Search Results (174)

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

Zeolites are naturally abundant, low-cost aluminosilicate minerals commonly found in sedimentary rock. The surface chemistry of zeolite can be modified via cationic surfactant loading, termed a surfactant-modified zeolite (SMZ), that can be used as an antimicrobial technology in water treatment processes. This raises the possibility that SMZs could be utilised to treat blooms of harmful algae and cyanobacteria; however, there is a lack of understanding of the toxicity of SMZs to non-target microorganisms, including non-problematic algae and cyanobacteria. To address this knowledge gap, this research investigates whether hexadecyltrimethylammonium-bromide (HDTMA-Br) SMZs are toxic to the cyanobacterium Synechococcus elongatus and the microalgae Chlorella vulgaris, Nannochloropsis oculata and Duniallela salina. The cells were exposed to natural zeolite, HDTMA-Br surfactant and HDTMA-Br SMZ for 24 h and analysed 2- and 26 h post-exposure via flow cytometry and imaging pulse amplitude modulated fluorometry. There was an overall trend of reduced cell density in the SMZ and surfactant treatments. The SMZ treatment reduced the effective PSII quantum yield (Y(II)) but increased the quantum yield of regulated energy dissipation for C. vulgaris. When exposed to the surfactant treatment, no Y(II) signals were detected from any species. We conclude that SMZs are toxic to non-target microorganisms, with resilience dependent upon cell wall structure. Full article

Desiccation tolerance is a critical adaptive trait that enables plants to survive extreme water loss, yet its physiological basis in tomato and its wild relatives remains poorly understood. In this study, chlorophyll a fluorescence imaging was used as a reliable tool to evaluate photosystem II (PSII) response to progressive desiccation. The analysis was conducted in cultivated tomato (Solanum lycopersicum) and five wild relatives (Solanum chilense, Solanum habrochaites, Solanum peruvianum, Solanum pimpinellifolium, and Solanum pennellii). Detached leaves were subjected to controlled desiccation for up to 50 h. During this period, tissue moisture content (TMC), relative water content (RWC), PSII photochemical efficiency [Fv/Fm; maximum quantum yield (QY_max)], minimal fluorescence (F0), maximal fluorescence (Fm), and variable fluorescence (Fv) were monitored to assess changes in photosynthetic performance. Desiccation caused a significant, moisture-dependent decline in PSII efficiency across all species, with QY_max showing a strong linear relationship with RWC (R² = 0.80–0.90). Interspecific variation was evident as S. chilense, S. habrochaites, S. peruvianum, and S. pimpinellifolium exhibited rapid PSII impairment, while S. lycopersicum showed moderate tolerance. In contrast, S. pennellii maintained higher PSII stability, with 50% loss of efficiency occurring only at lower RWC (30–35%). Overall, chlorophyll fluorescence imaging effectively captured functional diversity in desiccation tolerance, highlighting S. pennellii as a valuable genetic resource for improving drought resilience in tomato. Full article

Biostimulants offer a sustainable strategy to improve plant growth and stress resilience, particularly under limited water availability. We evaluated seven biostimulant treatments, including beneficial bacteria, mycorrhizal fungi, seaweed extract with humic acid, and their combinations, on early growth and physiological responses of tomato (Solanum lycopersicum L.) under well–watered and drought-stressed conditions. Plants were assessed before and after a seven-day controlled drought period using a range of morphological and physiological traits, including height, effective quantum yield of PSII (Φ_PSII), stomatal conductance (g_s), and leaf pigment profile. Results showed that microbial treatments that included Bacteria + Mycorrhizae (B + M) maintained Φ_PSII above 0.60 and preserved height gain relative to the control, while seaweed-based formulations with humic acid (S + H) exhibited significant reductions in height of up to 35% compared with full irrigation. In addition, the bacterial treatment (B) significantly increased the root/shoot ratio under drought, indicating enhanced carbon allocation to roots. These findings demonstrate that specific microbial-based biostimulant combinations can better maintain physiological performance and growth under water limitation, supporting their potential use in sustainable tomato production systems. Full article

