Search Results (1,278)

Rubisco activase (RCA) is an ATP-dependent enzyme that plays a crucial role in plant stress responses by regulating the catalytic activity of Rubisco. However, the alternative splicing and functional characteristics of the RCA gene exhibit notable species-specific diversity. The variable splice forms and functions of the RCA gene in mangrove plants remain poorly understood. Herein, we cloned the RCA cDNA in the leaves of mangrove plant Kandelia candel (L.) in response to combined flooding and salinity stress, and performed systematic expression analysis and functional validation. Our results demonstrated that the RCA gene undergoes alternative splicing to produce two isoforms, designated as KcRCA_l (GenBank accession: MG492021) and KcRCA_s (GenBank accession: MG492022), respectively. The KcRCA_l encodes a 440-amino acid protein (42.49 kDa) belonging to the β-isoforms, while KcRCA_s encodes a 474-amino acid protein (46.10 kDa) classified as the α-isoforms. Moreover, protein structure analysis revealed that both isoforms contain phosphorylation and lysine acetylation modification sites. Phylogenetic analysis indicated that KcRCA shares the closest evolutionary relationship with RCA from Cicer arietinum (chickpea) and Durio zibethinus (durian). Furthermore, RT-qPCR analysis revealed that the expression levels of KcRCA_l and KcRCA_s were significantly upregulated in K. Candel leaves under the combined stress condition. The following functional validation studies in transgenic Arabidopsis demonstrated that overexpression of the KcRCA cDNA enhances the plant’s tolerance to resist flooding and salinity stress while improving antioxidant capacity and increasing RCA and Rubisco activity, thereby maintaining photosynthetic efficiency under combined flooding and salinity stress. Our study not only provides new experimental evidence for understanding the molecular mechanisms of plant flooding and salinity stress, but also offers theoretical foundations for breeding flooding- and salinity-tolerant crops. Full article

This study aimed to assess, compare, and validate a satellite-based plant health and water stress indicator: Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) over Uganda. We used a direct agricultural drought indicator—the Standardized Precipitation and Evapotranspiration Index at scale 3 (SPEI-03)—and a plant water stress indicator—the crop water stress index (CWSI)—for the period of 1983–2013. Novel approaches such as spatial variability and trend analysis, along with correlation analysis, were used to achieve this. The results showed that there are six classes of highly variable photosynthetic activity over Uganda, dominated by class 4 (0.36–0.45). This dominant class encompassed 45% of the total land area, mainly spanning cropland. In addition, significant increases in monthly photosynthetic activity (FAPAR) and FAPAR-centered stress indicators (SFI < −1) were observed over 85% and 60% of total land area, respectively. The Standardized FAPAR Index (SFI) had a strong positive correlation with SPEI-03 over cropland, grassland, and forest lands, while SFI had a strong negative correlation with CWSI over 80% of the total area. These results highlight the state and variation in plant health and water stress, generate insights on ecosystem dynamics and functionality, and weigh in on the usability and reliability of satellite-based variables such as FAPAR in plant water monitoring over Uganda. We thus recommend satellite-based FAPAR as a robust proxy for vegetation health and water stress monitoring over Uganda, with potential application in crop yield prediction and irrigation management to inform effective agricultural planning and improve productivity. Full article

To reveal the mechanism by which exogenous dopamine (Da) regulates Shine Muscat grape (Vitis labrusca L. × Vitis vinifera L.) in response to low-temperature stress, annual Shine Muscat grape plants were used as material. Different concentrations of Da (0.2–1.0 mmol L⁻¹) were set to investigate its synergistic regulatory effects on grape photosynthetic protection, osmotic adjustment, ion homeostasis, antioxidant defense, and cold-responsive gene expression and to identify the optimal concentration and core pathways through correlation analysis. The results showed that low-temperature stress significantly inhibited plant growth, reduced photosynthetic efficiency, disrupted ion balance, induced oxidative damage, and downregulated the expression of cold-responsive genes. Da exhibited a “low-concentration promotion and high-concentration inhibition” effect, with the 0.4 mmol L⁻¹ treatment showing the best performance: growth indicators such as plant height and stem diameter increased by 22.4–52.2% compared with the low-temperature stress group; photosynthetic parameters and photosystem II (PSII) function were significantly improved; proline content increased by 40.3%; the Na⁺/K⁺ ratio decreased by 44.8%; activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) increased by 31.7–49.5%; and the expression of genes in the C-repeat binding factor (CBF) family was upregulated. Correlation analysis confirmed that the activity of SOD and catalase (CAT) showed a highly significant positive correlation with growth indicators (r > 0.8, p < 0.01) and a highly significant negative correlation with malondialdehyde (MDA) content (r < −0.8, p < 0.01), indicating that antioxidant defense is the core pathway. In conclusion, exogenous Da enhances the cold tolerance of Shine Muscat grape through multi-pathway synergy, with 0.4 mmol L⁻¹ the optimal concentration, which can provide a theoretical basis for cold-resistant cultivation of grapes. Full article

