Search Results (2,161)

Low temperature and low irradiance (LTLI) stress severely limits strawberry growth and productivity during winter protected cultivation. This study investigated the physiological responses of the short-day strawberry cultivar ‘Benihoppe’ to individual and combined LTLI stress and developed a quantitative damage evaluation index. Seedlings were exposed to four treatments for 20 d: control (25/15 °C, 600 μmol m⁻² s⁻¹), single low temperature (LT: 15/5 °C), single low irradiance (LI: 100 μmol m⁻² s⁻¹), and combined stress (LTLI: 15/5 °C, 100 μmol m⁻² s⁻¹). Compared to isolated stress factors, combined LTLI treatment exhibited a statistically verified synergistic damaging effect (two-factor ANOVA, LT × LI p < 0.01) on leaf structure and function. LTLI-treated plants showed severe reductions in leaf area, palisade tissue thickness, chlorophyll content, and net photosynthetic rate (Pn), alongside elevated malondialdehyde (MDA) accumulation. Chlorophyll a fluorescence (OJIP) analysis revealed that LTLI stress strongly blocked the electron transport chain at the PSII acceptor side, increasing the J-step relative variable fluorescence (Vj) and suppressing the performance index (PI). To quantify these impacts, a Low Temperature and Low Irradiance Damage Index (LTLDI) was derived from 12 core physiological and morphological variables. The LTLDI scores demonstrated that LTLI induced severe damage by day 10 (score: 0.69) and extremely severe damage by day 20 (0.87), which were substantially higher than the damage caused by LT (0.58 at 20 d) and LI (0.63 at 20 d) alone. The index reliability was confirmed by its strong correlation (r > 0.9) with key stress markers (Fv/Fm, Pn, and MDA). Overall, combined LTLI stress exacerbates structural degradation and PSII photoinhibition in strawberry leaves. The proposed LTLDI offers a practical, standardized tool for evaluating stress severity, facilitating timely environmental management in greenhouse strawberry production. Full article

Solanum lycopersicum is highly sensitive to water deficits, which negatively affect photosynthesis and increase oxidative stress. Although chitosan nanoparticles (ChNPs) offer a sustainable solution, research on their effects on this species is scarce. This study evaluated whether ChNPs mitigate the physiological and biochemical effects of water deficit on S. lycopersicum seedlings. Thirty-day-old seedlings were grown under greenhouse conditions, and two irrigation levels were established: 80% of substrate water-holding capacity (well-watered, WW), and 50% of water-holding capacity (mild-to-moderate water deficit, WD). Spherical ChNPs with a size of 39.52 ± 10.9 nm were suspended in 1% acetic acid and foliar-applied at 0, 60, or 120 mg L⁻¹. After 10 days, biomass accumulation, chlorophyll fluorescence parameters (F_v′/F_m′, ΦPSII, and ETR), gas exchange, and non-enzymatic antioxidant traits were determined. Even under this early-stage stress regime, water deficit significantly reduced shoot and root biomass, net photosynthesis, and stomatal conductance, while increasing lipid peroxidation. Foliar application of ChNPs, particularly at 60 mg L⁻¹, restored dry matter production and improved photochemical efficiency and electron transport rate by 14%; likewise, net CO₂ assimilation increased by 11.7%. In addition, this dose enhanced antioxidant activity and total phenols by 66% and 1.6-fold, respectively. ChNPs at 60 mg L⁻¹ mitigated the effects of WD in S. lycopersicum by increasing antioxidant and photosynthetic performances. Nevertheless, additional molecular studies, including enzymatic antioxidant characterization and compatible solute profiling, are required to elucidate the mechanisms involved. Full article

