Antibodies selected from naive antibody libraries usually have low affinity at the micromolar level. Meanwhile, the affinities of natural antibodies obtained by repeated immunization were also observed to have a limit around 100 picomole because of the inability to discriminate slower dissociation kinetics relative to intrinstric B cell receptor internalization rate. As an essential determinant for antibody function for therapeutic and diagnostics use, a lots of antibodies, either isolated from antibody libraries or cloned from monoclonal antibodies, have been targeted to generate high affinity by directed evolution. Affinity maturation in vitro could mimic the mutation and selection process of affinity maturation in vivo, it could help to improve the affinity of the antibodies derived from antibody libraries and make the natural antibodies to break through affinity ceiling. At the mutagenesis level, strategies to affinity maturation in vitro can be grouped in five categories: error prone PCR, DNA shuffling, mutator strains, site directed mutagenesis and chain shuffling. Error PCR could generate random mutations into antibodies throughout the whole antibodies gene. But it is notable that when the mutation rate increases, the active clones decreases exponentially. DNA shuffling includes random fragmentation and reassembly steps; it can be used with longer DNA sequences, and also allows for the selection of clones with mutations outside the binding or active site of the antibodies. By mutator strains, the mutations are produced after the transformation, which allows the randomly mutated libraries of even 1012-1014 clones be produced. However, by mutator strains, mutations are also produced in the vector part to cause deleterious effects. In site-directed mutagenesis, selected residues are targeted to be mutated. The most common sites for mutation are the CDR regions which directly contact with antigen. However, mutations that do not directly contact antigen can also result in enhanced affinity. And the mutation hotspots in affinity maturation in vivo can also be targeted to the mutation sites. In chain shuffling, a variable heavy or light chain of a specific antibody is recombined with a complementary variable domain library. In a lot of experiments, light chains were used to be shuffling, because heavy chain is crucial for the antigen binding. But there are also some reports on producing the affinity-matured antibodies by heavy chain shuffling. These mutagenesis methods have been used with various degrees of success. However, the efficiency of these methods was relatively low and there was a lack of a rational guidance to choose these methods. Knowledge gained on antibody structure through X-ray crystallography or computer-aided design could help to predict the paratope and mutation sites, which is one of the development trend of affinity maturation in vitro.

Eicosanoids, which mediate various physiological and pathophysiological processes, are mainly formed from C20 polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA, 20:4n-6) and eicosapentaenoic acid (EPA, 20:5n-3) through cyclooxygenases (COX), lipoxygenases (LOXs) and cytochrome P450 (CYPs) pathways, including prostaglandins (PGs), thromboxanes (TXs) and the lipoxin/leukotriene family of eicosanoids such as hydroperoxyeicosatetraenoic acids (HPETEs), hydroxyeicosatetraenoic acids (HETEs), and epoxyeicosatrienoic acids (EETs). Vast knowledge of eicosanoids stems from works in mammals. Lipid signaling that complicates our understanding of fatty acid signaling is highly complex and fine-tuned in mammal species. Fortunately, the small genetic model Drosophila melanogaster is considered to be an ideal model to investigate the flexible nature of eicosanoids signaling pathways. However, it seems that Drosophila possess a special lipid metabolic system which is different from mammals. Thus, before studying the physiological mechanism of eicosanoids by using Drosophila, it is necessary to clarify its metabolic characteristics to C20 PUFAs based on the detection of eicosanoids in Drosophila. Therefore, this study is aimed to develop a high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for the determination of eicosanoids in Drosophila. Fifteen metabolites of AA and EPA produced by human in COX, LOX and CYP pathway were chosen, and each pathway contained 1 or 2 metabolites as delegates to ensure the representative of the method. These eicosanoids included PGF2α, PGE2, PGF3α, PGE3, 15(S)-HETE, LTB4, 15(S)-HEPE, 11(12)-EET, 20-HETE, 17(18)-EpETE, 17,18-DiHETE, 15(S)-HpEPE, 15(S)-HpETE, PGH2 and 5(S)-HpETE, and PGE2-d4, 15(S)-HETE-d8 and 20-HETE-d6 were used as internal standards. Samples were prepared by solid phase extraction and separated on an EndeavorsilTM C18 column (1.8 μm, 100 mm × 2.1 mm). The analytes were detected by using multiple reaction monitoring (MRM) in a negative electrospray ion mode. The HPLC-MS/MS method to analyze 15 selected eicosanoids in Drosophila qualitatively and quantitatively was established by optimizing the sample pretreatment and the detection conditions. It was found that the recoveries were significantly influenced by the pH of sample adjusted by 1 mol/L sodium acetate buffer containing 5% methanol, and the optimized pH was at 6. The response values of analytes separated on a mobile phase of ultrapure water with 0.1% formic acid-acetonitrile were higher than these of ultrapure water with 0.1% formic acid-methanol, ultrapure water-acetonitrile or ultrapure water-methanol. To reduce the matrix interference, the blank Drosophila matrix was used to prepare the standard working solution. Obtained results showed that the calibration curves were of good linearity for the 15 metabolites in the range of 2.5100 ng/mL with the correlation coefficient (r) of 0.991. The limits of detection and quantitation were about 0.1-2.6 ng/g and 0.3-8.7 ng/g, respectively. Spiked recovery experiments showed that both recoveries (89.3%-111.5%) and relative standard deviations (1.0%-15.0%) met the requirements of analytical methods. In conclusion, our study has established a simple, specific and sensitive method that suitable for the determination of eicosanoids in Drosophila which serves an approach to clarify the metabolic characteristics of Drosophila to C20 PUFAs.

