Exploring hydrological controls on dissolved organic carbon export dynamics in a typical flash flood catchment using a process-based model.

The dynamics of dissolved organic carbon (DOC) export from headwater catchments are of critical importance for the global carbon balance and are driven by complex runoff processes. Most previous studies have used statistical relationships between runoff and DOC concentration to estimate DOC export dynamics. Thus, the coupling mechanisms between runoff generation and DOC export dynamics at the process level were obscured in the fitting parameters and have rarely been addressed. In this study, high-frequency (hourly) discharge and DOC export from a typical flash flood experimental headwater catchment with an area of 1.8 km2 were simulated using a process-based model (INCA-C). The results showed that the INCA-C model successfully captured the hourly dynamics of both discharge and DOC concentrations with a Nash-Sutcliffe efficiency (NSE) of 0.47-0.81 and 0.28-0.70 among moderate events and 0.81-0.85 and 0.19-0.90 among extreme events, respectively. The DOC was exported with distinct concentration dynamics, fluxes, and contributions from the four flow pathways under different storm intensities. At higher intensities, the DOC fluxes were exported by subsurface flows, particularly from shallow organic soil, with greater peaks and shorter time-to-peaks. Exported DOC is primarily sourced from subsurface runoff from the mineral layer (73 %-77 %) during moderate events, whereas it is primarily sourced from subsurface runoff from the organic layer (61 %-79 %) during extreme events. The two contrasting contributions suggest that hydrological pathway controls and DOC dynamic patterns can shift owing to runoff generation influenced by storm intensity. The distinct and variable controls of different flow pathways on DOC export highlight the need to explain the role of hydrology in regulating DOC storm exports through process-based modelling.

Different photosynthetic inorganic carbon utilization strategies in the heteroblastic leaves of an aquatic plant Ottelia ovalifolia.

The leaves of the heteroblastic aquatic plant Ottelia ovalifolia faces submerged and aerial environments during its life history. However, the acclimation of the submerged leaves and floating leaves to these two environments in morphology, physiology, and biochemistry remain unclear. In the present study, we investigated the acclimation of the CO2-concentrating mechanisms in these two types of leaves. We found that the submerged leaves were longer, narrower, and thinner than the floating leaves, which increased the specific surface area of the leaves and lead to better absorption of the inorganic carbon underwater. Meanwhile, the floating leaves absorbed atmospheric CO2 directly through the stomata to acclimate to the aerial environment. Both the leaf types had the ability to use HCO 3 - , but the capacity in submerged leaves was stronger than that in floating leaves. The extracellular carbonic anhydrase and anion exchanger were responsible for the HCO 3 - use in both types of leaves. The higher ratio of chlorophyll a/b and content of anthocyanin in floating leaves than that in submerged leaves indicated that the acclimation of aerial and submerged photosynthesis depended on changes in the photosynthetic pigments. Based on the stable carbon isotope ratio, key enzyme activities of the C4 pathway indicated that submerged leaves might have the ability to perform C4 metabolism while floating leaves only performed C3 metabolism. In summary, O. ovalifolia acclimates to submerged and aerial environments through changes in morphology, physiology, and biochemistry during different growth stages.

Impacts of bisphenol A on growth and reproductive traits of submerged macrophyte Vallisneria natans.

Bisphenol A (BPA) is considered a contaminant of emerging concern and interferes with the normal activities of living organisms. The toxicity of BPA is evident in animals and terrestrial plants. However, the response of aquatic plants to low BPA concentrations is still unclear. In the present study, effects of varying BPA loadings (targeting at 0.01, 0.1, and 1 mg/L) on the growth and reproductive traits of the dioecious annual submerged macrophyte Vallisneria natans were assessed through a 5-month experiment. The results showed that BPA inhibited the elongation of V. natans leaves but resulted in an increase in leaf number and ramet number under the highest BPA loading treatment (targeting at 1 mg/L). In addition, detectable biochemical changes in the total carbon and soluble sugar contents were found, which both were significantly higher at the highest BPA loading treatment. However, the total biomass did not alter significantly after the BPA treatments, indicating that BPA did not induce direct toxic effects on the growth of V. natans. At the highest BPA loading treatment, female individuals of V. natans allocated less number for ramet than male ones, showing a clear sexual dimorphism. No significant differences between the five treatments were found for the flower or fruit traits, while the germination rate was significantly inhibited for the seeds collected from the highest BPA loading treatment. In conclusion, V. natans tolerated low concentrations of BPA by making a trade-off between ramet (leaf) number and leaf elongation, as well as modulating the total carbon and soluble sugar contents. However, serious consequence of decline in seed viability implied that the impact of BPA on plant reproduction were usually underestimated.

