Table of Content

20 March 2022, Volume 31 Issue 3

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Canopy scale characteristics of grassland under different grazing intensities based on UAV lidar and multispectral data

Jie SHEN, Lei DING, Xiao-ping XIN, Xiang ZHANG, Da-wei XU, Lu-lu HOU, Rui-rui YAN

2022, 31(3):  1-15.  DOI: 10.11686/cyxb2020573

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Grazing activities not only affect ecological processes of grasslands， but also change the spatial pattern of grassland communities. This research utilized airborne lidar carried by an HS-600 unmanned aerial vehicle （UAV） with a RIEGL laser system and flying at a height of 119 m， and multi-spectral remote sensing to obtain grassland canopy data with sub-meter resolution. The grassland canopy spatial pattern and its scale characteristics under different grazing intensities were studied using wavelet analysis （i.e. the deconvolution of observed lidar waveforms to extract wavelet data）， to quantify the spatial characteristics and scales of three canopy parameters： canopy height （CH）， fractional vegetation cover （FVC） and normalized difference vegetation index （NDVI）， in terms of their response to grazing intensity. It was found that the wavelet variances of grassland CH， FVC， and NDVI show a downward trend with increase in grazing intensity， indicating that the periodic fluctuation energy of its spatial pattern decreases， and the overall grassland canopy spatial structure tends to be more uniform at higher grazing intensity. The analysis of wavelet variance and the real part of coefficients showed that the spatial pattern of FVC and NDVI has two main characteristic scales of 116-140 m and 170-180 m， and a spatial variation period of about 110 m， and the spatial pattern scale characteristics were comparatively stable with change in grazing intensity. The spatial pattern of CH was more complicated. The larger-scale pattern described above was evident， but moderate and heavy grazing resulted in many smaller patches forming with comparatively larger variation in CH and vegetation cover on a smaller spatial scale.

Definition of Comprehensive Sequential Classification System subclasses in Chinese montane grassland

Cai-he ZHANG, Chun-bin LI, Jing WU

2022, 31(3):  16-25.  DOI: 10.11686/cyxb2020585

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The Comprehensive and Sequential Classification System （CSCS） classifies vegetation types based on a two-dimensional coordinate map of seven thermal zones （Ⅰ-Ⅶ） and six humidity zones （A-F） to give 42 classes （ⅠA-ⅦF） and was originally developed in China for classification of diverse grasslands based on environmental factors. Grassland is an important part of the terrestrial ecosystem. The precise definition of grassland types is of great significance to the study of grassland resources. This study focused on montane grasslands in China and used the Digital Elevation Model （DEM） to quantitatively assess the areas of montane subclasses in China， identify grassland subclasses and analyze the spatial distribution characteristics of the subclasses. It was found that： 1） Based on criteria of relief and altitude， 20 montane subclasses were identified. The subclasses with the most extensive distribution area were mainly those of low relief. The distribution area of hilly and intermediate relief montane subclasses was similar， while the area of subclasses of high and extremely high relief was less. 2） Due to the spatial differences of water and heat conditions in mountainous areas， some grassland subclasses do not exist in particular environments. 3） At the CSCS class level， most widely distributed subclasses was frigid perhumid rain tundra alpine meadow （ⅠF36）； cold temperate perhumid taiga forest （ⅡF37） is the second； warm-perhumid deciduous-evergreen broad leaved forest （ⅤF40） is ranked third and subtropical-extrarid subtropical desert （ⅥA6） had the smallest distribution area. The research results provide an objective scientific basis for the development and utilization of grassland， cultivation， protection and management policies， and the formulation of sound animal husbandry practice.

Effects of vegetation characteristics of desert steppe in the non-growing season on near-surface dust flux under different stocking rates

Fang-fang NI, Shi-jie LV, Zhi-qiang QU, Lu BAI, Biao MENG, Bo-han ZHANG, Zhi-guo LI