Tomato yellow leaf curl virus (TYLCV) is one of the most destructive viral diseases causing severe yield losses in tomato production worldwide. This study investigated the effects of TYLCV infection on plant growth, photosynthetic physiological responses, and yield formation in greenhouse-grown tomatoes and evaluated the applicability of physiological trait-based yield prediction models. Two large-fruited tomato cultivars widely cultivated in Korean protected horticulture systems, ‘Daphnis’ and ‘Pink Star’, were inoculated with TYLCV under greenhouse conditions, and their growth, physiological responses, and yield characteristics were compared under high- and low-temperature growing seasons. TYLCV infection significantly reduced leaf length, leaf width, and leaf area index (LAI), and decreased both flowering truss number and fruit-setting truss number, resulting in reduced total yield. Physiological analyses showed that infected plants exhibited decreases in the OJIP fluorescence rise curve and Fv/Fm values, indicating a reduced photochemical efficiency in photosystem II. In addition, A–Ci response curve analysis revealed a reduction in net photosynthetic rate, suggesting limited carbon assimilation capacity. Total yield showed significant positive correlations with maximum net photosynthetic rate (Amax), Fv/Fm, and Ci300. GGE and GT biplot analyses further indicated that yield was closely associated with photosynthetic performance and canopy development traits. A multiple regression model based on physiological traits and virus infection status explained a significant proportion of the variation in tomato yield (R² = 0.367), indicating that TYLCV infection acts as a key limiting factor for yield reduction. These findings demonstrate that TYLCV infection restricts tomato productivity through reduced photosynthetic efficiency and altered canopy structure. Moreover, physiological trait-based yield prediction approaches may provide a useful framework for evaluating productivity under viral infection conditions and for developing data-driven crop management strategies in greenhouse tomato production systems. Full article

The progressive degradation of natural habitats, driven by anthropogenic pressures and climate change, constitutes one of the most serious threats to biodiversity. Peatland ecosystems, along with the valuable plant species associated with them, are particularly vulnerable to these processes. Salix lapponum, a glacial relict species, is undergoing a drastic decline in both its range and population size across Poland and Europe. This emphasizes the need for the implementation of conservation measures, including species translocation, as well as the development of effective methods for monitoring plant condition following introduction. The aim of this study was to evaluate the usefulness of selected physiological indicators for the rapid and reliable assessment of plant condition in active conservation efforts. The experimental material consisted of S. lapponum plantlets derived from tissue culture, which were introduced into five experimental sites in eastern Poland, differing in habitat conditions. Over two growing seasons, chlorophyll fluorescence parameters (F₀, F_m, F_v/F_m), the content of photosynthetic pigments and anthocyanins, relative water content, guaiacol peroxidase activity, and the presence of reactive oxygen species were analyzed. The results revealed clear seasonal variability in most of the studied physiological parameters, as well as their differentiation across habitat conditions. The highest sensitivity to environmental changes was observed for indicators related to photosynthetic performance (F_v/F_m), tissue hydration status (RWC), and enzymatic activity. Declines in photosystem II efficiency at the beginning of the growing season, reflected in F_v/F_m values decreasing to 0.47–0.49 indicate transient stress conditions in plants. Simultaneously, variation in relative water content (52–90%) and peroxidase activity reflects differences in water availability and the intensity of environmental stress across habitats. The findings confirm that selected physiological indicators can serve as effective tools for the early monitoring of plant condition and for assessing the success of S. lapponum translocation. Full article

This study evaluated the growth, physiological, chlorophyll fluorescence (JIP-test), and postharvest responses of a shoot-dominant (‘C-P’) and a root-dominant (‘J-L’) garlic material to graded salinity (0, 50, and 200 mM NaCl) in a hydroponic system, with or without seed-clove priming using LEAFENERGY^®, a commercial biostimulant mainly composed of naturally derived rare fatty acids. Results showed 50 mM NaCl significantly inhibited shoot growth, while 200 mM nearly arrested growth and induced clove decay. Under moderate salinity, biostimulant priming exhibited cultivar-dependent mitigation. In ‘C-P’, biostimulant priming increased clove soluble sugar content by 1.140 g 100 g⁻¹ FW under 50 mM NaCl and increased dry-weight-based clove water content after cold storage. In ‘J-L’, biostimulant priming increased SPAD values under 50 mM NaCl and reduced the salt-induced increase in clove yellowness index to a level not significantly different from the non-saline control. In conclusion, garlic’s response to salinity is fundamentally dictated by intrinsic resource allocation strategies. Rather than merely promoting growth, biostimulant priming optimizes photosynthetic energy fluxes and reshapes metabolism. This tailored approach effectively preserves the visual marketability of susceptible cultivars while enhancing osmoprotectant accumulation and hydration in vigorous morphotypes, providing a sustainable strategy to safeguard industrial raw materials in salinized controlled cultivation systems. Full article

