Table of Content

20 February 2024, Volume 33 Issue 2

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Evolution of soil phosphorus forms and factors influencing their formation based on ³¹P nuclear magnetic resonance analyses of degraded alpine wetland

Yuan-jun LUO, Yu-lin PU, Da-gang YUAN, Ya-li LI, Hong-yu QIAN

2024, 33(2):  1-12.  DOI: 10.11686/cyxb2023116

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The aim of this study was to clarify the patterns of soil phosphorus transformation and factors driving this process during alpine wetland degradation. Such information is useful for devising strategies to manage nutrient and carbon “sinks” in the ecological restoration of wetlands. Four types of marsh wetlands in Zoige Nature Reserve， including relatively pristine marsh （RPM）， lightly degraded marsh （LDM）， moderately degraded marsh （MDM）， and heavily degraded marsh （HDM）， were selected to investigate the evolution of phosphorus forms in soil， and factors affecting this process. Analyses were conducted using ³¹P nuclear magnetic resonance and a piecewise structural equation model. It was found that the degradation of alpine wetland led to a succession of plant communities from hygrophytes to mesophytes， and reductions in the soil organic matter and nitrogen contents. The contents of orthophosphate and phosphate monoesters displayed a parabolic trend with the maximum occurring in MDM along the gradient of marsh degradation. The orthophosphate content was 46.45% lower in HDM than in RPM. The phosphate monoesters content was 27.02%， 54.96%， and 41.74% higher in LDM， MDM， and HDM than in RPM， respectively. The contents of pyrophosphate and phosphate diesters continuously decreased with increasing severity of wetland degradation. The piecewise structural equation model indicated that microbial activity was a positive factor influencing soil orthophosphates， pyrophosphates， and phosphate diesters， and a negative factor influencing phosphate monoesters. Vegetation biomass was a positive factor influencing soil orthophosphates and phosphate diesters. Soil nutrients indirectly affected pyrophosphates and phosphate diesters by impacting microbial activity. Overall， wetland degradation promoted the decomposition of phosphate diesters by changing the vegetation community and decreasing soil nutrient availability and microbial activity. Soil phosphorus availability decreased in HDM because of the decline in the phosphate monoester mineralization rate and decreased orthophosphate content.

Establishment and application of a forage product quality and safety evaluation index system based on a ‘DPSIR’ model

Meng-ge ZHOU, Yong-hua LI

2024, 33(2):  13-27.  DOI: 10.11686/cyxb2023122

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An important foundational component of work for construction and improvement of a national ecological grass husbandry system is to construct a universal quality and safety index system， to evaluate the quality and safety level of forage products in various regions. In this study， under the conceptual framework of the driving forces-pressure-state-impact-response （DPSIR） model， based on published forage standards and related literature， the relevant indicators affecting the quality and safety of forage products were systematically identified， and 14 core indicators were selected. These were： per capita consumption of beef and mutton， the number of machinery items for livestock husbandry， the number of items of equipment for keeping produce fresh in storage， the annual sunshine duration， the annual precipitation， the crude protein content， the neutral detergent fiber content， the acid detergent fiber content， the dry matter digestibility， the annual yield or growth rate of beef， the annual yield growth rate of mutton， the total amount of beef and mutton， the number of regional regulations and standards， and the quality supervision. The analytic hierarchy process （AHP） was used to quantify the weight of each index. The weight of crude protein content was found to be the highest， followed by neutral and acid detergent fiber content， and the weight of the number of items of equipment for keeping produce fresh in storage was the smallest. Based on this evaluation index system， the quality and safety of natural forage products in Tongde County of Qinghai Province and Shandan County of Gansu Province was evaluated. It was found that the quality and safety of natural forage products in Tongde County was higher than in Shandan County， and the corresponding safety levels were Grade Ⅱ and Grade Ⅲ， respectively. The establishment of a quality and safety evaluation index system for forage products is expected to result in improvement of the quality and safety level of forage products. This initiative will therefore provide important scientific guidance for ensuring forage production practices will deliver high quality products to local animal industries.

