Acta Prataculturae Sinica

Response of aeolian activity to grazing intensities in the desert steppe， Northern China

Xin-lei LIU, He-qiang DU, Xiu-fan LIU, Ya-wei FAN

2023, 32(7): 1-11. DOI: 10.11686/cyxb2022310

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In this research we studied the effect of grazing intensity on aeolian sand movement in order to develop greater understanding the aeolian dynamic process and techniques for more accurately evaluating and preventing wind-blown sand disasters. The research was conducted at the Urat Desert-Grassland Research Station of the Chinese Academy of Sciences and the desert grassland of Inner Mongolia was the subject of our investigation. Two grassland types were studied： Shrub dominated grassland （SDG） and grass dominated grassland （GDG） and there were three grazing intensities： Prohibiting grazing as control （CK）， moderate grazing intensity （MG） and heavy grazing intensity （HG）. The near-surface wind speed profile， particle size distribution， wind-sand flow structure and other related parameters were measured and analyzed. It was found that： 1） The surface aerodynamic roughness length of the two grassland types was significantly influenced by grazing intensity and the effect of grazing intensity on the aerodynamic roughness length of GDG was greater than that on SDG. 2） Grassland type and grazing intensity had significant effects on soil erodible particle content （P<0.05）. With increase in grazing intensity， the content of soil erodible particles progressively decreased and the soil texture became coarser. 3） The aeolian sand flow functions in grazing areas all followed power functions， and the correlation coefficients ranged from 0.78 to 0.97. The horizontal sand fluxes in MG plots （6.468 g·m^-1·d^-1） and HG plots （9.294 g·m^-1·d^-1） were 7.13 and 10.25 times higher than those in CK plots （0.907 g·m^-1·d^-1）， respectively. The impacts of sand transport height and grazing intensity on sediment transport rate in SDG were less than in GDG. The above results showed that the influence of grazing disturbance on aeolian sand activity in GDG was much greater than that in SDG， and the horizontal sediment flux under grazing was much more than that of CK， even for MG. Therefore， decisions on grazing strategy based solely on vegetation carrying capacity are still seriously inadequate. In order to maintain the sustainable development of animal husbandry， the intensity of surface aeolian sand activity should be considered as an important index when developing grazing strategy.

Species diversity and phylogenetic diversity in Bayinbrook alpine grasslands： elevation gradient distribution patterns and drivers

Zi-li LYU, Bin LIU, Feng CHANG, Zi-jing MA, Qiu-mei CAO

2023, 32(7): 12-22. DOI: 10.11686/cyxb2022328

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Coastal gradient studies of plant community species diversity and phylogenetic diversity can clarify the influence of environmental conditions on community construction and can provide insight into community construction mechanisms. This research studied the trends in plant community species diversity and phylogenetic diversity and their environmental drivers along an altitude gradient from 2200-3000 m. a.s.l. in Bayinbrook alpine meadow， to explore the influence of environmental factors in the processes of species coexistence and diversity maintenance in community construction. It was found that： 1） With increase in altitude， the Shannon-Wiener diversity index and Simpson diversity index of the community showed a unimodal change trend， with peaks at 2400 and 2600 m， respectively. The community Pielou uniformity index showed a gradual downward trend； the PD index showed a downward trend as a whole， and the phylogenetic structure gradually changed from a dispersed status to an aggregated status. 2） The phylogenetic structure indexes NTI and NRI showed a significant negative correlation with the species diversity index （P<0.05）， and the PD index and species diversity index showed a significant positive correlation （P<0.05）. 3） The degree of influence of various soil factors on different diversity indices differed； NH₄⁺-N content was the main factor affecting species diversity and phylogenetic indexes， followed by total potassium content. Soil total nitrogen content had significant effects on NTI （P<0.05）. NRI was significantly affected by total potassium content （P<0.05）， the phylogenetic impact index PD was significantly affected by total phosphorus （P<0.05）， and species diversity index was significantly affected by pH （P<0.01）. The species diversity and phylogenetic diversity of coastal altitude gradient communities are interrelated， and the two show different response strategies along the altitude gradient due to the influence of environmental factors.

Important species’ niche characteristics of population in herbaceous communities at Picea asperata-Abies fargesii forest burned area on the northeastern margin of the Qinghai-Tibetan Plateau

Xiao-lei ZHOU, Fu-qiang YANG, Ming-jun WANG, Hai-xia HUANG, Qing TIAN, Xu-jiao ZHOU, An ZHAO, Wan-peng HE, Yan-li ZHAO, Li-hong JIANG

