Freezing events during winter and spring represent a primary constraint for Citrus production in cold-prone regions such as North Florida, often resulting in tree mortality and significant yield losses. Therefore, the screening of new Citrus scion selections is essential to identify cold-tolerant varieties. This study used chlorophyll fluorescence imaging and kinetic fluorescence analyses to phenotype nine new Citrus selections, including seedless mandarin hybrids (5 scions), seedless red grapefruit-like hybrids (2 scions), seedless lemon hybrid (1 scion), and dark red grapefruit (1 scion) grafted onto the cold-tolerant rootstock UFR-5. Plants were subjected to controlled freezing at − 4 °C for 2 h. Compared to non-treated plants, freezing induced heterogeneous photoinhibition across leaf surfaces in most scions (Fv/Fm < 0.8), while one of the scions evaluated maintained higher photosystem II efficiency. Among the 29 chlorophyll fluorescence parameters evaluated, five exhibited the highest sensitivity for discriminating photochemical changes induced by freezing in Citrus scions: ET0/RC, SS, and PhiE0 (electron transport-related parameters), Vi (relative variable fluorescence at the I-step), and DI0/RC (energy dissipation per reaction center). Three Citrus scions exhibited enhanced electron transport and elevated heat dissipation as photoprotective mechanisms, correlating with reduced cellular electrolyte leakage, low freezing damage, and high survival rates. In contrast, freezing-sensitive scions showed greater physiological impairment and low recovery (25
Metal contamination, particularly by copper (Cu) and lead (Pb), is a persistent environmental threat, yet the adaptive responses of Neotropical bryophytes to such stressors remain largely unexplored. This study evaluated biomass production, photosynthetic performance, and metal accumulation in two native Brazilian mosses (Campylopus savannarum (Müll.Hal.) Mitt. and Polytrichum juniperinum Willd. ex Hedw.) exposed to increasing concentrations of Cu and Pb under controlled laboratory conditions. We hypothesized that their contrasting morpho-anatomical traits, especially differences in lamellae structure, photosynthetic surface organization, and the presence of conduction tissues, would lead to distinct physiological strategies of metal tolerance. At the end of 240 days, biomass and maximum quantum efficiency of PSII (Fv/Fm) were assessed, and tissue metal concentrations were quantified. The moss P. juniperinum exhibited remarkable tolerance, maintaining stable biomass and photosynthetic capacity across all treatments, while C. savannarum presented pronounced declines, especially under high Pb exposure. Both species displayed dose-dependent metal accumulation but with distinct patterns: C. savannarum accumulated nearly 196-fold more Cu at the highest treatment compared to the control, whereas P. juniperinum stored about 44-fold more Pb than the control. These contrasting responses likely reflect species-specific strategies of metal tolerance. These results position Neotropical mosses as valuable bioindicators and potential agents for generating genomic data to improve our understanding of metal tolerance in bryophytes. Future research should investigate tissue-concentration metal partitioning and the molecular mechanisms underlying tolerance in native Brazilian bryophytes.
Tree seedlings play a key role in the conservation and regeneration of local diversity, are essential for the functioning of forest ecosystems and are more susceptible to environmental changes than adult trees due to their lower metabolic reserve and photosynthetic production capacity. To investigate the responses of young plants (seedlings, saplings, juveniles, and young) of different geographical origin to temperature increases, we conducted a systematic review and meta-analysis of experiments published until the last decade of temperature on young woody plants. We investigated the effects of rising temperatures on several leaf traits related to carbon balance, such as stomatal conductance, quantum efficiency of photosystem II, leaf mass per area, and others, in 62 species across 39 papers. Few studies have investigated internal and atmospheric carbon ratio, electron transport rate and maximum Rubisco carboxylation rate indicating a significant knowledge gap that necessitates additional data collection. There was a consistent pattern of acclimation in photosynthetic rate response to warming and an increase in dark respiration and photorespiration, disrupting the carbon balance and potentially affecting the growth and survival of young trees. Our results suggest that young plants exposed to warming may increase in photorespiration, as indicated by the rapid increase in the internal and atmospheric carbon ratio and the decline in maximum Rubisco carboxylation rate with increasing temperature. This evidence suggests that the increase in temperature could affect young plant growth and pose a challenge to forest regeneration in a warming world.
