Search Results (258)

We used chlorophyll fluorescence techniques to investigate seasonal variations in photosystem II (PSII) quantum yield in five-year-old saplings of the sclerophyllous Peumus boldus Molina (evergreen) and Colliguaja odorifera Molina (semideciduous) planted in a semiarid site with a Mediterranean-type climate. Chlorophyll fluorescence rise kinetics (OJIP) were monitored monthly for one year (September 2024 to September 2025). With this information, we estimated the relative deviation of the performance index (PI_ABS) of each species from the average PI_ABS in each season (denoted as ∆PI_ABS). P. boldus was associated with destruction of PSII reaction centers and incapacity for electron transport, i.e., higher values of parameters ABS/RC (effective antenna size of an active reaction center) and F₀ (minimal fluorescence), whereas C. odorifera was associated with higher photosynthetic performance i.e., higher values of PI_ABS, PI_TOT (total performance index), F_V/F₀ (ratio between variable and minimal fluorescence), and F_V/F_M (maximum quantum yield of primary PSII photochemistry). P_IABS exhibited a 52 and 38% reduction (i.e., −∆PI_ABS) during spring and winter in P. boldus, but an increase (i.e., +∆PI_ABS) of 52 and 37% in the same seasons for C. odorifera. P. boldus was considerably more depressed during the winter–spring season than the summer months. This suggests that PSII function in P. boldus is more sensitive to low temperatures in winter and spring than the lack of water and high temperatures during summer. Full article

Strawberry (Fragaria × ananassa (Weston) Rozier) is a high-value crop whose market success depends on fruit quality traits such as sweetness, firmness, and pigmentation. In sustainable agriculture, wood distillates are gaining interest as natural biostimulants. This study evaluated the effects of foliar application of two commercial wood distillates (WD1 and WD2) and one produced in a pilot plant at the Institute for Bioeconomy of the National Research Council of Italy (IBE-CNR) on strawberry physiology, fruit yield, and fruit quality under greenhouse conditions. Non-destructive ecophysiological measurements were integrated using optical sensors for proximal phenotyping, enabling continuous monitoring of plant physiology and fruit ripening. Leaf gas exchange and chlorophyll fluorescence were measured with a portable photosynthesis system, while vegetation indices and pigment-related parameters were obtained using spectroradiometric sensors and fluorescence devices. To assess the functional relevance of vegetation indices, a linear regression analysis was performed between net photosynthetic rate (A) and the Photochemical Reflectance Index (PRI), confirming a significant positive correlation and supporting PRI as a proxy for photosynthetic efficiency. All treatments improved photosynthetic efficiency during fruiting, with significant increases in net photosynthetic rate, quantum yield of photosystem II, and electron transport rate compared to control plants. IBE-CNR and WD2 enhanced fruit yield, while all treatments increased fruit soluble solids content. Non-invasive monitoring enabled real-time assessment of physiological responses and pigment accumulation, confirming the potential of wood distillates as biostimulants and the value of advanced sensing technologies for sustainable, data-driven crop management. Full article

Early post-germination physiological responses determine oak seedling establishment success under changing environmental conditions. This study investigated four oak species (Quercus cerris, Q. frainetto, Q. petraea, and Q. pubescens) through direct seeding experiments across four locations in Serbia representing varying habitat conditions. Physiological parameters (quantum yield of photosystem II, total stomatal conductance, and leaf vapor pressure deficit) were measured intensively during the first growing season, along with morphological traits and survival rates. Results revealed that microclimatic and soil conditions exerted stronger effects on seedling physiology than species identity, with air humidity, temperature, and soil moisture being primary drivers of photosynthetic performance. Surviving seedlings exhibited 18% higher PhiPSII and 128% higher stomatal conductance compared to non-survivors, demonstrating that physiological performance is a reliable predictor of establishment success. Species-specific differences were evident. Q. cerris and Q. frainetto maintained the highest photosynthetic activity across sites, Q. pubescens showed intermediate resilience, and Q. petraea displayed greater sensitivity to environmental stress. These findings highlight the dominant role of microsite conditions in shaping early seedling physiology and survival. Physiological measurements, particularly PhiPSII and gtw, provide useful early indicators of establishment success during the first growing season following direct seeding. Full article

