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Table of Content

    15 May 2021, Volume 23 Issue 5
    Impact of COVID\|19 Pandemic on Global Food Security and Countermeasures
    WANG Xiaomei§, HE Wei§, YANG Xiaowei§, KONG Lingbo, LIN Qiao
    2021, 23(5):  1-7.  DOI: 10.13304/j.nykjdb.2020.0628
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    The whole world is facing unprecedented food security challenges under COVID\|19 pandemic. In order to understand the global food situation, this paper analyzed the worlds and Chinas food supply situation and food security response strategies, and put forward strategy to guarantee China food security. It was found that global grain production was  generally stable as expected, and high impact resistant. Chinas main grain supply was guaranteed, but imported commodities were affected at certain extent such as soybeans. Due to the various situations in different countries, each country adopted measures to protect their domestic food supply, such as increasing financial and policy support, raising food stocks, building green channels, restricting food exports, reducing import tariffs, and implementing price controls. On this basis, this paper suggested to stabilize grain production by cracking supply bottlenecks, control grain prices by strengthening regulation, and stabilize social expectations by effectively guiding the market to ensure China food security and the stable operation of the food supply chain.
    Research on the  Application Difficulties and Countermeasures  of Food Safety Network Public Opinion Monitoring System in China
    WANG Ni, SUN Xiaohong, QI Haifeng, TAO Guangcan,
    2021, 23(5):  8-17.  DOI: 10.13304/j.nykjdb.2020.0475
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    Some problems exist in the food safety network public opinion monitoring system, such as inaccurate data collection and low efficiency, unsystematic and inadequate data analysis, narrow data application and weak scene, so it is urgent to find out the solution. This paper summarized the current research status and development trend of food safety public opinion monitoring at home and abroad, sorted out the basic characteristics of food safety public opinion monitoring, and mastered the technical system involved in food safety public opinion monitoring, and proposed a solution to the problems of food safety public opinion monitoring in data collection, data analysis and data application. First, using keyword database to form monitoring probe and building dynamic media database would be beneficial to improve the efficiency and accuracy of data collection. Second, increasing the diversity of data analysis methods, such as public opinion classification, public opinion event processing and classification, multidimensional analysis, public opinion group analysis, public opinion disposal analysis, public opinion early warning analysis and policy support analysis, would be conducive to fully mining important public opinion information. Thirdly, the implementation of scenario-based services among the government, enterprises and consumers would be conducive to the innovative application of food safety public opinion monitoring.
    Research Progress on Plant Growth, Development and Its Molecular Mechanism in Response to Sub-optimal Low Temperature
    SUN Yan, PU Wenxuan, WU Changzheng, HUANG Pingjun, SUN Mingxue, SONG Dean, LIU Laihua
    2021, 23(5):  18-26.  DOI: 10.13304/j.nykjdb.2019.0986
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    In recent years, the sub-optimal low-temperature disaster termed “late spring cold (LSC)” has frequently occurred, which seriously constrains the productivity and development of agroforestry, and consequently results in a significant economic loss. In order to alleviate and even avoid the impairment of the LSC on crops and further sustain their normal growth potential, farmers usually apply some remedial approaches such as foliar spraying of fertilizers to lower plant damage by cold. However, such currently  techniques show some limitations including laborious- and time-consuming as well as less effective reduction of the cold damage. Therefore, it is urgently necessary to develop new methods for tackling such problems. This paper  reviewed advances in research of the effects of sub-optimal low temperature on plant growth and development and the related physiological and biochemical processes. The effective role of exogenous application of hormones and other chemicals in relieving cold stress and possible molecular mechanisms of plant in response to chilling injury were discussed. This review was expected to provide valuable theoretical references for the exploration and improvement of plant tolerance to sub-optimal low temperature.
    Progress on Regulation Mechanism of Plant Seed Development
    HU Tingting, WANG Jiankang, DING Chengwei, GUO Rongliang, WU Yuling, XU Jiaan, WANG Youshuang, ZHAO Yipeng, HE Wanwan
    2021, 23(5):  27-34.  DOI: 10.13304/j.nykjdb.2020.0048
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    Plant seeds are one of the most important organ for  plant propagation, so it directly affects the plants development and the yield and quality of grain. The genetic and molecular mechanisms for the regulation of seed development are complicated and sophisticated, A large number of genes and influence factors genes regulate seed development have been identified. However, the interaction between these genes, how different regulatory pathways form networks to synergistically regulate seed development, and which new genes are involved,  still  need to further study. By sorting out the genes, regulators and regulation patterns involved in seed development, this paper discussed how to use allelic mutation needed by human to improve crop yield and quality, so as to provide theoretical support for plant seed development and genetic improvement of grain yield and quality.
