Salinity stress is one of the most detrimental abiotic factors affecting plant development, harming vast swaths of agricultural land worldwide. Silicon is one element that is obviously crucial for the production and health of plants. With the advent of nanotechnology in agricultural sciences, the application of silicon oxide nanoparticles (SiO-NPs) presents a viable strategy to enhance sustainable crop production. The aim of this study was to assess the beneficial effects of SiO-NPs on the morpho-physio-biochemical parameters of rice (Oryza sativa L., variety: DRR Dhan 73) under both normal and saline conditions. To create salt stress during transplanting, 50 mM NaCl was injected through the soil. 200 mM SiO-NPs were sprayed on the leaves 25 days after sowing (DAS). It was evident that salt stress significantly hindered rice growth because of the reductions in shot length (41 %), root length (38 %), shot fresh mass (40 %), root fresh mass (47 %), shoot dry mass (48 %), and root dry mass (39 %), when compared to controls. Together with this growth inhibition, elevated oxidative stress markers including a 78 % increase in malondialdehyde (MDA) and a 67 % increase in hydrogen peroxide (H2O2) indicating enhanced lipid peroxidation were noted. Increasing the chlorophyll content (14 %), photosynthetic rate (11 %), protein levels, total free amino acids (TFAA; 13 %), and total soluble sugars (TSS; 11 %), all help to boost nitrogen (N; 16 %), phosphorous (P; 14 %), potassium (K; 12 %), and vital nutrients. The adverse effects of salt stress were significantly reduced by exogenous application of SiO-NPs. Additionally; SiO-NPs dramatically raised the activity of important antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT), improving the plant's ability to scavenge reactive oxygen species (ROS) and thereby lowering oxidative damage brought on by salt. This study highlights SiO-NPs' potential to develop sustainable farming practices and provides significant new insights into how they enhance plant resilience to salinity, particularly in salt-affected regions worldwide.

Nanotechnology is an emerging tool which has the potential to stimulate photosynthetic process in stress related environment. Unfortunately, the role of nanotechnology on photosynthetic performance explaining photosystem II functionality and specific energy fluxes in crop plants are rather scarce. Photosystem II contributes 90% of the energy requirement in plants, therefore its participation in a sub-optimal environment cannot be ruled out. The current study not only elucidates the role of Zinc-NP on light harvesting efficiency of photosystem II and specific energy fluxes but also explains their subsequent involvement in physiological tolerance against salt stress in saline soil. Oryza sativa L. rice var. Diamond and Triticum aestivum L.wheat var. Benazir seeds were sown in plastic pots and were allowed to grow in natural condition. Fifteen-day-old plants were exposed to ZnO-NP at 0.02 g/L with or without salt stress (0, 75, and 150 mM) NaCl concentration. Application of nanoparticles in saline environment showed 22 to 36% increase in rice and 9 to 25% in wheat growth. Biomass accumulations and relative water content (RWC) were also increased from 10 and 111% in a suboptimal condition. Moreover, nanoparticles reduced the oxidative damages in both rice and wheat plants indicating -20.2 to -58.3% and -28.7 to -20.2% reduction in the MDA and H2O2 production under moderate to severe salt stress. Maximum quantum yield (Fv/Fm) was less affected in severe and moderate salt stress indicating -7 and -5.4% decrease in stress condition. Foliar application of ZnO-NP improves the size and number of active reaction centre of photosynthetic machinery (Fv/Fo) and performance index (PIabs) in saline soil. It was concluded that Zn-NP not only sustained light harvesting potential in both cereal plants under salinized soil but also increases the biomass accumulation and reduces oxidative damage in a sub-optimal environment.

