Since risk assessments of tropospheric ozone (O3) are crucial for agricultural and forestry sectors, there is a growing body for realistic assessments by a stomatal flux-based approach in Free-Air Controlled Exposure (FACE) facilities. Ozone risks are normally described as relative risks (RRs), which are calculated by assuming the biomass or yield at zero O3 dose as "reference". However, the estimation of the reference biomass or yield is challenging due to a lack of O3-clean-air treatment at the FACEs and the extrapolation without data in a low O3 range increases the bias for estimating the reference values. Here, we reviewed a current methodology for the risk assessment at FACEs and presented a simple and effective way ("modified Paoletti's approach") of defining RRs just using biomass or yield data with a range of expected impacts under the FACE conditions hypothesizing three possible scenarios based on prediction limits using 95% credible intervals (CI) (1. Best fit using the intercept as reference, 2. Optimistic scenario using a lower CI and 3. Worst scenario using an upper CI). As a result, O3-sensitive species show a relatively narrow effect range (optimistic vs. worst scenario) whereas a wide range of response may be possibly taken in resistant species. Showing a possible effect range allows for a comprehensive understanding of the potential risks and its uncertainties related to a species sensitivity to O3. As a supporting approach, we also recommend to use scientifically relevant tools (i.e., ethylenediurea treatments; mechanistic plant models) for strengthening the obtained results for the RRs against O3. Interestingly, the moderately sensitive or resistant species showed non-linear rather than linear dose-response relationships, suggesting a need for the flexible functional form for the risk assessment to properly describe the complex plant response such as hormesis, which depends on their plasticity to O3 stress.
Straw incorporation holds significant promise for enhancing soil fertility and mitigating air pollution stemming from straw burning. However, this practice concurrently elevates the production and emission of methane (CH4) from paddy ecosystems. Despite its environmental impact, the precise mechanisms behind the heightened CH4 production resulting from long-term straw incorporation remains elusive. In a 32-year field experiment featuring three fertilization treatments (CFS-chemical fertilizer with wheat straw, CF-chemical fertilizer, and CK-unamended), we investigated the impact of abiotic (soil physicochemical properties) and biotic (methanogenic abundance, diversity, and community composition) factors on CH4 production in paddy fields. Results revealed a significantly higher CH4 production potential under CFS treatment compared to CF and CK treatments. The partial least squares path model revealed that soil physicochemical properties (path coefficient = 0.61), methanogenic diversity (path coefficient = -0.43), and methanogenic abundance (path coefficient = 0.29) collectively determined CH4 production potential, explaining 77% of the variance. Enhanced soil organic carbon content and water content, resulting from straw incorporation, emerged as pivotal factors positively correlated with CH4 production potential. Under CFS treatment, lower Shannon index of methanogens, compared to CF and CK treatments, was attributed to increased Methanosarcina. Notably, the Shannon index and relative abundance of Methanosarcina exhibited negative and positive correlations with CH4 production potential, respectively. Methanogenic abundance, bolstered by straw incorporation, significantly amplified overall potential. This comprehensive analysis underscores the joint influence of abiotic and biotic factors in regulating CH4 production potential during multi-decadal straw incorporation.
Urban trees possess different capacities to mitigate ozone (O3) pollution through stomatal uptake. Stomatal closure protects trees from oxidative damage but limits their growth. To date, it is unclear how plant hydraulic function affect stomatal behaviour and determine O3 resistance. We assessed gas exchange and hydraulic traits in three subtropical urban tree species, Celtis sinensis, Quercus acutissima, and Q. nuttallii, under nonfiltered ambient air (NF) and elevated O3 (NF60). NF60 decreased photosynthetic rate (An) and stomatal conductance (gs) only in Q. acutissima and Q. nuttallii. Maintained An in C. sinensis suggested high O3 resistance and was attributed to higher leaf capacitance at the full turgor. However, this species exhibited a reduced stomatal sensitivity to vapour pressure deficit and an increased minimal gs under NF60. Such stomatal dysfunction did not decrease intrinsic water use efficiency (WUE) due to a tight coupling of An and gs. Conversely, Q. acutissima and Q. nuttallii showed maintained stomatal sensitivity and increased WUE, primarily correlated with gs and leaf water relations, including relative water content and osmotic potential at turgor loss point. Our findings highlight a trade-off between O3 resistance and stomatal functionality, with efficient stomatal control reducing the risk of hydraulic failure under combined stresses.