Climate change and increasing water scarcity are major threats to coffee production, particularly during the flowering phase of Coffea arabica L., which determines yield and bean quality. Drought and irregular rainfall can impair floral development, yet the underlying transcriptional and metabolic mechanisms remain poorly understood. This study analyzed flower buds of C. arabica “Catuaí Vermelho” grown under irrigated and non-irrigated conditions to identify differentially expressed genes (DEGs) and assess transcriptional variation across apical, medial, and basal branch positions. RNA sequencing was performed on the Illumina HiSeq platform, and the data were processed using the Galaxy pipeline. Under non-irrigated (drought) conditions, flowers upregulated genes, including nsLTP14 (non-specific lipid transfer protein); in contrast, irrigated flowers exhibited higher expression of selected biosynthetic transcripts (e.g., TPS [Terpene Sinthases] and LOX [Lipoxygenase] isoforms) associated with constitutive aroma outputs, as well as nsLTP, LEA6-like (Late Embryogenesis Abundant) and KIN2-like (Kinase) proteins. Metabolomic profiling of floral volatiles revealed differential accumulation of linalool, methyl salicylate, and hexanal, compounds involved in both aroma and drought signaling. Correlation analyses demonstrated coordinated regulation between the expression of biosynthetic genes and metabolite abundance, highlighting an integrated molecular response to water availability. Overall, this integrative omics approach provides new insight into how coffee flowers transcriptionally and metabolically adjust to drought, identifying key genes and volatiles that may support breeding strategies aimed at enhancing drought resilience while preserving floral and cup quality.
Global climate change has led to increased frequency and severity of high-temperature, posing a substantial risk to agricultural productivity worldwide. As a primary abiotic stress factor, heat stress (HS) impairs critical physiological processes in plants, ultimately reducing crop yield and quality. Addressing these challenges requires a comprehensive understanding of HS response mechanisms and the development of thermotolerant crop varieties. Heat shock proteins (HSPs) act as molecular chaperones in plants, maintaining protein folding and stability under HS. HSPs are essential for protecting plants from thermal injury by preventing protein denaturation. Moreover, HSPs reduce reactive oxygen species accumulation, which helps mitigate cellular damage and maintain cellular homeostasis. The compartment-specific functions of HSPs across different cellular organelles are also investigated to provide insight into their spatial dynamics during heat treatment. Notably, HSPs mediate thermomemory through specific histone modifications and chromatin remodeling, enabling sustained transcriptional activation of HSPs during recurrent HS in plants. In addition, HSPs enhance thermotolerance by modulating hormone biosynthesis, transport, and signaling pathways. This review synthesizes current knowledge on HSP-mediated thermotolerance mechanisms and explores their potential applications in breeding strategies to enhance crop resilience under global warming scenarios.
Recent proposals that plants could be engineered to function as large-scale climatic “thermostats” reflect growing confidence in molecular biology, genomics, and synthetic approaches to environmental problem-solving. While technologically ambitious, such visions rest on mechanistic assumptions about biological control, predictability, and causal hierarchy that are poorly aligned with contemporary understanding of plant organization. Here we argue that plants are not centrally regulated devices but decentralized, modular, and historically contingent systems whose behavior emerges from multilevel interactions across developmental, physiological, ecological, and temporal scales. Drawing on concepts from systems biology, process ontology, and circular causation, we examine how emergent organization, phenotypic plasticity, epigenetic regulation, and stress memory constrain the predictability of molecular interventions. We further discuss how extrapolations from gene-level engineering to agricultural or planetary outcomes overlook systemic socio-ecological and biogeochemical constraints governing food security and climate regulation. Engineering strategies that treat plants as programmable components of global control architectures risk overestimating biological leverage while underestimating ecological complexity and scale dependence. Rather than rejecting molecular tools, we advocate embedding them within conceptual frameworks that acknowledge reciprocity across levels, historical contingency, and environmental embeddedness. Replacing metaphors of centralized control with systemic perspectives offers a more realistic basis for evaluating the role of plant science in addressing global challenges.