    Morphological Characteristics and Its Hereditary Behavior of High-nodal-positionTillering in Rice#br#
    HUO Chuan, WANG Shiquan, SHEN Junhong, ZENG Hongyan
    2021, 23(5):  35-43.  DOI: 10.13304/j.nykjdb.2020.0246
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    Panicle number, grain number per panicle and 1 000-grain weight are the three elements for rice yield, tiller is important composition factor of panicle number, and high-nodal-position tillering is a special tillering way of rice. Wild-type R818 and its high-nodal-position tillering mutant W33 were taken as experimental materials, and pot planting and field experiments were conducted to study the morphological characteristics and genetic behavior of high-nodal-position tillering traits in rice. The results were as follows. ① During the seedling stage, the plant height, leaf size, root number and root length of W33 were not significantly different with R818. ② At the early tillering stage, there was obvious secondary tiller in W33; at the mid-late tillering stage, the tiller bud of R818 were gradually enterring a dormant state, while tiller buds of W33 were still in active state except for the panicle neck node, and there were significant or extremely significant difference in the plant height, leaf length of main stem, and the first, second, third and fourth tiller number between them  at the heading stage, the average number of tillers per plant in W33 reached 79.7, which was 7.5 times of  R818. ③ The average grain number and yield per panicle of R818 were significantly different with those of W33, however the average grain yield per plant was not significant different between them. ④ F1 of positive and negative cross of W33 and R818 did not show high-nodal-position tillering characteristics, and the backcrossing progeny of their F1 with W33 showed two phenotypes of non-high-nodal-position tillering and high-nodal-position tillering, in which the separation ratio of the two traits was suitable for 1∶1 by 2 test; F2 progeny of positive and negative cross exhibited two phenotypes of non-high-nodal-position and high-nodal-position tillering, and their separation ratio was consistent with 3∶1 by 2 test. The results showed the high-sectional divisional capacity of W33 was exuberant, and the number of divisions in the middle and late stages was  significantly higher than R818;  the high-nodal-position tillering capacity in W33 was strong, and the numbers of the first, second, third and fourth tillering were significantly or extremely significantly higher than those of R818 in the mid-late tillering. The characteristics of high-nodal-position tillering trait were shown as single-gene recessive inheritance. These results could provide reference theoretical for the further research and utilization of high-nodal-position tillering in rice.
    Metabolomics Analysis of Seed Dormancy Release of Traditional Chinese Medicine Plant Notopterygium incisum
    LI Aihua, JIANG Shunyuan, GUO Na, HUANG Luqi
    2021, 23(5):  44-51.  DOI: 10.13304/j.nykjdb.2020.1001
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    The seeds of Notopterygium incisum, a traditional Chinese medicine plant, are dormant, which limits its artificial domestication and cultivation. In order to analyze the metabolite changes and screen the key compounds during releasing dormancy of N. incisum seeds, seeds of N. incisum were pretreated with cold and warm stratification; and the pretreated seeds were treated with low temperature stratification (CS), ABA inhibitor fluridone (FL) and GA3 (GA), respectively. Then seeds of different treatments were detected with UPLC-MS/MS. The results showed that the whole treated process of N. incisum seeds could be divided into three stages: 0—60 d, 90—(150+30) d and (150+60)—(150+110) d, among which N. incisum seeds treated with  pretreatment+CS for (150+60) and (150+110) d  had germination capablity. The compounds represented by the principal component t[1] were the compounds that had undergone major changes of seed embryos during 0, 15, 60, 90, 120 d after pretreatments. The compounds represented by the principal component of t[2] were mainly changed during the release of physiological dormancy. The difference analysis showed that the content of orobanchyl acetate, a strigolactone compound, was accumulated significantly in released dormancy of N. incisum seed, which was increased by 12.1 times after FL treatment and 28.5 times after CS treatment. Therefore, orobanchyl acetate could be  crucial during the dormancy release of N. incisum seeds. This study provided a theoretical basis for dormancy release mechanism of N. incisum seeds and a practical significance for the development of Chinese medicine industry of N. incisum.