2023, 32(7): 23-37. DOI: 10.11686/cyxb2022391

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The ecological niche of plants in a given environment determines the relative stability of plant communities. Using the ‘space for time’ method， four plant communities at different stages of successional development since occurrence of fire （5， 15 and 23 years， and Climax i.e. no fire） on the northeastern margin of the Qinghai-Tibetan Plateau were chosen for study. Levins and Shannon-Wiener niche breadth indexes and Pianka and Schoener niche overlap indexes were used to calculate herbaceous population niche width and niche overlap degree， and the specialist and generalist species of communities were separated. It was found that the Levins and Shannon-Wiener niche breadth index of herbaceous species at different succession stages were basically the same， and there was a different niche breadth for the same species. The dominant species niche width of the four communities ranked 23 yrs>5 yrs>15 yrs>Climax. For the specialist and generalist species， respectively， there were 2 and 2 at 5 years， 4 and 2 at 15 years， 3 and 0 at 23 years and 3 and 5 in the Climax succession. Species pairwise numbers with severe niche overlap were the smallest at 23 years， while species pairwise numbers with slight niche overlap were smallest in the Climax succession. The ranking for species pairwise numbers of moderate niche overlap was Climax>5 years>15 years>23 years. After severe fire disturbance of Picea asperata-Abies fargesii forest， the plant communities representing 5 years early succession of the burned area and 23 years succession （disturbed by human beings） were rich in plant habitat resources. The niche width of each group was relatively large， the niche overlap was small， and the competition among the corresponding populations was small. At the moderate stage of succession （15 years）， the phenomenon of niche overlap and separation was obvious， most species in the community had great similarities in resource utilization， and interspecific competition was intensified. The Climax community can be considered more stable， with a relatively high niche width， the majority of species not having high niche overlap， and with a high similarity in resource utilization between the different species. Except for the Climax community， the ratio of specialist species to generalist species in each community succession stage was ≥50%， and the existence of specific habitats promote the appearance of specialist species. Appropriate human intervention can increase the niche width of species in the community， reduce the overlap of ecological niches between species， and form a relatively ecologically stable community.

Effects of broad-leaved grass inhibitors combined with nitrogen on soil characteristics of alpine meadow

Xin LU, Juan QI, Shang-li SHI, Mei-mei CHE, Xia LI, Shuang-shuang DU, Ning-gang SAI, Yan-wei JIA

2023, 32(7): 38-48. DOI: 10.11686/cyxb2022335

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This research investigated the effects of application of broad-leaved grass inhibitor and nitrogen on soil characteristics in a Gannan Alpine Meadow. The aim was to determine the optimal ratio of inhibitor concentration and nitrogen application for alpine meadow husbandry， so as to provide a scientific basis for the sustainable development of grassland and animal industries in alpine regions by exploring the effects of different concentrations of broad-leaved grass inhibitors （0， 0.9， 1.5 and 2.1 kg·ha^-1 42.5% MCPA and fluroxypyr） and different nitrogen levels （0， 75， 150 and 225 kg·ha^-1 Urea N≥46.0%） on the soil nutrients and enzyme activities of the alpine meadow. It was found that higher concentration of inhibitor （2.1 kg·ha^-1） had adverse effects on soil available N， available K and available P， which were decreased （P<0.05） by 4.89%， 11.52% and 14.19%， respectively， compared with the control. However， soil organic matter increased by 11.74% compared with the control and no significant difference was found for pH. Nitrogen addition alone， especially at a high rate （225 kg·ha^-1）， had significant effects on available N， available P and urease， which were increased （P<0.05） by 4.98%， 53.01% and 11.28%， respectively， compared with the control. However， nitrogen addition had no significant impact on the soil organic matter， available K and the pH levels. There were significant or extremely significant interaction effects of combined inhibitor and nitrogen addition on soil parameter except pH. Moreover， all soil indexes decreased at each level of nitrogen addition in combination with the high concentration inhibitor （Y₃， 2.1 kg·ha^-1）， which indicated that high concentration inhibitor significantly counteracted the effect of nitrogen addition. According to a multivariate Grey correlation analysis， high nitrogen （225 kg·ha^-1） combined with a low concentration inhibitor （0.9 kg·ha^-1） provides an obvious improvement to soil fertility. In this study， we provide a grassland management framework suitable for the alpine meadow area of the Qinghai-Tibetan Plateau.

Cloning and function analysis of MsPPR1 in alfalfa under drought stress

Shao-peng WANG, Jia LIU, Jun HONG, Ji-zhen LIN, Yi ZHANG, Kun SHI, Zan WANG

2023, 32(7): 49-60. DOI: 10.11686/cyxb2022425

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Drought is an important environmental factor affecting plant growth， development and yield. pentatricopeptide repeats （PPR） family proteins play important roles in plant growth， development， stress response and other physiological processes. In this study， an MsPPR1 gene was cloned from alfalfa （Medicago sativa） cv. Zhongmu No.1， and the drought resistance function of MsPPR1 was investigated through decreasing its expression in alfalfa using a virus induced gene silencing method and heterologous overexpression in tobacco （Nicotiana benthamiana）. It was found that the open reading frame contains 3213 bp， encoding 1070 amino acids， and the relative molecular weight of the encoded protein is 121.65 kDa. MsPPR1 is a typical member of the PPR protein family， containing multiple PPR repeat domains and locating in the cytoplasm. MsPPR1 was expressed most in leaves， followed by stems and roots， and least in flowers and induced by drought， mannitol and abscisic acid treatments. The expression of MsPPR1 was decreased by the virus induced gene silencing technology in alfalfa， and decrease of MsPPR1 expression significantly reduced the drought resistance of the plants. The MsPPR1-silenced plants were more wilted， the relative water content was significantly reduced， and the relative electrolyte permeability was significantly increased. The heterologous overexpression of MsPPR1 in tobacco enhanced the drought resistance of transgenic tobacco， while the malondialdehyde content significantly decreased and the proline content increased. This study indicates that MsPPR1 is a positive regulatory factor of alfalfa drought resistance and provides a candidate gene for molecular breeding of alfalfa for drought resistance.