Forest carbon sequestration capacity in China remains uncertain due to underrepresented tree demographic dynamics and overlooked of harvest impacts. In this study, we employ a process-based biogeochemical model to make projections by using national forest inventories, covering approximately 415,000 permanent plots, revealing an expansion in biomass carbon stock by 13.6 ± 1.5 Pg C from 2020 to 2100, with additional sink through augmentation of wood product pool (0.6-2.0 Pg C) and spatiotemporal optimization of forest management (2.3 ± 0.03 Pg C). We find that statistical model might cause large bias in long-term projection due to underrepresentation or neglect of wood harvest and forest demographic changes. Remarkably, disregarding the repercussions of harvesting on forest age can result in a premature shift in the timing of the carbon sink peak by 1-3 decades. Our findings emphasize the pressing necessity for the swift implementation of optimal forest management strategies for carbon sequestration enhancement.
Carbon Sequestration , Forests , Trees , China , Biomass , Carbon/analysis
This paper represents the first integrative assessment and documentation of taurine-induced hormetic effects in the biological and biomedical areas, their dose response features, mechanistic frameworks, and possible public health, therapeutic and commercial applications. Taurine-induced hormetic effects are documented in a wide range of experimental models, cell types and for numerous biological endpoints, with most of these experimental findings being reported within the past five years. It is suggested that the concept of hormesis may have a transformative effect on taurine research and its public health and therapeutic applications.
Hormesis , Models, Biological
Rutin is a flavonoid present in numerous fruits and vegetables and therefore widely consumed by humans. It is also a popular dietary supplement of 250-500 mg/day. There is considerable consumer interest in rutin due to numerous reports in the biomedical literature of its multi-system chemo-preventive properties. The present paper provides the first assessment of rutin-induced hormetic concentration/dose responses, their quantitative features and mechanistic basis, along with their biological, biomedical, clinical, and public health implications. The findings indicate that rutin-induced hormetic dose responses are widespread, being reported in numerous biological models and cell types for a wide range of endpoints. Of critical importance is that the optimal hormetic findings shown in in vitro systems are currently not achievable for human populations due to low gastrointestinal tract bioavailability. These findings have the potential to strengthen future experimental studies with rutin, particularly concerning study design parameters.
Hormesis , Rutin , Humans , Rutin/pharmacology , Flavonoids/pharmacology , Models, Biological , Vegetables
We hypothesized that anthocyanins act as a sugar-buffer and an alternative electron sink during leaf senescence to prevent sugar-mediated early senescence and photoinhibition. To elucidate the anthocyanin role, we monitored seasonal changes in photosynthetic traits, sugar, starch and N contents, pigment composition, and gene expression profiles in leaves exposed to substantially different light conditions within a canopy of an adult tree of fullmoon maple (Acer japonicum). Enhancement of starch amylolysis accompanied with cessation of starch synthesis occurred in the same manner independent of light conditions. Leaf sugar contents increased, but reached upper limits in the late stage of leaf senescence, even though leaf anthocyanins further increased after complete depletion of starch. Sun-exposed leaves maintained higher energy consumption via electron flow than shade-grown leaves during leaf N resorption. Thus, anthocyanins accumulated in sun-exposed leaves might have a regulative role as a sugar buffer, retarding leaf senescence, and an indirect photoprotective role as an alternative sink for electron consumption to compensate declines in other metabolic processes such as starch and protein synthesis. In this context, anthocyanins might be key substrates protecting both outer-canopy leaves (against photoinhibition) and inner-canopy leaves (via shading by outer-canopy leaves) from high light stress during N resorption.
The present paper provides a new perspective of previously published findings by Siwak (Food Chem 141:1227-1241, 2013) which showed that 15 structurally diverse flavonoids reduced toxicity (i.e., enhanced cell viability) from hypochlorite using the MTT assay within a pre-conditioning experimental protocol, with each agent showing a similar biphasic concentration response relationship. We use this Commentary to point out that each of the concentration response relationships are consistent with the hormetic dose response. The paper of Siwak (Food Chem 141:1227-1241, 2013) is unique in that it provides a comparison of a relatively large number of agents using the identical experimental protocol.