Spaceborne detection of solar-induced chlorophyll fluorescence (SIF) requires extremely high radiometric accuracy, and the polarization characteristics of an ultra-wide swath spaceborne fluorescence ultraspectral camera directly affect the accuracy of SIF retrieval. This study takes an ultra-wide swath camera based on an off-axis three-mirror anastigmat telescope combined with a Littrow–Offner spectrometer as the research object. A full-field-of-view (FOV), full-spectral, pixel-by-pixel polarization testing system was established based on the Stokes–Muller formalism, achieving for the first time fine characterization and calibration of the pixel-level polarization properties of such a payload. The results show that: (1) polarization sensitivity (LPS) exhibits a strong linear positive correlation with wavelength (R² > 0.97), with good uniformity (fluctuation < 1%) across the full ±15° FOV; (2) the polarization sensitive axis (PSA) shows a symmetric distribution across the FOV and gradually approaches 90° as the wavelength increases, with a clear deviation in the short-wavelength bands and stabilization in the mid-to-long wavelength bands; (3) through multiple sets of cross-validation and Monte Carlo statistics, the calibration accuracy reaches 0.1%, and the system uncertainty is better than 0.05%. This study can provide data support and a reference basis for high-accuracy spaceborne SIF retrieval, payload polarization correction, and optical design optimization. Full article

Controlled-release fertilizer (CRF) improves fertilizer-use efficiency through sustained nutrient release, but its rate-dependent effects on the growth and physiology of Paeonia delavayi seedlings remain unclear. In this study, germinated seeds of P. delavayi with radicles 3–4 cm in length were grown under container nursery conditions with four CRF application rates: control (CK, 0 kg·m⁻³), treatment 1 (T1, 0.6 kg·m⁻³), treatment 2 (T2, 1.2 kg·m⁻³), and treatment 3 (T3, 2.4 kg·m⁻³). Morphological traits, root characteristics, biomass accumulation, physiological parameters, and chlorophyll fluorescence were evaluated, and Pearson correlation and fuzzy membership analyses were used to compare overall treatment performance within the tested range. CRF significantly promoted seedling height, leaf number, petiole length, and biomass accumulation, although the promoting effect did not increase continuously with fertilizer rate. By June, seedling height in T2 was 160% greater than that in CK, while aboveground biomass increased by 552% and 574% in T2 and T3, respectively. Root morphological traits were not significantly affected, suggesting that CRF primarily promoted aboveground development and biomass production. Medium and high CRF rates increased leaf superoxide dismutase (SOD) activity by 42% and 103%, respectively, and peroxidase (POD) activity by 163% and 250%, respectively. Aboveground starch content was 45% higher in T2 than in CK. In contrast, photosynthetic pigment contents and the chlorophyll a/b ratio were not significantly affected by CRF. Chlorophyll fluorescence analysis showed that Fv/Fm remained stable among CRF treatments (0.78–0.82) and was significantly higher than that in CK (0.65), whereas the actual quantum yield of PSII [Y(II)] did not differ significantly among treatments. Relative to CK, the quantum yield of non-photochemical quenching [Y(NPQ)] increased from 0.20 to 0.40 in T2, while the quantum yield of non-regulated energy dissipation in PSII [Y(NO)] decreased from 0.37 to 0.24–0.22 in T2–T3. Pearson correlation and fuzzy membership analyses ranked the treatments as T2 > T3 > T1 > CK, indicating that T2 performed most favorably within the tested range, although its advantage over T3 was small. Overall, an appropriate CRF rate promoted P. delavayi seedling growth and was associated with changes in biomass accumulation, antioxidant enzyme activity, carbon assimilate storage, and chlorophyll fluorescence parameters. Full article