An efficient protocol for Zoysia japonica mesophyll protoplast isolation and transformation， and its application in subcellular localization and protein interaction analysis

Jin GUAN, Yi-di GUO, Ling-yun LIU, Shu-xia YIN, Ke TENG

2023, 32(7): 61-71. DOI: 10.11686/cyxb2022348

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An efficient leaf mesophyll protoplast isolation and transient gene expression system in Zoysia japonica is highly desirable for in vivo gene functional studies in its homologous system. The main factors influencing the isolation of protoplasts from Z. japonica were optimized by orthogonal design. The transformation protocol was used for protein subcellular localization and protein-protein interaction. In this study， a highly efficient protoplast （1.23×10⁷ protoplasts·mL^-1） was generated using 2% （w/v） cellulase R10 and 1.5% （w/v） macerozyme R10 for digestion over 7 h. FDA staining results showed that approximately 99% of protoplasts exhibited high activity. Repeated experiments showed that by adding 5-10 μg plasmid， the transformation efficiency reached more than 75%. Using this protocol to identify subcellular locations， ZjNOL and ZjNYC1 were proved to be localized in chloroplasts， and ZjZFN was visualized in nuclei. The bimolecular fluorescence complementation assay showed that ZjNOL and ZjNYC1 interacted with each other in the chloroplast. The protoplast isolation and transformation protocol， when combined with genetics and omics techniques， will allow further study of gene functions in Z. japonica.

Difference analysis of chloroplast genome sequence between two ecotypes of Leymus chinensis in Inner Mongolia

Xiao-dong YU, Hao-yang YU, Xu YANG, Dong-xu ZHAO, Lin-gang ZHANG

2023, 32(7): 72-84. DOI: 10.11686/cyxb2022338

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Leymus chinensis， a species of high-quality forage grass widely distributed in Inner Mongolia grassland， can be divided into two ecotypes according to the leaf color： gray-green and yellow-green， for which the chloroplastic differences have been previously described， but the molecular basis of the leaf color difference remains unclear. In this study， the chloroplast genomes of two ecotypes of L. chinensis， which were selected from Chilechuan grassland， are sequenced and analyzed using the Denovo sequencing platform. The results show that the gray-green type has a total length of 136816 bp， comprising a large single-copy region of 80973 bp， and a pair of inverted repeats with a length of 21560 bp； The yellow-green type counterpart has a total length of 136809 bp， a large single-copy region of 80962 bp， and a pair of inverted repeats with a length of 21562 bp. Meanwhile， it’s also found that each type contains a small single-copy region of 12723 bp， and each chloroplast genome contains 131 genes， encoding 84 proteins， 8 rRNAs and 39 tRNA genes. The two ecotypes share abundant repeats and differences， mostly located in the inter genic spacer. Moreover， a total of 14 mutated regions are found in the chloroplast genome sequences of the two， resulting in different contraction or expansion of the inverted repeat regions. Also， the phylogenetic analysis suggests kinship with the ancestor Psathyrostachys juncea. In conclusion， the chloroplast genome sequences of the two ecotypes in this study provide molecular information about the basis of the difference of leaf color. This information lays a foundation for the technology of chloroplast transformation.

Codon usage bias analysis of the chloroplast genome of Bothriochloa ischaemum

Shou-yu GAO, Yu-ying LI, Zhi-qing YANG, Kuan-hu DONG, Fang-shan XIA

2023, 32(7): 85-95. DOI: 10.11686/cyxb2022332

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The chloroplast genome is highly conserved and has a slow evolutionary rate. The study of chloroplast genome codon bias could clarify the expression efficiency of genes， and could even determine plant phylogeny and species evolution. In order to analyze the phylogenetic relationship between Bothriochloa ischaemum and its related species， we analyzed the codon usage pattern of the chloroplast genome of B. ischaemum using CAIcal and CodonW1.4.2 software， and a cluster map was constructed using relative synonymous codon usage （RSCU） of B. ischaemum and its related species. Results showed that the average guanine-cytosine （GC） content was 38.79% in the B. ischaemum chloroplast genome sequences which had been screened， and the content was GC₁>GC₂>GC₃. In these sequences， the third base of the codon was mostly A or U. The number of effective codons （ENC） ranges from 36 to 61 and indicates that the codon bias of B. ischaemum is weak. In addition， a total of 26 codons are used with high frequency， among which 25 codons end in A or U. Combined with the analyses of neutral plot， ENC-plot， ENC ratio and PR2-plot， we found that the codon bias of chloroplast genes of B. ischaemum is affected by both mutation pressure and natural selection， and the effect of mutation pressure is greater. Through the RSCU data analysis， a total of 15 optimal codons were screened from B. ischaemum chloroplast genome， and all of these end in A or U. In the present study， RSCU clustering showed that the codon usage pattern of B. ischaemum is different from that of related species. The present study therefore provides a reference for phylogenetic study of plants of the genus Bothriochloa.

Seed-borne bacterial diversity of oat and functional analysis based on Illumina MiSeq high-throughput sequencing