Flavonoids , Hormesis , Flavonoids/toxicity , Cell Survival , Dose-Response Relationship, Drug
Increased surface ozone (O3) pollution seriously threatens crop production, and ethylenediurea (EDU) can alleviate crop yield reduction caused by O3. However, the reason for the decrease in grain nitrogen (N) accumulation caused by O3 and whether EDU serves as N fertilizer remain unclear. An experiment was conducted to investigate the impacts of factorial combinations of O3 enrichment (ambient air plus 60 ppb) and EDU (foliage spray with 450 ppm solutions) on N concentration, accumulation and remobilization in hybrid rice seedlings. Compared to ambient condition, elevated O3 significantly inhibited the N accumulation in vegetative organs during anthesis and grain N accumulation during the maturity stage. Elevated O3 significantly decreased the total N accumulation during anthesis and maturity stages, with a greater impact at the latter stage. The decrease in grain N accumulation caused by O3 was attributed to a decrease in N remobilization of vegetative organs during the grain filling period as well as to a decrease in post-anthesis N uptake. However, there was no significant change in the proportion of N remobilization and N uptake in grain N accumulation. The inhibitory effect of O3 on N remobilization in the upper canopy leaves was greater than that in the lower canopy leaves. In addition, elevated O3 increased the N accumulation of panicles at the anthesis stage, mainly by resulting in earlier heading of rice. EDU only increased N accumulation at the maturity stage, which was mainly attributed to an increase in rice biomass by EDU. EDU had no significant effect on N concentration, N remobilization process, and N harvest index. The findings are helpful to better understand the utilization of N fertilizer by rice under O3 pollution, and can also provide a theoretical basis for sustainable nutrient management to alleviate the negative impact of O3 on crop yield and quality.
Oryza , Ozone , Edible Grain , Fertilizers , Nitrogen/pharmacology , Ozone/pharmacology
Tropospheric ozone (O3 ) is a phytotoxic air pollutant adversely affecting plant growth. High O3 exposures are often concurrent with summer drought. The effects of both stresses on plants are complex, and their interactions are not yet well understood. Here, we investigate whether drought can mitigate the negative effects of O3 on plant physiology and growth based on a meta-analysis. We found that drought mitigated the negative effects of O3 on plant photosynthesis, but the modification of the O3 effect on the whole-plant biomass by drought was not significant. This is explained by a compensatory response of water-deficient plants that leads to increased metabolic costs. Relative to water control condition, reduced water treatment decreased the effects of O3 on photosynthetic traits, and leaf and root biomass in deciduous broadleaf species, while all traits in evergreen coniferous species showed no significant response. This suggested that the mitigating effects of drought on the negative impacts of O3 on the deciduous broadleaf species were more extensive than on the evergreen coniferous ones. Therefore, to avoid over- or underestimations when assessing the impact of O3 on vegetation growth, soil moisture should be considered. These results contribute to a better understanding of terrestrial ecosystem responses under global change.
Ecosystem , Ozone , Droughts , Ozone/toxicity , Photosynthesis , Plant Leaves/physiology , Plants
This paper addresses how long lifespan can be extended via multiple interventions, such as dietary supplements [e.g., curcumin, resveratrol, sulforaphane, complex phytochemical mixtures (e.g., Moringa, Rhodiola)], pharmaceutical agents (e.g., metformin), caloric restriction, intermittent fasting, exercise and other activities. This evaluation was framed within the context of hormesis, a biphasic dose response with specific quantitative features describing the limits of biological/phenotypic plasticity for integrative biological endpoints (e.g., cell proliferation, memory, fecundity, growth, tissue repair, stem cell population expansion/differentiation, longevity). Evaluation of several hundred lifespan extending agents using yeast, nematode (Caenorhabditis elegans), multiple insect and other invertebrate and vertebrate models (e.g., fish, rodents), revealed they responded in a manner [average (mean/median) and maximum lifespans] consistent with the quantitative features [i.e., 30-60% greater at maximum (Hormesis Rule)] of the hormetic dose response. These lifespan extension features were independent of biological model, inducing agent, endpoints measured and mechanism. These findings indicate that hormesis describes the capacity to extend life via numerous agents and activities and that the magnitude of lifespan extension is modest, in the percentage, not fold, range. These findings have important implications for human aging, genetic diseases/environmental stresses and lifespan extension, as well as public health practices and long-term societal resource planning.
Hormesis , Longevity , Animals , Humans , Longevity/physiology , Hormesis/physiology , Aging/physiology , Caenorhabditis elegans/physiology , Stress, Physiological
As typical antibiotics, tetracycline (TC) and sulfadiazine (SDZ) enter the human body through the food chain. Therefore, it is necessary to understand their individual and combined toxicity. In this study, the effects of TC, SDZ, and their mixture on cell viability, cell membrane damage, liver cell damage, and oxidative damage were evaluated in in vitro assays with human liver cells Huh-7. The results showed cytotoxicity of TC, SDZ, and their mixture, which induced oxidative stress and caused membrane and cell damage. The effect of antibiotics on Huh-7 cells increased with increasing concentration, except for lactate dehydrogenase (LDH) activity that commonly showed a threshold concentration response and cell viability, which commonly showed a biphasic trend, suggesting the possibility of hormetic responses where proper doses are included. The toxicity of TC was commonly higher than that of SDZ when applied at the same concentration. These findings shed light on the individual and joint effects of these major antibiotics on liver cells, providing a scientific basis for the evaluation of antibiotic toxicity and associated risks.