Food security and human health are directly related to the condition of agricultural soils. Soil contamination by heavy metals is a global environmental problem. Lead (Pb) is a toxic and non-biodegradable element posing a significant risk to ecosystems and human health. 24-Epibrassinolide (EBR) has multiple benefits in plant metabolism, including maximizing gas exchange. In plants, exogenous application of dopamine (DOP) confers tolerance to abiotic stresses, minimizing interferences on growth. This study aimed to investigate whether the exogenous application of EBR and DOP, administered independently or jointly, can contribute to mitigating the oxidative stress and impacts on photosystem II in Pb-stressed tomato, evaluating parameters related to nutritional status, photosystem II activity, gas exchange, antioxidant enzymes, and biomass. Better results were observed with the isolated EBR application, improving the photosynthetic efficiency, as evidenced by the increases in chlorophyll contents, effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and electron transport rate, resulting in a higher net photosynthesis rate. Parallelly, treatment using both plant growth regulators (DOP and EBR) promoted significant increases of 14%, 18%, 13%, and 35% in the activities of superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase, contributing to the reduction in oxidative stress in photosystem II of Pb-stressed plants. Therefore, this research proves that the exogenous application of DOP and EBR, alone or in combination, attenuates the toxic effects generated by Pb in tomato plants. Full article

Accurate prediction of photosynthetic parameters is pivotal for precision viticulture, as it enables non-invasive monitoring of plant physiological status and informed management decisions. In this study, spectral reflectance data were used to predict key photosynthetic parameters such as assimilation rate (A), effective photosystem II (PSII) quantum yield (${\Phi }_{\mathrm{PSII}}$), and electron transport rate (ETR), as well as stem and leaf water potential (${\Psi }_{\mathrm{stem}}$ and ${\Psi }_{\mathrm{leaf}}$), in Vitis vinifera (cv. Müller-Thurgau) grown in an experimental vineyard in Lower Franconia (Germany). Measurements were obtained on 25 July, 7 August, and 12 August 2024 using a LI-COR LI-6800 system and a PSR+ hyperspectral spectroradiometer. Various machine learning models (SVR, Lasso, ElasticNet, Ridge, PLSR, a simple ANN, and Random Forest) were evaluated, both as standalone predictors and as base learners in a stacking ensemble regressor with a Random Forest meta-learner. First derivative reflectance (FDR) preprocessing enhanced predictive performance, particularly for ${\Phi }_{\mathrm{PSII}}$ and ETR, with the ensemble approach achieving R² values up to 0.92 for ${\Phi }_{\mathrm{PSII}}$ and 0.85 for A at 1 nm resolution. At coarser spectral resolutions, predictive accuracy declined, though FDR preprocessing provided some mitigation of the performance loss. Diurnal patterns revealed that morning to mid-morning measurements, particularly between 9:00 and 11:00, captured peak photosynthetic activity, making them optimal for assessing vine vigor, while midday water potential declines indicated favorable timing for irrigation scheduling. These findings demonstrate the potential of integrating hyperspectral data with ensemble machine learning and FDR preprocessing for accurate, scalable, and high-throughput monitoring of grapevine physiology, supporting real-time vineyard management and the use of cost-effective sensors under diverse environmental conditions. Full article