Soil salinization is increasingly recognized as a critical environmental challenge that significantly threatens plant survival and agricultural productivity. To elucidate the mechanism of salt resistance in poplar, physiological and transcriptomic analyses were conducted on 84K poplar (Populus alba x Populus glandulosa) under varying salt concentrations (0, 100, 200 and 300 mM NaCl). As salt levels increased, observable damage to poplar progressively intensified. Differentially expressed genes under salt stress were primarily enriched in photosynthesis, redox activity and glutathione metabolism pathways. Salt stress reduced chlorophyll content and net photosynthetic rate, accompanied by the downregulation of photosynthesis-related genes. NaCl (300 mM) significantly inhibited the photochemical activity of photosystems. The higher photochemical activity under 100 and 200 mM NaCl was attributed to the activated PGR5-cyclic electron flow photoprotective mechanism. However, the NAD(P)H dehydrogenase-like (NDH)-cyclic electron flow was inhibited under all salt levels. Salt stress led to reactive oxygen species accumulation, activating the ASA-GSH cycle and antioxidant enzymes to mitigate oxidative damage. Weighted gene co-expression network analysis showed that five photosynthesis-related hub genes (e.g., FNR and TPI) were down-regulated and nine antioxidant-related hub genes (e.g., GRX, GPX and GST) were up-regulated under salt stress conditions. PagGRXC9 encodes glutaredoxin and was found to be differentially expressed during the salt stress condition. Functional studies showed that overexpressing PagGRXC9 enhanced salt tolerance in yeast, and in poplar, it improved growth, FV/FM, non-photochemical quenching values and resistance to H2O2-induced oxidative stress under salt stress. This study constructed the photosynthetic and antioxidant response network for salt stress in poplar, revealing that PagGRXC9 enhances salt tolerance by reducing photoinhibition and increasing antioxidant capacity. These findings provide valuable insights for breeding salt-tolerant forest trees.

Soil salinization threatens sustainable agriculture, necessitating innovative restoration strategies. Suaeda salsa (L.) Pall., a halophyte with exceptional salt tolerance and vivid pigmentation, serves as an ideal model for salinity adaptation. This study integrates physiological and transcriptomic analyses to reveal how high salinity (400 mmolL(-)1 NaCl) upregulates 4,5-DOPA dioxygenase after 30 days of salt stress, promoting betacyanin accumulation to mitigate oxidative damage. Compared to the control, betacyanin content in the 200 mmolL(-)1 and 400 mmolL(-)1 NaCl groups increased to 1.975-fold and 3.675-fold, respectively, while chlorophyll a content decreased by 45.78% and 69.88%, chlorophyll b by 11.45% and 28.24%, and total chlorophyll by 30.28% and 53.06%. This trade-off in pigment allocation highlights the plant's adaptive strategy under salinity stress. The photosynthetic characteristics of S. salsa confirm that its photoprotective mechanisms are significantly enhanced under 400 mmolL(-)1 NaCl. At the molecular level, betacyanin biosynthesis alleviates oxidative stress, while transcriptional regulation of photosystem I (PSI) and photosystem II (PSII) genes-such as PsbY, PsaO, PsbM, and PsbW-partially restores photosynthetic activity. Stabilization of the electron transport chain by upregulated genes like PetA and PetH further enhances photosynthetic resilience. These findings highlight the synergy between betacyanin production and photosynthetic regulation in enhancing salinity resilience, providing insights for soil restoration and salt-tolerant crop breeding.

In recent decades, flash drought events have frequently occurred in the humid regions of southern China. Due to the sudden onset and rapid intensification of these droughts, they often cause severe damage to vegetation photosynthesis. However, our understanding of the spatiotemporal evolution characteristics of flash droughts across different vegetation types, as well as the response regularity of photosynthesis to flash droughts, especially early responses, remains limited. This study analyzes the spatiotemporal evolution characteristics of flash droughts for different vegetation types in the Middle and Lower Reaches of the Yangtze River Basin from 2000 to 2023. It uses solar-induced chlorophyll fluorescence (SIF) and fluorescence yield (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{{\upvarphi\:}}_{\text{F}\:}$$\end{document}) to explore the response regularity of vegetation photosynthesis to flash droughts, with a systematic analysis of the 2013 flash drought event. The results show that, over the past 24 years, the frequency of flash droughts for different vegetation types in the Middle and Lower Reaches of the Yangtze River Basin has decreased, but the total duration has increased, with forests experiencing the highest frequency of flash droughts, while cropland experiences the least. Cropland photosynthesis is the most sensitive to flash drought, showing an early response 8-16 days after the onset and reaching a negative anomaly between 24 and 32 days. Forests mainly show an early response between 16 and 24 days and a negative anomaly response between 32 and 40 days. During the 2013 flash drought, cropland showed an early response on the 10th day after the onset and a negative anomaly on the 26th day, while forest responses were later, with early responses on the 20th day and negative anomalies on the 36th day. These results align with long-term statistical data. This study contributes to a deeper understanding of vegetation photosynthesis response regularity to flash droughts and provides insights for developing effective flash drought management strategies.