Microhabitat plant diversity and biomass differences in abandoned karst farmland and their driving factors

Ying LEI, Jie LUO, Xu-man GUO, Er-ting BI, Jin-chun LIU

2024, 33(2):  28-38.  DOI: 10.11686/cyxb2023133

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An in-depth investigation of changes in species diversity and biomass in different ecological niches of typical abandoned arable land in karst areas of Chongqing was conducted to provide a theoretical basis for community restoration in the early vegetation succession following farmland abandonment. The former farmland under study had been abandoned for four to six years. The vegetation biomass and species diversity together with changes in soil physicochemical properties， and their relationships were studied in four microhabitats： homogeneous shallow soil， homogeneous deep soil， heterogeneous trapezoid and heterogeneous funnel. It was found that： 1） Soil water content increased with soil depth， but total nitrogen and carbon nitrogen ratio decreased with soil depth. In the two heterogeneous habitats， the coefficients of variation for soil depth and soil water content differed little and indicated high intensity of variation. 2） The richness index， Shannon-Wiener index and Pielou index were not significantly different among the different microhabitats. 3） There were no significant differences between the aboveground biomass of the four microhabitats， while the below-ground biomass and total biomass of heterogeneous habitats were higher than those of homogeneous habitats. 4） There was a significant negative correlation （P<0.05） between the biomass and species diversity data for microhabitats with heterogeneous funnel. However， there was no significant relationship in other habitats. Resource heterogeneity had a positive effect on community biomass in the early succession stages after abandonment of karst farmland， but biodiversity was not greatly affected by habitat at this stage. Medium-thickness soil was found to promote plant growth and maintain productivity， while high-thickness soils counterintuitively had lower productivity due to lower nutrient content and poor permeability. Therefore， in the early stages of vegetation restoration， the characteristics of each habitat type should be fully understood in order to manage the recovery to maintain the diversity and growth of the vegetation.

Trends in the evolution and promotion of animal husbandry in Gansu Province as determined using a competitive state model

Gui SHI, Ya WANG, Guo-jing YANG, Jun-hao LI, Li-hua ZHOU, Xiao-dong PEI

2024, 33(2):  39-56.  DOI: 10.11686/cyxb2023079

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The high quality and sustainable development of herbivorous livestock farming is an important part of China’s rural revitalization strategy. As such， it is increasingly important to understand the trends in livestock development in each region to ensure the healthy development of livestock farming and the revitalization of rural industries. In this study， we used data from the “China Rural Statistical Yearbook”， the “Gansu Rural Yearbook” and “Gansu Development Yearbook” to analyze the current situation of cattle （Bovini） and sheep （Caprinae） breeding， including the competitive state within the sector， patterns of livestock transfer， and the livestock center of gravity in Gansu Province at the provincial， municipal， and county scales from 1991 to 2019. These analyses were conducted using a competitive state model based on the ‘Boston Matrix’ and a center of gravity migration model， and included relevant factors related to socio-economic and natural resources. In our model livestock slaughter rates were used as a surrogate for company earnings in the original application of the Boston Matrix to share market analysis and growth in livestock numbers as a surrogate for market growth. It was found that： 1） The competitive state has shifted regularly between the low-quality cycle of “dog-young” （low slaughter rate and breeding rate-high slaughter rate and low breeding rate.） and the high-quality cycle of “star-cow” （high slaughter rate and breeding rate-low slaughter rate and high breeding rate）. It is challenging to achieve gains in development between these two cycles， but such gains were achieved in Gansu Province after 2006. 2） The shift in the competitive state of livestock breeding， the center of gravity of the migration of livestock and natural resources， and socio-economic conditions showed a high degree of fit. The shift in the competitive state can be used as an essential indicator for the selection of appropriate breeding strategies. 3） The next steps in Gansu Province should be to adopt an expansion strategy， expand the star breeding sites （high slaughter and breeding rates）， stabilize the cow breeding sites （low slaughter but high breeding rates）， and consider a tightening strategy for the dog （low slaughter and breeding rates） and young breeding sites （high slaughter but low breeding rates）. The results of this study provide a scientific basis and reference for the rational development of， and strategic planning for， the grass-fed animal husbandry at the regional level.

