With the rapid economic development and the impact of the coronavirus， goat milk and its products are more and more favored by consumers， and the goat milk industry has also become the second largest dairy product consumption industry in China. However， the goat milk industry has recently faced bottlenecks. The industry develops with the standards which is the guideline for the industry， and the quality safety of raw goat milk is the first checkpoint for the goat milk industry. The lack of standards is the main reason why the current goat milk industry faces bottlenecks. This paper systematically sorted out the status quo of the standards and the regulatory mechanism of raw goat milk. It was found that there were some problems in the current standard of raw goat milk， such as mixed use of national standard cattle and sheep， low social participation in standard formulation， long standard age， and imperfect supervision and implementation system. Combined with the current situation of the goat milk industry， corresponding countermeasures and suggestions were put forward from the aspects of speeding up the formulation of national standards and improving the supervision system and mechanism.
The development of artificial meat accords with the important strategic demand of green and low-carbon agriculture in China， which can ensure the increasing effective and safe supply of protein food， help to improve the national health level and control public health and safety risks. At present， the research and industrial development of artificial meat in foreign countries has started early and developed rapidly， and those in China are in the initial stage. In particular， the research and development of cultured meat in cells still have a long way to go， the main factors that restrict the development of artificial meat were the weakness of basic research， the high cost of industrialization， the unsound technical management standards， laws and regulations， and the low degree of public acceptance. In order to promote the development of artificial meat in China， it was necessary to create new ways to obtain protein resources with high efficiency， green and low carbon， strengthen basic research on artificial meat-related “Choking” problems， and intensify the integration and innovation of green and low-carbon industrial chains， perfect the system and mechanism of industrialization development.
A staxanthin belongs to the carotenoids. It has strong antioxidant activity and a variety of biological activities. Therefore， astaxanthin is widely used in food， chemical， medical and other fields. Astaxanthin has stereoisomerism and geometric isomerism. The different isomers have different biological activities and commercial applications. Nowadays， astaxanthin for commercial application mainly comes from chemical synthesis and extracts from microorganisms and Haematococcus pluvialis， but both of the methods have certain limiting factors. In order to open up a new astaxanthin biosynthesis pathway， more and more studies have reported that astaxanthin biosynthesis pathway is reconstructed in plants by genetic engineering technology to synthesize astaxanthin in recent years. At the same time， the stability of astaxanthin was improved to expand its application scope and enhance the absorption effect. the characteristics， main biosynthetic pathways and applications of astaxanthin were overviewed， and the development of plant genetic engineering research and active delivery system related to astaxanthin synthesis were summarized. It is expected that the combination and transformation of research results could promote the industrial application of astaxanthin in the future.
In order to enrich the genetic diversity of wheat cultivar resources in Ningxia， 251 wheat cultivar resources at home and abroad were as materials. The agronomic traits and quality traits were determined， and the genetic diversity of DNA level were analyzed using 47 pairs of SSR （simple sequence repeat） and 25 pairs of SRAP （sequence-related amplified polymorphism） markers. The results showed that 234 alleles were detected by 47 pairs of SSR primers， and the number of alleles and polymorphism information content （PIC） per primer were 3～11， 0.097～0.862 with the average 4.979 and 0.652， respectively. And 342 alleles were detected by 25 pairs of SRAP primers， and the number of alleles and PIC were 6～21， 0.651～0.932 with the average 13.680 and 0.826， respectively. It showed that 251 wheat cultivar resources contained the rich genetic diversity. The clustering analysis based on 72 pairs of primers of two types of markers divided 251 wheat cultivar resources into 4 groups， and the agronomic and quality traits of each group were analyzed. Group Ⅰ～Ⅳ included 100， 39， 81， and 31 varieties， respectively， and there were obviously differences among different groups. Group I showed the lowest moisture content and the highest in the average ear length， fertile spikelet， kernels per spike， grain weight per spike， thousand kernels weight， flour yield， volume weight， hardness index. Group Ⅳ showed the highest in the average ear stem length， spikelet number， crude protein content， wet gluten content， water absorptionand sedimentation value. It showed that group Ⅰ and Ⅳ were excellent groups of yield and protein traits， respectively， which provided theoretical guidance for genetic improvement and breeding of new varieties of wheat in Ningxia.