The morphophysiological, biochemical and molecular-genetic mechanisms of resistance of Amaranthus retroflexus (C4-NAD-ME) to moderate exposure to the following factors: drought (φ = − 0.3 MPa) and elevated temperature (eT, 35 ± 2 °C) at ambient (400 ppm) and elevated CO2 concentrations (eCO2, 800 ppm), were studied. The parameters of growth, water–salt metabolism, osmotic and oxidative imbalance, CO2/H2O gas exchange, the PSI and II efficiency, the expression of genes encoding components of electron transport chain (psaA, B, psbA, PGR5, PnsB5, FDI, FDII, FNR1) and dark CO2 fixation (rbcL, RbcS, Ppc1, 2, PPDK), and the concentration of the key carboxylation enzymes ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) were measured. Amaranthus retroflexus demonstrated drought and heat tolerance mediated by a complex adaptive response involving both the light and dark stages of photosynthesis and an antioxidant complex. Our findings indicate a specific response of A. retroflexus to all studied factors, except drought: increased expression of the PnsB5 gene, associated with NDH-dependent cyclic electron transport (CET) pathway of PSI, which supplies additional ATP for C4-NAD carbon concentrating mechanism (CCM). The greatest negative impact, leading to reduced growth, was caused by the combined effect of elevated temperature and drought, as well as the simultaneous presence of all three factors. Under these conditions, upregulation of genes in both CET PSI pathways was observed. The synergistic effect, namely an increase in growth (37
The colonization of new spaces in post-fire environments depends on habitat availability and the capacity of these environments to provide suitable microclimatic conditions for germination. Furthermore, the persistence of non-dormant woody species in fire-prone environments is influenced by the effects of fire passage on their seed germination. Thus, we investigated the effects of heat shocks on the imbibition and germination of Vochysia tucanorum Mart. (Vochysiaceae) seeds under temperature fluctuations simulating post-fire conditions in the cerrado sensu stricto. The seeds tolerated the applied heat shock without compromising the evaluated parameters, indicating that 70 °C for 5 min neither affected seed imbibition nor seed germination under temperature fluctuations. This ensures seed survival and germination in post-fire environments. Thus, this study provides new insights to evaluate persistence in other non-dormant species in post-fire environments.
Cowpea severe mosaic virus (CPSMV) represents a major constraint for cowpea (Vigna unguiculata (L.) Walp.) cultivation. However, the metabolic basis underlying CPSMV resistance remains poorly understood. Given the importance of metabolism for plant defence against pathogens, we hypothesized that cowpea resistance to CPSMV is associated to the activation of defence-related pathways from both primary and secondary metabolisms. We investigated the metabolic dynamics associated with CPSMV infection in the resistant cowpea genotype Macaibo using a time-resolved, network-based metabolomics approach. Conventional RT-PCR suggests that the intensity of the CPSMV coat protein band increased in the first eight Hours After CPSMV Inoculation (HAI) but appeared reduced in the following 72 HAI. Metabolomic analyses revealed that CPSMV infection had little impact on secondary metabolism, whereas several primary metabolites were significantly altered over time. Transient increases in fumarate, pyruvate, and several amino acids, including alanine, asparagine, glutamine, glutamate, isoleucine, leucine, proline, serine, threonine, and valine, were observed at 48 HAI compared with mock-treated leaves. Network analysis indicated that overall metabolic network density and heterogeneity remained relatively stable during infection. However, a highly connected metabolic module composed of the branched-chain amino acids (BCAAs) isoleucine, leucine, and valine emerged in infected leaves. Our results indicate that CPSMV infection reshapes primary metabolic dynamics without extensive alterations in secondary metabolism during early infection in cowpea leaves. Despite these metabolic adjustments, the overall metabolic network structure remained stable, suggesting that a robust metabolic reprograming, including the activation of BCAA-associated pathways, may help buffer viral perturbation in cowpea leaves.