The quality of tomato fruit represents a key determinant of consumer preference, while functional fertilisers significantly contribute to quality enhancement. Limited research has investigated the synergistic mechanisms between functional fertilisers and vermicompost in tomato cultivation systems. The present study was designed to investigate the effects of synergistic regulation between functional fertilisers and vermicompost on soil fertility, as well as the growth and quality of two tomato cultivars, with the ultimate goal of identifying the functional fertiliser treatment exhibiting optimal comprehensive performance. A completely randomised block design was adopted, involving two tomato cultivars (DRK0568 and Sangfen 180), five functional fertiliser treatments (T1–T5), and a water-only control (CK). Measurements included tomato growth parameters, photosynthetic characteristics, fruit quality indices, yield components, biomass accumulation, soil nutrient levels, and enzyme activities. The results demonstrated significant varietal-specific responses to different functional fertiliser treatments. In terms of growth and yield, the T1 treatment exhibited a significant advantage, as it significantly increased the plant height, stem thickness, biomass, and yield of both varieties (DRK0568 and Sangfen 180) by 6.86% and 10.41%, respectively, while also significantly reducing the malformed fruit rate. For photosynthetic analyses, the T1 treatment significantly increased the chlorophyll a and total chlorophyll content in Sangfen 180, as well as the transpiration rate of both tomato varieties. The T4 treatment resulted in the highest chlorophyll b content and optimal water use efficiency in Sangfen 180. Regarding nutritional quality, the T1 treatment significantly increased the vitamin C and soluble sugar content in DRK0568; both varieties exhibited higher sugar–acid ratios under the T3 and T4 treatments. A comprehensive evaluation using the entropy-weighted TOPSIS method for multiple quality indicators (excluding yield parameters) showed that the T4 treatment achieved the highest score. Soil nutrient analyses revealed that the T1 treatment significantly increased the soil organic matter and available potassium content in DRK0568, while the T4 treatment significantly increased the urease activity in Sangfen 180. In conclusion, the T1 treatment (mineral-sourced potassium fulvate fertiliser) exhibited excellent performance in both increasing yield and improving quality, while the T4 treatment (Type II algal polysaccharide fertiliser additive) demonstrated unique advantages in enhancing fruit quality indicators. Full article

In mycorrhizal symbiotic relationships, non-photosynthetic myco-heterotrophic plants are unable to supply photosynthates to their associated fungi. On the contrary, they rely on fungal carbon to sustain their own growth. Mycorrhizal fungi can mediate plant interactions with the rhizosphere microbiome, which contributes to the promotion of plant growth and nutrient uptake. However, the microbial community and key microbial species that function during the growth of the myco-heterotrophic plant Cheilotheca humilis remain unclear. In this study, we evaluated the microbial community associated with Cheilotheca humilis, which was confirmed via morphological characteristics typical of this plant species. Metagenomic analysis showed that the Afipia carboxidovorans was dominant at species level. Based on the LDA score, Bradyrhizobium ottawaense exhibited the higher abundance in the CH-B group (related to bud) while Afipia carboxidovorans was identified from the CH-F group (related to flower). Microbial co-occurrence networks showed that the Rhizobium genus, Herbaspirillum genus, and Cyanobacteriota were defined as core functional microbial species. To explore the potential microorganisms, metagenome-assembled genomes (MAGs) of the rhizosphere microbiome identified 14 medium- and high-quality MAGs, mainly involved in carbon fixation, nitrogen transformation, and phosphorus metabolism, possibly providing nutrients for the plant. Furthermore, a total of 67 rhizospheric and 66 endophytic microorganisms were isolated and obtained. In vitro experiments showed that the mycorrhizal helper bacteria (MHBs) Rhizobium genus and Pseudomonas genus possessed the ability of nitrogen fixation, phosphate solubilization, and siderophores production. Most importantly, the mycorrhizal fungus Humicolopsis cephalosporioides was obtained, which could potentially produce cellulase to supply carbohydrates for host. The findings suggest the mycorrhizal fungus Humicolopsis cephalosporioides and helper bacteria have great potential in the growth of the myco-heterotrophic plant Cheilotheca humilis. Full article