    Physiological Response of Tamarix leptostachys Bunge to Three Single Salt Stress
    LI Xing, HU Yang, MA Yuan, JIA Shouyi, LI Gangtie
    2021, 23(5):  52-60.  DOI: 10.13304/j.nykjdb.2019.0886
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    In order to study the physiological response of Tamarix leptostachys Bunge, a rare native tree species, to salt stress in Hetao irrigation area, NaCl, Na2CO3 and NaHCO3 were selected as three stress salts, and three gradients of moderate (T1), severe (T2) and extremely severe (T3) were set up. There were altogether 10 treatments, including NaHCO3 -T1, NaHCO3 -T2, NaHCO3 -T3, Na2CO3-T1, Na2CO3-T2, Na2CO3-T3, NaCl-T1, NaCl-T2, NaCl-T3, and salt-free sandy loam as control (CK). The two-year-old T. leptostachys seedlings were treated by pot experiment. The content of chlorophyll and malondialdehyde (MDA) and the activity of peroxide (POD), catalase (CAT) and root were determined to analyze the physiological response characteristics of T. leptostachys to three kinds of salt stress. The results showed that: ① Total chlorophyll contents of Na2CO3-T3 and NaCl-T3 treated for 40 d  decreased by 53% and 36%, respectively, compared with the corresponding treatment for 0 d, and showed a continuous decreasing trend with the extension of treatment. Other treatments showed a trend of decreasing firstly then increasing, which indicated  that extremely severe salt stress seriously affected the photosynthesis of T. leptostachys, while it could recover moderately in a short time under moderate and severe salt stress. ② The increase of MDA content under NaCl stress was the highest in all treatments, which indicated that the damage of NaCl stress to cell membrane system of T. leptostachys was more serious than those under NaHCO3 and Na2CO3 salt stress. ③ With the prolongation of stress time, the activities of POD and CAT in different treatments showed a trend of increasing firstly then decreasing. ④ The root activity of T. leptostachys was gradually decreased with the increase of salt stress concentration. It was demonstrated that under moderate and severe salt stress, T. leptostachys showed strong adaptability and was suitable for popularization and application in saline-alkali areas. However, under extremely severe salt stress, it was seriously damaged, thus its application should be further evaluated. The present research provided a theoretical foundation for the popularization and application of T. leptostachys.
    Advances in Research on Deep Learning for Crop Disease Image Recognition
    ZHOU Huiru, WU Boming
    2021, 23(5):  61-68.  DOI: 10.13304/j.nykjdb.2019.1041
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    In the process of crop production management, it is very important to diagnose crop diseases timely and accurately. Image recognition based on deep learning provided a new approach for automatic diagnosis of crop diseases. Compared with traditional pattern recognition methods which are used in image recognition, deep learning neural network models are able to extract features automatically, obtain high-dimensional features from low-dimensional features and achieve better learning results. This paper systematically reviewed the recent development of deep learning in automatic image recognition, and the concepts related to shallow networks were first introduced, on top of that, the advantages of deep learning methods were expounded, and the widely used image recognition algorithm, convolutional neural network was briefly introduced. Diagnosis of crop disease based on image recognition could be classified as diagnosis of a single disease in a single crop, multiple diseases in a single crop, and multiple diseases of various crops. After discussing and analyzing the research status of deep learning methods applied in these three areas, and the difficulties and challenges faced at present, prospective comments on the technology bottlenecks in this field 
    that might be broken through in the future were put forward.
    Desert Vegetation Classification Based on Object-oriented UAV Remote Sensing Images
    ZHANG Guanhong, WANG Xinjun, XU Xiaolong, YAN Linan, CHANG Mengdi, LI Yongkang,
    2021, 23(5):  69-77.  DOI: 10.13304/j.nykjdb.2020.0851
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    The sparse distribution and small leaf area of desert vegetation lead to the weak vegetation spectral characteristics in the image, which makes the classification difficult. In order to improve the accuracy of desert vegetation classification, the Gurbantunggut Desert was selected as the research area, the remote sensing image and digital surface model of drones were used as data sources, and the object-oriented random forest algorithm was used to enhance the basis of decorrelation stretched spectral information, and then analyze the change of classification accuracy before and after the correlation stretching. The results showed that: the overall classification accuracy of slightly, moderately and seriusly desertified areas based on decorrelation stretching combined with object-oriented and random forest algorithm was 91.01%, 95.34% and 93.18%, respectively, which was 19.94%, 16.10% and 17.61% higher than the original image classification accuracy. This study realized the high-precision classification of desert vegetation, and provided reference for obtaining the distribution of desert vegetation and desertification monitoring test.