Inorganic carbon utilization: A target of silver nanoparticle toxicity on a submerged macrophyte.

Submerged macrophytes play an important role in the global carbon cycle through diversified pathways of inorganic carbon (Ci) utilization distinct from terrestrial plants. However, the effects of silver nanoparticles (AgNPs), an emerging contaminant, were unknown on the Ci utilization of submerged macrophytes. In Ottelia alismoides, the only known submerged macrophyte with three pathways of Ci utilization, before absorption, AgNPs inhibited the external carbonic anhydrase activity thus reducing the capacity of the plant to use HCO3-. After entering the plant, AgNPs mainly aggregated at the cell wall and in the chloroplast. The internalized AgNPs inhibited ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity blocking CO2 fixation and disturbed C4 and crassulacean acid metabolism (CAM) by inhibiting phosphoenolpyruvate carboxylase (PEPC), pyruvate phosphate dikinase (PPDK), and NAD-dependent malic enzyme (NAD-ME) activities to alter intracellular malate biosynthesis and decarboxylation. Overall, our findings indicate that the Ci utilization of the submerged macrophyte is a target of AgNPs toxicity that might affect the carbon cycle in aquatic systems.

Multimedia distribution of polycyclic aromatic hydrocarbons in the Wang Lake Wetland, China.

The Wang Lake Wetland is a highly valued area that is protected due to its high biodiversity. The wetland has a complicated hydrological regime and is subject to frequent human disturbance. We hypothesize that fluctuating hydrology and human activities have varied contributions to the temporal and spatial variations of polycyclic aromatic hydrocarbons (PAHs) in the wetland. Soil (SS), sediment (SD), and water, to acquire dissolved phase (DP) and suspended particulate matter (SPM), samples were collected from eight locations during low- and high-flow periods to elucidate multimedia phase distribution and transport of PAHs. Following the onset of the rainy season, the concentration of SPM-associated PAHs increased significantly, while the DP PAHs remained stable. Individual PAH ratios showed that, although pyrogenic sources are common, petrogenic derived compounds are the main source of PAHs in the Wang Lake Wetland. During the high-flow period, the empirical values for logarithms of the organic carbon-normalized partition coefficients (log KOC) of individual PAH-congeners were lower than the corresponding field-observed log KOC values from the SPM-DP and SD-DP systems, reflecting the complexity in evaluating multi-phase PAH partitioning. During the high-flow period, temperature-driven changes may have changed the sediment from a sink to a source for some high molecular weight PAHs. It was determined that human activities governed the PAH loading in the low-flow period, whereas during high-flow conditions, increased rainfall, higher temperatures, and fishery activity are the main factors controlling PAH input to the Wang Lake Wetland.

Antidote or Trojan horse for submerged macrophytes: Role of microplastics in copper toxicity in aquatic environments.