Cotton bollworm, Helicoberpa armigera, was one of the most harmful pests in cotton-production areas all over the world. The transgenic insect resistant cotton with Bt gene from Bacillus thuringiensis was developed to control this pest in 1987. It was increased quickly in recent years, accounting for more than 93% of all cotton planted in China, and huge economic, social, and ecological benefits were obtained. The levels of Bt protein in cotton organs can directly affect the insect resistance of cotton plants. Many reports showed that the Bt cotton expressed the Bt protein at a high level in early season which provided good control of the second generation of cotton bollworm, but it was decreased in middle and late stages which lead to the decrease of the controlling efficacy to bollworm. However, few reports had been found about the levels of Bt protein in different organs and tissues during the whole growth stages of the transgenic hybrid cotton. Whole season levels of Bt protein in two transgenic hybrid cotton, Zheda 13-1 and Zheda 13-2, and their pure line parent, Zayou 2012, were investigated in 2014 in Hangzhou City, Zhejiang Province, located in southeast coastal region of China. Enzyme linked immuno-sorbent assay (ELISA) method was used to quantify Bt protein. The results showed that the Bt protein could be detected in all organs and tissues in the two hybrid cultivars and their parent, however, its levels changed significantly among the different organs from time to time. During the seedling stage, cotyledon was the highest organ, following by the first true leaf. The Bt protein level in root and stem was increased at the beginning, reached the peak value on 33 and 40 days after sowing, respectively for two cultivars, then decreased steadily afterward. In general, the Bt protein in root was much higher than that in stem. In the leaves of the two hybrid cottons, the upper third leaf, Bt protein was high in the early stage, declined in mid-season but rebounded in late-season. While for their parent, it was high in early season, then declined steadily in middle and latter season. The difference might relate to the growth habit of the hybrid cotton which kept growing in late-season for relatively long time. So it is suggested that the pesticide control might be necessary for the hybrid cotton in the mid-season of cotton growth. In addition, the study showed that Bt protein contents in the anther and stamens were much higher than those in leaves, squares, bolls, ovules, and petals. While for their parent, it was much lower in the anther and stamens than that in other organs and tissues. It should be studied further whether or not this phenomenon was resulted from the heterosis of the hybrid cotton, the high concentration of Bt protein in the anther and stamens was beneficial to the cotton bollworm control of the hybrid cotton as the cotton bollworms were more interested in the cotton reproductive organs.

Li Peng is the Chaetomium of chestnut (involucre of plant chestnut), also called the involucre of chestnut, thorn shell of chestnut, or Sarg. of chestnut etc. In the areas rich in Chinese chestnut, large amounts of waste Li Peng was produced, besides a small amount of which can be used for firewood, the rest will be discarded to rot or burned; however, it is not only a waste of resources, but also cause serious environmental pollution. Reports showed that Li Peng could be used as a raw material to cultivate chestnut mushrooms, but it was only an accessory ingredient, and the main ingredient was cotton seed shell of chestnut tree, so Li Peng has yet to be fully used. In some areas, the phenomenon of hyphae overgrowth occurred in chestnut mushrooms cultivated by Li Peng, the reason was due to its antibacterial effect. The purpose of this paper was to establish a simple and low-cost technique for extraction of antibacterial components from Li Peng. At the same time, a high sensitive, good repeatable and stable, simple and rapid method was used to determine the antibacterial ingredients of Li Peng. This paper used the single factor experiment and the orthogonal experiment optimization for the extraction process of antibacterial components in Li Peng. Furthermore, polysaccharide in the samples was precipitated by ethanol and the qualitative and quantitative combined determination of antibacterial components were carried out using reversed-phase high-performance liquid chromatography (RP-HPLC) method after protein removal. The results showed that the best way to extract the antibacterial composition of the 60-mesh fine slag in Li Peng was under 1∶40 material liquid ratio, 70 W ultrasonic reflux 20 min. Using Lichrospher C18 column (150 mm × 4.6 mm, 5 μm), methanol-0.1% phosphoric acid solution as the mobile phase, the flow rate of 1 mL/min, the detection wavelength at 280 nm, column temperature of 30 ℃ with the gradient elution program, the gallic acid, protocatechuic acid, and quercetin content in Li Peng could be better determined. The quality concentrations of each component with peak area showed a good linear relationship (r>0.999) in the measurement range. The average sample recovery (n=9) rate were 98.9%, 96.0%, 97.1%. The relative standard deviation (RSD) were 2.36%, 0.77%, 4.73%. We optimized the extraction of antibacterial ingredients in Li Peng. By simple operation, low energy consumption and high extract efficiency method increased the feasibility of this technology, and provides theoretical basis of mass industrial production for the extraction of antibacterial ingredients in Li Peng. Under the optimum conditions, we can extract 88.2% antibacterial components from chestnut at one time. The antibacterial component of gallic acid, protocatechuic acid, quercetin content in Li Peng was 0.176 0 mg/g (RSD=0.23%), 0.053 7 mg/g (RSD=0.16%), 0.019 6 mg/g (RSD=0.21%), respectively. The RP-HPLC is a high sensitive, good repeatable and stable method, which is also simple, convenient and accurate. This paper enriched the reference basis for the combined determination of the antibacterial components of Li Peng.

