Search Results (118)

Viral infections represent a critical threat to cultivated plant species. In papaya cultivation, two viral diseases—papaya mosaic (caused by papaya ringspot virus type P—PRSV-P) and papaya sticky disease (caused by a virus complex of papaya meleira virus—PMeV, and papaya meleira virus—PMeV2)—are prevalent and capable of devastating entire plantations, incurring substantial economic losses. Current diagnostic practices rely on visual identification of symptoms and elimination of infected plants (roguing). Monitoring photosynthetic efficiency in orchards prone to PRSV-P and PMeV2 coinfection may allow early intervention, mitigating productivity losses and reducing fruit quality. This study aimed to evaluate chlorophyll a fluorescence as a biomarker for photosynthetic impairment and symptom severity in papaya infected with PRSV-P and/or PMeV2 and to explore the feasibility of early detection of the infection by these dual pathogens, as an exploratory study under field conditions. Chlorophyll a fluorescence revealed details about the physiology of plants coinfected with the complex of PMeV2 and PRSV-P: the electron motive force within PSII decreases in infected plants and in those without visual symptoms of infection, being proportional to the age and developmental stage of the plants. A slowdown in the multiple electron transfer turnover of PSII and a decrease in the efficiency of the redox reactions of photosystem I were observed in plants with or without visual detection of infection. The evidence generated suggests that the chlorophyll a fluorescence technique can be used to monitor the pathophysiological state of plants under biotic stress. Full article

Miscanthus, a perennial grass, is renowned for its remarkable tolerance to abiotic stress. Excessive levels of drought severely impair plant growth and yield. Plant nuclear factor Y (NF-Y) transcription factors (TFs) play pivotal roles in regulating responses to drought stress in species such as Arabidopsis and maize. However, their functional roles in conferring drought tolerance in Miscanthus remain largely unexplored. This study’s genome-wide analysis and gene expression profiling of Miscanthus under dehydration/osmotic stress identified a transcription factors gene, MsNF-YA4, which was significantly upregulated under dehydration/osmotic stress. MsNF-YA4 overexpression in Arabidopsis significantly enhanced drought tolerance, leading to increased transcription of stress- and antioxidant enzyme-related genes. Compared with the wild type (WT), the transgenic lines exhibited markedly higher relative water content (RWC), chlorophyll content, proline level, and antioxidant enzyme activity. Furthermore, the MsNF-YA4/MsNF-YB3/MsNF-YC2 improved the transactivation of the Miscanthus P5CS1, SOD (Cu/Zn) and CAT1 promoters in the transient system. These results offer fresh perspectives on the role of Miscanthus NF-YAs in drought tolerance and offer promising genetic resources for developing drought-tolerant crops through breeding programs. Full article

Soil salinity is a crucial factor that limits agricultural production, negatively impacting the growth and physiological functions of salt-sensitive crops, such as beans. The present study examined the efficiency of Ulva rigida seaweed extracts (URE) as biostimulants to enhance the growth and photosynthetic ability of bean plants (Phaseolus vulgaris L.) under saline conditions (51.33 mM NaCl). Seaweed extracts were obtained by maceration and ultrasonic assistance at two concentrations, 25% and 50% (v/v), and applied as a foliar spray or irrigation. The most significant improvement was observed following foliar sprays of 50% ultrasonic extract (UP-50), with an increase of 96% in CCI compared to salt-stressed controls and by 71% compared to non-stressed controls. Stomatal conductance (SC) was also significantly improved with UP-50, reaching levels that were 146% higher than those of salt-stressed plants and 53% higher than those of non-stressed plants. The OJIP transients under salinity were significantly improved by both ultrasonic-assisted and maceration extracts; especially, 50% maceration extracts (MP-50) restored PSII quantum efficiency (ΦPo) and total performance index (PItotal) of salinity-stressed seedlings to 107% and 255% of non-stressed control and 122% and 314% of salt-stressed control, respectively. Root length and indole acetic acid (IAA) levels in treated plants were also enhanced, particularly in response to higher concentrations of the extract, suggesting improved root growth as well as hormonal homeostasis in the presence of salt stress. According to these findings, U. rigida extracts, specifically those applied at high concentrations as a foliar spray, serve as biostimulants that mitigate the adverse effects of salt stress on beans by preventing chlorophyll degradation and enhancing photosynthesis, root development, and hormonal balance. Full article