Zhen-fen ZHANG, Rong HUANG, Xiang-yang LI, Bo YAO, Gui-qin ZHAO

2023, 32(7): 96-108. DOI: 10.11686/cyxb2022427

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In this study， the high-throughput sequencing analysis method was used to analyze the difference in bacterial abundance， alpha diversity， beta diversity and species composition of bacterial communities in seven oat varieties from different regions. The PICRUSt and FAPROTAX functional prediction methods were used to analyze the differences in abundance among the seed-borne bacteria in various bands. The results showed： 1） A total of 5187 bacterial OTUs were obtained from the seven oat varieties， mainly belonging to 33 phyla， 180 orders and 435 genera. 2） Based on the abundance and annotation information of the OTUs， we found that Proteobacteria， Chloroflexbacteria， Cyanobacteria and Actinobacteria were the dominant phyla in the bacterial communities of the seven oat varieties. At the order level， the most abundant groups were Rickettsiales and Sphingomonadales. Dominant genera were Sphingomonas， Solibacter and Pseudarthrobacter. 3） The results of α diversity and β diversity analysis suggest that the bacterial community diversity and community structure of different oat varieties were quite different. Notably， variety LXY-5 had the largest alpha diversity. Additionally， LEFSe analysis further showed that the biomarkers differed by species for different oat cultivars. 4） The functional prediction analysis using PICRUSt and FAPROTAX showed that the bacterial community in the oat seed samples mainly comprised three metabolic categories： metabolism， organic systems and human diseases， which could be classified into 42 KEGG and 24 COG secondary metabolic pathways. Moreover， a total of 52 metabolic pathways were obtained after FAPROTAX functional annotation. This study provides a theoretical basis for clarifying the diversity of the bacterial load of oat seed， and potentially can contribute to development of new genetic resources.

Identification of Fusarium species from Scutellaria baicalensis root rot in Longxi， Gansu Province and effects on element contents of root

Jing-jing JIANG, Ai-chang CHEN, Zhou-quan WEI, Xing-ming SUN, Mei-rong XU, Xue-ping LI, Hui DU, Yong-hong QI

2023, 32(7): 109-121. DOI: 10.11686/cyxb2022318

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To determine the identity of pathogenic Fusarium strains causing Scutellaria baicalensis root rot disease， a total of 136 diseased roots were collected were isolated by a tissue separation method in Longxi， Gansu Province during the years of 2019 to 2021. Based on the pathogen morphological characteristics， and general primer， specific primer and translation elongation factor （TEF） sequence analysis of Fusarium， the pathogens from the collected samples were identified as belonging to 83 Fusarium strains identified as Fusarium oxysporum （39.8%）， Fusarium solani （36.1%）， Fusarium acuminatum （16.9%）， Fusarium redolens （4.8%）， Fusarium equiseti （1.2%） and Fusarium flocciferum （1.2%）. Hence， F. oxysporum and F. solani were the dominant pathogens. Pathogenicity testing showed that the pathogenicity of different Fusarium species differs， and the pathogenicity of each strain within the same species also varied significantly. The relative disease index of F. oxysporum was 9.0 and was the strongest， that of F. redolens was 1.2 and wasthe weakest. F. equiseti and F. flocciferum displayed no pathogenicity. The major nutrient element contents in S. baicalensis roots did not change significantly after infection， while the contents of micro elements Zn， Mn and Fe increased significantly （P<0.05）. This is the first report of F. acuminatum and F. redolens causing root rot on S. baicalensis in China， and these data provide a theoretical basis for scientific diagnosis of this disease and study of the response of S. baicalensis to Fusarium infection.

Effects of Lentilactobacillus buchneri combined with different sugars on nutrient composition， fermentation quality， rumen degradation rate， and aerobic stability of alfalfa silage

Wen-qing LING, Lei ZHANG, Jue LI, Qi-xian FENG, Yan LI, Yi ZHOU, Yi-jia LIU, Fu-lin YANG, Jing ZHOU

2023, 32(7): 122-134. DOI: 10.11686/cyxb2022343

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The aim of this experiment was to investigate the effects of Lentilactobacillus buchneri combined with different sugars on the nutrient composition， fermentation quality， rumen degradation rate and aerobic stability of alfalfa silage. Four treatments were employed： LB （1×10⁶ cfu·g^-1L. buchneri）， GLB （1×10⁶ cfu·g^-1L. buchneri and 2% glucose）， FLB （1×10⁶ cfu·g^-1L. buchneri and 2% fucoidan）， CK （no additive）. After 60 days of ensiling， the nutrient composition， fermentation quality， rumen degradation rate， and aerobic stability of alfalfa silages with the above four treatments were measured. It was found that in terms of nutrient composition， compared with the CK， all treatments significantly increased the alfalfa silage dry matter （DM）， crude protein （CP） and water-soluble carbohydrate （WSC） contents （P<0.05） and the DM and CP contents were highest in the GLB treatment， while the WSC content was highest in the FLB treatment. Compared to CK， all treatments significantly reduced the content of acid detergent fiber （ADF）（P<0.05） and the GLB treatment significantly reduced the content of neutral detergent fiber （NDF， P<0.05）. With respect to fermentation quality， the LB and GLB treatments significantly reduced the silage pH （P<0.05） compared with CK， while the GLB treatment significantly increased the content of lactic acid （LA） and propionic acid （PA）（P<0.05）， and significantly reduced the ammonia nitrogen∶total nitrogen ratio （AN∶TN）（P<0.05）. Compared to CK， the content of LA， acetic acid （AA） and AN∶TN in LB and FLB treatments decreased significantly （P<0.05）， while PA increased significantly （P<0.05）. In terms of rumen degradation， except GLB treatment， the effective degradation rate of ADF was not significantly improved （P>0.05）， the effective degradation rates of DM， CP， ADF and NDF in other treatments were significantly increased （P<0.05）. Compared to CK， the pH， the number of yeasts and aerobic bacteria in all treatments were significantly reduced after 6 days of aerobic exposure （P<0.05）， and FLB treatment was the best. Using to the membership function method， the treatments were ranked： GLB （0.76）>LB （0.53）>FLB （0.52）>CK （0.14）. In conclusion， LB， GLB and FLB treatments had positive effects on nutrient composition， fermentation quality， rumen degradation rate and aerobic stability of alfalfa silage， and the GLB treatment performed better than other treatments.