2022, 31(3):  26-33.  DOI: 10.11686/cyxb2020597

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The objective of this research was to study the relationship between plant community characteristics and dust flux at different near-surface heights under different stocking rates， in a Stipa breviflora desert steppe research area. The research utilized plots established as part of a long-term differential grazing and wind erosion monitoring experiment. Ungrazed （CK）， and light， moderate and heavy grazing intensities were included in the experiment. Aeolian soil were collected using “BSNE” samplers （as described by Fryrear in a 1986 publication and subsequently in the international literature）， and the plant community characteristics （plant community height， vegetation cover and litter weight） were researched in the 2018-2019 non-growing season. The results were as follows， 1） Wind erosion was significantly exacerbated by increased stocking rate， especially the dust flux at 10 cm height and the total dust flux for 0-50 cm height. For the total dust flux for 0-50 cm height， the dust flux of CK was the lowest， the dust flux of lightly， moderately and heavily grazed treatments were， respectively， 1.29， 1.81 and 2.20 times that of the CK treatment. 2） The plant community characteristics had a significant impact on the dust flux， plant community height， vegetation cover and litter weight were all negatively correlated with the dust flux. In particular， the plant community height had the greatest influence on dust flux across the range of height strata sampled. 3） The stocking rate significantly affected the characteristics of the vegetation， and with increased stocking rate， plant community height， vegetation cover and and litter weight were all reduced， which in turn increased the wind erosion of the desert steppe grassland in the non-growing season.

Differences in soil microarthropod community structure in alpine grasslands with differing degrees of degradation

Lei ZHOU, Xue WEI, Chang-ting WANG, Peng-fei WU

2022, 31(3):  34-46.  DOI: 10.11686/cyxb2021266

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Soil microarthropod communities are an important component of grassland ecosystems and community structures are highly sensitive to environmental changes. This study aimed to characterize the changes in soil microarthropod communities associated with alpine grassland degradation and to make tentative deductions on the roles of microarthropods in the process of degradation. Four alpine grasslands in Northwest Sichuan， comprising a degradation series including non-degraded， lightly degraded， moderately degraded and severely degraded grasslands， were selected for study and the soil microarthropod communities within the 0-20 cm soil layer were investigated in July 2019 and July 2020. Soil microarthropods were extracted from the soil samples for 48 h at 38 ℃ using the Tullgren method in the laboratory. It was found that： 1） The taxonomic composition and dominant taxonomic groups of soil microarthropod communities differed among the four different degradation stages. With increasing degradation， the density， number of taxonomic groups and Shannon diversity index of soil microarthropod communities initially increased then decreased （P<0.01）， while Simpson index initially decreased then increased （P<0.01）. 2） Different groups of soil microarthropods responded variously to degradation. The abundance of mites decreased steadily with each increase in alpine grassland degradation （P<0.01）， while the abundance of Collembola increased from non-degraded to moderately grassland but was decreased in severely degraded grasslands （P<0.01）. 3） The density and diversity of soil microarthropods were significantly correlated with soil environmental factors such as soil organic carbon， humidity， total N， pH， C/N ratio， height and species number of plant communities （P<0.001， 0.01 or 0.05）. The mite abundance differed significantly with differences in soil bulk density， soil organic carbon， total N， C/N ratio and pH （P<0.001， 0.01 or 0.05）， but none of these factors was significantly linked to change in the Collembola abundance （P>0.05）. The results indicate that the degradation of alpine grasslands affects the taxonomic composition， density and diversity of soil microarthropod communities mainly through soil environmental factors， and the abundance of mites can be used to monitor the degree of degradation of alpine grasslands.

Genome-wide identification and expression analysis of the bHLH transcription factor family in Cenchrus purpureus

Li-juan GAO, Zheng-she ZHANG, Yu WEN, Xi-fang ZONG, Qi YAN, Li-yan LU, Xian-feng YI, Ji-yu ZHANG

2022, 31(3):  47-59.  DOI: 10.11686/cyxb2020593

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The bHLH （basic helix-loop-helix） transcription factor family not only participates in plant growth and development， but also plays a key role in plant response to stress and secondary metabolism. In this study， we identified and analyzed at the whole genome level， the bHLH transcription factor family of Cenchrus purpureus （also called elephant grass， an important forage grass and energy plant）. We also analyzed the response of bHLH transcription factors to gibberellin （GA₃） and paclobutrazol （PAC） by using transcriptome data and quantitative RT-PCR. A total of 229 bHLH gene family members （CpbHLH001-CpbHLH229）， with complete conserved domains， and unevenly distributed on the 14 chromosomes， were identified. The results of phylogenetic analysis revealed that 229 CpbHLHs could be classified into 18 subgroups， of which a subgroup designated C contained the highest number （41）. The members of each subfamily had similar gene structures and conserved motifs. Expression profile analysis based on transcriptome data found that most bHLH genes responded to GA₃ and PAC in the meristems of the shoot apex， and nine genes with higher expression were randomly selected and further verified by qRT-PCR. It was found that these nine genes were differentially expressed in response to different exogenous GA₃ and PAC treatments， suggesting that these genes are associated with GA₃ and PAC mediated signaling pathways. This study lays the foundation for further research on the biological functions of the bHLH transcription factor family in elephant grass.