The photochemical efficiency of photosystem II (PSII) was monitored in two-year-old seedlings from six Chilean woody sclerophyllous species differing in foliage habits (evergreen, deciduous, semi-deciduous) and leaf orientation. A common garden experiment was established in July 2020 in a Mediterranean-type climate site under two watering regimes (2 L⁻¹ seedling⁻¹ week⁻¹ for 5 months versus no irrigation). Chlorophyll a fluorescence rise kinetics (OJIP) and JIP test analysis were monitored from December 2021 to January 2022. The semi-deciduous Colliguaja odorifera (leaf angle of 65°) exhibited the highest performance in processes such as absorption and trapping photons, heat dissipation, electron transport, and level of photosynthetic performance (i.e., parameters PI_ABS F_V/F_M, F_V/F₀, and ΔV_IP). In contrast, the evergreen Peumus boldus (leaf rolling) exhibited the opposite behavior for the same parameters. On the other hand, the deciduous Vachelia caven (small compound leaves and leaf angle of 15°) showed the lowest values for minimal and maximal fluorescence (F₀ and F_M) and the highest area above the OJIP transient (S_m) during the study period. Irrigation decreased S_m and the relative contribution of electron transport (parameter ΔV_IP) by 22% and 17%, respectively, but no clear effects of the irrigation treatments were observed among species and dates of measurement. Overall, V. caven and C. odorifera exhibited the highest photosynthetic performance, whereas P. boldus seemed to be more prone to photoinhibition. We conclude that different foliar adaptations among species influence light protection mechanisms more than irrigation treatments. Full article

Soybean (Glycine max (L.) Merrill) is highly sensitive to water deficit, particularly during the vegetative phase, when morphological and metabolic plasticity support continued growth and photosynthetic efficiency. We applied eleven water regimes, from full irrigation (W100) to total water withholding (W0), to plants grown under controlled conditions. After 14 days, we quantified morphophysiological, biochemical, leaf optical, gas exchange, and chlorophyll a fluorescence traits. Drought induces significant reductions in leaf area, biomass, pigment pools, and photosynthetic rates (A, g_s, ΦPSII) while increasing the levels of oxidative stress markers (electrolyte leakage, ROS) and proline accumulation. OJIP transients and JIP test metrics revealed reduced electron-transport efficiency and increased energy dissipation for many parameters under severe stress. Principal component analysis (PCA) clearly separated those treatments. PC1 captured growth and water status variation, whereas PC2 reflected photoprotective adjustments. These data show that progressive drought limits carbon assimilation via coordinated diffusive and biochemical constraints and that the accumulation of proline, phenolics, and lignin is associated with osmotic adjustment, antioxidant buffering, and cell wall reinforcement under stress. The combined use of hyperspectral sensors, gas exchange, chlorophyll fluorescence, and multivariate analyses for phenotyping offers a rapid, nondestructive diagnostic tool for assessing drought severity and the possibility of selecting drought-resistant genotypes and phenotypes in a changing stress environment. Full article

Manganese (Mn) excess and low pH often coexist in some citrus orchard soils. Little information is known about the underlying mechanism by which raising pH reduces Mn toxicity in citrus plants. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) seedlings were treated with 2 (Mn2) or 500 (Mn500) μM Mn at a pH of 3 (P3) or 5 (P5) for 25 weeks. Raising pH mitigated Mn500-induced increases in Mn, iron, copper, and zinc concentrations in roots, stems, and leaves, as well as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, iron, and zinc distributions in roots, but it mitigated Mn500-induced decreases in nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and boron concentrations in roots, stems, and leaves, as well as nutrient imbalance. Raising pH mitigated Mn500-induced necrotic spots on old leaves, yellowing of young leaves, decreases in seedling growth, leaf chlorophyll concentration, and CO₂ assimilation (A_CO2), increase in root dry weight (DW)/shoot DW, and alterations of leaf chlorophyll a fluorescence (OJIP) transients and related indexes. Further analysis indicated that raising pH ameliorated Mn500-induced impairment of nutrient homeostasis, leaf thylakoid structure by iron deficiency and competition of Mn with magnesium, and photosynthetic electron transport chain (PETC), thereby reducing Mn500-induced declines in A_CO2 and subsequent seedling growth. These results validated the hypothesis that raising pH reduced Mn toxicity in ‘Sour pummelo’ seedlings by (a) reducing Mn uptake, (b) efficient maintenance of nutrient homeostasis under Mn stress, (c) reducing Mn excess-induced impairment of thylakoid structure and PEPC and inhibition of chlorophyll biosynthesis, and (d) increasing A_CO2 and subsequent seedling growth under Mn excess. Full article