Since the first artificial hybrid was created in 1719, significant developments such as transgenic approach have been seen in the methods for crop breeding in recent hundreds of years. A lot of breeding-related data have been collected up to now. The big data technology was developed recently and has been successfully used in economics, IT (information technology) and other fields. With the increasing expansion of data in crops breeding, it becomes extremely necessary for breeders to take advantage of existing data in terms of efficient breeding technology, especially for the information generated from next-generation sequencing which could newly reach terabytes of data in a sequencing platform in one hour. In this study, we proposed a conceptual framework for big data-based crop breeding approach after we analyzed the genetic information flow of crop breeding program using an innovation tool, TRIZ
(theory of inventive problem solving). The expected new breeding technique tends to collect all breeding-related data (including data from phenotype, environments, references to molecular markers and sequences) for target crops and set up an automatic approach to collect breeding-related trait data. The technique will include a computer system to analyze the data and a human machine interface for users (breeders). We believe that big data has the potential to revolutionize the breeding of crops and the big data-based breeding approach is our future of crop breeding programs.

Due to the salinity-alkalinity stresses in agricultural environment, the production, quality and economic benefit of crops are seriously restricted. Salinity-alkalinity stresses not only decreased crop yields and affected crop quality, but also severely restricted sustainable and efficient crop production development. Therefore, it is of great significance to increase the crop resistance to salinity-alkalinity stresses for high-efficient and high-yield agriculture. γ-aminobutyric acid (GABA) is a non-protein amino acid, commonly exist in plant and animal tissues, which can indirectly affect plant growth and development under stress. However, there are few studies about the effect of exogenous GABA on seed germination under salinity-alkalinity stress. Thus, the experiment was carried out to screen the optimal concentration of GABA to improve the salt resistance of melon seeds. Salt-sensitive variety of melon (Cucumis melo L.) seeds (cv “Yipintianxia 208”), which is sensitive to salinity-alkalinity stresses, was chosen as experiment material. The effects of different concentrations (0, 5, 10, and 50 mmol/L) of exogenous GABA on germination index, radicle antioxidant enzyme activities, and GABA metabolism of melon seeds under 50 mmol/L salinity-alkalinity stress conditions (NaCl∶Na2SO4∶ NaHCO3∶Na2CO3 as molar volume ratio 1∶9∶9∶1) were studied. There were five treatments in this experiment (i) CK: Purified water presoaking and pre-germination; (ii) T1: Purified water presoaking and pre-germination under 50 mmol/L salinity-alkalinity stress; (iii) T2: 5 mmol/L GABA presoaking and pre-germination under 50 mmol/L salinity-alkalinity stress; (iv) T3: 10 mmol/L GABA presoaking and pre-germination under 50 mmol/L salinity-alkalinity stress; (v) T4: 50 mmol/L GABA presoaking and pre-germination under 50 mmol/L salinity-alkalinity stress. The results showed that salinity-alkalinity stresses significantly inhibited seeds germination and the growth of radicles and embryos of melon. Soaking seeds in different concentrations of GABA partly decreased the stress-induced inhibition on seeds germination of melon. Compared with the melon seeds in the treatment of salinity-alkalinity stress without GABA, a presoaking concentration of 5 mmol/L GABA improved superoxide dismutase (SOD) activity, and presoaking with 10 mmol/L GABA improved soluble protein content, endogenous GABA content and glutamate decarboxylase (GAD) activity in the radicles; presoaking with 50 mmol/L GABA improved seed germination rates, germination potential, vigor index, fresh mass, lengths of radicles and embryos, and peroxidase (POD), catalase (CAT) and GABA transaminase (GABA-T) activities and decreased malondialdehyde (MDA) content. It was concluded that 50 mmol/L GABA presoaking significantly alleviate the inhibition of melon seeds under salinity-alkalinity stress, and improved the salt tolerance of melon seeds.