    Research and Experiment of Dendrometer with Walking Stick
    TIAN Yi, FENG Zhongke, CHANG Chen
    2021, 23(5):  78-85.  DOI: 10.13304/j.nykjdb.2019.0922
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    In order to obtain the diameter breast height (DBH) and tree height of the standing timber easily, quickly, accurately and efficiently in the forest resource survey, this paper designed and developed a portable dendrometer measuring instrument with a fixed length stick as the main body and equipped with intelligence mobile phone and tree measurement software. Based on the traditional forestry survey equipment theory, the equipment utilized tree measurement, photogrammetry, machining, machine vision, image processing and other technologies to realize automatic identification, measurement of breast diameter, record and manually intercept the complete standing tree and obtain DBH calculus tree height function etc by image processing software in smartphones.  It could edit, store and export the final obtained DBH and tree height. Analysis results showed that the error of the breast diameter and tree height of the portable dendrometer was 24.9 and 0.48 cm, the relative error Bias% was 1.5%, 4.2%, and the root mean square error RMSE both was 0.70 cm . The RMSE% was 3.6% and 6.09%, respectively, which basically met the a thpe accuracy requirements of the second type of survey, and had certain application value and promotion potential.
    Recognition Algorithm of Extremum Point Clustering Seedling Belt Based on Offset Compensation Model
    XIAO Feifei, JIANG Ping, HU Wenwu, LIAO Ronghua, ZHANG Danhui, JIN Sheng
    2021, 23(5):  86-97.  DOI: 10.13304/j.nykjdb.2020.0792
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    In order to realize the automatic navigation driving of field management machinery and improve the recognition accuracy of seedling belt trajectory, this paper proposed an extremum point clustering seedling zone identification algorithm based on offset compensation model. Firstly, based on the steering gear leveling unit, the seedling belt data were collected by lidar to construct a 2.5 D point cloud image, and establish an offset compensation model through mathematical modeling to obtain correction parameters. Then, the cluster feature points were obtained through the extreme value detection algorithm, and hierarchical clustering combined with offset compensation model. Finally, the least square method was used to linearly fit the obtained seedling belt cluster points to realize the reconstruction of the seedling belt trajectory. Through the Matlab simulation of point cloud information for machine-transplanted paddy rice with a forward vision range of 2 000~3 000 mm and a standard row spacing of 220 mm. When the obtained seedling belt trajectory was compared with the real seedling belt trajectory, the maximum lateral deviation was 16 mm, the maximum median deviation was 6 mm, and the calculation took 1.50 s. Compared with the slope blur clustering seedling belt recognition algorithm, the maximum axial deviation reduced by 29 mm, and the operation time reduced by 0.14 s, which improved the accuracy of trajectory coincidence and enhanced the real-time performance of the algorithm. Above results provided theoretical basis for the navigation and driving of low-injury seedlings for paddy field management machinery.
    Detection of Honeybee Based on SSD Model
    LYU Chunyang, LIU Shengping, GUO Xiuming, XIAO Shunfu, LIU Dazhong, YANG Feifei, LI Luhua
    2021, 23(5):  98-107.  DOI: 10.13304/j.nykjdb.2019.0955
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    Traditional bee monitoring mostly relies on labourer and experience, and the level of information is low, so automatic monitoring of bees has been concerned widely. Recently, object detection based on deep learning has developed rapidly and achieved good results in many fields. SSD model is a target detection model based on convolutional neural network, which has the advantages of speed and accuracy. The light of the beehive gate area is changeable, and the environment are complex. Bee colony also has complex situations such as mutual occlusion and shadow.  In this paper, SSD model was used to detect honeybees in the hive gate  and to make data statistics analysis. The results showed that the precision of the method selected was 96.34%, 92.52% and 88.06% in the case of small, general and large bees’ number, which was 11%, 19% and 25% higher than that of the traditional method, respectively. Furthermore,  SSD model had strong adaptability to different environment such as illumination, weather, shooting distance and could detect and deal with complex conditions such as bee shadow, blur, occlusion, etc. The detection results provided strong support for monitoring outside the hive, and also laid a foundation for statistics of in-and-out number based on bee tracking.