Agricultural land management is a major determinant of terrestrial carbon (C) fluxes and has substantial implications for greenhouse gas (GHG) mitigation strategies. This study evaluated the net ecosystem carbon balance (NECB) of an agricultural field in an organic integrated crop–livestock system (ICLS) with a ley-arable rotation in northern Germany over two years (2021–2023). Carbon dioxide (CO₂) fluxes were measured using the eddy covariance (EC) method to derive net ecosystem exchange (NEE), gross primary production (GPP), and ecosystem respiration (RECO). This approach facilitated an assessment of the temporal dynamics of CO₂ exchange, alongside detailed monitoring of field-based C imports, exports, and management activities, of a crop sequence including grass-clover (GC) ley, spring wheat (SW), and a cover crop (CC). The GC ley acted as a consistent C sink (NECB: −1386 kg C ha⁻¹), driven by prolonged photosynthetic activity and moderate biomass removal. In contrast, the SW, despite high GPP, became a net source of C (NECB: 120 kg C ha⁻¹) due to substantial export via harvest. The CC contributed to C uptake during the winter period. However, cumulatively, it acted as a net CO₂ source, likely due to drought conditions following soil cultivation and CC sowing. Soil cultivation events contributed to short-term CO₂ pulses, with their magnitude modulated by soil water content (SWC) and soil temperature (TS). Overall, the site functioned as a net C sink, with an average NECB of −702 kg C ha⁻¹ yr⁻¹. This underscores the climate mitigation potential of management practices such as GC ley systems under moderate grazing, spring soil cultivation, and the application of organic fertilizers. To optimize CC benefits, their use should be combined with reduced soil disturbance during sowing or establishment as an understory. Additionally, C exports via harvests could be offset by retaining greater amounts of harvest residues onsite. Full article

The study focuses on determining the concentrations of nitrites, nitrates, ammonium, and mineral phosphorus in the waters of the Azov-Black Sea basin. It investigates the limitation of primary phytoplankton production in the region, and evaluates the impact of bifurcation (switching of limiting factors) on the natural conditioning of the marine environment concerning biogenic elements. The research was conducted during 2023–2024 in Streletskaya Bay (Sevastopol), coastal areas of the northeastern Black Sea, and the Sea of Azov. The limiting function was assessed using the Redfield equation. The key findings indicate that the dependencies of the Redfield parameter on phosphate (PO₄) concentration and total nitrogen compounds are described by power functions. A rule for natural regulation of phytoplankton communities was established: whenever the concentration of biogenic elements in the aquatic environment deviates from the region-specific stoichiometric ratio, the functioning of photosynthetic systems always acts to restore it. The validity of this rule was confirmed using a mathematical model and was supported by annual observational data on biogenic element concentrations in Streletskaya Bay. Full article