Construction and application of a graphic visualization tool for important forage omics data

Jia-hui CHEN, Wen-xian LIU

2024, 33(2):  57-67.  DOI: 10.11686/cyxb2023166

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The post-genomic era in biological science has commenced with the publication of genome and transcriptome sequencing data for numerous forage grasses enabled by the rapid advancement of high-throughput sequencing technologies. The focus of genomics research has shifted from understanding genome structure to the level of identifying and validating gene functions. What’s more， gene expression in different tissues plays an important guiding role in the mining of gene function. In previous studies， most expression data across different tissues in the field of breeding research have only been presented in formats such as histograms， tables， or basic heatmaps. However， the visualizations conveyed by these methods are relatively simple in form， and the results are not visually compelling， making it difficult for readers to obtain relevant information quickly and effectively. In order to display combinatorial data more intuitively， aesthetically， and comprehensively， this study developed a forage data visualization workflow， which uses TBtools software and ten important forage grasses and legumes， including Medicago sativa， Medicago truncatula， Leymus chinensis， and Melilotus officinalis as the species for investigation. By combining with a file drawn by Adobe Illustrator， a set of forage omics data and visualization workflow was constructed. The expression pattern of the MsSAP gene in alfalfa and the changes in expression under different stresses was taken as a case study to illustrate data acquisition， heatmap generation and result visualization when using the workflow. Compared with the traditional graphic display method， it was found that by using the forage SVG graphics files and visualization processes provided by us to visualize multi-omics data， researchers can more rapidly， efficiently and aesthetically visualize their own multi-omics research results， so as to provide a basis for the subsequent in-depth mining of functional genes and functional verification.

Effects of short-term nitrogen and phosphorus addition on soil greenhouse gas emissions under different moisture conditions in the Hui River Basin of Hulun Buir

Yan QU, Kun ZHAO, Zi-chen HAN, Shi-hai LV, Qiang WO, Yu-ping RONG

2024, 33(2):  68-79.  DOI: 10.11686/cyxb2023110

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The addition of nutrients as fertilizers greatly affects soil greenhouse gas （GHG） emissions in grassland， but the response of soil GHG emissions to nutrient addition in grasslands under different flooding conditions remains unclear. The effects of nitrogen （N）， phosphorus （P） and nitrogen plus phosphorus （N+P） on soil GHG fluxes （CO₂， CH₄， and N₂O） from seasonally flooded （PF） and non-flooded dry grassland （NF） at the edge of a riparian zone were investigated using a split-plot design in the Hulun Buir Hui River Basin in 2021. The results showed that： 1） The CO₂ emission from NF with P was significantly higher than that from PF with P （P<0.05）， and the CH₄ emission from NF with N+P was extremely significantly higher than that of PF with N+P （P<0.01）. Compared with N₂O fluxes from PF and NF without nutrient addition， those from PF and NF with N， P， and N+P were significantly increased by 38.81%， 90.09%， and 124.94%， respectively. 2） Nutrient addition increased the cumulative emissions of GHG from grassland soils with different moisture contents. The maximum cumulative GHG emissions were consistent in the PF and NF treatments after the addition of nutrients. The highest cumulative emissions of CO₂ from soil were in the N addition treatments， and were 95.92% and 49.01% higher in PF with N and NF with N， respectively， than in their respective controls. The highest cumulative emissions of CH₄ from soil were in the P addition treatments， and were increased by 190.64% and 32.62% in PF with P and NF with P， respectively， compared with their respective controls. The maximum cumulative emissions of N₂O from soil were in the N+P treatments， and were about three times higher than that in the control. 3） The global warming potential （GWP） of NF with added nutrients was higher than that of PF with added nutrients， and the GWP of NF and PF treatments was highest with P addition （32.66% and 178.69% higher than those of their respective controls， respectively）. 4） The structural equation model showed that flooding conditions negatively affected soil CO₂ and CH₄ fluxes， nutrient addition had a positive effect， and both flooding conditions and nutrient addition positively affected soil N₂O fluxes. Flooding conditions and nutrient addition affected soil CO₂ and CH₄ fluxes mainly by influencing soil physical properties and nutrient contents， and affected soil N₂O fluxes by influencing soil physical properties and nutrient contents and by changing the aboveground plant biomass.