A SSR marker analysis of genetic diversity and population genetic structure of bermudagrass in Henan Province

Xue-feng REN, Ya-bo DENG, Guo-zhang ZANG, Yi-qi ZHENG

2022, 31(3):  60-70.  DOI: 10.11686/cyxb2021196

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In this study， SSR molecular markers were used to analyze the genetic diversity and population genetic structure of bermudagrass （Cynodon dactylon） in Henan Province. A total of 173 bands were amplified by 10 pairs of primers， of which 163 bands （94.29%） were polymorphic， indicating that the polymorphism of tested accessions is rich. The coefficient of genetic differentiation among the 15 populations was 0.3857， meaning that 38.57% of the genetic variation occurred between populations and the majority of the genetic variation occurred within populations. The gene flow among populations was 0.7964， and there was a degree of gene communication among populations. The genetic identity among different populations ranged from 0.746 to 0.964， with an average of 0.767. A UPGMA cluster analysis among the 15 populations showed that the populations were not clustered completely according to geographical origin. A Mantel test between genetic distance and geographical distance matrix showed that there was no correlation between genetic distance and geographical distance among populations. The genetic distance between 288 bermudagrass accessions ranged from 0.0173 to 0.5205， with an average of 0.3113. According to the UPGMA cluster analysis results， the 15 studied bermudagrass populations fell into three groups. Meanwhile， structure analysis suggested that the 288 bermudagrass accessions could be grouped into two subpopulations and one mixed population， which was basically consistent with the grouping results based on UPGMA clustering. This indicated that the two subpopulations had a single genetic background， while the mixed population had additional germplasm gene penetration， and the genetic background was complex.

A transcriptomic study of physiological responses to drought and salt stress in sweet sorghum seedlings

Zhi-heng WANG, Yu-qing WEI, Yan-rong ZHAO, Yue-juan WANG

2022, 31(3):  71-84.  DOI: 10.11686/cyxb2020557

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This research aimed to explore the molecular mechanisms， metabolic pathways and physiological differences of responses to drought and salt stress in sweet sorghum， in order to strengthen the scientific information available to enhance sweet sorghum forage crop husbandry and breeding. Seedlings of sweet sorghum cultivar Liaotian No.1 were used to provide the plant material for study. Moderate drought stress was induced using 10% PEG-6000 solution and salt stress was simulated using 0.9% NaCl solution. Photosynthetic gas exchange parameters， endogenous hormone content， content of organic osmotic regulatory substances and antioxidant enzyme activities were determined on days 2 and 7 of stress exposure. Concurrently， transcriptome sequencing and bioinformatics analyses were carried out on seedling leaves， and qRT-PCR was used to verify the sequencing results. For sweet sorghum seedlings under salt stress， photosynthetic parameters， endogenous auxin concentration and degree of cytokinin inhibition were higher than under drought stress； Soluble sugar content was significantly higher under drought stress than under salt stress； Antioxidant enzyme activities and abscisic acid concentrations were higher under salt stress than under drought stress， indicating different physiological mechanisms of drought and salt stress response in sweet sorghum. Under drought stress on day 2， transcriptome sequencing identified 922 up-regulated and 975 down-regulated genes while under salt stress there were 2047 up-regulated and 1714 down-regulated genes. At day 7 under drought stress there were 157 up-regulated and 54 down-regulated genes while under salt stress there were 795 up-regulated and 722 down-regulated genes. Forty drought stress response genes and 493 salt stress response genes were also identified. Gene ontology （GO）-based enrichment analysis revealed that sweet sorghum seedlings under drought and salt stress were significantly enriched in pathways involving plant response to stress. Kyoto encyclopedia of genes and genomes （KEGG） enrichment analysis showed that genes up-regulated in response to drought stress tended to be involved in endoplasmic reticulum processing and shear body metabolism pathways， while salt stress response genes were generally associated with plant hormone signal transduction metabolic pathways. Analysis of the genes related to photosynthesis， plant hormone signal transduction， antioxidant enzymes and starch and sucrose metabolic pathways showed that the expression patterns of these genes were consistent with the observed changes in physiological indicators. Therefore， sweet sorghum adaptation to salt stress lags behind response drought stress at the transcriptional level. Meanwhile， the tolerance of sweet sorghum seedlings to moderate salt stress was lower than that under moderate drought stress. Soluble sugars played an important role in the resistance to drought stress of sweet sorghum seedlings. The joint regulation of plant hormone signal transduction and antioxidant enzyme activity changes was the key to the resistance of sweet sorghum seedlings to salt stress.