Chrysanthemum (Chrysanthemum morifolium Ramat.), a typical short-day plant (SDP), relies on photoperiod and light quality signals to regulate flowering and growth. Red light interruptions inhibit its flowering, whereas supplemental blue light can counteract this inhibitory effect. To investigate how “high-blue/low-red” mixed light (RBL) regulates chrysanthemum flowering and growth, we treated ‘Gaya Glory’ plants with 4 h of supplemental or night-interruptional RBL (S-RBL4 or NI-RBL4, 0 or 30 ± 3 μmol m⁻² s⁻¹ PPFD) under 10 h short-day and 13 h long-day conditions (SD10 and LD13; white light, WL; 300 ± 5 μmol m⁻² s⁻¹ PPFD), recorded as SD10, SD10 + S-RBL4, SD10 + NI-RBL4, LD13, LD13 + S-RBL4, and LD13 + NI-RBL4, respectively. Under SD10 conditions, S-RBL4 promoted flowering and enhanced nutritional quality, whereas NI-RBL4 suppressed flowering. Under LD13 conditions, both treatments alleviated flowering inhibition, with S-RBL4 exhibiting a more pronounced inductive effect. Chrysanthemums displayed superior vegetative growth and physiological metabolism under LD13 compared to SD10, as evidenced by higher photosynthetic efficiency, greater carbohydrate accumulation, and more robust stem development. Furthermore, S-RBL4 exerted a stronger regulatory influence than NI-RBL4 on photosynthetic traits, the activities of sugar metabolism-related enzymes, and gene expression. The photoperiodic flowering of chrysanthemum was coordinately regulated by the photoreceptor-mediated and sugar-induced pathways: CmCRY1 modulated the expression of florigenic genes (CmFTLs) and anti-florigenic gene (CmAFT) to transmit light signals, while S-RBL4 activated sucrose-responsive flowering genes CmFTL1/2 through enhanced photosynthesis and carbohydrate accumulation, thereby jointly regulating floral initiation. The anti-florigenic gene CmTFL1 exhibited dual functionality—its high expression inhibited flowering and promoted lateral branch and leaf growth, but only under sufficient sugar availability, indicating that carbohydrate status modulates its functional activity. Full article

Leaf senescence is a precisely regulated developmental process that is critical for grapevine growth and yield, which is easily influenced by environmental factors. High temperature is a major factor that accelerates senescence rapidly, adversely affects photosynthetic performance, severely hindering fruit nutrient metabolism and growth. This study investigated chlorophyll fluorescence and physiological traits in grape (Vitis vinifera L.) leaves at different senescence stages under natural high-temperature conditions in Turpan. Measurements included chlorophyll content, MDA levels, antioxidant enzyme activities, and chlorophyll fluorescence parameters. The results showed that (1) young leaves exhibited higher and more sustained chlorophyll content but were prone to wilting, whereas older leaves showed accelerated chlorosis and functional decline; (2) high temperature severely impaired PSII function, inhibiting electron transport and photochemical efficiency, reflected in increased ABS/RC, TR_o/RCC, and DI_o/RC, and decreased F_v/F_m, F_v/F_o, and PI_abs; (3) POD, SOD, CAT and MDA levels initially increased then decreased, correlating with photosynthetic changes and leaf age; and (4) young leaves maintained stronger photosynthetic capability and physiological resilience than older ones. Although partial recovery occurred after temperature reduction, photosynthetic and antioxidant activities did not fully revert. This suggests persistent heat-induced functional decline and accelerated senescence, providing insights for understanding heat-induced leaf senescence and developing strategies for cultivating grapevines. Full article

Bacterial wilt is a highly destructive disease affecting a wide range of crops, with no effective chemical control methods currently available. Consequently, the development of microbial strategies for disease management has become increasingly important. Among these, plant immunity-intensifying microbes have demonstrated promising efficacy in controlling bacterial wilt. However, the influence of environmental factors, particularly light intensity, on the effectiveness of these microbes remains unclear. Light intensity is a critical regulator of the photosynthetic system and plant biochemical functions, including defense responses. In this study, we specifically utilized Arabidopsis plants grown under distinct light intensities to systematically examine how light conditions affect the induction of plant immune responses and the occurrence of bacterial wilt. Our findings revealed that Arabidopsis grown under high light intensity exhibited significantly stronger immune responses and reduced disease severity, compared to plants grown under low light intensity. Further, application of Bacillus amyloliquefaciens PMB05, a plant immunity-intensifying strain, resulted in more pronounced immune signaling and disease control efficacy under high light conditions. Experiments using salicylic acid (SA)-deficient mutants demonstrated that disruption of the SA pathway abolished the enhanced suppression of bacterial wilt conferred by B. amyloliquefaciens PMB05 under high light intensity, indicating that the SA pathway is indispensable for PMB05-mediated disease resistance. Moreover, the validation experiments in tomato plants supported these results, with B. amyloliquefaciens PMB05 significantly reducing bacterial wilt development under high light intensity. Collectively, our study demonstrates that growing plants under varying light intensities provides critical insights into how environmental conditions modulate the effectiveness of plant immunity-intensifying microbes, offering a potential strategy for integrated disease management in crops. Full article