This study investigated the impact of the pretreatment of pea plants (Pisum sativum L. Ran 1) for five days by three times higher light intensity (360 μmol m⁻² s⁻¹) than the intensity for their cultivation (120 μmol m⁻² s⁻¹) on the photosynthetic apparatus’s ability to withstand moderately high temperatures. Photosystem II (PSII) performance was assessed by pulse amplitude-modulated (PAM) fluorometry—evaluation of F_v/F_m, Chl fluorescence decrease ratio—R_Fd, excitation pressure on PSII (1 − qP), non-photochemical quenching (NPQ) analysis, and PsbA (D1) abundance. The redox state of P700 was used to examine photosystem I (PSI), and the redox kinetics of P700 was evaluated as an estimate of cyclic electron flow (CEF). The energy distribution and interaction between the two photosystems were assessed by 77 K chlorophyll fluorescence. Diphenylhexatriene (DPH) fluorescence polarization and PsbS accumulation were followed to estimate alterations in thylakoid membrane characteristics. Our data show that pea plants pretreated with a higher level of light intensity showed higher resistance to temperature increase, maintaining R_Fd values similar to control plants, and the effect of high temperature on PSII excitation pressure (1 − qP) was mitigated. A significant difference between the two groups of plants was observed in terms of quantum yields in both types of non-photochemical quenching, with light pretreated plants showing no change in the energy partitioning ratio while the exposure of non-high light pretreated plants to elevated temperatures led to a more significant increase in quantum yield of constitutive non-photochemical quenching. When plants were exposed to higher temperature, the accumulation of PsbS, induced by high light treatment, was accelerated, and stabilization of thylakoid membrane also occurred. A complex mechanism behind the enhanced tolerance to higher temperature includes the reorganization of membrane pigment–protein complexes, which is regulated by the buildup of PsbS and the accompanying redistribution of excitation energy. Full article

Light availability drives Stevia rebaudiana productivity, yet how incident radiation interacts with genotype and site under tropical field conditions remains unclear. We evaluated four genotypes (L020, L102, L082, and ‘Morita II’) across three Caribbean locations in Colombia under two contrasting light levels (600 vs. 1800 μmol photons m⁻² s⁻¹) using a split-plot randomised complete block design with four replicates. Incident photosynthetic photon flux density (PPFD) was logged and, at 85 days after transplanting (DAT), net CO₂ assimilation, stomatal conductance, transpiration, and intercellular CO₂ concentration were measured alongside light-adapted chlorophyll fluorescence parameters, including the effective quantum yield of photosystem II (ΦPSII), the maximum efficiency of PSII in the light (Fv′/Fm′), photochemical quenching (qP), and electron transport rate (ETR); biomass and leaf yield were quantified at harvest. Data were analysed using factorial analysis of variance (ANOVA) and complementary multivariate approaches, including Pearson correlation analysis and principal component analysis (PCA). Radiation responses were strongly site-dependent: under 1800 μmol photons m⁻² s⁻¹, net CO₂ assimilation increased by 90.2% at El Carmen de Bolívar and 21.5% at Polonuevo but decreased by 36.4% at Montería. Leaf yield was highest in El Carmen de Bolívar (1951.46 ± 182.03 kg ha⁻¹), followed by Montería (1510.94 ± 173.75 kg ha⁻¹) and Polonuevo (576.31 ± 42.36 kg ha⁻¹). Genotype rankings shifted with environment and radiation, with L102 reaching 3256.25 ± 126.39 kg ha⁻¹ under direct radiation in El Carmen de Bolívar and ‘Morita II’ showing strong responsiveness in Montería. These results demonstrate that photosynthetic plasticity and leaf yield in S. rebaudiana depend on genotype × radiation × environment interactions, supporting location-tailored radiation management combined with targeted genotype deployment. Full article