Effects of phosphorus application on soil respiration rate and active organic carbon components of alfalfa

Kong-qin WEI, Jun-wei ZHAO, Qian-bing ZHANG

2024, 33(2):  80-92.  DOI: 10.11686/cyxb2023124

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This research aimed to investigate the effect of phosphorus application on soil respiration rate and active organic carbon content of alfalfa， and to clarify the relationship between soil respiration rate and soil active organic carbon fraction in alfalfa fields under different phosphorus application treatments. It was envisaged these data would support identification of practices to maximize soil carbon sequestration and sustainable development of artificial grassland. The experiment was laid out in a randomized group design with four levels of phosphorus application： 0 （P₀）， 50 （P₁）， 100 （P₂） and 150 kg·hm^-2 （P₃）， and replicated three times. Soil organic carbon （SOC）， microbial carbon （MBC）， dissolved organic carbon （DOC）， particulate organic carbon （POC）， easily oxidized organic carbon （EOC）， soil temperature and humidity and respiration rate （R_S） were studied in under the different levels of phosphorus application for soil horizons to 60 cm depth. It was found that， the contents of SOC， MBC， DOC， POC and EOC increased with increasing phosphorus application across the different soil depths， reaching a maximum of 15.77 g·kg ^-1， 0.42 g·kg ^-1， 0.34 g·kg ^-1， 4.68 g·kg ^-1 and 2.06 g·kg ^-1， respectively， under the P₃ treatment. These values were significantly （P<0.05） higher than under the P₀ treatment. Vertically， SOC， MBC， DOC， POC and EOC all had the highest distribution in the 0-20 cm soil layer， accounting for 38.35%-41.58%， 38.31%-39.49%， 45.54%-46.64%， 46.29%-47.35% and 40.40%-44.17%， respectively， of the total content. The phosphorus application treatments increased soil R_S by 0.31%-14.90% and the difference was significant before and after mowing （P<0.05）. The sensitivity indices for MBC， DOC， POC and EOC in each soil depth showed an increasing trend with increasing phosphorus application， and the MBC sensitivity index was higher than the DOC， POC and EOC sensitivity indices. The highest sensitivity index of microbial carbon was found in the 0-30 cm soil layer under phosphorus application， and the highest sensitivity index of easily oxidized organic carbon was found in the 30-60 cm soil layer. It is suggested that microbial carbon is an indicator of changes in surface soil organic carbon and oxidizable organic carbon is an indicator of changes in deep soil organic carbon. The efficiency of each reactive organic carbon component does not change significantly with increasing phosphorus application. The results of structural equation models indicate that phosphorus application can affect SOC content directly and also indirectly through changes in MBC， DOC， POC and EOC content. In conclusion， phosphorus application increased soil R_S， but sustained phosphorus input increased the SOC， MBC， DOC， POC and EOC contents in the various soil horizons of the alfalfa field， improving carbon sequestration potential and soil quality. These results provide scientific evidence of the dynamic changes of soil organic carbon in sown grassland ecosystems and will enhance sown grassland management with respect to optimizing phosphorous fertilizer use.

Differentially expressed genes and related pathways in root systems of Dactylis glomerata under flooding stress

Bing ZENG, Pan-pan SHANG, Bing-na SHEN, Yin-chen WANG, Ming-hao QU, Yang YUAN, Lei BI, Xing-yun YANG, Wen-wen LI, Xiao-li ZHOU, Yu-qian ZHENG, Wen-qiang GUO, Yan-long FENG, Bing ZENG

2024, 33(2):  93-111.  DOI: 10.11686/cyxb2023117

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In recent years， flooding has occurred frequently in southern China， and has seriously restricted the development of grass and animal husbandry industries. Dactylis glomerata is an important ecological grass species and a high-quality forage. However， it has poor flooding tolerance， so it is seldom grown in areas that are frequently affected by flooding. In this study， to explore the flooding response mechanism of D. glomerata， the physiological indexes and gene expression patterns in the roots of seedlings of the D. glomerata cultivar ‘Anba’ were analyzed at 0， 8， and 24 hours of flooding stress. The results showed that the contents of soluble sugars， soluble protein， and malondialdehyde in the roots increased significantly under flooding stress， and the relative conductivity decreased initially and then increased significantly during the 24 hours flooding treatment. After 8 hours of flooding stress （compared with 0 hours）， there were 5788 differentially expressed genes in the roots of D. glomerata， including 2872 up-regulated genes and 2916 down-regulated genes. After 24 hours of flooding stress， there were 8807 differentially expressed genes in the roots of D. glomerata， including 4123 up-regulated genes and 4684 down-regulated genes. Gene ontology enrichment analyses showed that these differentially expressed genes were mainly involved in polysaccharide metabolism， microtubule binding， cellulose metabolism， and the antioxidant response. The results of Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that the pathways responding to flooding in roots of D. glomerata were phenylpropanoid biosynthesis， carbon metabolism， glutathione metabolism， amino acid biosynthesis， starch and sucrose metabolism， and glycolysis/gluconeogenesis. Further analysis of differentially expressed genes involved in phenylpropanoid biosynthesis， carbon metabolism， and glutathione metabolism pathways suggested that HXK1， HXK2， ADH1， GST， and APX2 encode products with important roles in the response of D. glomerata to flooding stress. Genes encoding MYB， NB-ARC， WRKY， GRAS， and AP2 transcription factors were highly expressed under flooding stress， suggesting that these transcription factors are closely related to flooding tolerance in D. glomerata. The results of this study provide basic data for further exploration of the molecular mechanism of flooding tolerance of D. glomerata， and also provide theoretical support for breeding to improve flooding tolerance.