In order to explore the effects of nitrogen fertilizer application on nitrogen accumulation， distribution and transport in various vegetative organs of low prolamin transgenic barley after anthesis， to clarify the pattern of nitrogen changes from after barley anthesis to grain formation， the soil culture pot experiment was carried， and the genetically stable low-gliadin transgenic barley was as the test material with the receptor as the control （CK）. The four nitrogen applications were set including no nitrogen， low nitrogen （160 mg N·kg-1 soil）， normal nitrogen （230 mg N·kg-1 soil） and high nitrogen （300 mg N·kg-1 soil）. The grain yield， biomass and nitrogen accumulation and transport characteristics in vegetative organs after anthesis were determined. The results showed that， under the same nitrogen treatment， the grain yield and above-ground biomass of transgenic barley were higher than CK， plant height and 1 000-grain weight were significantly lower than CK， and the number of effective panicles and the number of grains per panicle significantly increased. The grain yield increased by increasing the number of tillers and effective panicles. And the protein content of genetically modified barley grains was significantly lower than CK with decrease of 0.58%~2.40%. With the increase of nitrogen application rate， the grain protein contents increased， the accumulation content of nitrogen in the vegetative organs of transgenic barley showed ear>leaf>stalk， and the highest nitrogen content in the panicle was at the blooming stage. The accumulation amount of nitrogen in above ground plant showed blooming period>filling period>maturity period， which indicated that the blooming period was the critical period affected barley nitrogen reuse. The significant correlation between grain yield and spike nitrogen content at the blooming stage was detected. Above results laid a foundation for the physiological mechanism of barley nitrogen transport and production and fertilization practices.
GbRLCK10 gene responsed to Verticillium wilt and hormone stress in Gossypium barbadense. To analysis the function of GbRLCK10 gene， it was introduced into tobacco by Agrobacterium mediated method， and the positive transgenic plants were got. The disease resistances of the transgenic plants were identified in greenhouse， and the expressions of salicylic acid pathway key genes （NtPR1 and NtNPR1）， ethylene pathway genes （NtEIN4 and NtNTHK2）， and jasmonic acid pathway genes （NtJAZ1 and NtAOS） were analyzed by qRT-PCR. The results showed that， before infection， the expressions of NtPR1， NtNPR1 and NtJAZ1 genes in transgenic plants were significantly higher than those in wild type， and the expressions of NtEIN4， NtNTHK2 and NtAOS genes in wild type were significantly higher than those in transgenic plants. After inoculation with Verticillium wilt， the disease index of transgenic plants was significantly higher than that of wild type. And after the wild-type plants were infected， the expressions of NtPR1， NtNPR1 and NtAOS genes were significantly higher than those of the control， while the expressions of NtEIN4， NtNTHK2 and NtJAZ1 genes were significantly lower than those of the control； after transgenic plants were infected， the expression levels of NtPR1， NtNPR1， NtEIN4 and NtAOS genes were significantly higher than those in the control， while the expression levels of NtJAZ1 and NtNTHK2 genes were significantly lower than those in the control. Compared with the wild type， the expressions of NtPR1 and NtAOS genes in transgenic plants were significantly lower， while the expressions of NtNPR1， NtEIN4， NtJAZ1 and NtNTHK2 genes were significantly higher than those in the wild type. In conclusion， GbRLCK10 gene affected tobacco Verticillium wilt resistance by regulating the expressions of key genes in hormone pathway， which provided important basis for further revealing the function of GbRLCK10 gene in response to cotton Verticillium wilt.
In order to investigate the microbial diversity of endophytic bacteria community in different tissues of sweet cherry， the V3~V4 regions of endophytic bacterial 16S rRNA from ‘Summit’ sweet cherry root， bark and branch were sequenced by Illumina high-throughput sequencing technology. The results showed that the diversity and function of endophytic bacterial community in different tissues of sweet cherry were significantly different. A total of 9 665 813 valid sequences and 1 386 OTUs were obtained from different tissues of sweet cherry. Species classification showed that endophytic bacteria in sweet cherry belonged to 20 phyla， 43 classes， 79 orders， 162 families and 346 genera. At the level of phylum， Proteobacteria was the dominant group， which was simultaneously found in different tissues. At genus level， the predominant genera in root were Streptomyces， Steroidobacter and Lactobacillus. The predominant genera in branch was Sphingomonas， and in bark was Bacteroides. PICRUSt （phylogenetic investigation of communities by reconstruction of unobserved states） function prediction analysis showed that the functions of endophytic bacteria in different tissues were involved in the biosynthesis of secondary metabolites such as polysaccharides， terpenes， ketones， enzymes and vitamins et al.. The reults showed that endophytic bacteria in sweet cherry had rich population diversity， which laid a foundation for the development and utilization of endophytic bacteria resources in sweet cherry in the future.