Due to climate change, seedling damage caused by drought stress is expected to increase in both afforestation sites and nurseries. Therefore, to ensure stable seedling production under high-temperature conditions and to cultivate seedlings with enhanced drought tolerance through hardening treatments, the development of an effective irrigation system is required. Conventional physiological methods for non-destructive drought detection, such as chlorophyll fluorescence and leaf temperature measurements, require expensive and manual operation, thereby limiting their real-time applicability in forest nurseries. This study evaluated the applicability of using image-based leaf angle measurements for drought stress detection in Quercus acutissima Carruth. seedlings. One-year-old seedlings were grown under two water regimes—well-watered (CT: control) and unwatered (DT: drought)—through Day 8. Statistical analyses (RMANOVA) revealed that changes in the leaf angle parameter PMD–MD (the difference between the previous and current measurement days) showed treatment effects similar to those of the physiological responses ΦNO (quantum yield of non-regulated energy dissipation) and qL (fraction of open PSII reaction centers) to drought on Day 6. Leaf angle reflected drought stress but did not precede physiological changes, indicating its role as a complementary rather than an early indicator. Multiple regression models identified AT (air temperature), SM (soil moisture), Fm′ (maximum fluorescence in the light-adapted state), and VPD (vapor pressure deficit) as the main factors influencing leaf angle variation. Although leaf angle was affected by combined environmental stresses such as high temperature, it was less sensitive to heat stress than physiological responses based on RMANOVA results. These results indicate the potential of image-based leaf angle measurements for drought stress detection. To establish plant-based smart irrigation systems, future studies should validate and refine this approach using larger datasets. Full article

Petroleum contamination significantly impacts soil microbial communities and vegetation; however, the long-term effectiveness of phytoremediation remains poorly understood. This study evaluated soil microbiological activity, polycyclic aromatic hydrocarbon (PAH) concentrations, and physiological responses five years after the remediation of a petroleum spill site in central Poland. Following a pipeline failure in June 2020 that released diesel fuel and gasoline into the riparian habitat, the contaminated area underwent remediation using Urtica dioica L. as the primary phytoremediator. Soil samples from five plots along a contamination gradient were analyzed for microbial abundance (total bacteria, fungi, fluorescent Pseudomonas sp.), PAH fractions (C6–C12, C13–C16, C17–C35), and physicochemical properties. Chlorophyll fluorescence (JIP test) on two species was used to assess plant photosynthetic efficiency. Results revealed that successful PAH degradation required high fungal abundance rather than optimal soil fertility. Plots with 8–9-fold higher fungal populations achieved 69–81% reduction in heavy PAHs (C17–C35), while the Control plot, despite superior physicochemical properties, maintained high contamination due to low fungal colonization. Urtica dioica exhibited exceptional tolerance (stable maximum quantum yield of PSII (Fv/Fm) and elevated photosynthetic performance index (PIabs)) across all contamination levels, whereas Poa trivialis L. showed significant stress responses. The principal component analysis confirmed that soil texture influences fungal establishment, with sandy soils favoring aerobic degradation despite lower nutrient retention. These findings demonstrate that phytoremediation success depends critically on fungal-mediated biodegradation rather than baseline soil quality alone. Full article