To address the issue of poor phytoremediation in Cd-contaminated saline soil caused by the biotoxicity of Cdsalinity, we constructed a symbiotic system of arbuscular mycorrhizal fungi (AMF) and the hyperaccumulator Solanum nigrum, and systematically elucidated the response strategies of Solanum nigrum and the enhancement mechanism of AMF for plant tolerance through cytological, physiological, and transcriptomic methods. The findings showed that Cd-salinity stress had synergistic aggravated Cd/Na enrichment, ultrastructural damage, photosynthetic inhibition, water loss, and reactive oxygen species (ROS) accumulation in plants. In response to the heterogeneity of Cd/salinity stress, AMF smartly regulated the Cd/salinity tolerance of host plants: AMF decreased intercellular CO2 concentration (Ci) under Cd stress to alleviate non-stomatal limitation induced by Cd, but increased Ci under salinity stress to alleviate the stomatal limitation induced by salinity; the role of AMF in strengthening the osmoregulation system was more prominent under salinity stress, thereby alleviated the more severe osmotic imbalance induced by salinity. AMF also enhanced signal transduction to consolidate resistance defense, upregulated antioxidant genes to activate antioxidant enzymes, and strengthened the AsAGSH cycle to mitigate oxidative damage. The enhancement of tolerance improved plant growth and Cd enrichment. Under high Cd-high salinity combined stress, Cd concentrations in shoots and roots increased by 14.28 % and 38.85 %, respectively, and the biomass also increased by over 30.00 % after AMF inoculation. In summary, inoculation with AMF serves as an effective and sustainable phytoremediation enhancement strategy that improves the host plants' stress resistance through multiple pathways, thereby increasing the phytoremediation potential.

Soil-borne pathogens can severely reduce vegetable crop output and quality. A disease complex may develop when many soil-borne pathogens attack a crop simultaneously, which can cause more damage. The soil-borne fungus Fusarium oxysporum (Fo) and the nematode Meloidogyne incognita (Mi) significantly reduce global tomato (Solanum lycopersicum L.) yields. After a soil-borne pathogenic infection, plants undergo numerous changes. Therefore, we conducted the present study to examine the impact of soil-borne pathogens Fo and Mi on the growth, physiology, biochemical, and root morphology of tomato cultivars Zhongza 09 (ZZ09) and Gailiang Maofen 802 (GLMFA and GLMFB) at 10, 20, and 30 days after-inoculation (DAI). The present study revealed that combined infections adversely damaged plant growth, photosynthetic pigmentation, gas exchange, biochemistry, and root morphology. The plant growth reduction in GLMFA and GLMFB was greater than in ZZ09. The chlorophyll content and photosynthetic indices declined dramatically; however, ZZ09 declined less than GLMFA and GLMFB plants. In GLMFA and GLMFB plants, the combined infection of Fo and Mi lowered plant-defense-related antioxidant activity compared to their single infection or control. ZZ09's antioxidants were greatly up-regulated, indicating pathogen tolerance. ZZ09 had significantly lower gall and wilt disease indices than GLMFA and GLMFB. Moreover, the microscopic examination of roots showed that Fo and Mi infection damaged GLMFA and GLMFB more than ZZ09 plants. Thus, combined infection induced severe root damage, reduced plant growth, reduced antioxidants, and increased reactive oxygen species (ROS) production compared to single inoculation. However, the ZZ09 cultivar exhibited significantly stronger tolerance to combined infection.