In addition to the genetic cultivar characteristic and cultivation strategy, the environmental condition is considered as another important factor affecting grain yield in rice. Previous studies were carried out on yield formation of rice under the low temperature and weak sunshine condition, however, the ecological adaptability such as yield formation, nitrogen accumulation and utilization of different thermos-photoperiod sensitive rice cultivars to the low temperature and weak sunshine is still obscure, as well as the response mechanism. The main objective of this study was to determine the ecological adaptability of different rice cultivars under the low temperature and weak sunshine condition in the middle and late growth duration. Field experiments were conducted in 2013 and 2014 in Guiyang which was regarded as the representative eco-site with low temperature and weak sunshine, 35 rice genotypes including released cultivars and potential rice combinations were used as tested materials, and two ecology-adaptive cultivars (Zhuyou606 and Qianyou108) and two ecology-sensitive cultivars (Y Liangyou2 and Y Liangyou302) were selected out as the tested materials to study the differences in grain yield and yield formation, nitrogen accumulation and distribution, root characteristics. The results showed that: When values were averaged across cultivars and years, compared with ecology-adaptive cultivars, ecology-sensitive cultivars obtained a lower grain yield by 13.8%, which was mainly caused by a 9.9% lower filled grain ratio and 15.5% lower 1 000-grain mass. In comparison with ecology-adaptive cultivars, ecology-sensitive cultivars achieved 18.8%, 10.8%, 14.5% lower nitrogen accumulation amount at the mid-tillering (critical stage of productive tillering), heading, maturity stage, respectively, resulting in 17.9% lower nitrogen recovery efficiency (RE). Furthermore, a higher nitrogen accumulation amount in stem-leaves at heading stage and a lower nitrogen accumulation amount in stem-leaves at maturity stage were found in ecology-sensitive cultivars, relative to ecology-adaptive cultivars, and the nitrogen translocation amount from stems and leaves to panicle achieved 3.41 kg/667m2, which was 24.6% lower than that in ecology-adaptive cultivars,the nitrogen translocation ratio from stems and leaves to panicle achieved 38.55%,which was 19.4% lower than that in ecology-adaptive cultivars. The root bleeding intensity of ecology-adaptive cultivars achieved 20.2 kg/(h·667m2) at heading stage and 4.55 kg/(h·667 m2) at maturity stage, which were 8.8% and 21.6% lower than that in ecology-adaptive cultivars, respectively. Accordingto the results, a strategy to increase the grain yield of ecology-adaptive cultivars is suggested: keeping a higher filled grain ratio and a higher 1 000-grain mass, which is able to be accomplished by increasing nitrogen accumulation during the growth period from heading to maturity. Moreover, these methods such as cultivating strong roots and improving root activity are helpful to increase the amount of nitrogen absorption.

Light condition is one of the important factors affecting plant growth. During plant growth, light deficiency will result in the decrease in carbon fixation, photosynthetic efficiency, and leaf senescence acceleration, and thus decrease yield evidently. Besides yield, light also affect the rice qualities through influencing the seed compositions such as protein. Many studies have been carried out to evaluate the effect of light on protein synthesis. For example, previous studies have been certified that the protein accumulation is increased during the seed filling stage, as well as amino acids. The enzymes of glutamine synthetase (GS), glutamic oxalo-acetic transaminase (GOT), and glutamate pyruvate transaminase (GPT) are considered as the key enzymes regulating the synthesis of protein. Almost 95% of N was absorbed through GS/glutamate synthetase (GOGAT) cycle in plants and converted into glutamic acid (Glu) and glutamine (Gln). The Glu and Gln are then converted into other amino acids which provide the precursor materials for protein synthesis through the transamination reactions of GOT and GPT. However, researches about the effect of the activities of GS, GOT and GPT on amino acid and protein synthesis of rice are limited, especially under stress conditions such as low light. Based on previous studies, we carried out this experiment to evaluate the effect of low light on key enzyme activities of nitrogen metabolism and protein accumulation during the seed filling stage. The aims of this study were to study the dynamic changes of GS, GOT and GPT under different low light conditions during the seed filling stage, and evaluate the relationships between the activities of enzymes and protein accumulation. The experiment was initiated at Sichuan Agricultural University, Ya’an, China, in 2013. Four cultivars including japonica cultivars Akitakomachi and Koshihikari, indica cultivar IR72, and hybrid indica cultivar Gangyou 527 were selected as the materials. All the cultivars were managed routinely till the flowering stage, then 25% shading (A1) and 50% shading (A2), were set respectively as the treatments till maturity by using shade net, and natural condition was set as CK. Each treatment plot was repeated 3 times and the rice panicles which grown uniformly were marked for further sample collection. After 10 days of treatments, the seed samples were collected per 7-day period till maturity and stored in freezer at -80 ℃. After harvest, the samples were used to measure GS, GOT and GPT activities, as well as soluble protein, total protein and amino acid contents. Results showed that the GS activities were significantly decreased by 2001%-3052% at A2 than A1 (1161%-1936%) compared with CK, whereas, the activities of GOT and GPT increased significantly at A2 (GOT increased by 2607%-3682% and GPT increased by 2607%-6107%) than A1(GOT increased by 1402%-2302% GPT increased by 1181%-3383%) compared with CK In consistent with GOT and GPT, patterns of soluble protein, total protein, as well as amino acids were also significantly increased under low light conditions especially at A2 (compared with CK, soluble protein increased by 3119%-7051%, total protein increased by 1602%-2889%, and amino acids increased by 1604%-2248% at A2). The correlation analysis showed that GS activity was negatively correlated to soluble protein, total protein and amino acids under low light conditions, however, GOT and GPT showed positive correlations with soluble protein, total protein and amino acids. Based on the results, we speculated that the synthesis of protein of rice grain was more significantly affected by GOT and GPT which tended to increase the accumulation of both protein and amino acids, compared with GS. In addition, in consistent with previous studies, the low light conditions were beneficial for protein and amino acid synthesis of rice grain during the seed filling stage.