Characteristics and driving factors of lactic acid bacteria communities in silage made from alfalfa in different regions of Gansu Province

Ying TANG, Xiao-jing LIU, Ya-jiao ZHAO, Lin DONG

2024, 33(2):  112-124.  DOI: 10.11686/cyxb2023113

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There is an overall goal to enhance the community structure and quality of alfalfa silage across diverse geographical regions， so it is important to identify the factors that influence these characteristics. In this study， we used single molecule real-time sequencing to comprehensively analyze the lactic acid bacteria communities in silage made from alfalfa grown in different areas of Gansu Province. It was found that the lactic acidbacteria communities in silage showed regional distribution patterns. In silage made from alfalfa grown in the arid and irrigated region of Hexi， Lactiplantibacillus plantarum was the dominant species. In silage made from alfalfa grown in the arid and semi-arid rain-fed regions of Longzhong and Longdong， L. plantarum， Lactobacillus rhamnosus， and Pediococcus pentosaceus were the main species present. In silage made from alfalfa grown in areas with abundant rain and a humid climate， the Lactobacillus community was dominated by Pediococcus acidilactici and P. pentosaceus. In silage made from alfalfa grown in high-altitude cold regions， the Lactobacillus community was dominated by L. plantarum and L. rhamnosus. A redundancy analysis showed that the epiphytic lactic acid bacteria communities had the greatest influence on the lactic acidbacteria communities in alfalfa silage （88.27%）， among which Lactobacillus and Pediococcus played the main roles. The environmental factors were ranked from strongest influence on alfalfa epiphytic lactic acid bacteria to weakest， as follows： annual average temperature>annual average precipitation>average relative humidity>annual average sunshine duration>elevation>latitude>longitude. In conclusion， the composition and abundance of epiphytic lactic acid bacteria in alfalfa was affected by the temperature and precipitation conditions， and this affected the composition of lactic acid bacteria communities in alfalfa silage. Therefore， regional climatic conditions are the driving factor affecting the regional distribution pattern of lactic acid bacterial communities in alfalfa silage， because they determine the types of naturally occurring lactic acid bacteria on alfalfa plants.

Effects of the degree of alpine meadow degradation on the rhizosphere soil fungal community and the ecological network of dominant species

Yuan MA, Xiao-li WANG, Yu-shou MA, De-gang ZHANG

2024, 33(2):  125-137.  DOI: 10.11686/cyxb2023106

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Changes in the diversity and stability of the rhizosphere fungi community can reveal the adaptive mechanisms of microorganisms to degraded ecosystems. The aim of this study was to clarify the influence of changes in dominant species on the diversity and stability of rhizosphere fungal communities. Samples were collected from alpine meadows on the eastern edge of the Qinghai-Tibetan Plateau with four different degrees of degradation （non-degraded grassland， lightly degraded grassland， moderately degraded grassland， and severely degraded grassland）. A combination of ITS rRNA gene sequencing technology， FUNGuild prediction， and molecular ecological network modeling methods was used to analyze the effects of alpine meadow degradation on rhizosphere fungal structure， functional groups， and molecular ecological networks. The results showed that the degree of grassland degradation significantly affected the Beta diversity， but not the Alpha diversity of rhizosphere soil fungi. The degree of degradation only affected the relative abundance of taxa， and had no effect on the dominant fungal communities. The dominant fungal populations in the rhizosphere soils of grasslands with different degrees of degradation were Basidiomycota， Mortierella， and Ascomycota. Linear discriminant analysis Effect Size （LEfSe） identified 29 biomarkers， most of which corresponded to Basidiomycota and Ascomycota. There was a major shift of rhizosphere fungal communities from symbiotic to saprophytic nutrient types with increasing severity of grassland degradation. The network analysis showed that there was a negative correlation between the number of operational taxonomic units （OTUs） of the rhizosphere fungal community and the degree of degradation of the grassland. Combined with data of the network topology parameters， these findings indicate that increasing severity of grassland degradation leads to a looser and more unstable rhizosphere fungal structure. In conclusion， alpine meadow degradation significantly changed the composition， structure， and functional types of rhizosphere fungal communities， especially those of dominant species， and reduced the stability and complexity of fungal communities. These results provide a scientific basis for further research on the adaptive responses of rhizosphere microbe communities to degradation of alpine meadows.

