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UNLABELLED Levels of cadmium (Cd), arsenic (As), mercury (Hg), lead (Pb), iron (Fe), and zinc (Zn) were investigated in 285 samples of 9 species of edible fungi (Lentinus edodes, Auricularia auricula, Pleurotus ostreatus, Tremella fuciformis, Flammulina velutipes, Agrocybe chaxinggu, Armillaria mellea, Agaricus bisporus, and Pholiota nameko), which were collected from markets in Beijing, China. In addition, edible fungi and culture substrates were collected from 7 cultivation bases to examine the role of the substrate in trace metal accumulation. Trace metal concentrations were determined on a dry weight basis. Data showed that all the edible fungi contained trace metals, the levels of which varied among species, and there were significant positive correlations between trace metal (Cd, Pb, and As) concentrations in mushrooms and their substrates. The concentrations of Cd, As, Hg, Pb, Fe, and Zn in the tested fungi ranged from 0.005 to 13.8 mg/kg, nd to 1.62 mg/kg, nd to 0.506 mg/kg, 0.011 to 22.1 mg/kg, 46.3 to 2514 mg/kg, and 14.6 to 289 mg/kg, respectively. In general, concentrations of Cd, As, Hg, Pb, Fe, and Zn were relatively high in L. edodes, whereas Tremella fuciformis and P. nameko had relatively low levels of trace metals. Furthermore, the estimated weekly intake of trace metals was calculated and compared with the WHO/FAO provisional tolerable weekly intake. The estimated weekly intake of Cd, As, Hg, Pb, Fe, and Zn from consuming edible fungi was lower than the provisional tolerable weekly intake. PRACTICAL APPLICATION This paper reports information about trace metal concentrations in edible fungi collected from Beijing, China. This paper provides useful information for consumers and regulators about levels of trace metals in edible fungi.

The great achievement of the development of intensive in agriculture in China can be partly attributed to substantial increases in mineral-nutrient application. However, whereas farmers tend to apply high levels of nitrogen (N) and phosphorus (P) application of potassium (K) has been neglected. A greater understanding of the relationship between maize (Zea mays L.) grain yield and K-application rate is thus required to provide an improved rationale for K fertilization for farmers in the various agro-ecological regions of China. In this study, a total of 2765 farmers' survey data and 3124 on-farm experiments across major maize agro-ecological regions in China were collected and evaluated for farmers' K-management status and to determine grain-yield response to K application. Nationally, the average K-application rate on farms was 26 kg K ha–1 and varied from 0 to 158 kg K ha–1, with a coefficient of variation of 107%, but the applied K-fertilizer rates were not related to grain yield. Maize grain yields at recommended K rates increased by 14.0%, 14.7%, 19.4%, and 4.3% in Northeast China, North China Plain, Southwest China, and Northwest China, respectively, compared to zero K fertilization (K0). Increased yield due to K fertilization (IYmax, difference between maximum yield across all treatments and K0-treatment yield for each experiment) averaged 1.4 t ha–1 but varied widely in different agro-ecological regions. Soil extractable K (NH4OAc-K) and intercounty variation resulted in large variation in IYmax in agro-ecological regions, as did other factors, such as use of particular maize hybrids, soil types, or years in different regions.

Aim To investigate broad-scale patterns of plant leaf ash content and their possible causes in China. Location Mainland China and Hainan island, with the geographic ranges for the data used from 18.7 degrees N to 49.2 degrees N and 76.0 degrees E to 128.3 degrees E. Methods By analysing a data set of 2022 leaf samples, involving 704 species of terrestrial plants. Results Leaf ash content increases with increasing latitude at an average rate of 2.7 mg ash g(-1) dry weight per degree latitude from south to north of China. Plant functional group shows a more powerful influence on the spatial variation in leaf ash than soil pH and climate. Fast-growing species or those with leaves with a short life span have higher leaf ash than slow-growing species or those with a long leaf life span. Plants from alkaline soils have higher leaf ash than those from acid soils (39.5 mg g(-1) increase in leaf ash content per unit increase of pH). Increasing precipitation significantly reduces leaf ash (with a mean rate of 4.8 mg g(-1) for every 100 mm rainfall), whereas the effect of temperature appears to be nonlinear. Main conclusions This study shows a significant latitudinal trend in leaf ash content in China. This geographic pattern is possibly shaped by the floral, edaphic and climatic factors that control the biogeochemical cycling of plant minerals. The results suggest that leaf ash content is a useful biogeographic indicator that can be used to explore the complex interactions between plants and the environment.