Light is an essential substrate for photosynthesis. However， excessive light could cause oxidative stress and severe damages of photosynthetic organisms. To cope with constantly changing light environments， cyanobacteria have developed flexible electron transport network. Cyclic electron transport （CET） around photosystem I （PSI） recycles electrons from ferredoxin to plastoquinone pool and generates ATP without NADPH accumulation. Two distinct CET pathways consisting of NDH-dependent route and PGR5-dependent route have been identified both in cyanobacteria and plants. Cyanobacterial flavodiiron proteins Flv1 and Flv3 functioning in Mehler-like reaction accept electrons after PSI to reduce oxygen to water without formation of reactive oxygen species. Here， we studied the function of CET routes and Mehler-like reaction in Synechocystis by physiological characterization under different light regimes and kinetic analysis of P700 oxidation/reduction using various CET and Flv mutants. It showed that NDH-1 complexes contributed over 90% of CET and sustained cell growth under steady high light condition， while Mehler-like reaction activated rapidly was responsible for releasing transient high light pressure. We proposed that NDH-1 dependent CET was the major mechanism in Synechocystis robustly supporting high light acclimation， whereas Mehler-like reaction was the spare route operating when the existing main path was largely insufficient. The fast responded FLV route could be a complementation of CET in the WT as well as NDH-1 defected mutant M55.
In order to further reveal the conveying mechanism of crushed corn stalks feed in the screw conveyor and improve the accuracy of the parameters used in discrete element simulation research during the screw conveying process of crushed corn stalks， the crushed corn stalks were divided into straw core， straw leaf and straw skin. The discrete element simulation parameters were calibrated. First， the average and range of the intrinsic parameters and contact parameters of core， leaf and skin were obtained through physical tests， and the contact parameters with a relatively large range were screened by Plackett-Burman test using their significance. The test results showed that the factors that had significant effect on the simulated stacking angle were the core-leaf rolling friction coefficient， the skin-leaf rolling friction coefficient， and the leaf-leaf static friction coefficient. Then， the evaluation index is set as the three significant parameters of the relative error value between the test and the actual stacking angle to carry out the steepest climbing test， and the value range of the three significant parameters was optimized and narrowed， and finally the accumulation angle and the second-order regression model between the angle and the saliency parameter were established by Box-Behnken test. The target value of the accumulation angle was set to 30.4° measured by the physical test， and the optimal value of the saliency parameters were obtained by optimization， which the leaf-core rolling friction coefficient， skin-leaf rolling friction coefficient and leaf-leaf static friction coefficient were 0.325， 0.377 and 0.411. And the simulated stacking angle obtained when each parameter was optimal was 30.77°. In order to further test the accuracy of the parameter values， the t test showed P was more than 0.05， indicating that there was no significant difference in the value of the stacking angle between the simulation and the physical test， which could verify the reliability of the optimal parameter values. The results showed that it was feasible to use the above physical tests and optimization tests to measure and calibrate discrete element simulation parameters， and the calibrated parameters could provide reference for other simulation tests of crushing corn stalks.
In order to improve the accuracy of greenhouse environmental monitoring and reduce the cost of environmental perception， this study designed a multi-point environmental monitoring system. Aiming at the difficulty of temperature management the increase of tomato disease rate in autumn and winter， the temperature in tomato greenhouse in Shandong province was continuously monitored. Based on the measured data， gaussian function was used to fit the daily variation curve of greenhouse temperature by least square multi-peak method， and the discrete data points were converted into continuous Gaussian function， and the optimal monitoring position of tomato in each growth cycle was obtained by integral calculation and comparison. The results showed that multi-peak fitting analysis of greenhouse temperature with gaussian function as the target had significant effect， and the lowest goodness of fit was 0.919； the absolute difference of integral area of temperature curve between monitoring points N15 and N10 and the greenhouse average temperature was the smallest in seedling and flowering and fruit-setting periods of tomato， so the best monitoring points at this growth period were N15 and N10； the locations of N10 and N3 monitoring points at tomato fruit period were closest to the average change level of greenhouse as a whole， which were the best monitoring position at this period. In conclusion， in different growth period of tomato， the monitoring point N10 in the middle of the greenhouse could better represent the overall level of the greenhouse. This method laid a foundation for the accurate monitoring of the greenhouse environment.