Effects of adding different nutrients on soil microbial carbon source utilization in degraded alpine wetland in the source region of the Yellow River

Peng DUAN, Rong-yi WEI, Fang-ping WANG, Bu-qing YAO, Zhi-zhong ZHAO, Bi-xia HU, Ci SONG, Ping YANG, Ting WANG

2024, 33(2):  138-153.  DOI: 10.11686/cyxb2023108

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The carbon source utilization capacity of soil microbes is an important evaluation indicator during the restoration of degraded wetlands. However， the effects of nutrient addition on carbon source utilization of soil microbes during the restoration of degraded wetlands remains unclear. The aim of this study， therefore， was to determine the effect of adding different nutrients on the carbon source utilization ability of soil microbes in a degraded alpine wetland. To this end， a field experiment was conducted in degraded alpine wetlands at various stages of degradation in the source region of the Yellow River. Nitrogen， phosphorus， and organic compound fertilizer were added to the soil， and the effects of these treatments on the vegetation characteristics， soil physicochemical properties， and carbon source utilization of soil microbes in wetlands at different stages of degradation were analyzed using conventional laboratory methods and the Biolog-Eco method. The results indicate that nutrient addition significantly improved the overall carbon source utilization ability of soil microbes in moderately degraded alpine wetland. However， the carbon source utilization ability of soil microbes in more heavily degraded wetland was not significantly improved by adding phosphorous or organic compound fertilizer. The addition of different nutrients affected the ability of soil microbes to utilize different carbon sources. In degraded wetland， the addition of nitrogen and organic compound fertilizer significantly increased the proportion of lipid and alcohol carbon sources utilized by microbes， and decreased the proportion of acid carbon sources utilized. After the addition of different nutrients， the overall carbon source utilization ability of soil microbes in the degraded alpine wetlands was mainly influenced by their ability to utilize esters， alcohols， and amino acids. Structural equation modeling showed that the addition of both nitrogen and organic compound fertilizer promoted the carbon source utilization of soil microbes by increasing the aboveground biomass of vegetation in degraded alpine wetland. However， the effect of adding organic compound fertilizer to enhance carbon source utilization by microbes was limited by lower soil moisture contents. These results provide a scientific basis for further research on， and development of， restoration strategies for degraded alpine wetlands and for the evaluation of the extent of restoration.

Effects of seed storage time on seed germination and cytological structure of covered oats and naked oats

Rui-rui YAO, Huan LIU, Gui-qin ZHAO, Jing-long WANG, Qi-yu WANG, Kai DONG, Ran ZHANG

2024, 33(2):  154-163.  DOI: 10.11686/cyxb2023136

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This research investigated the effects of seed storage time on the germination characteristics and cell organization structure of the covered oat variety ‘Longyan No. 3’and the naked oat variety ‘Baiyan No. 2’. The changes in germination index， viability index， shoot length， root length and electrical conductivity of two different oat germplasm lines after storage for 2， 4， 6 and 8 years were studied. Paraffin sectioning methods and transmission electron microscopy were used to observe and compare the changes with time and varietal differences in covered and naked oat seed anatomical structure， seed embryonic cell organization and mitochondrial ultrastructure and changes with storage time. It was found that with increase in storage time， the germination index， seed viability index and vitality of both oat germplasm lines decreased， while the electrical conductivity of seeds increased. The seed viability of ‘Longyan No. 3’ was more stable than that of ‘Baiyan No. 2’. The anatomical structure of aged oat seeds changed， and the cells of the paste layer were hydrolyzed， the ultrastructure of embryo cells and mitochondria in aged oat seeds was seriously damaged. The main changes observed were that the fat bodies in seed embryo cells were degraded； The structure of mitochondria was damaged， vacuolated and disintegrated. The nucleus structure was unclear and the chromatin was concentrated， nucleoli had disappeared， and nuclear edges were wrinkled.