Field experiments were conducted to evaluate the effects of improved crop management (OPT) for irrigated rice (Oryza sativa L.) on grain yield and N recovery efficiency in southwestern China. In the OPT treatment, rice seedlings were transplanted in a triangular spatial pattern and the N fertilizer was split, based on the difference between the estimated total N requirement and the soil and environmental N supply. Fine-tuning of application rates was achieved using leaf greenness measurements. The performance of OPT was tested in two adjacent fields in which the crops preceding rice were wheat (Triticum aestivum L.; R w ) and rapeseed (Brassica napus var. napus; R o ). The OPT and traditional farming practice (TRA) treatments both gave higher average grain yields than zero-N controls (CK). Rice yields were considerably smaller in R W than R o under CK. Compared with TRA, OPT led to significantly higher aboveground N uptake, biomass accumulation, and grain yield in R w . Over the 2 yr of the study, average rice grain yields under OPT increased by 19 and 22% compared with TRA and 30 farmers' fields, respectively. The OPT treatment performed better than TRA in 15 N recovery efficiency. Compared with TRA, OPT led to increased 15 N fertilizer recovery efficiency from 19% in TRA to 42% in OPT, and decreased loss from 68% in TRA to 39% in OPT. In conclusion, OPT practice is a feasible means to attain increased yield with efficient N use. This study provides guidance for farmers using rice-based cropping systems, especially in southwestern China.

Arabidopsis halleri is a well-known zinc (Zn) hyperaccumulator, but its status as a cadmium (Cd) hyperaccumulator is less certain. Here, we investigated whether A. halleri can hyperaccumulate Cd and whether Cd is transported via the Zn pathway. Growth and Cd and Zn uptake were determined in hydroponic experiments with different Cd and Zn concentrations. Short-term uptake and root-to-shoot transport were measured with radioactive Cd-109 and Zn-65 labelling. A. halleri accumulated > 1000 mg Cd kg(-1) in shoot dry weight at external Cd concentrations >= 5 mu m>, but the short-term uptake rate of Cd-109 was much lower than that of Zn-65. Zinc inhibited short-term Cd-109 uptake kinetics and root-to-shoot translocation, as well as long-term Cd accumulation in shoots. Uptake of Cd-109 and Zn-65 were up-regulated, respectively, by low iron (Fe) or Zn status. A. halleri was much less tolerant to Cd than to Zn. We conclude that A. halleri is able to hyperaccumulate Cd partly, at least, through the Zn pathway, but the mechanisms responsible for cellular Zn tolerance cannot detoxify Cd effectively.

Summary • Efficient root-to-shoot translocation is a key trait of the zinc/cadmium hyperaccumulators Thlaspi caerulescens and Thlaspi praecox, but the extent of variation among different accessions and the underlying mechanisms remain unclear. • Root-to-shoot translocation of Cd and Zn and apoplastic bypass flow were determined in 10 accessions of T. caerulescens and one of T. praecox, using radiolabels 109Cd and 65Zn. Two contrasting accessions (Pr and Ga) of T. caerulescens were further characterized for TcHMA4 expression and metal compartmentation in roots. • Root-to-shoot translocation of 109Cd and 65Zn after 1 d exposure varied 4.4 to 5-fold among the 11 accessions, with a significant correlation between the two metals, but no significant correlation with uptake or the apoplastic bypass flow. The F2 progeny from a cross between accessions from Prayon, Belgium (Pr) and Ganges, France (Ga) showed a continuous phenotype pattern and transgression. There was no significant difference in the TcHMA4 expression in roots between Pr and Ga. Compartmentation analysis showed a higher percentage of 109Cd sequestered in the root vacuoles of Ga than Pr, the former being less efficient in translocation than the latter. • Substantial natural variation exists in the root-to-shoot translocation of Cd and Zn, and root vacuolar sequestration may be an important factor related to this variation.

Metal hyperaccumulation has been proposed as a plant defensive strategy. Here, we investigated whether cadmium (Cd) hyperaccumulation protected Thlaspi caerulescens from leaf feeding damage by thrips (Frankliniella occidentalis). Two ecotypes differing in Cd accumulation, Ganges (high) and Prayon (low), were grown in compost amended with 0-1000 mg Cd kg(-1) in two experiments under glasshouse conditions. F-2 and F-3 plants from the Prayon x Ganges crosses were grown with 5 mg Cd kg(-1). Plants were naturally colonized by thrips and the leaf feeding damage index (LFDI) was assessed. The LFDI decreased significantly with increasing Cd in both ecotypes, and correlated with shoot Cd concentration in a log-linear fashion. Prayon was more attractive to thrips than Ganges, but the ecotypic difference in the LFDI was largely accounted for by the shoot Cd concentration. In the F-2 and F-3 plants, the LFDI correlated significantly and negatively with shoot Cd, but not with shoot zinc (Zn) or sulphur (S) concentrations. We conclude that Cd hyperaccumulation deters thrips from feeding on T. caerulescens leaves, which may offer an adaptive benefit to the plant.