Rice is one of the most important crops in the world, especially in Asia, where more than 90% of the world’s rice is grown and consumed. In recent years, with the increase of living quality, the requirement for rice improvement is not only limited to yield, but also to its quality. During rice development, genetic and environmental factors significantly affect both of the yield and quality. Among the environmental factors, fertilizer management and planting density are considered as the main factors affecting rice growth and development. Data from the previous studies on the impact of nitrogen application rate and planting density on rice yield and quality have been inconsistent due to the differences in regional ecological conditions. Therefore, it is necessary to continue exploring the influence of nitrogen application rate and planting density on rice yield and quality. Chengdu plain, the main rice cropping region in the southwest of China, has the unique light, heat and water resources. In order to promote the planting of a japonica rice variety (identified in our previous research) in this area, we investigated how nitrogen (N) application rate and planting density and their interactions affect grain yield and quality. Data from this study would provide information for japonica rice cultivation in the area for high yield and good quality. To investigate the effect of nitrogen application rate and planting density on rice grain yield and quality characteristics, we used japonica rice cultivar D46 as the test material in this study. Split plot experiments with N application rate (N 150, 225 and 300 kg/hm2) as main plot and planting density (20×104, 26.67×104 and 40×104 seedlings/hm2) as sub-plot were carried out. The experiment was conducted on sandy loam in 2013 at the experimental farm of Sichuan Agricultural University in Wenjiang, China. The results showed that both N application rate and planting density had significant effects on the yield of the japonica rice cultivar D46 (P<0.05). The combination of N application rate of 225 kg/hm2 and planting density of 26.67×104 seedlings/hm2 led to the highest yield (7.58×103 kg/hm2), and which was significantly higher than other treatments (P<0.05). Dry matter accumulation tended to increase with the increase of N application rate during the whole growth period, whereas, for planting density, it reached the maximum at 26.67×104 seedlings/hm2 rather than at 20×104 and 40×104 seedlings/hm2. Furthermore, N application rate and planting density were shown to have different degrees of influence on the rice quality. The processing quality, chalky rate and protein content increased as the N application increased from 150 to 225 kg/hm2 and then declined with any further increases in N supply. In contrast, increasing planting density was not conducive to improving rice quality. Based on the results, and considering the importance of improving both rice yield and quality, the optimal combination of N application rate and planting density for japonica rice cultivar D46 in the planting area of Chengdu plain is N 225 kg/hm2 and 26.67×104 seedlings/hm2, respectively.

As the fourth major food crop, potato growing area increased year by year, which was an important mainstay industry in some provinces of China. In recent years, continuous cropping became common in potato growing areas. However, continuous cropping obstacle is one of the main factors limiting potato industry, which can lead to yield and quality losses, diseases spreading, and unbalanced soil ecology system. Therefore, it is an urgent task to explore effective ways to reduce the continuous cropping obstacle of potato and improve the yield and quality. Crop rotation is an effective practice to overcome the continuous cropping obstacle. Many scientific researchers have demonstrated that the crop rotation can relieve soil sickness by improving soil quality, ecological microclimate and crop productivity. Therefore, the crop rotation practice can partly eliminate the continuous cropping obstacle, but the selection of appropriate companion crops is the key. In this study, maize was selected as a rotation successive crop, which is widely planted in mountainous area of southwest China. A short term (2 years) pot experiment with potato-maize rotation, maize-potato rotation compared with potato successive cropping was conducted to study the changes in soil nutrients and enzyme activities of rhizosphere soils. Meanwhile, the effects of potato-maize rotation on rhizosphere soil nutrient and enzyme activity were also discussed. The results showed that, in mature period, rhizosphere soil nutrient contents of potato continuous cropping were decreased compared with those before seeding.
Only total phosphorus of the rhizosphere soils in potato-maize crop rotation were increased by 3.32%, respectively. Total nitrogen, total phosphorus, and available phosphorus, total potassium and available potassium compared with those before seeding, maize-potato crop rotation were increased by 6.84%, 32.67%, 4.13%, 3.77% and 10.81%, respectively.
The total nitrogen, alkali-hydrolyzable nitrogen in maize-potato rotation and the alkaline hydrolysis nitrogen in potato-maize rotation were decreased in the mature period, which were still higher than those in the potato continuous cropping. It was showed that soil nutrients, especially the available nutrients were over used in potato continuous cropping, compared with those in the rotation cropping. Polyphenol oxidase activity had a significant difference in tuber bulking. For other soil enzyme activities of rhizosphere, in the mature stage of the maize-potato crop rotation, the activities of rhizosphere soil urease, catalase, invertase were increased by 5.71%, 2.19% and 4.85%, respectively, and also increased by 52.07%, 32.23% and 11.62% in potato-maize rotation, which were significantly higher than those in the potato continuous cropping system. In summary, potato-maize crop rotation system can effectively relieve the potato continuous cropping obstacle by improving soil enzyme activities, and accelerating physiological and biochemical reactions of rhizosphere soils. Furthermore, the rotation system can relieve the potato continuous cropping obstacle effectively, and provide a theoretical basis for solving the problem of potato continuous cropping obstacle.