Salt stress is a severe threat to medicinal plants, adversely affecting their growth, yield, and quality. As a key antioxidant tripeptide, glutathione (GSH) confers salinity stress resilience in plants. However, how GSH shapes the plant tolerance to salt stress remains a mystery, especially in medicinal plants, including Pogostemon cablin. In this study, we investigated the regulatory effects of exogenous GSH on P. cablin seedlings under salt conditions. The results showed that GSH significantly improved seedling quality under both normal and salt conditions, evidenced by the increased shoot and root dry weight, plant height, and root length. Moreover, GSH effectively protected the photosynthetic system against salt-mediated damage via raised chlorophyll a, chlorophyll b, carotenoids, quantum yield of photosystem II [Y (II)], and PSII maximum efficiency (Fv/Fm). Furthermore, GSH stimulated the antioxidant defense system, including GSH, AsA, SOD, CAT, APX, POD, and GR, to restrain salt-induced malondialdehyde production and ROS burst. In addition, GSH treatment promoted the biosynthesis of secondary metabolites, including total polyphenol and flavonoid. RNA-seq analysis revealed that the activation of the flavonoid biosynthetic pathway significantly enhanced salt tolerance in P. cablin. Notably, several key regulatory genes within this pathway, including PAL, 4CL, C4H, CHI, ANS, F3′H, and CYP93, were significantly upregulated 24 h following GSH application under salt conditions. Therefore, exogenous GSH alleviates salt-induced oxidative stress in P. cablin via enhancing the antioxidant defense system and flavonoid biosynthetic activation. These findings provide valuable insights into the dual defense strategies of GSH for conferring salt resistance in plants. Full article

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

Oats (Avena sativa L.) are a staple grain and forage crop with substantial market demand. In China, they are the second most-imported forage grass, only after alfalfa (Medicago sativa L.). Enhancing the salt tolerance of oats to facilitate their cultivation in saline areas can thereby increase forage yield and promote the utilization of saline land, which constitutes an important reserve land resource in China. This study aimed to identify the bacterial strain Bacillus sp. LrM2 (hereafter referred to as strain LrM2) to determine its precise species-level classification and evaluate its effects on oat photosynthesis and growth under salt stress through indoor pot experiments. The results indicated that strain LrM2, capable of urease production and citrate utilization, was identified as Bacillus mojavensis. The strain LrM2 had a positive effect on shoot and root growth of oats under 100 mM NaCl stress conditions. Strain LrM2 inoculation modulated osmotic stress in oats under 100 mM NaCl stress by significantly increasing soluble sugar and decreasing proline content in leaves. It inhibited Na⁺ uptake and promoted K⁺ absorption in the roots, thereby reducing Na⁺ translocation to the leaves and mitigating ionic toxicity. Inoculation with strain LrM2 significantly increased photosynthetic pigment content (chlorophyll a, carotenoids), improved gas exchange parameters (stomatal conductance, transpiration rate, net rate of photosynthesis), enhanced PSII photochemical efficiency (maximum quantum yield, coefficient of photochemical quenching, actual photosynthetic efficiency of PSII, electron transfer rate), and reduced the quantum yield of non-regulated energy dissipation. These improvements, coupled with increased relative water content and instantaneous water use efficiency, thereby collectively enhanced the overall photosynthetic performance. In conclusion, strain LrM2 represents a promising bio-resource for mitigating salt stress and promoting growth in oats, with direct applications for developing novel biofertilizers and sustainable agricultural strategies. 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

To investigate the effects of varying degrees of shading on the photosynthetic characteristics of Spuriopinnella brachycarpa (Kom.) Kitag. experiments were conducted under five shading treatments: 0% (full sunlight), 20%, 40%, 60%, and 80%. The results demonstrated that shading significantly influenced plant growth and photosynthesis. Plant height, stem diameter, and leaf area in the control group (0% shading) were significantly greater than those in shaded treatments, although a 40% shading treatment notably increased the aboveground harvestable biomass, demonstrating greater potential for economic yield compared to the control. All shading treatments significantly enhanced the net photosynthetic rate of S. brachycarpa compared to the control; however, excessive shading (i.e., 80% shading) led to a reduction in the net photosynthetic rate, falling below that observed under full sunlight. The 40% shading treatment yielded the most substantial improvement in net photosynthetic rate. Shading also significantly enhanced the maximum quantum yield of PSII, facilitating improved use of light energy for photosynthesis while reducing energy dissipation as heat. Additionally, antioxidant activity in shaded plants was markedly higher than in the control, with the highest levels observed under 40% shading. These findings suggest that moderate shading, particularly at 40%, is optimal for improving photosynthetic efficiency, light energy utilization, and antioxidant activity in S. brachycarpa 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