High temperature has an adverse effect on apple production worldwide. Photosynthesis is a process especially vulnerable to heat stress, which can reduce photosynthetic efficiency, plant growth, development, and ultimately yield. Although the effects of heat stress on apples have been partially examined, the photochemical reactions and heat tolerance of specific rootstocks have still not been sufficiently investigated. Identification of rootstocks with better photosynthetic performance and adaptation to heat stress enables the selection of rootstocks, which could contribute to stable yields and good fruit quality even at elevated temperatures. In this study, chlorophyll a fluorescence (ChlF) induction kinetics was used to investigate the heat tolerance between two apple rootstocks (M.9 and G.210). In addition, we employed lipid peroxidation measurements, hydrogen peroxide quantification, proline content, and total phenolic and flavonoid assessments. Analysis of chlorophyll fluorescence parameters and OJIP curves (different steps of the polyphasic fluorescence transient; O–J–I–P phases) revealed significant differences in their responses, with higher values of the PI_ABS parameter indicating better PS II stability and overall photosynthetic efficiency in M.9 rootstock. The higher contents of chlorophyll, carotenoids, proline, and significant increase in the accumulation of phenolics, and flavonoids in this rootstock also contributed to its better adaptation to heat stress. Oxidative stress was more pronounced in G.210 through higher H₂O₂ and MDA levels, which could point to its lower capacity to adjust to heat stress conditions. This research can provide a scientific basis for further breeding programs and growing plans due to climate change and the occurrence of extremely high temperatures. Full article

Light variability is a key environmental stressor influencing the physiology and productivity of marine macroalgae. This study examined the ecophysiological and biochemical responses of Lessonia spicata (Ochrophyta) during a natural light deprivation event caused by a solar eclipse. We measured the in vivo chlorophyll a (Chla) fluorescence, photoinhibition, and photosynthetic capacity, along with the pigment content, phenolic compound accumulation, and antioxidant capacity, to evaluate short-term photosynthetic adjustments. Dark-adapted conditions during the eclipse peak led to reduced photosynthetic and biochemical activity, while post-eclipse recovery involved the increased accumulation of photosynthetic pigments and photoprotective compounds. Carotenoids showed high antioxidant potential under eclipse exposure, contrasting with declines in chlorophyll content and productivity under pre-eclipse high irradiance. This study provides valuable insights into the rapid acclimation mechanisms of Lessonia spicata to transient light stress, highlighting its sensitivity and resilience to sudden shifts in solar irradiance. These findings contribute to the broader field of marine macroalgal photobiology and stress physiology, enhancing our understanding of how intertidal brown algae adapt to dynamic environmental conditions. Full article

Meeting the rising demand for staple grains now requires cultivars that combine high yield, enhanced nutritional value, and strong chemical resilience. Blue-kernel landraces from central Mexico are rich in anthocyanins yet remain highly susceptible to post-emergence herbicides, whereas modern hybrids detoxify these compounds through cytochrome P450 (CYP450) enzymes. We crossed the anthocyanin-rich variety Polimaize with a CYP450-tolerant hybrid and evaluated the two parents and their F₁ segregants (designated “White” and “Yellow”) under greenhouse applications of mesotrione (75 g a.i. ha⁻¹), nicosulfuron (30 g a.i. ha⁻¹), and their mixture. Across 160 plants, the hybrid retained 95% of control dry matter and showed ≤7% foliar injury under all treatments, whereas Polimaize lost 28% biomass and exhibited 36% injury after nicosulfuron. The Yellow class matched hybrid performance while maintaining a blue pericarp and a β-carotene-rich endosperm, demonstrating that nutritional and agronomic traits can be stacked. The White class displayed heterosis-driven compensatory growth, exceeding its untreated biomass by 60% with nicosulfuron and by 82% with the mixture despite transient bleaching. Chlorophyll and carotenoid fluorescence revealed rapid, zeaxanthin-linked photoprotection in all tolerant genotypes, consistent with accelerated CYP450-mediated detoxification. These findings show that broad-spectrum herbicide tolerance can be introgressed into pigment-rich germplasm through conventional breeding, providing a non-transgenic path to herbicide-ready, anthocyanin-rich maize. The strategy preserves local biodiversity while delivering cultivars suited to intensive, weed-competitive agriculture and offers a template for integrating metabolic resilience into other native crops. Full article