Effects of gibberellin and its inhibitors on growth and gene expression in Poa pratensis

Li-qing ZHAO, Zhi-gang HAO, Xiao-yan CUI, Xiang-yong PENG

2022, 31(3):  85-91.  DOI: 10.11686/cyxb2020550

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The effects of different concentrations of gibberellin （GA₃） and gibberellin inhibitors on the growth and development， and the expression of gibberellin-related genes of Poa pratensis were studied. P. pratensis plants cultivated with 1/2 Hoagland nutrient solution were randomly divided into 7 groups. Three plant growth regulators： GA₃， uniconazole or paclobutrazol were applied to determine the effects on plant growth， chloroplast distribution， chlorophyll content， and gibberellin-related gene expression measured. Compared with the control， exogenous uniconazole and paclobutrazol significantly inhibited leaf elongation and fresh and dry weight accumulation of P. pratensis， but increased root∶shoot ratio， chlorophyll a， chlorophyll b and carotenoid contents （P<0.05）. The number of mesophyll cell layers was also increased and Chloroplasts were evenly distributed in mesophyll cells between the upper and lower epidermis. The expression of key enzyme genes PpKAO， PpKS1， PpGA₃ox and PpGA₂ox in the gibberellin biosynthesis and metabolism pathways were significantly down-regulated， and the protein receptor gene PpGID1 in the gibberellin signal transduction pathway was significantly up-regulated （P<0.05）. Exogenous gibberellin promoted the elongation of P. pratensis roots and leaves， and increased the fresh and dry weights of roots and leaves， decreased the root∶shoot ratio and significantly upregulated the PpGA₂ox expression of gibberellin-related genes （P<0.05）. In summary， the effects of uniconazole and paclobutrazol on the growth and gene expression of P. pratensis were opposite to those of gibberellin， but there was no significant concentration effect. The growth inhibition from spraying uniconazole or paclobutrazol diluted 1000 times after lawn mowing would have significantly reduced the labor cost of lawn maintenance ， enhanced lawn visual appearance and ornamental value and promoted ease of management and turf persistence in landscaping applications.

Effect of mowing in different phenological growth stages on shoot regrowth， root morphology and forage yield of Leymus chinensis

Cheng-zhen ZHAO, Qiang LI, Rong-zhen ZHONG

2022, 31(3):  92-100.  DOI: 10.11686/cyxb2020565

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Mowing is a common practice in the utilization of Leymus chinensis grassland. In this field experiment a single mowing in late season on August 15 （control treatment， CON） was compared with treatments initially mown at various earlier growth stages， and again on August 15， to explore the effect of mowing at different phenological growth stages on the regrowth and yield of L. chinensis. Mowing treatments were： at elongation stage on May 15 （ES）， at heading stage on June 1 （HS） and at flowering stage on June 15 （FS）. It was found that the HS and FS treatments increased （P<0.05） the dry matter （DM） yield compared to CON， while the ES treatment decreased yield （P<0.05）. All mowing treatments had increased crude protein yield compared to CON. The regrowth processes of L. chinensis differed between the treatments mown at different phenological growth stages. The ES treatment had the lowest fine root length， root surface area， and root volume. The FS treatment had highest net photosynthetic rate of L. chinensis in the later stages of regrowth， but the water soluble carbohydrate （WSC） content in roots was lower （P<0.05） than other treatments. The root morphology and root WSC contents of the HS and CON treatments did not differ significantly. Although the regrowth processes of L. chinensis in various phenological growth stages of mowing were different， the regrowth yields were similar， especially those of ES and HS treatments. This was because that longer regrowth cycle was offset by lower regrowth efficiency. Therefore， the total DM accumulation was mainly determined by the pre-mowing DM yield. In conclusion， initial mowing at heading stage should be adopted to increase the production of L. chinensis and ensure its persistence in grassland in northeast China.