We evaluated the impact of acute ozone (O3) on photosynthesis of energy cane and sugarcane, hypothesizing that energy cane –known for its resilience to environmental disturbances– would exhibit higher tolerance to O3 than sugarcane. Under growth chamber conditions, plants were exposed to three O3 concentrations (0, 150, and 300 ppb) for three consecutive days. Leaf CO2 assimilation declined in both crops after one day of exposure at 150 and 300 ppb O3. While sugarcane maintained similar performance at both 150 and 300 ppb O3, energy cane showed the lowest photosynthetic rates at 300 ppb O3. Such higher sensitivity of energy cane was driven by reduced photochemical efficiency (ΦPSII) at 150 ppb O3 and by low stomatal conductance and ΦPSII at 300 ppb O3. Notably, sugarcane showed significant stomatal closure after three days of exposure to 150 ppb O3, preventing further O3 influx and maintaining CO2 assimilation. However, this protective mechanism was not effective under 300 ppb O3. PEPCase and Rubisco carboxylation rates decreased in both crops after three days under O3 exposure. The rates of decline in leaf CO2 assimilation due to increasing air O3 concentration were higher in sugarcane and in energy cane, i.e., 0.2 and 0.3 mmol m⁻2 s⁻1 per 10-ppb O3 increase, respectively. Contrary to our initial hypothesis, energy cane was more sensitive to acute O3 exposure. Sugarcane exhibited greater short-term photosynthetic tolerance to O3 linked to stomatal regulation and photochemical stability.
Climate change threatens tropical ecosystems, particularly due to increasing global temperatures. This study investigated how leaf thermal tolerance and thermoregulating structural traits vary among deciduous and evergreen tree species of the Amazonian savanna and whether these traits are reliable predictors of thermal tolerance and contribute to maintaining positive thermal safety margins as air temperatures rise. We measured leaf thermotolerance, thermal safety margins based on air temperature, and morpho-anatomical traits in ten dominant species. Most species exhibited upper thermal limits slightly above the current maximum temperatures. However, under future climate scenarios of + 3 °C and + 6 °C, all species would present negative thermal safety margins. Leaf traits such as spongy parenchyma thickness, abaxial epidermis thickness, total leaf thickness, and stomatal aperture and density were significantly correlated with thermotolerance. Deciduous species showed greater sensitivity to future warming, suggesting that they may be more vulnerable to temperature increases, which could lead to shifts in community composition and structure in the Amazonian savanna. Our results indicate that morpho-anatomical traits play a key role in predicting species’ physiological responses to global warming.
Adverse environmental conditions, including salinity, significantly threaten crop production worldwide, necessitating innovative strategies to improve plant resilience. This study comprehensively compared the effects of mycobiogenic (AgNPb) and synthetic (AgNPs) silver nanoparticles with ionic silver (AgNO3) on sorghum growth and physiology. We also evaluated AgNPb seed priming to mitigate salinity effects, hypothesizing that salinity tolerance conferred by this priming is mediated by optimizing photosynthesis and enhancement of the antioxidant defense system, leading to reduced oxidative damage. In an initial experiment, sorghum seeds were treated with 0, 1.1 mg L-1, or 10.8 mg L-1 of each silver form. AgNO₃ at 10.8 mg L-1 proved highly phytotoxic, inhibiting germination, reducing biomass, and inducing severe oxidative imbalance (elevated H₂O₂ and TBARS). In contrast, AgNPb exhibited lower toxicity and, at 10.8 mg L-1, promoted sorghum growth and increased photosynthetic performance. Synthetic AgNPs showed intermediate effects. Crucially, in a subsequent experiment, AgNPb seed priming (1.1 mg L-1) successfully mitigated salinity effects (100 mM NaCl), improving photosynthetic efficiency and reducing oxidative damage markers in salt-exposed seedlings compared to non-primed controls. Our findings demonstrate that the form of silver (ionic vs. NP; biogenic vs. synthetic) is a critical determinant of phytotoxicity. Mycobiogenic AgNPs show significant potential for both growth promotion and, via priming, enhancement of salinity tolerance.