Perchlorate (ClO4 -) is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility, poor degradability, and widespread distribution. However, the impacts of perchlorate on aquatic autotrophs such cyanobacterium are still unclear. Herein, Synechocystis sp. PCC6803 (Synechocystis) was used to investigate the response mechanisms of perchlorate on cyanobacterium by integrating physiological and transcriptome analyses. Physiological results showed that perchlorate mainly damaged the photosystem of Synechocystis, and the inhibition degree of photosystem II (PSII) was severer than that of photosystem I (PSI). When the exposed cells were moved to a clean medium, the photosynthetic activities were slightly repaired but still lower than in the control group, indicating irreversible damage. Furthermore, perchlorate also destroyed the cellular ultrastructure and induced oxidative stress in Synechocystis. The antioxidant glutathione (GSH) content and the superoxide dismutase (SOD) enzyme activity were enhanced to scavenge harmful reactive oxygen (ROS) in Synechocystis. Transcriptome analysis revealed that the genes associated with photosynthesis and electron transport were significantly regulated. For instance, most genes related to PSI (e.g., psaf, psaf) and the electron transport chain were upregulated, whereas most genes related to PSII (e.g., psbA3, psbD1, psbB, and psbC) were downregulated. Additionally, perchlorate also induced the expression of genes related to the antioxidant system (sod2, gpx, gst, katG, and gshB) to reduce oxidative damage. Overall, this study is the first to investigate the impacts and mechanisms of cyanobacterium under perchlorate stress, which is conducive to assessing the risk of perchlorate in aquatic environments. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Copper (Cu) holds a significant importance in plant metabolism as it serves as an essential micronutrient but becomes toxic at higher concentrations. Nitric oxide (NO), a key signaling molecule, and nitrogen (N) play essential roles in combating toxicity of some metals. This study explores the potential of interactive effects of NO as 100 mu M SNP (sodium nitroprusside, NO source) and N (80 mg N kg-1 soil) in mitigating Cu (100 mg Cu kg-1 soil) stress in mustard (Brassica juncea L.) plants. The impaired physio-biochemical changes, photosynthetic efficiency, and the expression level of genes associated with photosynthesis, and N assimilation under Cu stress were ameliorated with the exogenous application of NO and N. The combined treatment of NO and N conspicuously lowered reactive oxygen species (ROS) and its related impacts. It also enhanced the activity and relative expression of antioxidant enzymes, including ascorbate peroxidase (APX), glutathione reductase (GR), and superoxide dismutase (SOD) as well as N assimilation enzymes, such as nitrate reductase (NR) and nitrite reductase (NiR). The supplementation of NO and N also triggered the expression of rbcL (large subunit of Rubisco), photosystem (photosystem II D1 protein; psbA and photosystem II protein B; psbB) and markedly improved photosynthetic capacity under Cu stress. The study highlights the significance of NO and N as a potential strategy to counteract Cu-induced stress in crops. It suggests a synergistic or interactive effect between the two substances as a phytoremediation strategy for enhancing crop growth and productivity in Cu-contaminated soils. Understanding the mechanisms behind NO and N mediated stress alleviation could facilitate the development of targeted approaches to enhance plant resilience against heavy metal stress.

BackgroundSalt stress is considered to be one of the major abiotic stresses influencing rice growth and productivity. To improve rice crop productivity in saline soils, it is essential to choose a suitable variety for mitigating salt stress and gain a deep understanding of the underlying mechanisms. The current study explored the salt tolerance mechanism of wild rice 'HD96-1 (salt resistive)' and conventional rice 'IR29 (salt sensitive)' by evaluating morph-physiological, transcriptomic, and metabolomic approaches.ResultsPhysiological data indicated that HD96-1 had higher chlorophyll content, higher photosynthetic efficiency, more stable Na+/K+, less H2O2, and lower electrolyte leakage under salt stress compared with IR29. Transcriptomic and metabolomic data showed that the expression of NHXs in IR29 was significantly down-regulated under salt stress, leading to a large accumulation of Na+ in the cytoplasm, and that the expression of CHLH, PORA, and PORB was significantly down-regulated, inhibiting chlorophyll synthesis. HD96-1 maintained the balance of Na+ and K+ by increasing the expression of NHX4, and there was no significant change in the expression of genes related to chlorophyll synthesis, which made HD96-1 more resistant to salt stress than IR29. In addition, HD96-1 inhibited the excessive synthesis of hydrogen peroxide (H2O2) and alleviated oxidative damage by significantly down-regulating the expression of ACX4 under salt stress. HD96-1 promoted the accumulation of isoleucine by up-regulating genes of branched-chain amino acid aminotransferase 2 and branched-chain amino acid aminotransferase 4 and might promote the synthesis of raffinose and stachyose by up-regulating the expression of the gene for galactitol synthase 2, which, in turn, maintained a stable osmotic pressure and relieved osmotic stress. We also found that IR29 and HD96-1 alleviated the inhibition of photosynthesis by salt stress by down-regulating the expression of light-harvesting chromophore protein complex (LHCH II)-related genes and reducing the excessive accumulation of glucose metabolites, respectively. In addition, HD96-1 enhances salt tolerance by regulating C2H2 and bHLH153 transcription factors.ConclusionUnder salt stress, HD96-1 maintained ionic balance and photosynthetic efficiency by up-regulating the expression of NHX4 gene and reducing the overaccumulation of glucose metabolites, respectively, and mitigated osmotic stress and oxidative stress by down-regulating the expression of ACX4 and promoting the accumulation of isoleucine, respectively, thereby enhancing the adaptability to salt stress. IR29 maintained photosynthetic efficiency under salt stress by down-regulating the expression of light-harvesting chromophore protein complex (LHCH II)-related genes, thereby enhancing adaptation to salt stress.