Pollution of rivers and large water bodies, including reservoirs, by wastewater from various sources is one of the most critical issues in the Donetsk region, requiring continuous monitoring and assessment of surface water quality. The research aims to assess the state of the Kalmius River under anthropogenic pressure, as well as to find correlations between the species composition, photosynthetic activity of phytoplankton, and the degree of water pollution. This study presents the results of biomonitoring of the Kalmius River and its tributaries within Donetsk City, which are under intense anthropogenic pressure. Pollution of the river channel by phenol, anionic surfactants, Ferrum ions, chlorides, and sulfates was identified. Based on the combinatorial pollution index, the water in the Kalmius River and its tributaries can be classified as polluted. The pigment composition of water samples was analyzed, and the species composition of river phytoplankton was determined. Dominant species include Chlorella vulgaris Beij., Dictyosphaerium pulchellum H.C.Wood, Scenedesmus quadricauda Brébisson, and Oscillatoria agardhii M.A.Gomont. Photosynthetic activity of the river’s algal flora was assessed based on chlorophyll fluorescence induction curves of natural phytoplankton. A correlation was established between surface water pollution levels and changes in the photosynthetic apparatus of microalgae cells. A strong negative correlation was found between the content of nitrate nitrogen in the aquatic environment and the photosynthetic activity, pigment composition, and abundance of the main dominant forms of phytoplankton, particularly the microalgae of the genus Cyclotella. The data obtained shows that the Kalmius River’s pollution has a significant impact on phytoplankton biodiversity, leading to the growth of cyanobacteria species. Full article

We present an active pulsed system (APS) designed for the long-term monitoring of plant photosynthetic efficiency. The specific design features and technical specifications of the system are described in detail. Experimental evaluations, conducted using both a model fluorophore and live plants, demonstrated the instrument’s robust performance across a broad range of illumination, temperature, and humidity conditions. Furthermore, the results confirm the validity and reliability of the acquired data. The system’s capability to detect the onset and progression of plant stress induced by moisture deficit was successfully verified. Full article

Phycobiliprotein linker polypeptides (PBLPs) are essential structural components of phycobilisomes (PBS), yet their composition, evolutionary trajectories, and regulatory functions in Pyropia haitanensis remain poorly understood. Here, we performed the first genome-wide identification and functional characterization of PBLPs in P. haitanensis. Nineteen PBLP genes were identified and classified into three subfamilies (LR, LRC, LC), exhibiting substantial physicochemical diversity and distinct gene structures. Phylogenetic and synteny analyses revealed extensive paralogous diversification driven primarily by dispersed duplication, with most duplicated pairs under strong purifying selection. Notably, the LCM subfamily was absent in P. haitanensis and P. yezoensis, suggesting lineage-specific gene loss and potential neofunctionalization of LR/LRC members. Transcriptome profiling demonstrated pronounced expression divergence between the wild-type (ZD) and red pigment mutant (RED) strains, with six PBLP genes showing significant differential expression validated by qRT-PCR. Under five irradiance levels, PBLP genes displayed distinct light-responsive transcriptional patterns. Mantel tests further revealed strong associations between PBLP expression and phycobiliprotein contents, photosynthetic pigments, and chlorophyll fluorescence parameters, indicating functional specialization within the family. Overall, this study provides comprehensive insights into the evolution, expression dynamics, and regulatory potential of PBLPs in P. haitanensis, highlighting their central roles in PBS assembly, pigment metabolism, and photophysiological acclimation. These findings establish a foundation for elucidating PBS regulatory mechanisms and improving pigment-related traits in economically important red algae. Full article

This study evaluated the effects of two silicon sources (silicic acid and Agrisil) and increasing Si concentrations on physiological responses, total polyphenol content, photochemical performance, nutrient uptake, and phenolic metabolism in sour passion fruit (Passiflora edulis Sims) grown under soilless culture conditions. The experiment was conducted in a greenhouse using increasing concentrations of Si applied through the nutrient solution. Gas exchange parameters, chlorophyll index (SPAD), chlorophyll fluorescence variables, leaf temperature, and the contents of Si, nitrogen, and total polyphenols in leaves and roots were evaluated. Moderate Si concentrations enhanced stomatal conductance and transpiration, improving intrinsic water use efficiency, and maintaining higher chlorophyll levels and photochemical performance. In contrast, higher Si concentrations increased Si deposition in leaf tissues, reduced stomatal regulation and transpiration, and increased leaf temperature. These changes were associated with reductions in chlorophyll index and photochemical performance index (PI), as well as increased F₀/Fm. Net CO₂ assimilation remained relatively stable. Silicon uptake differed between sources, with silicic acid showing faster absorption and Agrisil a more gradual release. Silicon fertilization also increased nitrogen uptake and stimulated the accumulation of phenolic compounds in roots. Overall, moderate silicon supplies enhanced physiological stability, whereas excessive accumulation imposed photochemical constraints. Full article