Effects of different additives on fermentation quality of bamboo shoot shell and growth performance and rumen fermentation function of Hu Sheep

Hao-qian DANG, Juan-qing QIN, Yu-kang GUO, Fu ZHANG, Ying-gang WANG, Qing-hua LIU

2023, 32(7): 135-148. DOI: 10.11686/cyxb2022333

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The aim of this experiment was to investigate the effects of different additives on the nutrient composition and fermentation quality when fermenting bamboo shoot shells， and to investigate the effects of the various ensilage products on production performance， meat amino acids， blood biochemical indexes and rumen fermentation parameters of Hu Sheep. Three silages were tested： CK （no additives）， FM （formic acid 10 mL·kg^-1+EM composite bacteria 20 mL·kg^-1） and FCM （formic acid 10 mL·kg^-1+cellulase 150 mL·kg^-1+EM composite bacteria 20 mL·kg^-1） were screened out through the pre-experiment， and the bamboo shoot shells were ensiled for 45 days， at which point a Hu Sheep feeding experiment was carried out. In the feeding experiment， 30 healthy， disease-free male Hu Sheep with similar body weight were selected and randomly divided into 3 groups with 10 sheep in each group. After a pre-experiment adaptation period of 7 days， the diet-evaluation period was 60 days. To explore effects of the three silages on the sheep weight gain and physiological indicators， meat amino acids， blood biochemical indexes and rumen fermentation parameters of the Hu Sheep were monitored. It was found that： 1） Dry matter （DM） contents were 35.58% and 36.60%， respectively in the FM and FCM silages while and crude protein （CP） contents were 11.27%， 12.09%， respectively. The values for FCM silage were significantly higher than for FM silage （P<0.05） and the treated silage DM and CP values were all significantly higher than corresponding values for the CK silage （33.20%， 9.75%）（P<0.05）. Neutral detergent fiber （NDF） values in FM and FCM silages differed significantly （39.46%， 37.09%）（P<0.05）； And were significantly lower （P<0.05） than those in CK silages （44.16%）， while acid detergent fiber （ADF） values of FM and FCM silages （38.09%， 37.49%） were significantly lower （P<0.05） than in CK silage （41.62%）. 2） The body weight， carcass weight， net meat weight， and eye muscle area content in Hu Sheep fed FCM silage were 22.11 kg， 10.41 kg， 9.48 kg， 14.41 cm²， respectively； These values were all significantly higher than those of sheep fed CK silage （20.79 kg， 9.74 kg， 8.71 kg， 11.62 cm²）（P<0.05）. 3） The weights of liver， rumen， abomasum， spleen， small intestine， large intestine and rumen organ index in sheep fed FCM silage were 332.76 g， 475.32 g， 85.15 g， 32.55 g， 434.63 g， 303.48 g， 2.15%， respectively， significantly higher （P<0.05） than those fed FM silage （319.78 g， 447.18 g， 75.05 g， 29.01 g， 416.62 g， 286.70 g， 2.04%） and CK silage （297.88 g， 418.76 g， 60.09 g， 26.05 g， 399.01 g， 279.36 g， 2.01%）； The liver and rumen weights of sheep fed FM silage were significantly higher than those in the CK group （P<0.05）. 4） Levels of superoxide dismutase in the blood plasma of sheep fed FM and FCM silages were 27.16， 30.96 U·L^-1， respectively， significantly higher （P<0.05） than those in sheep fed CK silage （20.69 U·L^-1）. Similarly， high density lipoprotein levels in the blood plasma of sheep fed FM and FCM silages were 1.72， 1.77 mmol·L^-1， respectively， higher than those of sheep fed CK silage （1.12 mmol·L^-1）. Furthermore， contents of malondialdehyde in blood plasma of sheep fed FM and FCM silage （0.57， 0.59 nmol·mL^-1） were significantly lower （P<0.05） than those of sheep fed CK silage （1.17 nmol·mL^-1） and glutathione peroxidase in blood plasma of sheep fed FCM silage （328.39 U·mL^-1） was significantly higher （P<0.05） than that in sheep fed CK silage （278.01 U·mL^-1）. 5） The contents of valine， isoleucine and phenylalanine in the longissimus dorsi muscle of sheep fed FCM silage were 2.75， 8.49， 7.35 g·kg^-1， respectively， significantly higher than those of the sheep fed FM silage （1.92， 5.19， 6.17 g·kg^-1） and CK silage （1.66， 5.96， 6.03 g·kg^-1）（P<0.05）， while histidine and serine contents of sheep fed FCM silage were 3.87， 6.70 g·kg^-1， significantly higher than those in sheep fed CK silage （2.20， 5.43 g·kg^-1）（P<0.05）. To sum up， the FCM treatment significantly improved the nutritional value of bamboo shoot silage， and Hu Sheep fed FCM silage performed the best.