Physiological effects of different Cd concentrations on maize root architecture and classification

Chang WEI, Qiu-juan JIAO, Hai-tao LIU, Jing-jing ZHANG, Feng-min SHEN, Ying JIANG, Xue-hai ZHANG, Luan-zi SUN, Fang YANG, Zhen LIU

2022, 31(3):  101-113.  DOI: 10.11686/cyxb2021294

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In this research， a hydroponics experiment was conducted to apply different concentrations of cadmium （Cd） （0， 5， 10， 25， 50， 100， 200 μmol·L^-1） to maize seedlings with two leaves and one new leaf， in order to explore the effects of the different Cd concentrations on the maize seedling growth， Cd absorption kinetics and root morphology and classification. After 5 days of Cd stress， the maize seedings were sampled， the plant height， main root length， aboveground and underground biomass， root architecture， Cd content and photosynthesis and related parameters were measured. It was found that with increasing Cd stress， the plant height， main root length， biomass and tolerance index of shoots and roots， total root length， root surface area， root volume， root forks and root tips all decreased significantly； Root average diameter and root∶shoot increased significantly （P<0.05）. Meanwhile root parameters （root length， root surface area and root volume） of root diameter classes designated Ⅰ-Ⅲ （0-1.5 mm） showed a decreasing trend， which had a significant （P<0.05） negative correlation with root Cd concentration. The proportion of root length， root surface area and root volume with diameter between 0-0.5 mm showed a downward trend under Cd stress. Under Cd stress， Cd concentration and accumulation in underground and aboveground parts of maize seedlings increased significantly， chlorophyll content decreased， and photosynthesis was inhibited. This study has shown that Cd affected root development mainly by inhibiting the growth and morphology of fine roots， and inhibited photosynthesis， elongation and biomass accumulation of the aboveground and underground parts of the maize seedings.

P accumulation and P removal potential of a P-accumulating ecotype of Polygonum hydropiper for different manure types

Yu-jie LI, Qi-wei SHEN, Ao ZHANG, Dan LIU, Dai-hua YE, Ting-xuan LI

2022, 31(3):  114-123.  DOI: 10.11686/cyxb2021008

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The study of P accumulation and P removal potential of P-accumulating plants for different manure types provides data for the development of methodology for extracting excess soil P and reducing non-point source pollution of P. Two pot experiments were conducted to investigate the characteristics of P accumulation and P removal potential of a mining ecotype （ME） of Polygonum hydropiper grown in soilsfertilized with poultry manure （P）， swine manure （S） or dairy manure （D）. In the first experiment， different manure doses （0， 25， 50， 75， 100 g·kg^-1； M₀， M₂₅， M₅₀， M₇₅， M₁₀₀， respectively） were applied to investigate the P accumulating capacity of the ME. In the second experiment， the optimum doses of each kind of manure were applied to clarify periodic P accumulation and P removal potential of the ME over four growth periods （6， 8， 10， 12 weeks）. It was found that： 1） Across the range of manure application doses， shoot biomass and P accumulation of the ME were maximized for the respective manure types for treatments PM₇₅， SM₁₀₀ and DM₁₀₀. The greatest shoot P accumulation values for the three manure types were 158.64， 204.05 and 128.92 mg·plant^-1， respectively， and these values were 5.47-8.66 times higher than those of the M₀ treatments. 2） Under the optimum application dose of each manure type （i.e. treatments PM₇₅， SM₁₀₀ or DM₁₀₀）， the maximum ME shoot biomass was observed at week 12， and the maximum P accumulation at week 8. Hence the P accumulation rate for a regrowth interval was optimized at 6-8 weeks of regrowth. After 8 weeks， the P-removal capacity of the ME under the optimum manure application changed slightly； Its P extraction ratio was 5.84%-19.36% and the plant effective number was 4-6 plants. Based on these results， harvesting after 8 weeks regrowth is the recommended harvest interval for the ME under the optimum manure application rates. 3） The P accumulation of the ME varied among the different manure types. During the first 6 weeks of regrowth， the apparent P accumulation rate of the ME under the DM₁₀₀ treatment was higher than under treatments with lower application doses， whereas the P accumulating rate of the ME increased rapidly under PM₇₅ or SM₁₀₀ treatments after 6 weeks. At the 8th week， the ME shoot P accumulation of the PM₇₅ and SM₁₀₀ treatments was， respectively， 1.19 and 1.27 times higher than for DM₁₀₀. In summary， the mining ecotype of P. hydropiper showed greatest potential for P accumulation and P removal from soil fertilized with poultry manure at 75 g·kg^-1， swine manure at 100 g·kg^-1 or dairy manure at 100 g·kg^-1， among the tested manure application doses. The ME P extraction in soil fertilized with swine manure or poultry manure was superior to that after dairy manure application. These results will assist in developing efficient practices for reduction of excessive P loss from farmed soils into the environment.