Phthalates, particularly di-n-butyl phthalate (DBP), are persistent plasticizers that pose serious ecological risks to aquatic environments. This study evaluated the phytotoxic effects of DBP on the aquatic fern Azolla pinnata through morphological, biochemical, and photosynthetic responses. Plants were exposed to graded DBP concentrations (0–10 mg/L) for 4 and 8 days. Increasing DBP levels caused visible symptoms including frond chlorosis, necrosis, and root inhibition. Biochemically, total chlorophyll content declined by up to 95%, while malondialdehyde (MDA) levels increased by approximately 300% at 10 mg/L, confirming severe lipid peroxidation. Antioxidant enzymes showed biphasic trends: superoxide dismutase (SOD) and catalase (CAT) activities rose under moderate stress but declined by ~73% and ~78%, respectively, at the highest concentration, indicating oxidative enzyme suppression. Chlorophyll fluorescence analysis revealed strong, dose-dependent inhibition of photosystem II efficiency, characterized by reduced performance indices (PIabs, PIcs) and quantum yields (фPo, фEo), alongside increased фDo and Fo/Fm, indicating enhanced energy dissipation and photoinhibition. Overall, DBP exposure disrupted oxidative balance and PSII function in A. pinnata, demonstrating its high sensitivity to phthalate toxicity and validating chlorophyll fluorescence as a rapid, non-invasive biomonitoring tool for assessing aquatic pollutant stress. Full article

Avocado trees (Persea americana Mill.) grown in Mediterranean conditions are exposed to high temperatures and intense solar radiation during summer, factors that can severely compromise plant water status and key physiological processes. To minimize these stressful conditions, the use of shade nets is an agronomical technique that permits the creation of an optimal microclimate for crop development. Thus, the aim was to evaluate the effects of shade netting on the physiological response of young avocado trees commercially grown under Mediterranean climatic conditions. The main results showed similar circadian rhythms of plant water status under both crop systems (open-air and shaded) in both seasons. However, the use of shading nets altered the circadian rhythm of leaf gas exchange. In summer, stomatal conductance (g_s) remained significantly more open after midday in shaded trees, allowing higher leaf transpiration (E_leaf) and cooler leaf temperature (T_leaf). A similar daily pattern was observed in chlorophyll a fluorescence parameters, including the effective quantum yield of photosystem II (ΦPSII) and the electron transport rate (ETR), with the lowest values occurring at midday. In shaded plants, ΦPSII and ETR remained higher after midday than in open-air, suggesting a lower photochemical inhibition of photosynthesis caused by heat stress and photoinhibition. Thus, the use of shade nets represents an agronomic alternative technique for cultivating avocados in Mediterranean climate conditions. Full article

Cobalt (Co) is an essential micronutrient for many organisms, but, at higher concentrations, it becomes harmful, primarily due to competitive interactions with other metal ions. Enzyme inhibition and disruption of nutrient homeostasis may lead to oxidative stress in Co-exposed cells. Compared to other heavy metals, such as Cd, Cu, Cr, Pb, or Ni, this element has been less studied in algae with respect to its toxicity and tolerance. Taking into account Co-induced oxidative stress and antioxidant response, the studies on algae usually did not cover a wider range of antioxidants and ROS-detoxifying enzymes monitored in one model. The aim of this study was to assess the impact of CoCl₂ on the model green microalga Chlamydomonas reinhardtii from a broader perspective. We monitored algal growth, photosynthetic pigment content, the maximum quantum yield of photosystem II (F_v/F_m), the efficiency of nonphotochemical quenching of chlorophyll fluorescence (NPQ), and oxidative stress markers (superoxide production, lipid peroxidation). The measured antioxidants included soluble thiols, ascorbate (Asc), proline (Pro), α-tocopherol (α-Toc), and plastoquinol (PQH₂-9). The superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were also determined. Exposure to CoCl₂ resulted in increased levels of thiols, Asc, α-Toc, PQH₂-9, and CAT activity. At lower concentrations of CoCl₂, no increase in oxidative stress markers was observed, suggesting efficient antioxidant protection. On the contrary, exposure to higher concentrations of CoCl₂ caused the inhibition of growth and chlorophyll (Chl) synthesis, as well as the reduction in the Chl a/Chl b ratio, the F_v/F_m parameter, the efficiency of NPQ induction, and the levels of lipophilic antioxidants, along with an increase in lipid hydroperoxides. An interesting and novel result is the inhibitory effect of Co toxicity on state transitions in exposed algae. Full article