The important function of polar lipids in the biochemical chains of photosynthesis, the outstanding biochemical process on our planet, has been mentioned in many publications. Over the last several years, apart from the known function of lipids in creating a matrix for photosynthetic complexes, most attention has been paid to the role of lipids in building up and functioning of the photosynthetic complexes. The lipid molecules are found inside the complexes of photosystem II (PSII), photosystem I (PSI), and cytochrome b₆f (Cyt b₆f) together with other cofactors that accompany proteins and chlorophyll molecules. Super complexes PSII-light-harvesting complex II (PSII-LHCII) and PSI-light-harvesting complex I (PSI-LHCI) also include lipid molecules; part of the lipid molecules is located at the borders between the separate monomers of the complexes. Our interest is in the exact localization of lipid molecules inside the monomers: what are the protein subunits with the lipid molecules in between and how do the lipids contact directly with the amino acids of the proteins? The photosystems include very few classes of all the polar lipids, three groups of glyceroglycolipids, and one group of glycerophospholipids make up the quartet of polar lipids. What are the reasons they have been selected for the role? There are no doubts that the polar heads and the fatty acids chains of these lipids are taking part in the processes of photosynthesis. However, what are the distinct roles for each of them? The advantages and disadvantages of the head groups of lipids from thylakoid membranes and those lipids that for various reasons could not take their place are discussed. Attention is focused on those bound fatty acids that predominate or are characteristic for each class of thylakoid lipids. Emphasis is also placed on the content of each of the four lipids in all photosynthetic complexes, as well as on contacts of head groups and acyl chains of lipids with specific proteins, transmembrane chains, and their amino acids. This article is devoted to the search for answers to the questions posed. Full article

To effectively address the issues of poor ventilation, light deficiency, increased pest and disease pressure, and declining fruit quality in closed-canopy walnut orchards, this study was conducted in a standard, densely planted ‘Xinwen 185’ walnut orchard. Three treatments were established: an unthinned control (CK), a 1-year thinning treatment (T1), and a 2-year thinning treatment (T2). All parameters were uniformly investigated during the 2023 growing season to analyze the effects of thinning on orchard population structure, microenvironment, leaf physiological characteristics, fruit quality, and yield. The results demonstrated that tree thinning significantly optimized the population structure: crown width expanded by 6.22–6.76 m, light transmittance increased to 27.74–33.64%, and orchard coverage decreased from 100% to 75.94–80.51%. The microenvironment was improved: inter-row temperature increased by 2.34–4.08 °C, light intensity increased by 5.38–25.29%, and relative humidity decreased by 2.15–3.30%. Furthermore, leaf physiological functions were activated: in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively; the leaf carbon-to-nitrogen ratio increased by 18.67%; the net photosynthetic rate (Pn) during fruit expansion increased by 34.21–46.10%; and the intercellular CO₂ concentration (Ci) decreased by 10.18–10.31%. Fruit quality and yield were synergistically enhanced: single fruit weight increased by 23.39~37.94%, and kernel weight increased by 26.79–41.13%. The total sugar content in inner-canopy fruits increased by 16.50–16.67%, while the protein and fat content in outer-canopy fruits increased by 0.69–12.50% and 0.60–2.18%, respectively. Yield exhibited a “short-term adjustment and long-term gain” pattern: the T2 treatment (after 2 years of thinning) achieved a yield of 5.26 t·ha⁻¹, which was 20.38% higher than the CK. The rates of diseased fruit and empty shells decreased by 65.71% and 93.22%, respectively, and the premium fruit rate reached 90.60%. This study confirms that tree thinning is an effective measure for improving the growing environment and enhancing overall productivity in closed-canopy walnut orchards, providing a scientific basis for sustainable orchard management and increased orchard profitability. Full article

