chlorophyll fluorescence under fluctuating light in tomato (Solanum lycopersicum) seedlings grown with different N conditions. After transition from low to high light, the induction speeds of net CO2 assimilation (AN), stomatal conductance (gs) and mesophyll conductance (gm) delayed with the decline in leaf N content. The times to reach 90% of maximum AN, gs and gm were negatively correlated to leaf N content. This delayed photosynthetic induction in plants grown under low N concentration was mainly caused by the slow induction response of gm rather than that of gs. Furthermore, the photosynthetic induction upon transfer from low to high light was hardly limited by photosynthetic electron flow. These results indicate that decreased leaf N content declines carbon gain under fluctuating light in tomato. Increasing the induction kinetics of gm has the potential to enhance the carbon gain of field crops grown in infertile soil.

IntroductionPutrescine, a polyamine involved in plant growth and stress responses, has shown potential in mitigating abiotic stress effects. However, little is known about the exogenous addition of putrescine regarding salt tolerance in trees. MethodsThis study was conducted to investigate whether exogenous putrescine application via foliar spray enhances growth in a hybrid poplar (Populus nigra x maximowiczii, clone NM6) under a short duration of salt stress. Salt stress was induced by irrigating roots with 100 mM and 200 mM NaCl, followed by foliar spraying of putrescine on several days. Measurement of growth including plant height and stem diameter for each plant were recorded in the greenhouse every 15 days throughout the experiment. Gas exchange, total chlorophyll, carotenoids, soluble sugars and proteins, amino acids, polyamines, and relative water content were analyzed in foliage collected 3, 6, 7, 13, 20, 35 days after treatment. ResultsPutrescine spray on the salt-treated plants caused a significant increase in plant growth. Putrescine application caused a significant increase in fructose, glucose, and galactose in all plants, but putrescine spray had a variable impact on the sucrose content of 100 mM NaCl-treated plants. Based on metabolic responses, plants treated with 100 mM NaCl fared better when sprayed with putrescine than those treated with 200 mM NaCl. DiscussionExogenous application of putrescine mitigated growth inhibition effects of salinity. These finding highlight the potential of putrescine as a practical approach to increase salt tolerance in young poplar trees, with implications for forestry and land reclamation in saline environment.

Background and AimsLight plays a dual role in plants, serving as both an energy source and a regulator of development from seedling to senescence. Recently, far-red (FR) radiation has gained attention in the controlled environment agriculture (CEA) science and grower community for its potential to enhance yield through canopy expansion and improved light capture, contributing positively to photosynthesis. This study explores how supplemental FR light promotes lettuce growth and morphology across weekly intervals as well as analyzing photosynthetic parameters, pigment accumulation, and anthocyanin gene expression. MethodsRed leaf lettuce (Lactuca sativa Red Fire) was grown in a commercial plant factory with artificial light for six weeks. 5000K white (W) light was maintained at 300 mol m-2 s-1, and FR, when supplemented, was added at 100 mol m-2 s-1 in addition to the 300 mol m-2 s-1 of W light. Four lighting treatments were tested under a 16 h photoperiod: (1) W for all 6 weeks ("W"), (2) 4 weeks of W followed by 2 weeks of supplemental FR ("W to W+FR"), (3) 4 weeks of FR supplementation followed by 2 weeks of only W ("W+FR to W"), and (4) W+FR for all 6 weeks ("W+FR"). Key ResultsThe shoot dry weight after 6 weeks in "W+FR", "W+FR to W" and "W to W+FR" was greater than "W". Both "W+FR" and "W+FR to W" showed a tendency for greater canopy expansion compared to "W" as well as "W to W+FR". There were no significant differences in stomatal conductance among the treatments. On the other hand, in both "W" and "W+FR to W" plants, CO2 assimilation rates were enhanced when FR light was supplemented during measurement, compared to when FR was not provided. Anthocyanin accumulation was greater in both "W" and "W+FR to W", consistent with the expression of key genes involved in the anthocyanin biosynthesis pathway, including anthocyanin synthase (ANS), flavanone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR). ConclusionsThis study demonstrates that FR supplementation during the early growth stages of lettuce promotes biomass accumulation by enhancing both canopy expansion and photosynthetic activity, while maintaining high levels of functional compounds such as anthocyanins.

Plants are highly sensitive to changes in the light environment and respond to alternating light conditions by coordinated adjustments in foliar gene expression and metabolism. Here we assessed how long-term growth under high irradiance and elevated temperature, a scenario increasingly associated with the climate change, affects foliar chemical composition of Brassicaceous plants. Transcript profiling of Arabidopsis suggested up-regulation of phenylpropanoid metabolism and down-regulation of processes related to biotic stress resistance and indole glucosinolates (GSL). These observations prompted metabolite profiling of purple (Black Magic) and pale green (Half Tall) varieties of kale, an economically important crop species. Long-term acclimation to high light and elevated temperature resulted in reduced levels of 4-methoxy-indol-3-yl-methyl GSL in both kale varieties. The total levels of aliphatic GSLs increased under these conditions, although the profiles of individual GSL structures showed cultivar-dependent differences. Black Magic became rich in 4-methylsulfinylbutyl GSL and 2-phenylethyl GSL, which have health-promoting effects in human diet. Additionally, the purple pigmentation of Black Magic became intensified due to increased accumulation anthocyanins, especially derivatives of cyanidin. These findings demonstrate that the potentially stressful combination of high light and elevated temperature can have beneficial effects on the accumulation of health-promoting metabolites in leafy vegetables.