The regulation of dormancy is very essential in the production of potato. To satisfy the demand of different sowing dates and to keep high rate of emergence and growth potential in seed potato, it always requires prolonging or shortening the dormancy stage to guarantee the field emergence. Meanwhile, when potatoes are treated as food, the dormancy period should be prolonged as long as possible to keep the potatoes fresh. Physical and plant growth regulator treatments are two main methods that regulate the dormancy in potato. The physical treatment requires high cost of labor and material resources, while the plant growth regulator treatment has advantages of convenience and cost saving over the physical treatment. The conventional plant growth regulators were used to adjust the plant dormancy including
sprouting inhibitors chlorpropham (CIPC), abscisic acid (ABA), and sprouting promoter gibberellin A3 (GA3). There were numerous reports about the regulating effects of these regulators, but only a few investigations have been done to compare the regulating effects of these regulators on potato. To comprehensively study the effects of different growth regulators on the germination and main carbon-nitrogen metabolites contents of potato during storage, a laboratory experiment was conducted from May to August in 2014. The potato cultivar “Chuanyu-117” was used in this research. Potato tubers were dipped in aqueous solutions of CIPC, ABA and GA3 with efficacious concentrations for 30 minutes, respectively. The results indicated that GA3 could release potato dormancy in advance, and the intensity and amplitude of tubers dormancy, when treated with GA3, reduced by 17 days and 11 days, respectively, the length/diameter ratio of bud was much higher than that of control (CK), showing that GA3 could accelerate potato tubers germination and bud growth. Whereas, ABA significantly prolonged the dormancy, the dormancy amplitude reduced by 11 days but the dormancy intensity increased by 6 days, and the length/diameter ratio of bud was lower than that of CK, which showed that ABA could accelerate the speed, vigor and uniformity of bud growth after germination. The CIPC had a more obviously suppressive effect with a 70-day interval between the beginning of treatment and germination, and the germination period was also expanded to at least 40 days in contrast with CK. The change regulations of carbon-nitrogen metabolites contents in different treatments were the same, but the degrees of changes were quite different. The starch contents of potatoes treated with GA3, ABA and CIPC for 12 weeks reduced by 13.36%, 11.30% and 5.93%, respectively; while the soluble sugar contents reduced by 48.3%, 58.9% and 56.1%, respectively, when compared with those of the beginning of treatments. Both of the soluble protein content and the crude protein content showed a high-low trend line. The soluble protein content of GA3, ABA and CIPC treatment at the previous time of storage increased by 25.73%, 39.68% and 31.32%, respectively, and then reduced by 19.17%, 33.22% and 17.74% at later storage period, respectively. The crude protein content of GA3, ABA, and CIPC treatments increased by 4.77%, 12.67% and 12.65% at the previous time of storage, respectively, and then reduced by 11.37%, 18.02% and 8.71% at later storage period, respectively. The C/N ratio of the sprouting promoter treatment was higher than those of the sprouting inhibitor treatments, and all of them showed a downward tendency. In conclusion, GA3 could release the dormancy of potato in advance, the bud grew faster and the carbon-nitrogen metabolism activity was strong. Whereas, CIPC could prolong the dormancy period and inhibit the bud growth, the carbon-nitrogen metabolism activity of potato tuber was weak and the nutrient consumption was also less. ABA also prolonged the dormancy period but enhanced the germination uniformity and bud growth and the carbon-ni

Divalent heavy metal cation cadmium (Cd2+) causes phytotoxicity in plants. The high bioaccumulation index in plants and soil will also threat the human health through food chain. It has been shown that Cd will inhibit germination of seeds and exert a wide range of adverse effects on growth and metabolism of plants. It was reported that high concentration of Fe2+ in paddy soil could exert some impacts on plant growth and Cd2+ accumulation. Cadmium and ferrous with high concentration in soil, are known to cause oxidative damage to plants either directly or indirectly by triggering an increased level of production of reactive oxygen species (ROS). Plants have antioxidative enzymes, such as superoxide dismutase (SOD), catalase and peroxidase (POD), which can scavenge ROS to avoid oxidative damage. Malondialdehyde (MDA) level is used as an index of lipid peroxidation under stressful conditions in plants. Therefore activity of antioxidative enzymes (SOD and POD) and MDA level can be used to monitor the oxidative stress of plants. In anaerobic waterlogged environment, rice can form iron plaque around root surface and screen metals by adsorption and co-precipitation. Thus, the availability and balance of Fe/Cd in the rhizosphere of rice will be influenced. Many researchers investigated the impacts of ferrous and cadmium respectively on rice growth, while few efforts were made in interaction of these two metal ions, which exist in production conditions. In order to investigate mechanisms of Fe and Cd stress on rice in real production condition, the pot experiment with 4 soil Fe2+ levels (577, 677, 777 and 977 mg/kg) and 2 soil Cd2+ concentrations (0.413 and 5.413 mg/kg) was conducted. The rice cultivar