Fruit sunburn is a major abiotic stress limiting apple production worldwide, with losses potentially reaching 50% due to climate change-driven heat events. This study aimed to evaluate sustainable strategies to mitigate or reduce sunburn on ‘Gala Galaxy Selecta’ apple trees. Field trials conducted in summer 2021 compared eight treatments: silicon-based application (Eckosil^®), foliar fertilization with algae extracts, macro- and micronutrients, and amino acids, increased irrigation (+35% ET_c), mineral particle films (Surround^®, Vegepron Sun^®, Agrowhite^®, Sunstop^®), and an untreated control. Randomized block designs with replicates were used. Agronomic parameters, including particle film coverage, trunk cross-sectional area, yield, and fruit quality (color, sunburn incidence, firmness, soluble solids content, dry matter, starch), were measured at harvest. Physiological responses, such as net photosynthesis, maximum quantum yield of Photosystem II, specific leaf area, fruit surface temperature, photoprotective pigments, antioxidants, and heat shock protein gene expression, were also assessed. Foliar fertilization, Agrowhite^®, and water reinforcement produced the highest yield per trunk cross-sectional area, with increased soluble solids content and enhanced red pigmentation. Surround^® minimized sunburn incidence but reduced photosynthetic activity, as did Vegepron Sun^®. Agrowhite^® balanced sunburn protection with maintenance of fruit quality and physiological function. These findings provide practical guidance for growers to select effective treatments, balancing sunburn mitigation, fruit quality, and tree physiological performance, while offering researchers insights into integrating agronomic and physiological strategies for climate-resilient apple production. Full article

One way to counteract the effects of environmental stresses, including drought, is to use products with growth-promoting properties for plants. Such agents include quercetin, which is known for its antioxidant and photosynthesis-enhancing properties. In the conducted experiment, the influence of the quercetin–copper complex (Q-Cu (II)) treatment, characterized by strong high solubility in water and strong antioxidant properties, was investigated. The pot experiment demonstrated the effect of spraying with Q-Cu (II) solutions (0.01, 0.05 and 0.1%) on wheat plants growing under drought stress conditions. Two treatments of Q-Cu (II) solutions were applied, and chlorophyll content and chlorophyll fluorescence (the maximum quantum yield of photosystem II (PSII) photochemistry (F_v/F_m), the efficiency of the water-splitting complex on the donor side of PSII (F_v/F_o), and the photosynthetic efficiency index (PI)), as well as gas exchange (photosynthetic network intensity (P_N), transpiration rate (E), stomatal conductance (g_s) and intercellular CO₂ concentration (C_i)), were measured 1 and 7 days after each treatment. In addition, antioxidant enzyme activity (catalase (CAT), peroxidase (SOD) and guaiacol peroxidase (GPOX)) and reactive oxygen species (ROS) levels were determined. Drought stress caused a decrease in chlorophyll content, and values of parameters F_v/F_m, F_v/F_o, PI and P_N, E, g_s, C_i, as well as an increase in ROS levels and antioxidant enzyme activity. Exogenous Q-Cu (II) improved photosynthetic indices and modulated redox status in a dose-dependent manner: 0.01–0.05% reduced ROS, whereas 0.1% increased ROS while concomitantly enhancing antioxidant enzyme activities and photosynthetic performance, consistent with ROS-mediated priming. The conducted research indicates the possibility of using Q-Cu (II) as a product to enhance the efficiency of the photosynthetic process under drought stress. Full article