Responses of different oat cultivars to low-nitrogen stress

Ying LUO, Cong LI, Pei WANG, Li-hua TIAN, Hui WANG, Qing-ping ZHOU, Ying-xia LEI

2024, 33(2):  164-184.  DOI: 10.11686/cyxb2023105

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In this study， we aimed to investigate the morphological and physiological responses of oat （Avena sativa） to low-nitrogen stress， and to screen for A.sativa cultivars that are tolerant to low-nitrogen conditions. Eighteen A. sativa cultivars were grown using a hydroponic system with two different nitrogen concentrations： sufficient nitrogen （4 mmol·L^-1， CK） and low nitrogen （0.4 mmol·L^-1， LN）. After 21 days of treatment， seven morphological indexes and 14 physiological indexes were measured and analyzed. The data were subjected to correlation analysis and principal component analysis， and a comprehensive evaluation was carried out by combining a cluster analysis and a membership function analysis. The results showed that： 1） Under low-nitrogen stress， the plant height， aboveground biomass， nitrate nitrogen content， nitrate reductase activity， glutamine synthase activity， glutamate dehydrogenase activity， soluble sugars content， and soluble protein content showed a decreasing trend； glutamate synthase activity， malondialdehyde content， and reactive oxygen species content showed an increasing trend； and the changes in root length， underground biomass， and root-shoot ratio varied. 2） Among the 21 physiological indicators， 12 pairs showed significant correlations. Among these 12， the root：shoot ratio and root dry weight were significantly positively correlated， and glutamine synthetase activity and soluble protein content were significantly negatively correlated. 3） Biomass， nitrogen metabolism factors， photosynthetic factors， antioxidant factors， and osmotic regulatory factors of A. sativa under low-nitrogen stress were identified as important indicators of tolerance to low-nitrogen conditions. 4） The 18 cultivars of A. sativa were divided into three categories： strongly tolerant， moderately tolerant， and sensitive. The strongly tolerant varieties included Qinghai sweet oat and Qinghai 444. The sensitive varieties included Haywire and Qingyan No. 2.

Effects of different mixed sowing patterns and sowing ratios of alfalfa on grassland productivity and community stability in grass-legume mixtures

Yong-liang ZHANG, Ze TENG, Feng HAO, Tie-feng YU, Yu-xia ZHANG

2024, 33(2):  185-197.  DOI: 10.11686/cyxb2023161

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This research aimed to identify the optimal mixed sowing pattern for grass-legume mixes in Horqin Sandy Land. Alfalfa （Medicago sativa） was sown into 2-month-old smooth bromegrass （Bromus inermis） in two patterns （inter-row sowing， A₁， and crossed row sowing， A₂） at eight mixed sowing ratios （5%， 10%， 15%， 20%， 25%， 30%， 35% and 40%， calculated based on single plant density； Treatments B₁-B₈， respectively）. Three cuts were made during the growing season and bromegrass yield， alfalfa yield， and total herbage yield were determined for each cut and on an annual basis. Comparing sowing patterns A₁ and A₂， grass yield and legume yield differed only in Cut 3， with A₂>A₁ for grass yield and A₁>A₂ for legume yield while for combined grass+legume yield there was a significant difference （P<0.05） for all three cuts and in the annual total with A₁>A₂ in all cases. Across the mixed sowing ratios B₁-B₈， alfalfa and total herbage yield increased， while smooth bromegrass yield decreased （P<0.05）. With respect to relative density （RD）， grass RD was significantly higher （P<0.05） in the A₂ than the A₁ sowing pattern in Cuts 2 and 3， but legume RD did not differ between A₁ and A₂ sowing patterns in any of the three cuts. Across the mixed sowing ratios B₁-B₈， RD generally decreased for grasses in cuts 2 and 3 and for the legume component in all three cuts （P<0.05）. The relative yield （RY） differed between A₁ and A₂ sowing patterns for bromegrass only in Cut 3 （A₂>A₁） and for alfalfa only for the annual total （A₁>A₂； P<0.05）. For both bromegrass and alfalfa， RY decreased （P<0.05） across the mixture ratio series from B₁ to B₈ for all three cuts， and for the annual total. The results of fuzzy multivariateanalysis showed that the A₂B₄ combination was the best， followed by the A₂B₃ combination. Considering forage yield and stability of the sown mixture， the recommended practice based on these data is cross-sowing alfalfa into 2-month-old smooth bromegrass stands at a plant density of 15%-20% of the grass single-plant sowing rate.