Seed priming has emerged as a promising strategy to enhance early vigour, metabolic efficiency, and resilience in crop plants. This study investigates the comparative effects of five seed priming treatments magnesium nitrate (T2), boric acid (T3), a combination of magnesium nitrate and boric acid (T4), hydropriming with deionized water (T5), and an unprimed control (T1) on biochemical, antioxidant, and protein expression responses in wheat during vegetative development. Key parameters assessed at 30, 45, and 60 days after sowing (DAS) included plant height, chlorophyll concentration, total soluble protein, proline accumulation, and the activities of antioxidant enzymes such as superoxide dismutase (SOD), glutathione reductase (GR), and ascorbate peroxidase (APX). Additionally, SDS-PAGE was employed to characterize treatment-induced changes in protein expression profiles. The results demonstrated significant enhancement in growth and metabolic attributes in all primed treatments compared to the control. The combined treatment (T4) exhibited a pronounced synergistic effect, resulting in the highest concentration of antioxidant enzyme activity, protein accumulation, and chlorophyll concentration. Boric acid priming (T3) was particularly effective in increasing nitrate reductase and proline concentration, while magnesium nitrate (T2) enhanced chlorophyll biosynthesis. SDS-PAGE analysis revealed greater band intensity and diversity in primed treatments, especially in T4, indicating elevated protein synthesis and responsive gene expression. Collectively, the findings underscore the potential of micronutrient-based seed priming, particularly the combined application of magnesium and boron, as a strategic tool to optimize physiological performance, bolster antioxidant defence, and regulate proteomic changes during the critical vegetative growth stages in wheat.
The indoor cultivation of Matricaria chamomilla represents a promising strategy for optimizing medicinal plant production. This research evaluated the effects of LED spectral composition on the morphological and biochemical development of chamomile in an aeroponic system. Three light treatments were applied: Red predominant + Far-red + Blue (Rh + FR + B), Blue predominant + Red + Far-red (Bh + R + FR), and Red + Blue (R + B), with a photosynthetic photon flux density (PPFD) of 255.96 ± 5.8 µmol m−2 s−1. Seedlings were germinated under controlled conditions and later transferred to an aeroponic system with mist irrigation. The treatment Bh + R + FR significantly enhanced flowering, increasing flower and bud production, floral head diameter, and petal length. In contrast, R + B promoted higher chlorophyll accumulation and nitrogen balance index, favoring greater leaf expansion, particularly in pinna length. Although anthocyanin and flavonoid concentrations increased over time in all treatments, their accumulation was not significantly affected by spectral composition. These findings highlight that optimizing chamomile flower production requires a higher proportion of blue light, while a balanced red-to-blue ratio is more effective for maximizing leaf development. This study provides new insights into spectral optimization for controlled M. chamomilla cultivation, supporting its application in the medicinal and aromatic plant industry.
Large-scale mining disasters in tropical regions impose long-term pressures on ecosystems by degrading soil fertility and exposing native vegetation to chemical and physical disturbances. This study investigates whether Eugenia florida, a native tree species found in both tailings-impacted and reference areas of the Rio Doce Basin in Brazil, exhibits physiological adjustments that confer resilience to combined edaphic and thermal constraints. We assessed soil properties and 16 physiological traits related to nutrient status, photosynthetic efficiency, photoprotection, and thermal tolerance. Soils in the impacted area exhibited markedly lower organic matter, cation exchange capacity, and nutrient concentrations, along with increased iron concentration. Despite a 10
Salinity first strikes crops via osmotic shock, collapsing the soil-to-leaf water gradient long before toxic ions build up. To disentangle this early phase, we exposed two contrasting Chilean quinoa (Chenopodium quinoa) ecotypes—AZ2 (coastal lowland) and AZ9b (salares desert)—to 0, 150, and 300 mM NaCl for seven days and quantified root hydraulics, leaf gas exchange, and whole-plant water status. Both genotypes initiated osmotic adjustment, as evidenced by higher root-sap osmolality and a decrease in stem water potential (Ψstem). However, only desert ecotype AZ9b deployed a xerophyte-like hydraulic strategy: root hydraulic conductivity (Lpr) remained constant, stomatal conductance (gs) remained twice that of AZ2 at 150 mM, and Ψstem declined just enough to preserve leaf turgor. Even at 300 mM, AZ9b’s Lpr was triple that of AZ2. Microscopic observations confirmed that AZ2 roots underwent cortical collapse and early suberization, whereas AZ9b maintained an intact cortex with minimal barrier formation, keeping radial water flow open. Thus, swift coordination of Lpr, gs, and osmotic adjustment stabilizes Ψstem and safeguards the water balance within the first week of salt exposure. Early hydraulic resilience, not late-stage ion exclusion, has emerged as a practical breeding target for enhancing quinoa performance in saline marginal soils.