To solve the problems of replanting disease and Helicobasidium mompa Tanaka in C. tangshen Oliv. under continuous cropping system， an experiment was carried out to investigate the effects of microbial fertilizers （Chongchaling and Xinteruijun） on the growth and soil enzyme activity of continuous cropping C. tangshen Oliv.. The results showed that， compared with the control （CK）， the seedling survival rates were significantly increased by 42.3% and 38.4% after using Chongchaling and Xinteruijun for 2 years， respectively. The incidence rate of Helicobasidium mompa Tanaka followed the order of CK （13.4%）> Xinteruijun （3.4%）> Chongchaling （0%）. These two microbial fertilizers could effectively control Helicobasidium mompa Tanaka， among which Chongchaling had better control effect than Xinteruijun. Compared with the CK， Chongchaling significantly increased the fresh weight and yield by 20.3% and 71.4%， respectively； Xinteruijun significantly increased the fresh weight and yield by 34.6% and 85.7%. Chongchaling and Xinteruijun significantly increased the chlorophyll a content of C. tangshen Oliv. by 4.9% and 2.6%， respectively. Meanwhile， Chongchaling and Xinteruijun significantly increased the total chlorophyll content by 5.3% and 3.0%， respectively. Furthermore， compared with the CK， the activities of catalase， peroxidase and superoxide dismutase under the Chongchaling were decreased respectively. Moreover， the contents of malondialdehyde and O2-· were decreased， while the contents of soluble sugar and soluble protein were increased. The soluble protein content under Xinteruijun was increased. Compared with the CK. Chongchaling significantly decreased the total protein content （15.6%~16.5%）， Xinteruijun significantly increased the lobetyolin content （10.1%~15.3%）. The responses of soil enzyme activities to the application of two microbial fertilizers were similar. Compared with the CK， Chongchaling and Xinteruijun significantly improved the activities of urease， alkaline phosphatase and accharase， while decreased the activity of catalase. In conclusion， microbial fertilizers could promote the growth and control the Helicobasidium mompa Tanaka of continuous cropping C. tangshen Oliv. mainly by regulating photosynthetic metabolism， antioxidation， and soil enzyme activity.
Polyethylene （PE） is one of the most widely used plastic， which has stable structure， difficult to degrade and causes great pollution to the environment. In this study， the changes of PE in gut of Galleria mellonella L. larvae were investigated， the appearance of carbonyl （C-O） and hydroxyl （R-OH） functional groups indicated that the long chain structure in PE plastic film was depolymerized. Based on culture-independent method， high-throughput metagenomic and metaproteomic analysis of the microorganism in the intestinal contents of Galleria mellonella L.， two PE degrading enzyme encoding genes， POD8747 and Ahpc5341， were identified. Heterologous expression， purification and characterization were performed for both genes in Escherichia coli. The results showed the optimal temperature and optimal pH for both POD8747 and AhpC5341 were 50 ℃ and 8.0， respectively. The purified enzyme was evaluated for biodegradation of PE， after treated by POD8747 and AhpC5341， the PE film’s hydrophilicity increased and its contact angle of the PE film decreased from 100° to （90.07±3.45） and （91.73±1.70）°， respectively. These results indicated that POD8747 and AhpC5341 could exert surface oxidation ability in PE degradation， and could be used for PE degradation along with other enzymes in future.