Acetolactate synthase (ALS) is an important enzyme in plant branched-chain amino acid biosynthesis and the target of several major herbicide classes. Despite its agronomic importance, the role of ALS genes in stress adaptation in the invasive weed Amaranthus palmeri remains unstudied. In this study, four ApALS genes with high motif conservation were identified and analyzed in A. palmeri. Phylogenetic analysis classified ApALS and other plant ALS proteins into two distinct clades, and the ApALS proteins were predicted to localize to the chloroplast. Gene expression analysis demonstrated that ApALS genes are responsive to multiple stresses, including salt, heat, osmotic stress, glufosinate ammonium, and the ALS-inhibiting herbicide imazethapyr, suggesting roles in both early and late stress responses. Herbicide response analysis using an Arabidopsis thaliana ALS mutant (AT3G48560) revealed enhanced imazethapyr resistance, associated with higher chlorophyll retention. Furthermore, high sequence homology between AT3G48560 and ApALS1 suggests a conserved role in protecting photosynthetic function during herbicide stress. This study provides the first comprehensive analysis of the ALS gene family in A. palmeri and offers important insights into its contribution to stress resilience. These findings establish a vital foundation for developing novel strategies to control this pervasive agricultural weed and present potential genetic targets for engineering herbicide tolerance in crops. Full article

Cytokinins (CKs) are central regulators of leaf senescence, yet their cultivar-specific functions in cereals remain insufficiently understood. Here, we examined dark-induced senescence (DIS) in three barley (Hordeum vulgare L.) cultivars: Carina, Lomerit, and Bursztyn, focusing on responses to exogenous benzyladenine (BA) and inhibition of endogenous CK biosynthesis via the mevalonate (MVA) pathway using lovastatin (LOV). Bursztyn, a winter cultivar, displayed a previously uncharacterized stay-green phenotype, characterized by delayed chlorophyll and protein degradation and reduced sensitivity to BA with respect to chlorophyll retention. In contrast, Carina (spring) senesced rapidly but exhibited strong responsiveness to BA. Lomerit (winter) showed an intermediate phenotype, combining moderate natural resistance to senescence with clear responsiveness to BA. CK application suppressed SAG12 cysteine protease accumulation in all cultivars, serving as a marker of senescence and N remobilization, stabilized photosystem II efficiency, preserved photosynthetic proteins, and alleviated oxidative stress without promoting excessive energy dissipation. Although BA only partially mitigated the decline in net CO₂ assimilation, it sustained ribulose-1,5-bisphosphate regeneration, supported electron transport, and stabilized Rubisco and Rubisco activase. Moreover, LOV-based inhibition of the MVA pathway of CK biosynthesis revealed that endogenous CK contributions to senescence delay were most pronounced in Lomerit, moderate in Bursztyn, and negligible in Carina, indicating genotype-specific reliance on MVA-versus methylerythritol phosphate (MEP) pathway-derived CK pools. Collectively, these findings identify Bursztyn as a novel genetic resource for stay-green traits and demonstrate that BA delays DIS primarily by maintaining photosynthetic integrity and redox balance. The results highlight distinct regulatory networks shaping CK-mediated senescence responses in cereals, with implications for improving stress resilience and yield stability. Full article

Urban expansion alters environmental conditions, influencing tree physiology and performance. Urban trees provide cooling, sequester carbon, support biodiversity, filter contaminants, and enhance human health. This study examines how two common urban trees—Norway Maple (Acer platanoides L.) and Little-leaved Linden (Tilia cordata Mill.)—respond to urban site conditions by assessing leaf morphology, stomatal, and gas exchange traits across street and urban park sites in Chicago, IL. Street trees exhibited structural trait adjustments, including smaller leaf area, reduced specific leaf area, and increased stomatal density, potentially reflecting acclimation to more compact and impervious conditions. Norway Maple showed stable photosynthetic assimilation (A), stomatal conductance (g_s), and transpiration (E) across sites, alongside higher intrinsic water-use efficiency (_iWUE), indicating a conservative water-use strategy. In contrast, Little-leaved Linden maintained A and g_s but showed elevated E and _iWUE at street sites, suggesting adaptive shifts in water-use dynamics under street microenvironments. These findings highlight how species-specific physiological strategies and local site conditions interact to shape tree function in cities and underscore the importance of incorporating functional traits into urban forestry planning to improve ecosystem services and climate resilience. Full article