Ascorbic acid, the most abundant soluble antioxidant, and the phytohormone abscisic acid (ABA) are major players in the signalling networks that allow plants to acclimate to challenging environments. In fact, the gene expression of a key enzyme in ascorbic acid synthesis is regulated by transcriptional factors linked to ABA metabolism and environmental factors. In this work we hypothesized that ABA regulates ascorbic acid accumulation in leaves of Arabidopsis thaliana (L.) Heynh rosettes and modulates its concentration responding to the incident irradiance. Mutant genotypes affected in ABA synthesis (aba1-6, aba2-1 and aba3-1) or sensitivity (abi2-1) were used. Five-week-old rosettes were treated with increased irradiance and ABA (10 and 100 μM) for 48 h. Mutant genotypes exhibited higher leaf ascorbic acid concentration (compared to wild-type) at basal irradiance, which decreased with the application of exogenous ABA. On the other hand, the typical increase in foliar ascorbic acid concentration in response to increase in incident irradiance observed in the wild type was markedly attenuated in the deficient mutants and partially restored with exogenous ABA treatment in aba2-1 and aba3-1 genotypes. The results suggest that ABA negatively modulates the accumulation of ascorbic acid in Arabidopsis leaf tissues but it could positively modulate the increase in leaf ascorbic acid concentration in response to increased irradiance affecting crucial points of its synthesis pathway such as concentration of precursors (soluble sugars), gene expression and activity of ascorbic acid synthesis enzymes and respiration (which is a critical process that regulates ascorbic acid synthesis in mitochondria).
Ultra-weak photon emission (UPE) offers a non-invasive window into plant physiological states, particularly in response to adverse conditions. This study refines the spectral analysis of UPE in 7-week-old Arabidopsis thaliana plants subjected to mechanical injury, directly addressing well-documented detection challenges in the longer-wavelength regions and enhancing the utility of UPE as a biomarker for oxidative damage. Previous investigations utilized cut-on absorption filters and CCD imaging, which suffered from imprecise spectral resolution due to poor filter characteristics and reliance on subtraction methods for band emission computation. In contrast, our current study employs bandpass optical filters covering the 400–750 nm range in 50 nm increments, significantly improving the accuracy of UPE spectral data. We measured UPE kinetics after applying a standardized mechanical injury by sharp leaf incision. The study evaluates the suitability of these bandpass filters for discerning UPE spectral patterns in both spontaneous and induced emission scenarios in Arabidopsis leaves. It optimizes detection of crucial longer-wavelength emissions often indicative of reactive oxygen species (ROS) formation. Given that UPE intensity directly correlates with the rate and extent of ROS formation, monitoring these changes provides a robust, non-invasive means to assess oxidative metabolic states and internal responses. Our findings reveal that a significant increase in total UPE following mechanical injury occurs in the 700–750 nm spectral range (band B7), emerging as the dominant contributor to total UPE. Furthermore, our analysis indicates that UPE also includes a significant emission from the 750–870 band and presence in ultraviolet (UV) region. This research demonstrates that bandpass filters offer a accurate and reliable method for characterizing UPE photobiological responses of plants to mechanical injuries.
This study investigated seasonal fluctuations in the antioxidant system of the moss Brittonodoxa subpinnata (Sematophyllaceae) across two Brazilian phytogeographic domains: Atlantic rainforest and Cerrado. Key antioxidant enzyme activities, Superoxide dismutase (SOD), Catalase (CAT), Ascorbate peroxidase (APX), Glutathione reductase (GR), and non-enzymatic antioxidant concentration (ascorbate and glutathione), hydrogen peroxide, a reactive oxygen species (ROS), and malondialdehyde (MDA), a marker of lipid peroxidation, were quantified. Antioxidant activity increased markedly during the dry season, indicating physiological adjustments to drought. Unexpectedly, MDA concentrations were higher during the rainy season, suggesting that elevated temperature and solar radiation may also drive oxidative damage. Despite regional environmental differences, seasonal variation played a greater role in modulating redox responses. These findings contribute to our understanding of how tropical bryophytes physiologically adapt to seasonal disturbances and underscore their potential vulnerability to climate change.