Drought is a major environmental constraint that disrupts photosynthetic processes. This study investigated the effects of foliar-applied commercial humic acid (HA) at different concentrations (1, 3 and 5 mg/mL) on the photosynthetic apparatus of sweet basil (Ocimum basilicum L. Italiano classico) under PEG-induced stress. The responses of the photosynthetic machinery were evaluated using chlorophyll a fluorescence analyses (JIP-test and PAM), leaf pigment composition, and assessments of membrane integrity. Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired Q_A⁻ reoxidation, reduced open PSII reaction centers (qP), diminished electron transport (ETo/RC, REo/RC), and substantial declines in performance indices (PI_ABS, PItotal). Energy dissipation increased (DI₀/RC), with regulated energy losses (Φ_NPQ) rising more strongly than non-regulated losses (Φ_NO). Drought also elevated oxidative stress markers (MDA and H₂O₂), leading to enhanced membrane injury. Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress. This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides and increased the proportion of open reaction centers (qP). Improved PSII photochemistry corresponded with more efficient Q_A⁻ reoxidation, facilitated its interaction with plastoquinone, and caused the overall stabilization of photosynthetic functions under drought. The protective effects of HA were also evident for both PSI subpopulations. The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC). In contrast, lower HA concentrations (1 and 3 mg/mL) provided insufficient protection. This study clearly demonstrates that HA enhances drought tolerance in basil in a concentration-dependent manner by protecting the structural and functional integrity of the photosynthetic apparatus, supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions. Full article

Hulless barley (Hordeum vulgare L. var. nudum) on the Qinghai–Tibet Plateau is consistently exposed to intense solar irradiance, yet whether and how reproductive spikes and flag leaves partition photoprotection remains unclear. Here, we compared a pigmented black landrace (Cai Peng Zi, CPZ) with a white cultivar (Zang Qing 3000, ZQ3000) across early, middle, and late spike coloration stages under field conditions. By integrating measurements of anthocyanin and chlorophyll contents, chlorophyll fluorescence parameters, and rapid light-response curves, we dissected organ-specific strategies in photochemistry and energy dissipation in spikes and flag leaves. The results showed that anthocyanin accumulation in CPZ spikes increased significantly during spike coloration, while chlorophyll a and the chlorophyll a/b ratio declined, indicating a shift from light harvesting to photoprotection in reproductive tissues. This pigment transition coincided with reduced PSII performance (declines in QY_max, qP, and qL) but stable non-photochemical quenching (NPQ and qN), pointing to reduced photochemical capacity with relatively stable energy dissipation in the spike. In contrast, CPZ leaves maintained higher QY_max than ZQ3000 but exhibited a pronounced decline in NPQ and qN at late stages, reflecting CPZ’s attenuated regulated energy dissipation capacity. Rapid light-response analysis further supported differences between organs and cultivars. Under high PAR, ZQ3000 spikes exhibited steeper declines in Y(II) and stronger downregulation of ETR(II), whereas CPZ spikes showed more moderate decreases; in leaves, ZQ3000 maintained consistently lower Y(NO) and higher Y(NPQ), indicating greater reliance on regulated energy dissipation. Collectively, our results reveal how pigment-mediated screening in reproductive structures and dynamic regulation of energy dissipation in leaves are coordinated to optimize light-use efficiency in high-altitude environments, providing physiological insights for breeding resilient hulless barley varieties. Full article