Pharmaceuticals can be found in the aquatic environment and cause unwanted effects on organisms. The present work aimed to characterize the toxic mode of action of the antidepressant fluoxetine (FLX) on the freshwater microalga Raphidocelis subcapitata. With this aim, the microalga was exposed to low levels (µg/L) of FLX for 72 h. Exposure to 20–30 µg/L FLX arrested algal growth, which can be explained by the blockage of algal nuclear division. In addition, FLX (15–30 µg/L) deeply altered the alga’s metabolism, which was reflected by an increase in esterase activity, mitochondrial dysfunction (hyperpolarization of inner mitochondrial membrane), and reduction in the content of photosynthetic pigments: chlorophyll a (chla) and carotenoids (car). A sharp decline in photosynthetic performance, revealed by the reduction in maximum photochemical quantum yield (F_v/F_m), effective photochemical quantum yield (ΦPSII), and photosynthetic electron transport rate (ETR) of photosystem II (PSII), was also observed. FLX, at 30 µg/L, induced the intracellular accumulation of reactive oxygen species (ROS) and lipid peroxidation, with a marginal loss (1%) of cell membrane integrity. The results presented here contribute to the elucidation of the toxic mode of action of FLX on the microalgae R. subcapitata and, simultaneously, warn of the negative impact of the presence of pharmaceutical compounds in freshwater aquatic environments. Full article

Selenium (Se) is an essential micronutrient for human health, yet its dietary intake is insufficient in many populations worldwide. Agronomic biofortification represents an effective strategy to enrich crops with Se, and Totally Controlled Environment Agriculture (TCEA) provides a reliable platform to evaluate cultivar-specific responses under standardized conditions. This study evaluated the effects of foliar sodium selenate doses of 0, 5, 10, and 15 µM on two basil (Ocimum basilicum L.) cultivars, ‘Fine Verde’ (FV) and ‘Red Rubin’ (RR), in a micro-TCEA system. The yield was not significantly different at 5–10 µM but declined by 21% at 15 µM, particularly for FV. RR out-yielded FV (+14%), whereas FV produced taller shoots. The 5 µM Se concentration did not affect the total chlorophyll content and quantum yield of photosystem II under control conditions. The highest Se dose (15 µM) decreased the chlorophyll content and electron transport rate by 18% and 12%, respectively, while increasing the stomatal conductance (50%) and transpiration rate (120%). The total phenolics content in RR was double that in FV and increased with Se, whereas the NO₃⁻ concentration in RR decreased by 9% at 10 µM. Principal component analysis separated treatments by Se dose (PC1 = 44.5%) and cultivar (PC2 = 42.7%), showing RR’s stronger connection of RR to biomass and antioxidant accumulation under moderate Se. Overall, a single foliar application of 5 µM sodium selenate appears optimal to achieve effective Se enrichment while maintaining productivity and quality. These findings support basil as a promising candidate for Se biofortification in TCEA systems, with potential contributions to dietary Se intake. Full article

Non-photochemical quenching (NPQ) is a key photoprotective mechanism in Symbiodiniaceae, enabling photosystem II (PSII) to dissipate excess excitation energy under stress. The balance between regulated (Φ_NPQ) and unregulated (Φ_NO) energy dissipation influences thermal tolerance, yet the temperature thresholds at which this balance shifts remain poorly defined. Here, we used the Phenoplate, a high-throughput fluorometric platform integrating rapid light curves with controlled temperature ramping, to examine short-term thermal responses in Breviolum minutum across 6–71 °C. We identified a sharp transition at 41 °C where Φ_NPQ collapsed and was replaced by Φ_NO, indicating loss of regulated photoprotection. This switch coincided with a pronounced drop in PSII effective quantum yield (Φ_II) and substantial reductions in cell density, marking a thermal Achilles’ heel in the photoprotective capacity of this species. Despite this regulatory breakdown, a fraction of cells persisted for at least three days post-exposure. These results demonstrate that B. minutum maintains regulated photoprotection up to a discrete threshold, beyond which unregulated becomes the dominant pathway and survival is compromised. Identifying such thermal inflection points in coral symbionts provides mechanistic insight into their vulnerability under acute heat stress and may inform early-warning indicators for coral bleaching susceptibility. Full article