    Comprehensive Quality Evaluation and Impact Factor Analysis of Medium Indica Hybrid Rice in Anhui Province from 2009 to 2019
    RUAN Xinmin, SHI Fuzhi, CONG Xihan, DU Hongyang, ZHAN Xinchun, WANG Yuanlei, XIA Jiafa, LUO Zhixiang
    2021, 23(5):  108-115.  DOI: 10.13304/j.nykjdb.2020.0754
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    In order to clarify the variation trend and key impact factors of rice quality of  medium Indica rice in Anhui province from 2009 to 2019, the comprehensive evaluation function of Indica rice quality in projection pursuit was established based on the latest quality standards of edible rice varieties of Ministry of Agriculture and Rural Affairs by using the projection pursuit model of accelerated genetic algorithma. The variation trend of comprehensive quality of Indica rice in Anhui province and its influencing factors were analyzed by this model. The results showed that the comprehensive rice quality of medium Indica rice in Anhui province increased significantly. The analysis result of the projection pursuit model was consistent with the change trend of the proportion of high-quality rice above grade 3 tested by the participating combinations in each year. The trend of the proportion of high-quality rice above grade 3 among the approved varieties also confirmed this law. The remarkable progress of Anhui medium Indica rice breeding in head rice rate, chalky grain rate and chalkiness promoted the improvement of the comprehensive quality of rice. Chalky grain rate, chalkiness and amylose content were the key factors affecting the comprehensive quality of Anhui medium indica rice varieties. In  future, reducing the chalky grain rate and chalkiness, maintaining an appropriate amylose content, and increasing the polished rice rate would get be  the main direction of Anhuis future quality breeding. At the same time, we must also pay attention to the improvement of alkali depreciation traits.
    Combined Effect of Grapefruit Seed Extract Treatment and Polyethylene Packaging on Postharvest Quality of Toona Sinensis
    BAIGETUMUER Ayitula, LI jie, CHEN Cunkun, LIU hui, LI Xiangyang, LIN Shaohua
    2021, 23(5):  116-123.  DOI: 10.13304/j.nykjdb.2020.0939
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    The young leaves and sprouts of the Toona sinensis are nutritious and special flavour. However, as a seasonal vegetable, Toona sinensis is highly perishable, thus has a short shelf life. Grapefruit seed extract (GSE) is a naturally strong antioxidant and preservative. Toona sineasis was packaged by polyethylene (PE) film with a thickness of 0.02 mm and treated by GSE of a concentration of 0.1%, 0.3% and 0.5%. The sensory quality and physicochemical indexes of the toon during storage under different treatments were studied. The results showed that: different treatments had a certain preservation effects. Among them, 0.5% GSE+PE treatment could significantly delay browning and rot of toona sinensis, reduce weight loss, control the increase of chlorophyll content, and inhibit respiration rate and ethylene release rate. The research results provided an important theoretical basis and practical reference for the fresh-keeping of toona sinensis after harvest.
    Research on the Effect Mechanism of Biochar on Farmland N2O Emissions
    HE Tiantian, LIU Tian, YUN Fei, MA Caijuan, FU Yunpeng
    2021, 23(5):  124-131.  DOI: 10.13304/j.nykjdb.2019.1081
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    N2O is one of the main greenhouse gases affecting global climate change, and also plays a catalytic role in the depletion of the ozone layer. Farmland soil is the second largest source of greenhouse gas emissions, and how to reduce its N2O emissions has become a major subject. Biochar is a high specific surface area and porous material formed by pyrolysis of carbon-rich biomass under anoxic conditions. Biochar has many advantages such as improving soil fertility and promoting crop growth, and has become a current research subject. Its effect mechanisms on farmland N2O emissions have been studied, but no unified conclusion has been formed. This paper reviewed the N2O emission mechanism and the effects of biochar characteristics, the interaction of biochar and environmental factors on farmland N2O emissions based on previous studies, and future more gave some research priority recommendations and utilization of biochar on greenhouse gas emissions.