Root regulation of soil scourability in hybrid sorghum grass during the growing period

Rui-jie YANG, Shu-qin HE, Shu-feng ZHOU, Jing-yue YANG, Yu-xian JIN, Zi-cheng ZHENG

2023, 32(7): 149-159. DOI: 10.11686/cyxb2022411

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This experiment investigated water and soil conservation functions of hybrid sorghum grass. Changes in soil scourability resistance were measured at different growth stages through the growing season， in order to clarify the role of the root system in promoting soil stability. A stand of the hybrid sorghum grass Chuannong Liangcao No.1 （CL1） was used in this experiment and soil samples were collected at three positions 0-15 cm， 15-30 cm and 30-45 cm distant from individual plant bases in both the horizontal （H） and vertical （V） directions. The seasonal changes in sediment content of runoff at different crop growth stages were studied using an undisturbed soil scouring method and a soil anti scour index calculated in each case. In conjunction with these measurements a WinRHIZO2000 root analysis system was used to obtain root length， root surface area， root volume and average root diameter data in order to explore the effect of roots on soil scourability resistance at various stages during the growth period of CL1. It was found that： 1） The runoff sediment content and soil anti-scourability index of CL1 have different horizontal and vertical directional trends. In the horizontal direction the runoff sediment content was H_0-15 （0.10 g·L^-1）<H_15-30 （0.14 g·L^-1）<H_30-45 （0.17 g·L^-1）， while in the vertical direction values were V_15-30 （0.08 g·L^-1）<V_0-15 （0.10 g·L^-1）<V_30-45 （0.14 g·L^-1）. The soil anti-scourability index was negatively correlated with the runoff sediment content in the horizontal direction， but there was no significant correlation in the vertical direction. Specifically， values were： V_15-30 （152.09 min·g^-1）>V_30-45 （118.74 min·g^-1）>V_0-15 （95.65 min·g^-1）. 2） As the growing season progressed， the relationship between the runoff sediment content of CL1 was as follows： heading and maturity stage （0.05 g·L^-1）<prophase of jointing stage （0.11 g·L^-1）<seedling stage （0.14 g·L^-1）<late jointing stage （0.17 g·L^-1） and heading， and the relationship between its soil anti-scourability index was as follows： maturity stage （233.30 min·g^-1）>prophase of jointing stage （56.64 min·g^-1）>late jointing stage （51.30 min·g^-1）>seedling stage （44.33 min·g^-1）. 3） During the growth period of CL1， the enhanced soil anti-scourability value ranged from 1.10-364.52 min·g^-1， with the enhancement rate being between 2.29%-462.27%. The increase in root parameters ranged from 2.87%-326.87%， and was positively correlated with the enhancement of soil scourability resistance. In summary， during the growth period of CL1， the soil scourability resistance was significantly improved in both horizontal and vertical directions， and it was closely related to the root radiation growth at various growth stages. The implementation of daily management and protection measures during the planting stage could be adjusted for further enhancement of water and soil conservation.

Effects of combined nitrogen and phosphorus application on root characteristics of alpine meadow

Xiao-qin LIAO, Chang-ting WANG, Dan LIU, Guo TANG, Jun MAO

2023, 32(7): 160-174. DOI: 10.11686/cyxb2022316

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The root system is a vital organ for plants to fix and support plant body， and it is also an important carbon pool in grassland ecosystems. In order to better understand the growth characteristics， carbon allocation pattern and nutrient cycle of roots in alpine meadow， we analyzed the morphological characteristics and physiological functions of roots with different diameters under four levels of nitrogen （N） and phosphorus （P） application rates. The minirhizotron observation method was applied to monitor the dynamics of root standing crop， production， death and turnover under CK （0 g·m^-2 fertilizer）， NP₁₀（N 5 g·m^-2+P 5 g·m^-2）， NP₂₀ （N 10 g·m^-2+P 10 g·m^-2） and^{NP₃₀（N 15 g·m^-2+P 15 g·m^-2） treatments in northwest Sichuan， and the relationships between root characteristics and environmental properties were examined. The results showed that： 1） The standing crop of the total roots differed significantly between soil horizons. In 0-10 cm， fertilization （NP₁₀， NP₂₀， NP₃₀） reduced the standing crop of roots ≤0.3 mm significantly， and NP₃₀ reduced the standing crop of the total roots as well as the roots >0.3 mm significantly； In 10-20 cm， the standing crop of the total roots as well as the roots >0.3 mm in NP₂₀were significantly higher than that in other treatments （P<0.05）. 2） There were significant differences in total root production and mortality between soil layers. In 0-10 cm， the production and mortality of the roots ≤0.3 mm varied slightly， while the mortality of the roots >0.3 mm increased significantly in NP₃₀； In 10-20 cm， the production and mortality of the roots ≤0.3 mm in fertilization treatments were significantly lower than that in CK， and the production and mortality of the roots >0.3 mm in NP₂₀ and NP₃₀ were significantly higher than that in CK （P<0.05）. 3） The root turnover varied insignificantly between soil horizons and fertilization treatments， but the turnover of the roots ≤0.3 mm was higher than that of the roots >0.3 mm. 4） The structural equation model suggested that the root standing crop and production were directly affected by the soil nutrients （total carbon and total nitrogen） and the root diameter， and the soil nutrients had a positive effect on root turnover. In summary， the combined N and P application had significant effects on the total root standing crop and mortality. Low and middle levels of NP （NP₁₀ and NP₂₀） application could reduce the biomass allocation of roots ≤0.3 mm while invest more to enhance the biomass of roots >0.3 mm. High level of NP （NP₃₀） application could reduce both coarse and fine root biomass and increase root mortality， thus reducing root carbon accumulation.}

Nitrogen metabolism response mechanism to different drought stresses in leaves and roots of Cynodon dactylon