Anti-Bacterial Agents , Sulfadiazine , Humans , Sulfadiazine/toxicity , Anti-Bacterial Agents/toxicity , Tetracycline/toxicity , Liver , Hepatocytes
Microplastics have emerged as a significant pollutant in terrestrial ecosystems, with their accumulation in agricultural fields influencing soil greenhouse gas emissions. Nevertheless, the specific impact of microplastics, particularly in relation to their varying shapes, and how this effect manifests across diverse soil types, remains largely unexplored. In this study, a 56-day incubation experiment was conducted to assess the influence of microplastic shapes (fibers, films, and spheres) on CO2 and N2O emissions in three types of soils (Chernozems, Luvisols, and Ferralsols), while also investigating potential associations with the compositional and functional characteristics of soil bacterial communities. When compared to the control group, the introduction of microplastic fibers resulted in an increase of 21.7 % in cumulative CO2 emissions and a 31.4 % rise in cumulative N2O emissions in Ferralsols. This increase was closely linked to the proliferation of the Actinobacteria and Bacilli classes and the orders of Catenulisporales, Bacillales, Streptomycetales, Micrococcales, and Burkholderiales within the bacterial communities of Ferralsols, alongside an observed elevation in N-acetyl-glucosaminidase enzyme activity. The inclusion of microplastic fibers did not result in significant alterations in greenhouse gas emissions within Chernozems and Luvisols. This is likely attributed to the inherent buffering capacity of these soils, which helps stabilize substrate and nutrient availability for microbial communities. These findings highlight that the response of greenhouse gas emissions to microplastic additions is contingent upon the shape of the microplastics and the specific soil types.
Actinobacteria , Greenhouse Gases , Microbiota , Soil , Greenhouse Gases/analysis , Microplastics , Plastics , Agriculture , Carbon Dioxide/analysis , Nitrous Oxide/analysis , Bacteria
Artificial intelligence (AI) is advancing rapidly and continually evolving in various fields. Recently, the release of ChatGPT has sparked significant public interest. In this study, we revisit the '100 Important Questions Facing Plant Science' by leveraging ChatGPT as a valuable tool for generating thought-provoking questions relevant to plant science. These questions primarily revolve around the utilization of plants in product development, understanding plant mechanisms, plant-environment interactions, and enhancing plant traits, with an emphasis on sustainable product development. While ChatGPT may not capture certain crucial aspects highlighted by scientists, it offers valuable insights into the questions generated by experts. Our analysis demonstrates that ChatGPT can be cautiously employed as a supportive tool to facilitate, streamline, and expedite specific tasks in plant science.
Artificial Intelligence , Language , Phenotype
Forest ecosystems cover a large area of the global land surface and are important carbon sinks. The water-carbon cycles of forests are prone to climate change, but uncertainties remain regarding the magnitude of water use efficiency (WUE) response to climate change and the underpinning mechanism driving WUE variation. We conducted a meta-analysis of the effects of elevated CO2 concentration (eCO2 ), drought and elevated temperature (eT) on the leaf- to plant-level WUE, covering 80 field studies and 95 tree species. The results showed that eCO2 increased leaf intrinsic and instantaneous WUE (WUEi, WUEt), whereas drought enhanced both leaf- and plant-level WUEs. eT increased WUEi but decreased carbon isotope-based WUE, possibly due to the influence of mesophyll conductance. Stimulated leaf-level WUE by drought showed a progressing trend with increasing latitude, while eCO2 -induced WUE enhancement showed decreasing trends after >40° N. These latitudinal gradients might influence the spatial pattern of climate and further drove WUE variation. Moreover, high leaf-level WUE under eCO2 and drought was accompanied by low leaf carbon contents. Such a trade-off between growth efficiency and defence suggests a potentially compromised tolerance to diseases and pests. These findings add important ecophysiological parameters into climate models to predict carbon-water cycles of forests.