    Hyperspectral Inversion of Soil Organic Matter Content Based on Continuous Wavelet Transform
    CHEN Haoyu, YANG Guang, HAN Xueying, LIU Xin, LIU Feng, WANG Ning
    2021, 23(5):  132-142.  DOI: 10.13304/j.nykjdb.2020.0742
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    Taking organic matter contents of 120 soil samples and corresponding spectral data in Tuoketuo County as data sources, the feasibilities of hyperspectral inversion of soil organic matters under different type of soils and lands  of different use were explored. The original spectrum (R), spectral reciprocal (1/R), spectral logarithm (LnR) and spectral first-order differential (R′) were decomposed by continuous wavelet transform to generate wavelet coefficients, and the correlation between soil organic matter and wavelet coefficients was analyzed, and BP neural network and support vector machine (SVM) were established by extracting the characteristic bands. The results were followed. ①The correlation coefficients between R, 1/R, LnR, R′ and soil organic matter were increased by 0.204, 0.090, 0.199 and 0.252 after continuous wavelet transform, respectively, which showed that continuous wavelet transform could deeply mine the potentially spectral information and enhance the correlation with organic matter content. ② Before continuous wavelet processing, SVM could not predict the content of soil organic matter, while after processing, the accuracies (R2) of SVM-CWT-R and SVM-CWT-R′ were 0.50 and 0.56, Root mean square errors (RMSE) were 0.17 and 0.15, residual predictive deviations (RPD) were 1.62 and 1.53, respectively, which realized the effective estimation of SOM. ③ After continuous wavelet transform, the results of BP neural network prediction model were improved. Among them, BP-CWT-LnR prediction model had the best effect, R2 was 0.76, which was higher than BP-lnR, RMSE was 0.15 reduced by 0.04, RPD was 2.12 increased by 0.87. Therefore, the BP-CWT-LnR hyperspectral inversion model could provide theoretical reference and technical support for precision agriculture.
    Effects of Crop Residue and Mineral Fertilizer on Physiological Characteristics of Barley Leaves and Yield under Double-cropping Rice Field
    SHI Lihong, TANG Haiming, XIAO Xiaoping, LI Chao, Liu Qu, CHENG Aiwu, CHENG Kaikai, LI Weiyan, WEN Li
    2021, 23(5):  143-152.  DOI: 10.13304/j.nykjdb.2020.0492
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    In order to explore the effects of long-term application of crop residue and mineral fertilizer on physiological characteristics in plant leaves and yield of barley (Hordaum vulgare L.) under barley and double-cropping rice triple crops planting pattern, a long-term field experiment established by 33 a in Ningxiang county of Hunan Province was carried out, the protective enzyme activities and photosynthetic characteristics of barley leaves, and yield of barley with different  fertilizer treatments were investigated from 2018 to 2020 in the present paper. The experiment included three different fertilizer treatments: without fertilizer  (CK1),  chemical fertilizer alone (CK2) and  crop residue and chemical fertilizer (RF). The results showed that activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in barley leaves of RF and CK2 treatments  increased when compared with CK1 treatment at different main growth stages of barley. Meanwhile, compared with CK1 treatment, the content of malondialdehyde (MDA) and proline (Pro)  in  leaves of RF and CK2 treatments  decreased at different main growth stages of barley. ANOV result indicated that activities of SOD, POD and CAT in leaves of  RF treatment were significantly higher (P<0.05) than those of CK1 treatment, and the MDA and Pro contents in leaves  of RF treatment were significantly lower (P<0.05) than those of CK1 treatment at different main growth stages of barley. Meanwhile, the transpiration rate, stomatal conductance and net photosynthetic rate in leaves of   RF treatment were significantly higher (P<0.05) than that of CK1 treatment at different main growth stages of barley. The order of barley yield with different fertilizer treatments from 2018 to 2020 were showed as RF>CK2>CK1, and the grain yields of  RF treatment were significantly higher (P<0.05) than those of CK1 treatment. Compared with CK1 treatment, the grain yield of  RF treatment was increased by 571.5 and 576.9 kg·hm-2 from 2018 and 2020. As a result, it was an effective way to improve protective enzyme activities and photosynthetic characteristics in leaves of barley  by appling crop residue and chemical fertilizer, which provided the physiological basis for higher grain yield of barley.