Dissolved organic matter (DOM) plays a central role in estuarine carbon cycling and exhibits dynamically coupled interactions with chlorophyll-a (Chl-a). Under increasing nutrient loads, elevated Chl-a concentrations and shifts in DOM composition serve as key indicators of eutrophication in estuarine aquatic ecosystems. Previous studies have mainly focused on the composition and fluorescence properties of DOM in rivers and lakes. Here, 84 water samples were collected from the Ganjiang River Estuary of Lake Poyang during wet, normal, and dry seasons across the mainstream, middle, and south branches. The average Chl-a concentration showed wet season (6.61 μg·L⁻¹) > normal season (4.54 μg·L⁻¹) > dry season (2.01 μg·L⁻¹). By employing EEM-PARAFAC, five fluorescent components were identified, including C1, C2, C3, C4, and C5. Notably, microbial humic-like substances remained consistently high during the wet season. Two-dimensional correlation spectroscopy was further employed to evaluate sequential changes in DOM components, while a moving window was used to identify temporal variation characteristics. Based on Noda’s rules, the DOM response sequence was identified as C3→C2→C1→C4→C5. Kernel PCA showed that the variable cluster represented by PC1, which consisted of organic pollutants and nutrients, co-varied negatively with Chl-a, whereas the PC2 cluster, representing biogenic organic matter, co-varied positively with Chl-a. Moreover, partial least squares path modeling showed that humic-like and tryptophan-like substances were positively correlated with Chl-a, with the path coefficients of 0.47 and 0.19, respectively. These findings revealed the interaction patterns between DOM components and Chl-a at the river-lake confluence zone, thereby enhancing our understanding of the factors influencing the spatio-temporal variations in Chl-a concentration, and further providing a guide for the control of algal blooms. Full article

Currently, the escalating global problem of soil salinization severely limits the yield and quality of processing tomatoes. However, the differential responses and salt-tolerance strategies among processing tomato genotypes with different salt tolerances under salt stress remain largely elusive. Therefore, this study used salt-tolerant genotype ‘S39’ and salt-sensitive genotype ‘S37’ as materials. Seeds were sown in plug trays, and seedlings at the two-leaf-one-heart stage were transplanted into hydroponic containers filled with Hoagland nutrient solution. When seedlings reached the four-leaf-one-heart stage, they were exposed to NaCl treatments of 0 mM (control), 120 mM (Na120), and 180 mM (Na180). Plant samples were collected at 3, 6, and 9 days after treatment to determine growth parameters, physiological indices, and gene expression levels, aiming to reveal the dynamic differential responses to salt stress between the two processing tomato genotypes. The results demonstrated that the inhibitory effect of NaCl on the growth of processing tomatoes was aggravated with increasing NaCl concentration and treatment duration. The most significant difference in salt tolerance between the two genotypes was observed at 9 days under 180 mM NaCl treatment. At this sampling point, the relative salt-stress indices of superoxide dismutase (SOD) activity, peroxidase (POD) activity, soluble sugar content, proline content, chlorophyll a, chlorophyll b, and total chlorophyll (a + b) in ‘S39’ were significantly higher than those in ‘S37’ by 31.55%, 53.40%, 66.70%, 65.07%, 20.80%, 15.74%, and 19.44%, respectively. In addition, Na contents in roots and stems, as well as K contents in stems and leaves, were significantly higher in ‘S39’ than in ‘S37’ by 43.40%, 8.67%, 22.08%, and 21.99%, respectively. In contrast, relative electrolyte leakage and malondialdehyde (MDA) content in ‘S37’ were 15.54% and 12.44% higher than those in ‘S39’. In addition, photosynthetic parameters, including net photosynthetic rate (A_net), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), transpiration rate (E), and chlorophyll fluorescence parameters, were more stable in ‘S39’ than in ‘S37’. In conclusion, ‘S39’ possesses stronger salt tolerance via a multi-level regulatory strategy involving an enhanced antioxidant enzyme system, elevated accumulation of osmoregulatory substances, improved mineral ion balance, and increased stability of the photosynthetic apparatus. This study provides a comprehensive multi-level analysis of the differential salt tolerance mechanisms in processing tomato genotypes with contrasting salt tolerances and lays a theoretical basis for the screening and identification of salt-tolerant germplasm in processing tomatoes. Full article