Regulation of endogenous isoflavones on alfalfa nodulation and nitrogen fixation and nitrogen use efficiency

Chang-chun TONG, Xiao-jing LIU, Yong WU, Ya-jiao ZHAO, Jing WANG

2022, 31(3):  124-135.  DOI: 10.11686/cyxb2021011

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This research compared alfalfa varieties “LW6010” with high nitrogen absorption and utilization efficiency and “Longdong” with low nitrogen absorption and utilization efficiency， in order to investigate the relationship between isoflavone concentrations and nodulation， nitrogen fixation and nitrogen use efficiency in alfalfa. The isoflavone concentrations and nitrogen fixation characteristics， together with the expression of isoflavone synthase （IFS） and nodulation signaling pathway （nod） genes of the two alfalfa varieties with contrasting nitrogen use efficiencies were studied at five different nitrogen levels. It was found that the isoflavone content of alfalfa was significantly correlated with the number of nodules， the total nodule weight per plant， the whole plant nitrogen-fixing potential. At lower nitrogen levels， the isoflavone content and nodule number， total nodule weight per plant and nitrogen fixation potential of alfalfa all showed a significant increase. Under nitrogen deficit or over-supply stress， the number of upregulated IFS genes and magnitude of up-regulation in the stems， leaves and roots of the nitrogen-efficient LW6010 variety were greater than those of the nitrogen-inefficient Longdong alfalfa variety， thus promoting high expression of the nod genes and， ultimately， improved nitrogen use efficiency. Therefore， 1） The nodulation and nitrogen fixation of alfalfa is significantly positively correlated with the isoflavone content. When the concentration of exogenous nitrogen decreases， alfalfa is able to increase the isoflavone content in the plant tissues through the expression of different IFS genes in the stems， leaves and roots， thereby stimulating the expression of nod genes to promote nodulation and increase the plant nitrogen fixation potential； 2） The difference in isoflavone content in alfalfa is an important physiological determinant of its nitrogen efficiency. Nitrogen-efficient alfalfa promotes isoflavone synthesis through the high expression of multiple IFS genes under nitrogen stress， thereby stimulating nodulation and nitrogen fixation， thus achieving high nitrogen absorption and nitrogen use efficiency.

Effects of combined application of microbial fertilizer and chemical fertilizer on the growth of Lolium perenne

Dong-rong HAN, Tuo YAO, Hai-yun LI, Shu-chao HUANG, Yan-shan YANG, Ya-min GAO, Chang-ning LI, Yin-cui ZHANG