    Influences of Exogenous Selenium Mineral Powder on Protective Enzyme Activity, Yield and Selenium Content of Foxtail Millet
    ZHANG Yujie, GUO Pingyi, GUO Meijun, ZHOU Hao, YUAN Xiangyang, DONG Shuqi, WANG Yuguo
    2021, 23(5):  153-159.  DOI: 10.13304/j.nykjdb.2020.0752
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    In order to study the effect of selenium mineral powder application on the protective enzyme activity, yield and selenium content of millet, by Jingu 21 and Zhangzagu 10 as experimental materials, this paper carried out a field experiment to study the effects of different dosage selenium mineral powder (0, 204, 394.8, 789.45 kg·hm-2)on the growth and development of millet and the selenium content in grain. The results showed that: with the increase in the amount of selenium mineral powder, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaf of millet at each growth stage showed an increase first and then a decrease trend, the content of malondialdehyde (MDA) decreased first and then increased, and both reached the extreme value during T2 treatment. Compared with the control, the T2 treatment had the most significant effect on the ear weight, ear grain weight, 1 000-grain weight and yield of millet. The yield of Jingu 21 and Zhangzagu 10 increased by 8.64% and 664%, respectively. The application of selenium mineral powder could increase the selenium content in millet grains. Under T2 treatment, the selenium content in Jingu 21 grains reached the highest 0.131 mg·kg-1, which was 3.5 times higher than the control. Soil selenium application of 394.8 kg·hm-2 could be used as the recommended application rate of selenium mineral powder in the production of selenium-rich millet.
    Impacts of Orchard Herbage-mulching on Photosynthetic Characteristics and Leaf Quality of Apples in Arid Desert Area
    CHEN Jun, ZHANG Qi, YANG Mengyu, YUAN Zhenyang
    2021, 23(5):  160-167.  DOI: 10.13304/j.nykjdb.2019.1011
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    In order to explore the effect of natural herbage-mulching on photosynthetic characteristics and leaf quality of apple in arid desert area, apple variety Fuji was selected, the effects of different treatments on diurnal variation of photosynthetic characteristics and leaf quality of apple were studied by setting up clear tillage and herbage-mulching treatments. The results showed that the diurnal changes of relative humidity (RH) and net photosynthetic rate (Pn), stomatal conductance (Gs),  water use efficiency (WUE) and light energy use efficiency (LUE) of apple leaves in herbage-mulching treatment were similar to those in clean tillage treatment. Herbage-mulching increased the levels of Pn, Gs, RH, WUE and LUE of apple leaves, and decreased those of Ci, Tr and air temperature (Ta). Path analysis showed that Ta had a limiting effect on Pn in clean tillage treatment, and Gs, CiTr  and RH were the main determinants of Pn. Ta and RH had a limiting effect on Pn  in herbage-mulching treatment, GsCiand Tr were the main determinants of Pn. Fresh weight, dry weight, specific leaf weight, chlorophyll content and K+ content of leaves  increased in herbage-mulching treatment, compared to clean tillage treatment. The present research demonstrated that herbage-mulching in orchard was suitable for popularization and application in arid desert areas, and provided  basis reference for herbage-mulching of orchard in arid desert area.
    Effect of Drying Density on Change of Main Nitrogen Compounds in Drying Process of Cigar Tobacco
    DENG Yige, DING Songshuang, ZHU Jiaming, TIAN Yuli, QIAO Baoming, SHI Xiangdong
    2021, 23(5):  168-175.  DOI: 10.13304/j.nykjdb.2020.0047
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    In order to fully grasp the changes of nitrogen metabolites during the drying process of cigar tobacco leaves, to formulate a reasonable modulation process, the cigar tobacco variety ‘Gu-5’ was used as material to study the effects of different air-drying densities (40, 60 and 80 pieces·rod-1) on the changes of the main nitrogen compounds in cigar tobacco leaves. The results showed that, under different air-drying densities, the changing trends of various nitrogen-containing compounds in tobacco leaves were basically consistent. Among them, the change of total nitrogen content showed a “bimodal curve”, and the total nitrogen content was the lowest at the end of air-drying; soluble protein degradation mainly occurred during the wilting phase and the yellowing phase, and the accumulation of amino acids proceeded with protein degradation simultaneously, showing a "fast-slow-fast" variation trend; the total alkaloid content  decreased slightly; nitrate did not change much between before and after air-drying. Among different air-drying densities, total nitrogen, protein and alkaloids of tobacco leaves were degraded the fastest under the treatment of 40 pieces·rod-1, and the three chemical components  all reached the lowest value at 25 d after air-drying; amino acids content was fully accumulated during air-drying process and eventually reached 7.61 mg·g-1; its nitrate content was always the lowest during the whole air-drying process. Taken together, the drying density of 40 pieces·rod-1 was more conducive to improving the quality and industrial availability of cigar tobacco leaves.
    Ability of Nano-Se Production of Three Potential Probiotic Bacillus sp.
