Chloroplastic photoprotective strategies differ between bundle sheath and mesophyll cells in maize (Zea mays L.) Under drought.

Bundle sheath cells play a crucial role in photosynthesis in C4 plants, but the structure and function of photosystem II (PSII) in these cells is still controversial. Photoprotective roles of bundle sheath chloroplasts at the occurrence of environmental stresses have not been investigated so far. Non-photochemical quenching (NPQ) of chlorophyll a fluorescence is the photoprotective mechanism that responds to a changing energy balance in chloroplasts. In the present study, we found a much higher NPQ in bundle sheath chloroplasts than in mesophyll chloroplasts under a drought stress. This change was accompanied by a more rapid dephosphorylation of light-harvesting complex II (LHCII) subunits and a greater increase in PSII subunit S (PsbS) protein abundance than in mesophyll cell chloroplasts. Histochemical staining of reactive oxygen species (ROS) suggested that the high NPQ may be one of the main reasons for the lower accumulation of ROS in bundle sheath chloroplasts. This may maintain the stable functioning of bundle sheath cells under drought condition. These results indicate that the superior capacity for dissipation of excitation energy in bundle sheath chloroplasts may be an environmental adaptation unique to C4 plants.

The Possible Transmission and Potential Enterotoxicity of Bacillus cereus on Lettuce Farms in Five Chinese Provinces.

Bacillus cereus is a well-characterized human pathogen that produces toxins associated with diarrheal and emetic foodborne diseases. To investigate the possible transmission of B. cereus on lettuce farms in China and determine its enterotoxicity, (I) a total of 524 samples (lettuce: 332, soil: 69, water: 57, manure: 57, pesticide: 9) were collected from 46 lettuce farms in five Chinese provinces, (II) multilocus sequence typing (MLST) was used to classify B. cereus isolates and for trace analysis, and (III) the presence of toxin genes and enterotoxins (Hbl and Nhe) was detected in 68 strains. The results showed that one hundred and sixty-one lettuce samples (48.5%) tested positive for B. cereus at levels ranging from 10 to 5.3 × 104 CFU/g. Among the environmental sample categories surveyed, the highest positive rate was that of the pesticide samples at 55.6%, followed by soil samples at 52.2% and manure samples at 12.3%. Moreover, one hundred isolates of B. cereus yielded 68 different sequence types (STs) and were classified into five phylogenetic clades. Furthermore, Nhe toxin genes (nheA, nheB, nheC) were broadly distributed and identified in all 68 strains (100%), while Hbl toxin genes (hblA, hblC, hblD) were present in 61 strains (89.7%), entFM was detected in 62 strains (91.2%), and cytK was found in 29 strains (42.6%). All strains were negative for ces. As for the enterotoxin, Nhe was observed in all 68 isolates carrying nheB, while Hbl was present in 76.5% (52/68) of the strains harboring hblC. This study is the first report of possible B. cereus transmission and of its potential enterotoxicity on lettuce farms in China. The results showed that soil and pesticides are the main sources of B. cereus on lettuce farms in China, and the possible transmission routes are as follows: soil-lettuce, manure-lettuce, pesticide-lettuce, manure-soil-lettuce, and water-manure-soil-lettuce. Furthermore, the B. cereus isolates, whether from lettuce or the environment, pose a potential risk to health.

Experimental and theoretical studies of nonlinear dependence of the internal resistance and electrode thickness for high performance supercapacitor.

In this study, the internal resistance with the increasing of electrode thickness in a typical nanoporous carbon-based supercapacitor and their corresponding electrochemical performances were designed and investigated in detail. As for the carbon-based double electrode layer electrochemical system, electrochemical experiments greatly support the fact of nonlinear dependence and indicate that the curve of internal resistance vs. electrode thickness can have a minimum value when the thickness increasing from 10 to 140 µm. To explain the underlying mechanisms responsible for the nonlinear dependence, a theoretical model based on a porous electrode/electrolyte electrochemical system was proposed. As expected, the results of calculations carried out in the framework of the proposed model can be very good agreement with the experimental data. According to the calculation, the optimized electrode thickness is 53.1 µm corresponding to the minimum value of SC internal resistance. Obviously, the current research results might greatly support the nonlinear conclusion instead of linear relationship between the internal resistance and the electrode thickness and may shed some light on the fabrication and exploration of supercapacitors with high power density.

A multi-residue method for the determination of 124 pesticides in rice by modified QuEChERS extraction and gas chromatography-tandem mass spectrometry.

A modified QuEChERS method for simultaneous determination of 124 pesticide residues in rice was established and validated. The rice samples were initially extracted with acetonitrile (MeCN), and the targeted pesticides were purified following the dispersive solid phase extraction (d-SPE) cleanup method and detected by gas chromatography-tandem mass spectrometry (GC-MS/MS). The efficiency of citrate-buffered and unbuffered method in liquid extraction procedure was compared; the amount of primary secondary amine (PSA) was optimised. In the method validation, correlation coefficients (r(2)) were higher than 0.990 with the linear ranging from 10 to 200 µg kg(-1). At the fortification levels of 20-200 µg kg(-1), average recoveries ranged from 70% to 122.7% with the RSD <20%.

[Effects of herbivorous insect stress on the growth and yield-related traits of insect-resistant transgenic rice].

A field experiment was conducted to test the effects of high and low herbivorous insect stresses on the growth, development and yield-related traits of insect-resistant transgenic rice. Three Bt transgenic rice Bt63, R1 and R2 were selected as the test materials, and non-transgenic rice Shanyou63 was taken as the control. The differences in the vegetative growth, seed-setting, and stem borer resistance between transgenic and non-transgenic rice were compared. Under herbivorous insect stress, the transgenic rice fully displayed the stem borer-resistance of exogenous gene. Under the high stress, the stem borer-damaged degree of the three transgenic rice lines was much lower than that of the control. The plant height, tillers per plant, aboveground fresh mass, panicle length, panicle fresh mass, productive panicles per plant, filled grains per plant, grain mass per plant, seed setting rate, and 1000-grain mass of the three transgenic rice lines excelled the control, but had no significant differences except plant height, tillers per plant, and panicle length. Therefore, introducing exogenous Bt gene into rice had no negative effect on rice seed-setting, and high herbivorous insect stress had less impacts on transgenic rice yield.