To realize the resource utilization of agricultural straw waste， and to explore the effects of tobacco stalk carbon and nitrogen fertilizer on maize seedling growth， nutrient absorption， soil fertility and enzyme activities，pot experiment was carried out， in which two biochar levels （BC1，22.5 t·hm-2， low carbon and BC2，67.5 t·hm-2， high carbon） and two nitrogen fertilizer levels（N1， 180 kg·hm-2， low nitrogen and N2， 270 kg·hm-2， high nitrogen）were set without tobacco stalk carbon and nitrogen fertilizer as control （CK）， to analyze maize growth and nutrient uptake， soil nutrient content and enzyme activities after 60 days of maize growth. The results showed that， compared with CK， the application of tobacco stalk char and nitrogen fertilizer alone and in combination with each other significantly increased the maize growth，nutrient uptake， soil nutrient contents. And soil pH， total nitrogen and cation exchange were most significantly increased by N1+BC2 treatment， which were 1.29， 2.12 and 1.34 times higher than CK， respectively； soil organic matter， available nitrogen， available phosphorus， and available potassium were highest in N2+BC2 treatment， which were 3.4， 7.0， 1.5 and 2.5 times higher than CK， respectively. In addition， the soil treated with N2+BC1 had the maximum urease， sucrase and catalase activities， which were 74.74， 7.92 and 1.14 mL·100 g-1 soil， respectively. Biochar and nitrogen fertilizer applications significantly enhanced the activities of sucrase and catalase， compared with CK， the improvements of two enzyme activities were up to 63%~88% and 24%~79%， respectively. The results showed that low biochar rate promoted the activities of urease， sucrase and catalase， while a high biochar rate inhibited the enzyme activities. Correlation analysis revealed that a significant correlation was established between the available nitrogen content and activities of sucrose and catalase but not with the urease activity； and highly significant positive correlations were detected among soil enzyme activities. The results might provide a reference for the effectiveness of recycling tobacco straw， and serve as a reference for new ideas for reducing fertilizer application and improving efficiency.
In order to investigate the diversity of bacterial community in oat rhizosphere soil under different fertilization treatments， 7 treatments were set including no fertilization （CK）， commercial fertilizer only （T2） and commercial fertilizer combined with organic fertilizer according to ratios of 9∶1 （T3）， 8∶2 （T4）， 7∶3 （T5）， 6∶4 （T6） and 5∶5 （T7）. The contents of soil nutrient and the diversity of bacterial community were analyzed. The results showed that， compared with CK， the treatments of commercial fertilizer combined with organic fertilizer increased significantly the contents of available potassium and available phosphorus， and decreased significantly the content of soluble salt. Among 7 treatments， the biomass of oat in T4 treatment was highest. At the phylum level， a total of 28 taxas were obtained from samples of 7 treatments. Compared the bacterial communities among treatments， linear discriminant analysis effect size （LEfSe） found that the dominant bacterial communities of T4 and T5 treatments were more conducive to soil forward succession and plant growth. The results of redundancy analysis （RDA） showed that the contents of total nitrogen， available phosphorus， organic carbon and organic potassium had more significant effects on the bacterial community. Comprehensive analysis showed that T4 treatment was more conducive to the sustainable production of soil and plants.
Poor water retention of coal gangue substrate is the primary obstacle to plant settlement， so the L（34） orthogonal experiment was conducted to study the effects of different ratios of loess， water retention agent， biochar and bio-fertilizer on the moisture characteristics of the gangue substrate and the germination of Setaria viridis （L.） Beauv.. The experimental results showed that， except for bio-fertilizer， three other kinds of amendment significantly reduced the capacity and cumulative infiltration rate of gangue matrix（P<0.01）， and the treatment effect was soil to gangue ratio > water retention agent > biochar > bio-fertilizer. Furthermore， water retention agent， biochar and bio-fertilizer significantly increased the field capacity of gangue matrix， and the treatment effects were soil-to-gangue ratio > water retention agent > biochar > bio-fertilizer（P<0.05）. Finally， application of four kinds of amendment had no significant effects on the germination rate， but advanced the germination start time from 14 d to 7～12 d， and significantly increased the dry weight accumulation of S. viridis（P<0.05）， because the dry weight of S. viridis in CK was only 19.7 mg·pot-1， but the dry weight of S. viridis in treatment group ranged from 28.3～71.2 mg·pot-1， with the highest increase of 2.61 times. The results of the orthogonal experiments showed that the best suitable ratio of amendment was soil-to-gangue ratio 2∶1 + water retention agent 0.1% + biochar 1% + bio-fertilizer 1%， in which， the water retention of gangue matrix and the sprouting and early growth of S. viridis were significantly improved，which could provide theoretical reference for coal gangue matrix improvement.