2022, 31(3):  136-143.  DOI: 10.11686/cyxb2020581

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This experiment investigated the effect on perennial ryegrass （Lolium perenne） herbage yield in a pot experiment， of substituting 20% or 40% of a standard chemical fertilizer （CF） dressing with microbial fertilizer （MF）. The CF applied to the control treatment was 300 kg·ha^-1 of a proprietary fertilizer formulation with percentage nutrient analysis N∶P₂O₅∶K₂O=14∶16∶15. MF was prepared by addition of bacterial cultures to a substrate of charcoal and crushed corn stalk and incubation for 7-10 days. The experimental treatments comprised a 20% or 40% reduction in CF （i.e. 240 or 180 kg·ha^-1， respectively） and replacement with MF at 60， 90， 120， 150 or 180 kg·ha^-1 making a total of ten CF-MF fertilizer combinations. Effects on agronomic traits including root morphology， nutritional quality and antioxidant enzyme activities of perennial ryegrass were measured. It was found that for the combination 80% CF with 90 kg·ha^-1 MF， plant height， branch number and numbers of perennial ryegrass root tips， forks and link segments were increased（P<0.05） by 12.35%， 60.40% and 85.10%， respectively， compared with the control plants. For the treatment combination of 80% CF with 120 kg·ha^-1 MF， ryegrass stem thickness， aboveground dry weight， underground dry weight， total root length， total root surface area， total root volume， root tip number， crude protein content and crude fat content were increased （P<0.05） by 29.41%， 16.84%， 45.54%， 21.15%， 14.59%， 166.67%， 47.35%， 5.71% and 37.98%， respectively， compared to the control plants. For the same treatment combination， shoot ascorbate peroxidase， super oxide dismutase， and peroxidase activities were decreased by 33.12%， 10.66% and 19.51% compared to control plants， while malondialdehyde concentration was 14.54% lower than in the control plants （P<0.05）. MF applied at rates of 150 or 180 kg·ha^-1 appeared to cause plant stress. The results indicate the optimal fertilizer combination to be a 20% reduction in chemical fertilizer and 90-120 kg·ha^-1 microbial fertilizer.

Effects of row configuration on characteristics of the light environment and light use efficiency in maize/alfalfa intercropping

Yu-huan WU, Zi-kui WANG, Ya-nan LIU, Qian-hu MA

2022, 31(3):  144-155.  DOI: 10.11686/cyxb2020595

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This research explored the effects of intercrop row configuration on light environment characteristics， yield， and light use efficiency （LUE） in maize/alfalfa intercropping， in order to provide recommendations for optimal planting pattern for farm use on the Loess Plateau. Five planting patterns were investigated： sole alfalfa （SA）， sole forage maize （SM）， one row of maize intercropped with two rows of alfalfa （I₁₂）， two rows of maize intercropped with two rows of alfalfa （I₂₂） and two rows of maize intercropped with four rows of alfalfa （I₂₄）， and the research included field experiments （in 2018 and 2019）， and mathematical simulation. The dry matter yield and canopy transmission of photosynthetically active radiation （PAR） for the five planting patterns were measured. A light transmission model considering the geometrical relationship between light angle and canopy structure was developed to simulate PAR transmission in each monoculture or intercropping system and measured values in field experiments were used to validate the light transmission model. The yield of monoculture alfalfa was significantly greater than that of intercropped alfalfa in 2018 （P<0.05）. However， in 2019 the production of alfalfa in I₁₂， I₂₂， and I₂₄ treatments was greater （197.8， 180.3 and 197.0 g·m^-2， respectively） than that in SA treatment （1473.5 g·m^-2）. The total dry matter yield of maize in I₁₂， I₂₂ and I₂₄ treatments， averaged over two years， was increased by 12.1%， 0.9% and 23.9%， respectively， compared with SM. The land equivalent ratio （LER） of all intercropped sowings was greater than 1.0 in 2019， indicating intercropping advantages. The radiation transmission model accurately simulated the PAR at the bottom of the maize/alfalfa canopy in intercropping systems. The mean absolute errors of simulation results and the corresponding root mean square errors were 59.0 and 66.6 μmol·m^-2·s^-1， respectively. The PAR reaching the top of the alfalfa canopy in intercropped plantings was significantly lower than that in SA （P<0.05）. LUE of maize in I₁₂， I₂₂ and I₂₄ were calculated as 52.5%， 9.3% and 51.7%， respectively， higher than that of SM in 2018， and 28.5%， 9.6% and 21.0%， respectively， higher in 2019 （P<0.05）. In 2019，LUE of intercropped alfalfa in I₁₂, I₂₂ and I₂₄ were 19.2%, 32.4% and 20.9% higher (P<0.05), respectively, than those of SA. In summary， appropriate maize/alfalfa intercropping patterns improved the light environment of intercropped alfalfa and enhanced crop LUE. It was found that the planting configuration I₂₄ was optimal for light transmission and system productivity. Thus， the I₂₄ planting regime is recommended be applied in areas with similar climate.