Yi-long ZHANG, Wen LI, Qi-kun YU, Pei-ying LI, Zong-jiu SUN

2023, 32(7): 175-187. DOI: 10.11686/cyxb2022352

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Drought will affect plant nitrogen metabolism， thereby seriously restricting plant growth and forage quality. In order to clarify the changes in nitrogen metabolism indexes of Cynodon dactylon leaves and roots under drought stress， this experiment explored the nitrogen metabolism response mechanism of C. dactylon strains with differing drought resistance to different levels of drought stress， and varieties were screened for the key traits. C. dactylon plants were grown for 10 days under different water gradient treatments， and physiological data such as organic nitrides （proline， soluble protein， free amino acid）， inorganic nitrides （total nitrogen， nitrate nitrogen， ammonium nitrogen）， and the activities of nitrogen metabolism related enzymes ［nitrate reductase （NR）， nitrite reductase （NiR）， glutamine synthetase （GS）， glutamate synthetase （GOGAT）］ were collected for leaves and roots. It was found that with increased intensity of drought stress， total nitrogen of leaf and root decreased， organic nitride increased， the leaf nitrate nitrogen initially decreased and then increased， the root nitrate nitrogen decreased， and the ammonium nitrogen and nitrogen metabolic enzymes in leaves and roots initially increased and then decreased. Under moderate and severe stress， drought resistant materials accelerated the process of nitrogen metabolism due to their high nitrogen metabolism enzyme activity and inorganic nitride content， resulting in the rapid increase of organic nitride content in leaf and root of drought resistant strains to levels significantly higher than those of drought sensitive materials. Under drought， C. dactylon was able to largely overcome negative impacts on leaves by transporting， redistributing and utilising the nitrogen absorbed by the root. Redundancy analysis showed that GOGAT and GS were strongly associated with leaf and root drought resistance traits in drought resistant materials under moderate stress. Meanwhile， under severe stress， drought resistance was correlated proline， free amino acid and soluble protein levels. Path analysis showed that root soluble protein （decision coefficient -0.739）， leaf （0.530） and root free amino acid （0.498） were highly correlated with drought resistance of C. dactylon under drought. The results of this experiment enhance understanding of drought resistance and related nitrogen metabolism responses of C. dactylon， and also provide reference for the breeding of drought resistant resources.

Physiological response and transcriptome analysis of the desert steppe dominant plant Lespedeza potaninii to drought stress

Hao ZHANG, Hai-ying HU, Hui-xia LI, Hai-ming HE, Shuang MA, Feng-hua MA, Ke-chen SONG

2023, 32(7): 188-205. DOI: 10.11686/cyxb2022326

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Drought is the greatest threat to grassland plants， and research on drought-tolerant grassland plants will contribute to a better understanding of the regulatory mechanisms behind the adaptive responses of plants to drought. Lespedeza potaninii is a high quality， perennial， strongly drought tolerant forage species that is widely distributed in desert grassland areas in some parts of China. Current research on drought resistance in L. potaninii focuses on changes in osmoregulatory substances and functional gene sequence analysis， but the underlying mechanism of its drought resistance is still unclear. In this study， a single-factor water control experiment was conducted with soil moisture content of 70%-80% of the field water holding capacity for the control group （CK） and 20%-30% of the field water holding capacity for the severely drought stressed group （Tr）. After 4 weeks of treatment， tests on physiological and biochemical indicators such as biomass distribution， water use， osmoregulation and root distribution were carried out on L. potaninii， while leaves and young roots were collected for transcriptome sequencing analysis. The results showed that under drought stress conditions， L. potaninii exhibited increased content of proline （Pro）， a higher soluble protein content （SP）， increased soluble sugar， increased K⁺ ions for osmoregulation to maintain hydration of the plant tissues， increased δ¹³C indicating improved water use efficiency and increased malondialdehyde indicating oxidant stress， reduced relative water content， reduced leaf internal CO₂ concentration and stomatal conductance， reduced biomass and increased root to crown ratio， among other changes， in response to drought stress. By RNA-Seq differential gene expression analysis， 4058 differential genes were found in leaves and 2172 differential genes in roots， making a total of 744 differential genes in leaves and roots. These differential genes （DEGs） include those responding positively （up-regulated） or negatively （down-regulated） to drought. Up-regulated differentially expressed genes in leaves are mainly related to plant-pathogen interactions and phytohormone signaling， while down-regulated differentially expressed genes are mainly related to photosynthetic metabolism including carbon fixation， photosynthetic antenna protein synthesis， and photosynthetic process product metabolism. In roots， up-regulated differential genes were mainly related to arginine and proline metabolism， protein processing in the endoplasmic reticulum， and down-regulated differential genes were mainly related to starch and sucrose metabolism， isoflavone biosynthesis， and flavonoid biosynthesis. The main transcription factors differentially expressed in L. potaninii leaves were AP₂/ERF-ERF， NAC， bHLH， WRKY， C₂H₂， and in roots were HSF， MYB， AP₂/ERF-ERF， WRKY. The transcription factor bHLH was specifically down-regulated and HSF was specifically up-regulated. The expression of P5CR， PLD and P4H was up-regulated in roots and leaves. In leaves， ProDH was down-regulated， which will produce more proline and 4-hydroxy-proline， and AST was up-regulated which produces more 4-hydroxy-ketoglutarate and enhances the osmoregulatory ability and ensures water uptake and use by L. potaninii. Therefore， the main response to drought stress in L. potaninii was to initiate various physiological and metabolic activities through differential expression of genes related to hormone signal transduction， osmoregulation and gas exchange.