Rhododendron L., a renowned ornamental species and one of the ten famous flowers in China, is highly regarded for its aesthetic value and extensive applications in landscaping. However, its growth and quality are significantly compromised by drought stress, particularly in regions with dry conditions. To elucidate the drought response mechanisms of Rhododendron, two cultivars, ‘SaKeSiZhiXing’ (SKSZX) and ‘TuRuiMeiGui’ (TRMG), were subjected to natural drought stress, and changes in chlorophyll fluorescence and transcriptomic profiles were examined at 0 days (d), 4 d, and 8 d of drought exposure. An OJIP fluorescence transient (O-J-I-P) analysis revealed a progressive decline in the F_P parameter and an increase in the F_J parameter as drought stress intensified. Additionally, a delayed fluorescence (DF) analysis showed a gradual reduction in the I₁ and I₂ values within the induction and decay curves under prolonged drought conditions. The 820 nm curve indicated the deactivation of a transient phase characterized by a rapid decline, followed by a slow recovery in the modulated reflection (MR) signal. A transcriptomic analysis of leaves identified 24,352, 18,688, and 32,261 differentially expressed genes (DEGs) in SKSZX at 0 d, 4 d, and 8 d of drought treatment, respectively. In contrast, TRMG exhibited more pronounced and earlier drought-induced alterations. These DEGs were primarily enriched in pathways related to phenylpropanoid biosynthesis, plant hormone signaling, photosynthesis, and photosynthesis-antenna proteins. Additionally, 565 transcription factors (TFs) were identified, including bHLH, WRKY, bZIP, MYB-related, MYB, C2H2, and HSF families. The drought-induced changes in TRMG were more substantial and occurred earlier compared to SKSZX, with a greater impairment in the electron transfer capacity at both the donor and acceptor sides of photosystem II (PSII). This study provides valuable insights into the molecular mechanisms underlying drought tolerance in Rhododendron and offers a foundation for molecular breeding strategies aimed at enhancing drought resistance in future cultivars. Full article

Heavy metal and cyanide contamination in soil presents serious environmental and ecological concerns due to their persistence, bioavailability, and toxicity to soil biota. In this study, a novel solid-phase direct contact bioassay kit was developed using immobilized Chlorella vulgaris spheres to evaluate the toxicity of soils contaminated with mercury (Hg²⁺), silver (Ag⁺), copper (Cu²⁺), and cyanide (CN⁻). The assay was designed using 25 mL glass vials in which algal spheres were directly exposed to spiked soils for 72 h without the need for pollutant extraction. Oxygen evolution in the headspace was measured as the primary endpoint, alongside optical density and chlorophyll a fluorescence (OJIP) to assess photosynthetic inhibition. The assay demonstrated high sensitivity and reproducibility, with strong correlations (R² > 0.93) between oxygen evolution and optical density. EC₅₀ values based on oxygen evolution were 4.43, 4.18, 3.10, and 61.3 mg/kg for Hg²⁺, Ag⁺, CN⁻, and Cu²⁺, respectively, and 7.8, 7.4, 2.9, and 29.7 mg/kg based on optical density. The relatively higher EC₅₀ for copper was attributed to its biological role as an essential micronutrient. OJIP transient profiles supported the observed photosynthetic inhibition, particularly under Hg²⁺, Ag⁺, and CN⁻ exposure. The present study overcomes the limitations of conventional chemical analyses by providing a rapid, low-cost, and ecologically relevant tool for direct soil toxicity assessment, with potential applications in environmental monitoring and contaminated site evaluation. Full article

Global kelp farming is garnering growing attention for its contributions to fishery yields, environmental remediation, and carbon neutrality efforts. Kelp farming systems face escalating pressures from compounded climatic and environmental stressors. A severe outbreak disaster caused extensive kelp mortality and significant economic losses in Rongcheng, China, one of the world’s largest kelp farming areas. This study investigated the growth and physiological responses of Saccharina japonica to combined stressors involving three levels of N:P ratios (10:1 as a control; 100:1 and 500:1 to represent phosphorus deficiency stress) and two temperature/light regimes (12 °C, 90 μmol photons m⁻² s⁻¹ as a control, and 17 °C, 340 μmol photons m⁻² s⁻¹ to represent thermal and high-light stress). The results demonstrated that phosphorus deficiency significantly inhibited the relative growth rate of kelp (24% decrease), and the strongest growth inhibition in kelp was observed at the N:P ratio of 500:1 combined with thermal and high-light stress. The algal tissue was whitened due to its progressive disintegration under escalating stress, coupled with damage to its chloroplasts and nucleus ultrastructures. Phosphorus-deficiency-induced declines in photochemistry (27–56% decrease) and chlorophyll content (63% decrease) were paradoxically and transiently reversed by thermal and high-light stress, but this “false recovery” accelerated subsequent metabolic collapse (a 60–75% decrease in the growth rate and a loss of thallus integrity). Alkaline phosphatase was preferentially activated to cope with phosphorus deficiency combined with photothermal stress, while acid phosphatase was subsequently induced to provide auxiliary support. S. japonica suppressed its metabolism but upregulated its nucleotides under phosphorus deficiency; however, the energy/amino acid/coenzyme pathways were activated and a broad spectrum of metabolites were upregulated under combined stressors, indicating that S. japonica employs a dual adaptive strategy where phosphorus scarcity triggers metabolic conservation. Thermal/light stress can override phosphorus limitations by activating specific compensatory pathways. The findings of this study provide a foundation for the sustainable development of kelp farming under climate and environmental changes. Full article