Due to their unique surface structures and physicochemical properties, microplastics (MPs) can adsorb other contaminants, thus impacting their toxicity and fate in aquatic ecosystems. In the present study, the adsorption and transportation of copper ions (Cu2+) in polyethylene (PE, 5 and 150 µm) and their combined effects on four submerged macrophyte species were assessed. Results demonstrated that the addition of PE reduced the Cu2+ concentration in copper sulfate (CuSO4) solution and the adsorption of Cu2+ in PE (10 mg/L) increased with CuSO4 concentration (100-600 µmol/L). PE alone exhibited no inhibitory effects on macrophytes, while Cu2+ showed fatal toxicity toward the macrophytes. However, the combination of PE and Cu2+ showed lower inhibitory effects on macrophytes and the toxicity attenuation varied among species. Additionally, PE may act as a carrier (like a Trojan horse) for the environmental transfer of Cu2+, thereby hosting Cu2+ toxicity against macrophytes in the imported environment. Our findings indicate that PE acts as both an antidote to and carrier of Cu2+ toxicity in macrophytes. This study should help in clarifying the combined effects and risk assessments of MPs and heavy metals in future studies.

Bladder entrance of microplastic likely induces toxic effects in carnivorous macrophyte Utricularia aurea Lour.

The global distribution of microplastic (particle size < 5 mm) is of growing concern, especially in aquatic environments where it may cause adverse effects on resident organisms. To date, however, few studies have focused on the impacts of microplastic on aquatic plants. Here, we conducted a microcosm study to investigate the toxic effects of microplastic on the carnivorous aquatic macrophyte Utricularia aurea Lour. Based on microscopic images and Raman spectrum analysis, we found that most polyvinyl chloride (PVC) particles were smaller than the valve of U. aurea bladders, thus allowing entrance into the plant, but this was not so for polyethylene (PE) particles. Furthermore, PVC (50 mg L-1) had significantly negative effects on growth and physiological parameters such as macrophyte length, chlorophyll content, and fluorescence, whereas, at the same concentration, PE had no such effects. Further analysis revealed that after bladder removal, the macrophytes did not respond to PVC particle toxicity. Thus, intake of microplastics (i.e., PVC) through bladders is likely responsible for inducing toxic effects to the growth and physiological parameters of U. aurea.

Is the Cooking Salt Safe in China? Assessment of Chemical Contaminants in Cooking Salt.

Global environmental pollution is becoming more serious, and most dietary salts come from nature. We postulated that chemical pollutants could affect the quality of salt. Forty-five different types of salt were collected from supermarkets, convenience stores, and online retailers in Shanghai, 2015. These comprised more than 90% of all cooking salts consumed in Shanghai, China. We measured and analyzed heavy metal elements, fluoride, potassium ferrocyanide, and 16 phthalate plasticizers. Lead was detected in only two types of salt at concentrations recorded of 0.047 mg/kg and 0.077 mg/kg. The concentrations of total arsenic, total mercury, cadmium, and barium were under limit of detection (LOD) in all samples. The maximum fluoride concentration of salts was 2.50 mg/kg. The median fluoride concentration of domestic salts was significantly lower than foreign-produced salts, and it was significantly higher in sea salt than in other types of salt (P < 0.05). The maximum potassium ferrocyanide concentration in 12 types of salts was 9.20 mg/kg, which was under the Chinese national standard. Just three salt types had low levels of diethylhexyl phthalate concentrations that were above the LOD, at 0.208 mg/kg, 0.375 mg/kg, and 0.380 mg/kg, respectively. All other phthalate indicators were below the LOD in all samples. The level of chemical pollutants in salt is either very low or under LOD. We believe that dietary salt products are safe at retail, and the long-term dietary exposure of cooking salts will not pose any significant health risk.

[Assessment of chemical pollutant levels of dietary salt in Shanghai in 2015].

OBJECTIVE: To detect the chemical pollutants concentrations of dietary salt and to comprehend the effect of chemical pollutants on the quality of salt. METHODS: 45 kinds of salt with different countries, brands and types were collected in Shanghai during May to June in 2015. Five different heavy metal elements, fluoride, potassium ferrocyanide and 16 phthalate plasticizers were measured, and the result were analyzed with the standard. RESULTS: The salt of largest consumption was domestic halite/well salt in Shanghai, accounting for 87. 6% of the total salt consumption. Lead was detected in only two types of salt at concentrations recorded of 0. 047 and 0. 077 mg/kg, which were far below the Chinese national standard. The concentrations of total arsenic, total mercury, cadmium, and barium were lower than the limit of detection( LOD) in all samples. The median fluoride concentration of salts was 0. 16 mg/kg( maximum 2. 50 mg/kg). The median fluoride concentration of domestic salts was significantly lower than foreign-produced salts( P < 0. 05), and it was significantly higher in sea salt than in other types of salt. The median potassium ferrocyanide concentration in 12 types of salts was4. 30 mg/kg( maximum 9. 2 mg/kg), which was lower than the Chinese national standard. Just 3 salt types had low levels of bis( 2-ethylhexyl) phthalate concentrations that were above the LOD, at 0. 208, 0. 375 and 0. 380 mg/kg, respectively. CONCLUSION: The level of chemical pollutants in salt is either very low or absent.