Progress in studies of molecular mechanisms and applications of somatic cell regeneration during genetic transformation

Yu-zhu LI, Jiang-di YU, Fei-fei DING, Jia-min MIAO, Xiao-ming BAI, Shang-li SHI

2024, 33(2):  198-211.  DOI: 10.11686/cyxb2023147

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Plant genetic transformation is the key of transgenic technology， genome editing， functional genomics research and molecular breeding. Species and genotype differences are often the main bottlenecks limiting the efficiency of genetic transformation and the wide application of gene editing technology. With the molecular mechanism of de novo shoot organogenesis and somatic embryogenesis being gradually explored， the growth and developmental regulatory genes involved in the synthesis， response and signal transduction of auxin and cytokinin in callus formation， proliferation and regeneration are used to improve genetic transformation efficiency. In this study， we first review the different ways and means of achieving somatic cell regeneration after genetic transformation， and the molecular mechanisms of regeneration for the transformed cells through indirect organogenesis and somatic embryogenesis. Then， the application of regeneration-promoting genes related to auxin and cytokinin in improving regeneration efficiency， shortening transformation time， and realizing genetic transformation of recalcitrant species and genotypes was discussed. Finally， the potential for application of regeneration-promoting genes when working with transgenic and gene-edited cells were summarized and current research directions were discussed.

Progress of research on hormone regulation of branching or tillering in plants

Fen-qi CHEN, Jin-qing ZHANG, Hui-ling MA

2024, 33(2):  212-225.  DOI: 10.11686/cyxb2023118

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Branching （or tillering in grasses and related taxa） is an important trait of plant architecture and the result of axillary bud initiation and growth， which plays a crucial role in determining the seed yield of crops and forage yield. Multiple hormones and their interactions play key regulatory roles in the occurrence， growth and development of plant branching or tillering. In addition， environmental factors also regulate branching or tillering by changing the hormone contents and their balances within the plant. This study reviews multiple aspects of the mechanisms by which plant branching or tillering is regulated various hormones， including auxin， cytokinin， strigolactones， brassinosteroids， abscisic acid and gibberellins， ethylene， jasmonic acid， and complex regulatory networks formed by the interaction of different hormone signals. The aim is to establish a foundation for using hormone regulation mechanisms to cultivate new high-yielding crop plant growth forms with ideal plant architecture. The current issues with hormone regulation mechanisms controlling plant branching or tillering are also analyzed， and future research directions for hormone regulation mechanisms controlling plant branching or tillering are discussed， with the aim of providing a theoretical basis for using hormones to cultivate good varieties.

Progress in research on fungal diseases of the genus Elymus

Long-hai XUE, Jia-qi LIU, Chun-jie LI

2024, 33(2):  226-241.  DOI: 10.11686/cyxb2023132

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Elymus species are widely used as forage grasses on the Tibetan Plateau and widely grown in alpine pasture areas such as Gansu， Qinghai， Xinjiang， Tibet and Sichuan Province， China. Disease is one of the important factors limiting the production and utilization of the genus Elymus. In sown grassland， disease will directly affect the yield and quality of forages. In natural grassland， Elymus plants are also an important vector contributing to the spread of many pathogens. This pathogen spread seriously affects the productivity of grassland agricultural ecosystems. Based on a review of published domestic and international literature， the etiology， conditions of occurrence and control measurements for Elymus diseases are reported. Domestic research progress is compared with international efforts， and future development ideas for Elymus disease research are also presented. Up to March， 2023， a total of 16 fungal diseases that can infect the leaves， leaf sheaths， stems， spikes， and seeds of Elymus had been recorded worldwide. The more important among these were rust， smut， powdery mildew， ergot， choke and leaf spot diseases. At present， the main control methods for fungal diseases of Elymus are to breed and use resistant varieties， treat seed before sowing， and increase the use of ecological management strategies and chemical controls in the field. In addition， screening or breeding new varieties of Elymus species which carry Epichlo? endophytes is expected to be one of the breakthroughs in the research into Elymus disease resistance.