Traditional maize (Zea mays L.) breeding approaches use directly measured phenotypic performance to make decisions for the next generation of crosses. Indirect assessment of cultivar performance can be utilized using various methods such as genomic predictions and remote sensing. However, some secondary traits might expand the breeder’s ability to make informed decisions within a single season, facilitating an increase in breeding speed. We hypothesized that assessment of photosynthetic performance with chlorophyll a fluorescence (ChlF) might be efficient for in-season predictions of yield and grain moisture. The experiment was set with 16 maize hybrids over three consecutive years (2017–2019). ChlF was measured on dark-adapted leaves in the morning during anthesis. Partial least squares models were fitted and the efficiency of indirect selection was assessed. The results showed variability in the traits used in this study. Genetic correlations among all traits were mainly very weak and negative. Heritability estimates for all traits were moderately high to high. The model with 10 latent variables showed a higher predictive ability for grain yield (GY) than other models. The efficiency of the indirect selection for GY using biophysical parameters was lower than direct selection efficiency, while the indirect selection efficiency for grain moisture using biophysical parameters was relatively high. The results of this study highlight the significance and applicability of the ChlF transients in maize breeding programs. Full article

The MYB family plays a vital role in regulating plant stress resistance. However, the MYB protein in blue honeysuckle remains largely unexplored. In this study, the LcMYB90 gene from blue honeysuckle ‘Lanjingling’ was stably transformed into tobacco and transiently transformed into blue honeysuckle to characterize its function. Subcellular localization analysis revealed that the LcMYB90 protein is localized in the nucleus. Transgenic plants overexpressing LcMYB90 exhibited enhanced growth performance and higher survival rates under drought and salt stress conditions. These plants also showed increased levels of proline and chlorophyll, along with elevated activities of catalase, peroxidase, and superoxide dismutase. Conversely, malondialdehyde content and relative conductivity were lower, indicating that LcMYB90 enhances tolerance to drought and salt stress. Under salt treatment, genes induced by osmotic stress, such as NHX1 (Na⁺/H⁺ antiporters 1) and SOS1 (salt overly sensitive 1), as well as antioxidant defense system genes like SOD (superoxide dismutase) and CAT1 (catalase 1), were more highly induced in overexpression lines compared to the wild type, supporting the hypothesis that LcMYB90 promotes salt tolerance by enhancing osmotic stress resistance and antioxidant capacity. Simultaneously, the transcription levels of genes involved in the abscisic acid pathway, including NCED1/2 (9-cis-epoxycarotenoid dioxygenase 1/2, PYL4/8 (pyrabactin resistance-Like 4/8), and CBL1 (Calcineurin B-like protein 1), were increased under drought stress conditions in the overexpression lines. These results suggest that LcMYB90 maintains cellular homeostasis by promoting the expression of stress-related genes and regulating osmotic and oxidative substances, thereby improving tolerance to drought and salt stress. Full article

Light quality is a fundamental factor in greenhouses, since different light wavelengths affect plant photosynthesis and photomorphogenesis differently, they thus affect crop growth and productivity. The aim of this study was to evaluate the effect of an experimental greenhouse cover film with UV-to-Red spectral shifting properties on photosynthesis, plant growth, fruit yield, and the quality of two crops spanning over a year-long cultural cycle: aubergines (Solanum melongena L.), as a spring–summer crop, followed by strawberries (Fragaria × ananassa Duch.), as an autumn–spring crop. Trials were carried out in a multispan greenhouse where two sectors were covered, each one with a different light diffusing polyethylene film: one sector was covered with a UV-to-Red photoluminescent film, doped with a blend of rare-earth elements partially converting the UV solar radiation into Red wavelengths, while a light diffusing polyethylene film was used as the control. At the physiological level, spectral shifting affected the chlorophyll fluorescence parameters related to the photochemistry of photosynthesis, which were found to be positively related to crop yield. Moreover, differential analysis of the fast Chlorophyll a fluorescence transients (or OJIP kinetics) showed that spectral shifting affected different steps of the plant photochemical metabolism. Full article