To explore the health risk of eating pod peppers cultivated in Zunyi municipality and the difference in the absorption and accumulation of risk element（Cd） by pod peppers， the health risk of heavy metals （Cd， As， Pb， Cu， and Zn） from consuming three types of peppers （the finger， the taper， and the circular） were comprehensively evaluated using target hazard quotient， and the mechanism of the difference in the absorption of Cd by the three types of pod peppers were studied in pot experiment. The results showed that there was Cd concent of three types of pod peppers over the limit value. The biological enrichment factor （BCF） of soil Cd by finger peppers， taper peppers and circular peppers were 0.35， 0.25， 0.15， respectively. There was the highest hazard quotient from consuming finger peppers. And there was the lowest hazard quotient from consuming circular peppers. The Cd content of three types of pod pepper fruits in the pot experiment was as follows： the finger pepper > the taper pepper > the circular pepper. The Cd content of the finger pepper and the taper pepper exceeded the limit value （>0.1 mg·kg-1）， respectively， while the Cd content of the circular pepper fruits did not exceed the limit value. The BCF of soil Cd by the circular pepper and the transport factor of Cd from stems and leaves to fruits （TFfruits/stems and TFfruits/leaves） were significantly lower than those of the finger pepper. And the difference in the transport factor of Cd from roots to shoots （TFshoots/roots） between the finger pepper and the circular pepper was not significant. Correlation analysis also showed that Cd content in fruits of pod pepper was significantly positively correlated with BCF， highly significantly and positively correlated with TFfruits/stems or TFfruits/leaves， and insignificantly correlated with TFshoot/root. It could be seen that the low Cd biological enrichment factor of soil Cd by the circular pepper and the weak redistribution capability of Cd by its aboveground vegetative organs （stems and leaves） were responsible for its low Cd risk. In conclusion， it was recommended that residents in the study area should cultivate and consume circular peppers and take barrier control measures to reduce the risk of Cd in pepper fruits.
In order to clarify the response of Artemisia desert plant stems， leaves， roots and soil carbon （C）， nitrogen （N） and phosphorus （P） contents and their stoichiometric characteristics to fencing， the vegetation and soil C， N and P contents of desert grassland in the fenced area（2 years） and the grazed area were measu and analyze. The results showed that， compared with the grazed area， short-term sealing had no significant effect on the C， N and P contents of Artemisia desert plant community stems， leaves and roots， while the N∶P ratio of plant community stems was significantly reduced by 14.27%. The C content， C∶N and C∶P ratios of the roots in the 20—30 cm soil layer of the closed area increased significantly by 45.00%， 80.72% and 41.58% compared to the grazed area， while the N content and N∶P ratio of the 30—50 cm roots decreased significantly by 21.81%， 37.56% and 22.22% compared to the grazed area. However， P content significant increased by 22.22% and C∶N of the 50—70 cm root system also increased significantly by 64.53%. Short-term sealing significantly reduced N by 36.76% in the 0—5 cm soil， 37.34% and 25.35% in the 5—10 cm soil and 12.5% in the 50—70 cm soil， respectively. In addition， soil C：P at 20—30 cm and soil N：P at 10—20 cm were significantly reduced by 36.93% and 23.45%， respectively， in the blocked area. Therefore， short-term sealing did not achieve the effect of vegetation and soil restoration， and a combination of measures should be taken to promote the restoration of degraded grassland， such as extending the sealing period and adding phosphorus fertiliser.
In order to study the mechanism of new composite hydrogels for Cd and the alleviating effect of Cd stress on tobacco seedlings， using the synthesized new biochar composite hydrogel （PVA/AA/B） and modified biochar composite hydrogel （PVA/AA/MB） as materials， Cd adsorption and tobacco pot experiments were carried out. The results showed that the adsorption mode of two composite hydrogels for Cd was mainly multi-molecular layer adsorption， and the maximum adsorption capacity of Cd by PVA/AA/B and PVA/AA/MB were 314.17 and 371.83 mg·g-1 respectively. Compared to the results of CK， PVA/AA/B and PVA/AA/MB treatments significantly increased plant fresh weight by 172.94% and 231.32%， significantly increased dry weight by 135.29% and 188.24%， significantly decreased soil available Cd content by 36.27% and 65.18%， significantly decreased the content of Cd in the plants by 54.47% and 63.23%， and significantly increased SPAD value and antioxidant enzyme activity of the leaves. Both of the two new synthesized materials could effectively relieve the toxicity of Cd stress on tobacco seedlings and promote the growth of tobacco seedlings under Cd stress， among which PVA/AA/MB showed the better effect.The results provided theoretical basis for alleviating tobacco Cd stress.