Meta-cresol (m-cresol) is highly corrosive and toxic, and is widely present in industrial wastewater. As a pollutant, it adversely affects various aspects of human production and daily life. To evaluate the feasibility of using sunflowers to remediate m-cresol-contaminated wastewater, this study used Helianthus annuus L. as the test subject to analyze its tolerance and the wastewater purification efficiency under different m-cresol concentrations. The results showed that the net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), and light energy utilization efficiency (LUE) of Helianthus annuus L. exhibited an overall decreasing trend, while the intercellular CO₂ concentration (Cᵢ) initially increased and subsequently decreased with increasing m-cresol concentration. When m-cresol concentration reached or exceeded 60 mg·L⁻¹, the net photosynthetic rate and intercellular CO₂ concentration in the leaves showed opposite trends with further increases in m-cresol stress. The inhibition of net photosynthesis in sunflowers by m-cresol was mainly attributed to non-stomatal factors. The maximum photochemical efficiency (F_v/F_m), actual photochemical efficiency (ΦPSII), photochemical quenching coefficient (q^P), PSII excitation energy partition coefficient (α), and the fraction of absorbed light energy used for photochemistry (P) all decreased with increasing m-cresol concentration. In contrast, non-photochemical quenching (NPQ), the quantum yield of regulated energy dissipation [Y(NPQ)], and the fraction of energy dissipated as heat through the antenna (D) first increased and then decreased. Under low-concentration m-cresol stress, sunflowers protected their photosynthetic system by dissipating excess light energy as heat as a stress response. However, high concentrations of m-cresol caused irreversible damage to Photosystem II (PSII) in sunflowers. Under m-cresol stress, chlorophyll a exhibited strong stability with minimal degradation. As the m-cresol concentration increased from 30 to 180 mg·L⁻¹, the removal rate decreased from 84.91% to 11.84%. In conclusion, sunflowers show good remediation potential for wastewater contaminated with low concentrations of m-cresol and can be used for treating m-cresol wastewater with concentrations ≤ 51.9 mg·L⁻¹. Full article

Climate change poses a significant threat to crop production, particularly in tropical and semi-arid regions. Sorghum (Sorghum bicolor (L.) Moench), a resilient C₄ cereal, has high photosynthetic efficiency and abiotic stress tolerance, making it a key crop for food, fodder, and feed security. This study evaluated agronomic and physiological traits influencing the yield performance of 20 sorghum varieties under field conditions in Kerala, India. The data were analyzed using a randomized block design (RBD) in GRAPES software, and a principal component analysis was performed in R. Variety CSV 17 exhibited the highest grain yield (GY) (3760 kg ha⁻¹) and harvest index (HI) (43), with early flowering, early maturity, a high chlorophyll content (CHL), and minimal nitrogen (N), phosphorus (P), and potassium uptake. Conversely, CSV 20 produced the highest stover yield (22.5 t ha⁻¹), associated with greater leaf thickness (LT), lower canopy temperature, taller plant height (PH), increased leaf number (LN), and extended maturity. Leaf temperature (T_leaf) was negatively correlated with the quantum yield of photosystem II (ΦPSII) and panicle length (PL), which were strong predictors of grain weight. The principal component analysis revealed that PC1 and PC2 explained 21% and 19% of the variation in the grain and stover yield, respectively. Hierarchical partitioning identified the potassium content (K%), CHL, T_leaf, leaf area index (LAI), ΦPSII, and LT as key contributors to the GY, while the SY was primarily influenced by the LN, nitrogen content (N%), maturity duration, PH, and ΦPSII. These findings highlight the potential of exploiting physiological traits for enhancing sorghum productivity under summer conditions in Kerala and similar environments. Full article