used in the experiment was Hang43. Shoots of rice collected at booting stage were ground with liquid nitrogen and were homogenized in phosphate buffer (pH 7.8). The extracted supernatant was used to assay SOD activity, POD activity and MDA level, by NBT method, guaiacol colorimetric method and the thiobarbituric acid method, respectively. Fe and Cd concentrations in shoots and roots were determined by flame atomic absorption spectrophotometer (FAAS) after digestion procedures. Fe and Cd contents in iron plaque on the roots were extracted using dithionite-citrate-bicarbonate (DCB) method, and were measured by AAS. The experimental results showed that ferrous and cadmium in soil had interaction on the activities of lipid peroxidation, antioxidative enzymes and uptakes of these two metals. Cd2+ remarkably decreased MDA levels by about 31.1%, meanwhile depressed activities of superoxide dismutase (SOD) and peroxidase (POD) enzyme. Whereas, those adverse effects were mediated by increasing Fe2+ concentration in soil (especially at 977 mg/kg Fe2+). Variations of SOD activity and POD activity had similar trend in all the treatments, though POD activity was more stabilized, indicating SOD undertakes more protection responsibility under experimental conditions. Fe contents in iron plaque maintained 1-2 g/kg under all treatments, while Cd concentration in iron plaque declined quickly with the increase of soil ferrous level. Ferrous in soil stimulated the uptakes of Cd at a certain range but a relatively higher ferrous concentration in soil decreased the Cd contents in roots and shoots. It can be concluded that iron plaque helps to screen Cd2+ in the rhizosphere and inhibits the uptake of Cd2+ in rice. Fe2+in soil can alleviate the stress of Cd2+ by restraining the accumulation of Cd2+.

Polychlorinated biphenyls (PCBs) are a group of synthetic organic compounds and comprise a family of 209 possible congeners. PCBs are hazardous due to their persistence, hydrophobic character and toxic properties. Although they have been banned on a global scale since 1972, PCBs are still routinely found throughout the world and cause many ecotoxicological problems. Therefore, it is necessary to continue developing analytical methods for the analysis of PCBs in environmental samples. Analysis of PCBs in water is usually performed by gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS) combined with liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase disk extraction (SPDE), solid phase microextraction (SPME), headspace SPME (HS SPME), (magnetic) dispersive solid phase extraction (DSPE), dispersive liquid-liquid microextraction (DLLME) and membrane-assisted solvent extraction (MASE). Among these sample preparation methods, SPE, SPDE, SPME, and HS SPME usually suffer from high cost, sample carry-over, and time-declining performance. DLLME is easy to over-extraction and some matrix could be easily condensed. LLE as a reliable and simple method is often used for water sample pretreatment in large volumes. But after LLE, the extracts are usually required for further clean-up using concentrated sulfuric acid or SPE. (Magnetic) DSPE is quick, easy, cheap, effective, rugged and safe, but it is also subject to adsorbent. Besides, the extraction process is tedious, including dispersed, isolate, transfer, elute and even further purification. Therefore, the objective of this study was to develop an improved DSPE clean-up method to replace concentrated sulfuric acid or SPE after LLE, which needs less time and operation steps. Now, a simple, rapid, efficient, sensitive, and low matrix interference method for determination of seven PCBs (including PCB28, PCB52, PCB101, PCB118, PCB153, PCB138, PCB180) in water samples using gas chromatography-electron capture detector (GC-ECD) combined with automated LLE and DSPE has been described. In the designed experiment, water samples were firstly extracted with n-hexane, and then the extracts were directly purified by a suitable adsorbent. The kinds and amounts of adsorbent were optimized. Primary secondary amine (PSA) sorbent was chosen for DSPE purification, which could eliminate interferences to PCB28 and PCB52. But there were still some impurities to PCB52 and PCB28 by DSPE purification with C18 as sorbent as well as concentrated sulfuric acid purification. It may be because PSA could effectively remove carbohydrates, fatty acids, organic acids, polyphenols, sugar and polar pigments on the objective compounds, while C18 was mostly used to remove some non-polar disruptors such as fat and esters. By increasing the amount of PSA sorbent from 0 to 100 mg, the purify efficiency values increased significantly, and the recoveries of seven PCBs were almost invariant when the amount of sorbent ranged from 100 to 200 mg. As PSA could also adsorb n-hexane, increasing amount of PSA would result in a decrease of supernatant after centrifugation. Hence, 100 mg PSA sorbent was used, at this point, good purify efficiency and satisfactory recoveries were both achieved. Furthermore, the present DSPE process only needed less than 5 min for dispersion and centrifugation. The linearity of this method ranged from 1.25 μg/L to 100 μg/L, with correlation coefficients ranging between 0.999 0 and 0.999 8. The detection limits for seven PCBs were 0.000 2-0.000 3 μg/L. The recoveries of spiked PCBs at different concentration levels in water samples of Qiandao Lake and seawater samples of Daiquyang sea area were 74%-105%, and 71%-107%, respectively, with relative standard deviations (RSDs) of 3.1%-6.2%, and 3.5%-5.9% (n=5), respectively. It was concluded that this method could be successfully applied for the determination of PCBs in water samples with good accuracy and pre