Straw is one of the main agricultural wastes in China， which can produce biogas， organic fertilizer， feed and so on by resource treatment， but the added value of products is not high. In recent years， a type of anaerobic fermentation technology based on chain elongation （CE） has been developed that can produce medium-chain fatty acids （MCFAs）， significantly increasing the added value of the product and providing a new idea for the comprehensive utilization of straw. Straw can serve as a suitable substrate for the synthesis of MCFAs through biological and thermochemical transformation， and the directional production of MCFAs can be realized through process regulation. The content of caproic acid in fermentation broth was currently about 10 and 2 g·L-1·d-1 based on the process of biological and thermochemical transformation， and the simultaneous extraction could reach 57.4 g·L-1·d-1. This study summarized the regulation characteristics of electron donors and electron acceptors， as well as the significant influencing factors and strengthening methods affecting CE efficiency， in order to effectively transform and synthesize MCFAs from straw. It also reviewed the typical transformation path and metabolic characteristics of functional microorganisms. This research could provide a theoretical reference for the next application and improvement of the added value of straw transformation products， and technical support for the realization of high-value utilization of straw.
In order to study the effects of rhizobia on main active ingredients of three kinds of licorice， improve the quality and yield of licorice and develop a high quality rhizobia bacteria， three kinds of rhizobias （Rhizobium mongolense subsp.loessense strain CCBAU 7190B， Agrobacterium tumefaciens IAM 13129， Agrobacterium tumefaciens strain CCBAU 65237） were inoculated in the underground part of three types of licorices （Glycyrrhiza uralensis Fisch.， G. glabra L. and G. inflata Bat.） with 10 mL·plant-1 （675×10-6 CFU·mL-1）， and the untreated hay as the control. The contents of glycyrrhizic acid， liquiritin， liquiritigenin， isoliquiritin and isoliquiritigenin were determined by high performance liquid chromatography（HPLC）. The results showed that， compared with control， rhizobia treatment increased significantly the contents of 5 active ingredients in Glycyrrhiza uralensis Fisch.， G. glabra L. and G. inflata Bat.. This suggested that rhizobia-licorice symbiosis could significantly increase the accumulation of glycyrrhizic acid， liquiritin， liquiritigenin， isoliquiritin and isoliquiritigenin， which provided reference for improving the quality and yield of licorice.
Biochar has the effect of improving soil， saving water， retaining fertilizer and increasing yield. In response to the problem of low water and fertilizer retention capacity of sandy soil in Yulin， the effects of biochar application amounts and drip irrigation amounts on soil physicochemical characters and potato growth were studied by combining biochar with drip irrigation fertilization. There were two irrigation levels： 80% ETC（W1） and 100% ETC（W2）， and five carbon application levels： 0 （B0）， 10 （B10）， 20 （B20），30 （B30） and 50 t·hm-2 （B50）， a total of 10 treatments. Soil bulk density， organic carbon， soil water content， available potassium， nitrate nitrogen， dry matter accumulation amount and yield were observed during the growth period. The results showed that soil bulk density in 0—20 cm soil layer was decreased significantly with the increase of biochar， while soil porosity， soil organic carbon content and the content of available potassium were increased significantly， and the content of NO3--N and soil water content in the 0—20 cm soil layer were first increased and then decreased with the increase of biochar. With the increase of irrigation amount， soil bulk density in the 0—20 cm soil layer was decreased， and soil porosity and water content were increased. The effect of biochar application on potato dry matter accumulation amount was significant only at the late growth stage， which was first increased and then decreased with the increase of biochar. The potato tuber yield and water use efficiency were first increased and then decreased with the increase of biochar， and the tuber yield was increased with the increase of irrigation amount， and yield reached the maximum of 58 263.89 kg·hm-2 at W2B30 treatment， but there was no significant differences with W1B20， W1B30 and W2B20， while the maximum water use efficiency was W1B20 treatment， Therefore， considering the yield， water use efficiency and economy， W1B20 treatment could be a suitable water-carbon combination under the experimental conditions.