    ZHANG Pengbo, PENG Qing, QIAO Yu, XU Xiaoqing, ZHANG Yuwei, TIAN Dandan, HUANG Ying, MA Lan, SHI Bo
    2021, 23(5):  176-186.  DOI: 10.13304/j.nykjdb.2019.1003
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    Nano-selenium is widely used in various fields because of its easy absorption, low toxicity, anti-tumor, anti-oxidation and enhancing immunity, etc. In order to study the ability of different probiotic Bacillus to prepare nano-selenium, taking Bacillus aryabhattai SI9, Bacillus amyloliquefaciens AT34 and Bacillus coagulans LB-9 as research objects, the ability of transforming Na2SeO3 into nano-selenium was compared, and the nano-selenium particles prepared by them were characterized by morphology and content determination. The results showed that B. aryabhattai SI9 had the strongest ability to produce nano selenium, followed by B. amyloliquefaciens AT34 and B. coagulans LB-9. With the increase of Na2SeO3 concentration, the growth of three strains was inhibited; when Na2SeO3 concentration was 200 μg·mL-1, the nano-selenium yields of three strains were 48.3%, 36.3%, 34.8%, the extraction rates were 96.9%, 95.0% and 94.0%, respectively; the purity was 73.2%, 78.1% and 89.4%, respectively; and the conversion rates of Na2SeO3 were all 100%. It was showed that the sizes of selenium nanoparticles extracted by the three strains were 70~500 nm under field emission scanning electron microscopy (SEM). The present research could provide theoretical support for the preparation of nano-selenium by microbial transformation.
    Contents of Carnosic Acid, Carnosol and Rosmarinic Acid Determined Simultaneously by HPLC
    LIN Shuangshuang, ZHANG Haifeng, CHE Jianmei, GE Cibin
    2021, 23(5):  187-193.  DOI: 10.13304/j.nykjdb.2020.0722
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    In order to optimize process of simultaneous determination of carnosic acid, carnosol and rosmarinic acid, the detection wavelength, precision, stability, repeatability and recovery rate of HPLC method were screened and optimized. The recovery rates of rosmarinic acid, carnosol and carnosic acid were 86.4%, 85.6% and 88.8%, respectively, with the correlation coefficient above 0.999 in the concentration range of 5~100 mg·L-1. After testing it showed that the contents of carnosic acid (25 585 mg·kg-1) and carnosol (11 823 mg·kg-1) in the leaf of Rosmarinus officinalis "Pine"were the highest. The content of rosmarinic acid in the leaf of Rosmarinus officinalis "Rex" was the highest (7 572.67 mg·kg-1). The highest contents of carnosic acid (1 570.00 mg·kg-1), carnosol (1 603.33 mg·kg-1) and rosmarinic acid (1 304.67 mg·kg-1) were determinated in the stems of Rosmarinus officinalis L. among the four varieties. HPLC method was stable, reliable and efficient after optimization, which  provided a basis for the development and utilization of non-volatile components of rosemary.
    Mutation Breeding of Azotobacter chroococcum with High Nitrogenase Activity by Atmospheric and Room Temperature Plasma
    DUAN Saifei, HUANG Yanna, WANG Jinbin, SHU Shiyuan, ZHOU Maochao, TANG Xueming,
    2021, 23(5):  194-201.  DOI: 10.13304/j.nykjdb.2020.0117
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    In order to enhance the nitrogenase activity of bacteria so as to improve the nitrogen-fixing ability of nitrogen-fixing bacteria, Azotobacter chromococcus CICC21686 was treated by atmospheric and room temperature plasma (ARTP) mutagenesis technology. The mutant strain 28s-20 with high nitrogenase activity was screened by acetylene reduction method, and the genetic stability of the enzyme activity of the mutant was observed. The optimum growth temperature and initial pH of medium for mutant strain were determined by setting gradient temperature and pH cultivation. Pot experiment was conducted to investigate the effect of mutant strain on dry weight and total nitrogen content of maize plants. The results showed that after two rounds of screening, the nitrogenase activity of the mutant strain 28s-20 was increased by 101.72% compared with that of the original strain. After 5 generations cultivation, it was demonstrated that its nitrogenase activity had good genetic stability. The optimum growth temperature of the mutant was 28 ℃, and the initial pH of culture medium was 7.5. Compared with the wild strain, the mutant strain significantly increased the dry weight and total nitrogen content of maize by 21.16% and 34.36%, respectively. The mutant strain with high nitrogenase activity provided technical support for strain optimization of A. chroococcum and agricultural biological nitrogen fixation.