The fast climate change affects yield in Vigna mungo via enhancing both biotic and abiotic stresses. Out of all factors, the yellow mosaic disease has the most damaging effect. However, due to lack of reference genome of Vigna mungo, the complete mechanism associated with MYMIV (Mungbean Yellow Mosaic Indian Virus) resistance in Vigna mungo remain elusive to date. Considering this, the authors made an attempt to release new transcriptome and its annotation by employing computational approaches. Quality assessment of the generated transcriptomes reveals that it successfully aligned with 99.03% of the raw reads and hence can be employed for future research. Functional annotation of the transcriptome reveals that 31% and [~]14% of the total transcripts encode lncRNAs and protein-coding sequences, respectively. Further, analysis reveals that, out of total transcripts, only 4536 and 78808 are significantly down and up-regulated during MYMIV infection in Vigna mungo, respectively. These significant transcripts are mainly associated with ribosome, spliceosome, glycolysis /gluconeogenesis, RNA transport, oxidative phosphorylation, protein processing in the endoplasmic reticulum, MAPK signaling pathway - plant, methionine and cysteine metabolism, purine metabolism and RNA degradation. Unlike the previous study, this is for the first time, the present study identified these pathways may play key role in MYMIV resistance in Vigna mungo. Thus, information and transcriptomes data available in the present study make a significant contribution to understanding the genomic structure of Vigna mungo, enabling future analyses as well as downstream applications of gene expression, sequence evolution, and genome annotation.

The relationship between nitrogen (N) sources and photosynthetic capacity of leaf differs between species. However, the leaf anatomical variabilities related to photosynthesis (A) of shrubs under different forms of N remain imperfectly known. Here, Lonicera Japonica (a shrub) was grown hydroponically in the presence of three forms of N (sole NH4+, 50%/50% NH4+/NO3- and sole NO3-). A and photosynthetic N use efficiency significantly decreased under sole NH4+ supply, in parallel with down-regulated stomatal conductance (gs), mesophyll conductance (gm), and electron transfer rate (J). Up to the total A decline of 41.28% in sole NH4+ supply (compare with sole NO3-), the gm attributed to 60.3% of the total limitations. Besides, the decreased internal air space explained the increase of gas-phase resistance, and the increased liquid-phase resistance in sole NH4+ supply was ascribed to the thicker cell wall thickness (Tcw) and decreased chloroplasts exposed surface area per unit leaf area (Sc/S). The discrepancy of Sc/S could be interpreted by the altered chloroplasts numbers and the distance between adjacent chloroplasts (Dchl-chl). These results indicate the alteration of Tcw and chloroplast numbers were the main causes of the difference in gm in coping with varied N sources. HighlightCell wall and chloroplast variability determining the mesophyll conductance under different nitrogen forms

Cold waves restrict the distribution of mangroves. This study examined the contribution of PSII heterogeneity and stomatal functioning to sustaining photochemistry and photoprotection in mangroves during a cold wave. We exposed eight populations of Kandelia obovata (cold-tolerant) and, Bruguiera gymnorhiza (cold-susceptible) from different latitudes to 27/20{degrees}C (favorable) and 10/3{degrees}C (chilling; simulated cold wave) day and night temperatures. Multiple trait responses imply that cold waves affected K. obovata the least. Significant changes in chlorophyll fluorescence transients (photosystem II [PSII]) with a slight decrease in the redox status of P700 (photosystem I [PSI]) imply a greater impact of a cold wave on PSII. During the cold wave, photochemical efficiency of PSII, efficiency of the water-splitting complex, light absorptance, stomatal pore area, cyclic electron flow, nonphotochemical quenching, and number of active PSII and PSII QB reducing centers decreased, while light transmittance, night respiration, and inactive PSII QB nonreducing, PSII{beta}, and {gamma} centers increased in both species. The population of K. obovata from the coldest latitudinal site (Fujian, China) was least affected by cold wave due to local evolutionary adaptations. Modulation of PSII heterogeneity and stomatal functioning is important to sustaining photochemistry and photoprotection in mangroves to cope with cold waves. HighlightsPSII heterogeneity and stomatal functioning support mangroves to cope with cold waves. Local evolutionary adaptations promote the cold tolerance of mangrove populations.

Duckweeds are free-floating aquatic organisms with species ranging from 2 mm-10 mm, where each plant is a single leaflike structure. Recognized as an emerging food crop, their fast growth rates offer potential for cultivation in closed systemsHowever the majority of available duckweed clones lack information regarding habitat origin and physiology. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats and profiled for growth, photosynthesis and photoprotection (Non Photochemical Quenching, NPQ) responses. Multiple ecotypes of three Lemna species and one ecotype of Spirodela polyrhiza, were grown under low light (LL:100 mol m-2 s-1) and high light (HL:350 mol m-2 s-1). We found species and ecotypic variation in photosynthesis acclimation. Duckweeds grown under HL exhibited lower growth rate, biomass, chlorophyll and quantum yield of photosynthesis. In HL-compared to LL, carotenoid de-epoxidation state and NPQ were higher whilst photosystem II efficiency ({phi}PSII) and chla:b ratios were unchanged. Interestingly dLL plants showed relatively stronger acclimation to HL compared to dHL plants: These ecotypes achieved faster growth in HL: by area and colony gain, higher carotenoid levels and less degradation of chlorophyll. We conclude that adaptation to local habitat among ecotypes strongly affects performance under controlled conditions.