MdWRKY9 overexpression confers intensive dwarfing in the M26 rootstock of apple by directly inhibiting brassinosteroid synthetase MdDWF4 expression.

Dwarfing rootstocks enable high-density planting and are therefore highly desirable in modern apple (Malus domestica) production. M26 is a semi-dwarfing rootstock that is used worldwide, but identifying intensive dwarfing rootstock is a major goal of apple breeding programs. Herein, we show that MdWRKY9 mediates dwarfing by directly inhibiting the transcription of the brassinosteroid (BR) rate-limiting synthetase MdDWF4 and reducing BR production. We found that the transcriptional factor MdWRKY9 is highly expressed in all tested dwarfing rootstocks. Transgenic lines of M26 rootstock overexpressing MdWRKY9 exhibit further dwarfing, which resulted from the reduced BR levels and was reversed via exogenous brassinolide treatment. Both an in vivo chromatin immunoprecipitation (ChIP) analysis and an in vitro electrophoretic mobility shift assay (EMSA) indicated that MdWRKY9 binds to the promoter of MdDWF4. Furthermore, MdWRKY9 repressed MdDWF4 expression in stable transgenic apple plants as determined by quantitative PCR. In addition, RNA-interfered expression of MdWRKY9 in transiently transformed apple calli led to a significant increase of MdDWF4, suggesting MdWRKY9 plays a critical role in regulating the expression of MdDWF4. We report a novel dwarfing mechanism in perennial woody plants that involves WRKY-controlled BR production, and present a new dwarfing M26 rootstock for potential applications in apple production.

Melatonin Improves Waterlogging Tolerance of Malus baccata (Linn.) Borkh. Seedlings by Maintaining Aerobic Respiration, Photosynthesis and ROS Migration.

Waterlogging, one of the notorious abiotic stressors, retards the growth of apple plants and reduces their production. Thus, it is an urgent agenda for scientists to identify the suitable remedies for this problem. In the current study, we found that melatonin significantly improved the tolerance of apple seedlings against waterlogging stress. This was indicated by the reduced chlorosis and wilting of the seedlings after melatonin applications either by leaf spray or root irrigation. The mechanisms involve in that melatonin functions to maintain aerobic respiration, preserves photosynthesis and reduces oxidative damage of the plants which are under waterlogging stress. Melatonin application also enhances the gene expression of its synthetic enzymes (MbT5H1, MbAANAT3, MbASMT9) and increases melatonin production. This is the first report of a positive feedback that exogenous melatonin application promotes the melatonin synthesis in plants. A post-transcriptional regulation apparently participated in this regulation. When exogenous melatonin meets the requirement of the plants it is found that the protein synthesis of MbASMT9 was suppressed. Taken together, the results showed that melatonin was an effective molecule to protect plant, particularly apple plant, against waterlogging stress.

Chloroplastic biosynthesis of melatonin and its involvement in protection of plants from salt stress.