Ecological stoichiometry is a comprehensive and effective method to learn the relationship and regularity of the elements in the biogeochemical cycle and the ecological process. The ecological stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) are significant in ecological systems. Soil C, N and P in wetlands significantly affected the productivity of the ecosystem, which are also important indicators of environmental status of wetland. At present, the research on C, N and P of wetlands is more concentrated on eastern part of China. Fewer research were focused on the characteristics of ecological stoichiometry of wetland in arid and semi-arid regions of Northwest China. The study area in this paper is Ningxia plain, which located in the arid area of Northwest China. As the Yellow River run through the plain, wetlands are widely distributed in this region. Due to the influence of agricultural irrigation and other factors, the eutrophication of wetland is a concerned problem, and the distribution of C, N and P of the wetlands have their unique characteristics. In order to clarify the spatial distribution characteristics of soil nutrients and its influencing factors in wetland of Ningxia plain, the combination of “3S” technologies (remote sensing, geographical information system, and global positioning system), typical sampling and laboratory determination were used, nine plots of the wetlands soil in Yellow River, lakes and marshes were sampled, and the content of soils ［soil organic carbon (SOC), N and P］ and their stoichiometric ratios were measured. The distribution characteristics of SOC, N and P were further analyzed. The results indicated that the average values of SOC, TN and TP in wetland soil of Ningxia plain are 9.61 mg/g, 0.94 mg/g and 0.45 mg/g, respectively. SOC are significantly correlated with TN and TP (P<0.05). SOC and TN are cumulative in surface 10-20 cm layer cross the longitudinal section of all plots. TP content is stable a cross the longitudinal section. The contents of SOC, TN and TP of the nine plots in northern and southern side of the plain are higher than the middle part. The spatial distribution characteristics of C/N and C/P are similar, both show higher in middle plain and lower in northern and southern sides of the plain. The N/P ratios in northern and southern sides of the plain are higher than that in the middle part of the plain. Among different wetlands, the highest TN, TP and N/P were observed in lakes, the highest SOC, C/N and C/P were observed in marshes, and lowest SOC, TN, TP, C/P and N/P were observed in rivers. The SOC, TN and TP of rivers showed a higher spatial variation over the plain. The contents of C, N and P and their stoichiometric ratios are impacted by environmental factors including wetland origin, vegetation type, soil properties and human activities including tourism, urban construction, industrial and agricultural pollutions. Soil C and P are key factors that determining the differences of C/N and C/P, and the C/P and N/P were more influenced by the moisture and salinity of soil. The typical stoichiometry property of C, N and P of Ningxia wetlands is that the C/P value is significantly lower than the average value of China, indicating that the organic phosphorus of microorganisms were mineralized in this region.

The investigation on the expression and interaction of Bax, Bcl-2 and Caspase-3 in the spontaneous mammary gland tumors of Sprague-Dawley (SD) rats was of great importance to provide a reference for the prevention and treatment of clinical mammary gland tumors. One hundred and thirty (half male and female) SD rats were dissected after feeding 60 weeks, then the tumors were collected for pathological observation, and to measure the protein expression of Bax, Bcl-2 and Caspase-3 by immunohistochemistry (IHC), and the mRNA expression of the above factors were detected by real-time fluorescence quantitative PCR （RTFQ-PCR） method. Gross anatomy and pathology showed that 14 female rats had mammary gland tumors, the total incidence of tumors was 1077% (14/130). However, in male rats, breast tumor had not been observed, meanwhile, the tumor occurrence rate in females was 2154% (14/65), including 7 cases of breast fibroadenoma, 3 cases of mammary adenocarcinoma, 2 cases of mammary papillary carcinoma, and 2 cases of mammary invasive ductal carcinoma, respectively. IHC results showed that in the control group (n=5), the protein expression of Bax, Bcl-2 and Caspase-3 were 975±004, 813±035 and 660±004, respectively; in the benign group (n=7), the protein expression levels of these three factors were 816±016, 914±022 and 443±01, respectively, while in its malignant lesion group (n=7) were 649±032, 924±081 and 303±010, respectively. In addition, compared with the control group, the expression of Bax and Caspase-3 was significantly reduced (P<001) in the diseased groups, and the expression of Bcl-2 in lesion groups was significantly increased (P<005). Moreover, in the control group, the Bcl-2/Bax ratio was less than 1, which was more than 1 in benign and malignant groups. Compared with the IHC results, the RTFQ-PCR results showed that the mRNA expression of above factors were consistent with the protein expression, also showed highly significance (P<001). It is concluded that female rats have a high incidence of mammary tumors, which was not observed in males; Bcl-2, Bax and Caspase-3 are closely related to spontaneous mammary gland tumor, which may provide a new idea for diagnosis, treatment and prognosis of clinical breast tumor.