Ecosystem , Water , Carbon , Climate Change , Carbon Dioxide , Forests , Plant Leaves/chemistry , Plants
Ozone (O3) pollution is harmful to plants and ecosystems. Several chemicals have been evaluated to protect plants against O3 deleterious effects. However, they are not adequately efficient and/or the environmental safety of their application is questioned. Hence, new chemicals that provide sufficient protection while being safer for environmental application are needed. This study investigates the response of two O3-sensitive plant species (Phaseolus vulgaris L. cv. Pinto and Nicotiana tabacum L. cv. Bel-W3) leaf-sprayed with deionized water (W, control), ethylenediurea (EDU, 1 mM) or melatonin at lower (1 mM) or higher (3 mM) concentrations (Mel_L and Mel_H, respectively), and then exposed to a square wave of 200 ppb O3, lasting 1 day (5 h day-1) for bean and 2 days (8 h day-1) for tobacco. In both species, the photosynthetic activity of O3-exposed plants was about halved. O3-induced membrane damage was also confirmed by increased malondialdehyde (MDA) byproducts compared to control (W). In EDU- and Mel-treated bean plants, the photosynthetic performance was not influenced by O3, leading to reduction of the incidence and severity of O3 visible injury. In bean plants, Mel_L mitigated the detrimental effect of O3 by boosting antioxidant enzyme activities or osmoprotectants (e.g. abscisic acid, proline, and glutathione transferase). In Mel_L-sprayed tobacco plants, O3 negatively influenced the photosynthetic activity. Conversely, Mel_H ameliorated the O3-induced oxidative stress by preserving the photosynthetic performance, preventing membrane damage, and reducing the visible injuries extent. Although EDU performed better, melatonin protected plants against O3 phytotoxicity, suggesting its potential application as a bio-safer and eco-friendlier phytoprotectant against O3. It is worth noting that the content of melatonin in EDU-treated plants remained unchanged, indicating that the protectant mode of action of EDU is not Mel-related.
Air Pollutants , Melatonin , Ozone , Antioxidants/pharmacology , Nicotiana , Melatonin/pharmacology , Ozone/toxicity , Ecosystem , Plants , Air Pollutants/toxicity
Eucalyptus plantations are usually characterized by low biodiversity due to allelopathy effects. Wood vinegar is considered a complex growth regulator that can promote plant growth at low concentrations. However, there is information scarcity about the co-application of eucalypt leaf water extract and wood vinegar on plants. This study aimed at clarifying whether wood vinegar can protect seed germination against suppression by eucalypt-induced allelopathy. We examined germination behavior and seedling elongation characteristics in rapeseed (Brassica rapa L.) treated with different solutions of wood vinegar and eucalypt leaf water extract. The results showed that eucalypt leaf water extracts, wood vinegar solutions, and their mixture allelopathically suppressed seed germination rate. After rapeseed sprouting, eucalypt leaf water extracts promoted root elongation, stem elongation, and fresh weight elongation. Malondialdehyde content was also lower under the influence of eucalypt leaf water extract. Mixture of high concentration of eucalypt leaf water extract and lower concentration of wood vinegar significantly promoted root elongation. Therefore, both eucalypt leaf water extract and wood vinegar are complex plant growth regulators, which can be used to inhibit or stimulate plants at different ontogenic stages. During the seed germination period, both eucalypt leaf extracts and wood vinegar could be used as weed inhibitors. Conversely, during the period of sprouting (seedling establishment), low concentrations of eucalypt leaf extracts and wood vinegar can promote growth.
Acetic Acid , Brassica napus , Brassica rapa , Eucalyptus , Methanol , Germination , Allelopathy , Seedlings , Plant Extracts/pharmacology , Water
Quercetin is a polyphenol present in numerous fruits and vegetables and therefore widely consumed by humans with average daily dietary intakes of 10-20 mg/day. It is also a popular dietary supplement of 250-1000 mg/day. However, despite the widespread consumer interest in quercetin, due to its possible chemopreventive properties, the extensively studied quercetin presents a highly diverse and complex array of biological effects. Consequently, the present paper provides the first assessment of quercetin-induced hormetic concentration/dose responses, their quantitative features and mechanistic foundations, and their biological, biomedical, clinical, and public health implications. The findings indicate that quercetin-induced hormetic dose responses are widespread, being independent of biological model, cell type, and endpoint. These findings have the potential to enlighten future experimental studies with quercetin especially with respect to study design parameters and may also affect the appraisal of possible public health benefits and risks associated with highly diverse consumer consumption practices.
Hormesis , Quercetin , Humans , Quercetin/pharmacology , Models, Biological , Dose-Response Relationship, Drug