Exogenous melatonin alleviates the physiological effects of drought stress in sweet sorghum seedlings

Jia LIANG, Zhao-yang HU, Zhi-ming XIE, Liu-feng MA, Yun CHEN, Zhi-gang FANG

2023, 32(7): 206-215. DOI: 10.11686/cyxb2022340

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In order to explore the possible physiological mechanism of exogenous melatonin alleviation of drought stress in sweet sorghum seedlings， a pot experiment was set up to investigate the effects of spraying melatonin （100 μmol·L^-1） on the growth and physiological characteristics of ‘Dalish’ sweet sorghum seedlings under natural drought conditions. It was found that drought stress resulted in water imbalance in plant shoots， damaged the chloroplast structure and produced intracellular oxidative stress， which significantly inhibited the growth of the sweet sorghum seedlings. Spraying 100 μmol·L^-1melatonin significantly reduced the malondialdehyde content in leaves， facilitated increased accumulation of soluble protein and proline， increased the water content of leaves， promoted orderly arrangement of the granula lamellae of chloroplast， and increased the content of photosynthetic pigment. Spraying melatonin also significantly increased the activities of peroxidase and nitrate reductase in leaves. In conclusion， spraying 100 μmol·L^-1 melatonin enhanced the protective effect of antioxidant systems in sweet sorghum leaves under drought conditions， which helped to maintain plant water balance， improve chloroplast structure and increase the photosynthetic pigment content through osmotic regulation and synergistically enhanced nitrogen metabolism. At the same time， exogenous melatonin enhanced nitrogen metabolism and promoted the plant growth， resulting in alleviation of drought damage to sweet sorghum seedlings.

A multivariate evaluation of production performance and nutritional quality of different varieties of silage maize in the dry plateau area of Longdong

Cong-ze JIANG, Na SHOU, Wei GAO, Ren-shi MA, Yu-ying SHEN, Xian-long YANG

2023, 32(7): 216-228. DOI: 10.11686/cyxb2022350

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In order to select silage maize （Zea mays） varieties suitable for cultivation in the Longdong dry plateau area， the agronomic performance， nutrient content and water and nitrogen （N） utilization of eight silage maize varieties were compared using a field experiment， and their comprehensive performance data were quantitatively evaluated using Grey correlation analysis. The results showed significant varietal differences for the main agronomic traits of silage maize （P<0.05）. The variety with the highest plant height and greatest leaf length was Yu silage 23 （299.6 and 83.3 cm， respectively）； the variety with the greatest stem diameter was Dongdan No.60 （29.5 mm）； the variety with the greatest leaf width was Jingke silage 516 （9.6 cm）； the variety with the largest single plant fresh weight was Zhongketian 928 （1147.1 g·plant^-1）， and the variety with the largest single plant dry weight was Jingke silage 516 （341.1 g·plant^-1）. In terms of yield traits， the varieties with fresh yield exceeding 80 t·ha^-1 were Yu silage 23， Dongdan No.60 and Zhongketian 928， while Dongke 301 had the highest hay yield （29.0 t·ha^-1） and crude protein yield （1.85 t·ha^-1）. In terms of nutritional quality， the variety with the highest whole plant crude protein content was Wenyu No.3 （7.42%）， while the variety with the highest crude ash content was Zhongketian 928 （4.58%）. Jingke 301 had the lowest neutral detergent fiber （28.87%） and acid detergent fiber （12.63%） contents. In terms of water and N resource use， Dongke 301 had the highest dry matter water use efficiency （77.0 kg·ha^-1·mm^-1） and partial productivity of N fertilizer （161.2 kg·kg^-1）. The grey correlation analysis showed that both the equal-weighted correlation and weighted correlation provided similar results and indicated that Yu silage 23， Wenyu No.3 and Dongke 301 had advantages of high yield， enhanced quality and water and N resources utilization. Thus， the three varieties can be recommended for cultivation in the Longdong dry Plateau area.

Identification of Medicago ruthenica hybrids and heterosis analysis of main agronomic traits in F₁ and F₂

Jia-qi DONG, Yan-ting YANG, Wen-qiang FAN, Jia-ni WANG, Feng-ling SHI

2023, 32(7): 229-239. DOI: 10.11686/cyxb2022337

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Medicago ruthenica is a leguminous forage crop with strong resistance to various stress factors and rich genetic diversity， which can be used as a cross breeding parent within the same forage genus as a source of rich genetic resources. Identification of a procedure to obtain true hybrids is an important component of cross breeding and heterosis utilization. In this study， in order to obtain new germplasm materials of M. ruthenica with more abundant genetic characters， two hybrid combinations were made by reciprocal crosses， using M. ruthenica cv. ‘Zhilixing’ with upright growth form and high yield， and a yellow-flowered variant of wild M. ruthenica var. Sojak with strong stress resistance as parents. 85 true hybrids were identified from 118 F₁ hybrids by sequence-related amplified polymorphism （SRAP） molecular marker technique. F₂ material was obtained from the true cross F₁ plants with excellent performance of M. ruthenica ‘Zhilixing’ ♀×M. ruthenica Sojak ♂， and further heterosis analysis was carried out on the main agronomic characters of 13 F₁and 20 F₂ plants for traits such as plant height， plant growth form， number of primary branches， approximate leaf area， leaf∶stem ratio and single plant aboveground biomass of single plants. It was found that the coefficients of variation of phenotypic values of F₁ traits ranged from 18.82% to 45.72%， among which the aboveground biomass per plant， leaf∶stem ratio and primary branch number varied most greatly. The parental dominance of each trait ranged from -54.2% to 26.9%， but only the leaf stem ratio （8.22%） showed superparental dominance. The coefficient of variation （19.66% to 41.63%） of each trait in F₂ was lower than that in F₁， and the heterosis （-52.38% to 19.75%） was weakened. In addition， the mid- and super-parent vigor of yield-related traits in F₁ and F₂ were mostly negative and the intraspecific heterosis was weak. This study will provide new germplasm for the improvement of M. ruthenica and other forages of the Medicago genus.

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