Within the chloroplasts reactive oxygen species (ROS) are generated during photosynthesis and stressful conditions. Excessive ROS damages chloroplasts and reduces photosynthesis if not properly detoxified. In this current study, we document that chloroplasts produce melatonin, a recently-discovered plant antioxidant molecule. When N-acetylserotonin, a substrate for melatonin synthesis, was fed to purified chloroplasts, they produced melatonin in a dose-response manner. To further confirm this function of chloroplasts, the terminal enzyme for melatonin synthesis, N-acetylserotonin-O-methyltransferase (ASMT), was cloned from apple rootstock, Malus zumi. The in vivo fluorescence observations and Western blots confirmed MzASMT9 was localized in the chloroplasts. A study of enzyme kinetics revealed that the Km and Vmax of the purified recombinant MzASMT9 protein for melatonin synthesis were 500 µM and 12 pmol/min·mg protein, respectively. Arabidopsis ectopically-expressing MzASMT9 possessed improved melatonin level. Importantly, the MzASMT9 gene was found to be upregulated by high light intensity and salt stress. Increased melatonin due to the highly-expressed MzASMT9 resulted in Arabidopsis lines with enhanced salt tolerance than wild type plants, as indicated by reduced ROS, lowered lipid peroxidation and enhanced photosynthesis. These findings have agricultural applications for the genetic enhancement of melatonin-enriched plants for increasing crop production under a variety of unfavorable environmental conditions.

[Effects of nutrition intervention among students in primary school for children of migrant workers in Shanghai].

OBJECTIVE: To evaluate effects of nutrition intervention on nutrition knowledge, attitude and practice and lunch nutrition situation of students in primary school for children of migrant workers in Shanghai, to provide evidence for promoting children 's growth and development and health education. METHODS: A total of 4 primary schools for children of migrant workers in Shanghai were selected by stratified cluster sampling in 2014- 2015, and then were randomly assigned to intervention or control group. All students of 4and 5 grades were selected as subject. Nutrition intervention included the school canteen and students. Survey was implemented before and after intervention, and included demographic questionnaire, physical test and nutrition survey using dietary recall. RESULTS: The average rise in quantity of weight, BMI, the power of gripping, nutrition attitude accuracy and paper folding test score in intervention group were significantly higher than control group. Intervention was helpful to improve the awareness rates of dietary guidelines and the favor rate of school lunch. Except fat, the average rise in intake of energy and main nutrients in intervention group were significantly higher than control group. The average rise in intake of food grains, soybeans and soy products and vegetables and the average falling in intake of animal food in intervention group were significantly higher than control group. All of the differences were statistically significant( P < 0. 05). The average intake of energy, main nutrients and some kinds of food in intervention group were more close to the standard. CONCLUSION: Nutrition intervention has a positive impact on students ' growth and development, nutrition knowledge and attitude, cognitive ability and dietary intake, and should be put into widespread application.

Overexpression of MzASMT improves melatonin production and enhances drought tolerance in transgenic Arabidopsis thaliana plants.

Melatonin is a potent naturally occurring reactive oxygen species (ROS) and reactive nitrogen species (RNS) scavenger in plants. Melatonin protects plants from oxidative stress and, therefore, it improves their tolerance against a variety of environmental abiotic stressors. N-acetylserotonin-O-methyltransferase (ASMT) is a specific enzyme required for melatonin synthesis. In this report, an ASMT gene was cloned from apple rootstock (Malus zumi Mats) and designated as MzASMT1 (KJ123721). The MzASMT1 expression was induced by drought stress in apple leaves. The upregulation of MzASMT1 in the apple leaf positively relates to melatonin production over a 24-hr dark/light cycle. Purified MzASMT1 protein expressed in E. coli converted its substrates to melatonin with an activity of approximately 5.5 pmol/min/mg protein. The transient transformation in tobacco identified that MzASMT1 is located in cytoplasm of the cell. When MzASMT1 gene driven by 35S promoter was transferred to Arabidopsis, melatonin levels in transgenic Arabidopsis plants were 2-4 times higher than those in the wild type. The transgenic Arabidopsis plants had significantly lower intrinsic ROS than the wild type and therefore these plants exhibited greater tolerance to drought stress than that of wild type. This is, at least partially, attributed to the elevated melatonin levels resulting from the overexpression of MzASMT1. The results elucidated the important role that membrane-located melatonin synthase plays in drought tolerance. These findings have significant implications in agriculture.