Analysis of the grain related traits of 77 naked oat varieties

Ji-cheng SHEN, Lei WANG, Cai-xia ZHAO, Fa-hui YE, Shi-kai LV, De-mei LIU, Rui-juan LIU, Huai-gang ZHANG, Wen-jie CHEN

2022, 31(3):  156-167.  DOI: 10.11686/cyxb2021217

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The objective of this study was to measure the grain quality and other traits of 77 naked oat （Avena nuda） varieties， and use the cluster analysis method to classify and compare the measurement indicators， and use the gray correlation degree for a multivariate evaluation， to identify naked oat varieties most suitable for planting in Qinghai. The main findings were as follows： 1） The coefficient of variation of 1000-grain weight was the highest at 49.29%， followed by grain crude fat and crude protein contents （12.23% and 9.83%， respectively）. The highest significant positive correlations with 1000-grain weight were for grain length， width and diameter. The grain crude protein and starch contents were significantly negatively correlated with grain moisture content， and the grain crude protein content was extremely significantly negatively correlated with crude fat content. 2） The results of multivariate evaluation of multiple indicators of the tested oat varieties using grey system theory showed that three varieties with the best multivariate score among the 77 different naked oat varieties were No. 5 （0.679）， No. 73 （0.676） and No. 26 （0.649）. 3） Cluster analysis of the same traits of the tested varieties yielded six groups， and among these group Ⅵ included 70% of the top 10 varieties identified by multivariate evaluation， including the 3 varieties with the highest multivariate score （Nos. 5， 73 and 26）. This group can therefore be regarded as identifying excellent naked oat varieties.

Phenotypic diversity and podding characteristics of 70 Chinese milk vetch （Astragalus sinicus） germplasm lines cultivated in Southern Henan

Meng ZHANG, Peng-fei SHI, Ben-yin LI, Chun-zeng LIU, Chun-feng ZHENG, Cheng-lan ZHANG, Xiao-yan GUO, Li-xia ZHANG, Yu-hu LV, Chun-mei HE, Wei-dong CAO

2022, 31(3):  168-180.  DOI: 10.11686/cyxb2020600

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Astragalus sinicus is one of the most important winter green manure crops in paddy fields of China. By comparing the differences in agronomic traits and podding characters between the local and introduced germplasm resources， phenotypic variation and seed production potential of 70 germplasm lines of A. sinicus in Southern Henan Province were studied. It was found that all tested lines could complete their life cycle. The coefficient of variation （CV） of the 19 traits ranged from 1.3% to 73.2%， among which canopy area （CV=45.9%-73.2%）， height of the first pod （CV=46.0%-52.9%）， number of reproductive branches and reproductive branch ratio （CV=34.6%-48.4%）， number of secondary branches （CV=41.2%-41.3%）， plant height at the spring regreening period （CV=30.2%-39.2%）， and seed yield （CV=24.4%-35.7%） exhibited higher variability. The leaf color of six local lines， including Xinzi No.1 and XYHY-1， appeared purple during the wintering period and the spring regreening period. Seed yield was significantly positively correlated with plant height at the spring regreening period， plant height at the full-bloom period， canopy area in the wintering period， height of the first pod， number of reproductive node sites per branch and 1000-seed weight. 1000-seed weight was significantly positively correlated with plant height at the spring regreening period， plant height at the full-bloom period， canopy area in the wintering period， height of the first pod， number of reproductive node sites per branch and reproductive branch ratio， and significantly negatively correlated with days from seedling emergence to full-bloom， total nitrogen and total phosphorus contents. The average seed yield of the introduced germplasm lines was 1015.5 kg·ha^-1， and that of the local lines was 1096.5 kg·ha^-1. A. sinicus showed high economic benefit in Southern Henan compared with winter rapeseed and wheat， and is a suitable winter option for transplanted-rice cultivation systems.

The dynamic analysis of forage yield and interspecific competition in alfalfa-grass mixed pasture

Qi-yu LIU, Lan YUN, Yi-fan CHEN, Hong-yu GUO, Zhen LI, Zhi-qi GAO, Jun WANG, Feng-ling SHI

2022, 31(3):  181-191.  DOI: 10.11686/cyxb2020589

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Legume-grass mixed pastures were established on slightly alkaline soil in central Inner Mongolia， China. Three different grass species （Psathyrostachys juncea， Bromus ciliatus and Elytrigia elongata） were each sown with the alfalfa cultivar Caoyuan No.3 （Medicago varia） in legume∶grass ratios of 1∶1， 1∶2 or 1∶3. These 4 species were chosen because trial plantings in the area had confirmed they are suited to the local climate. Three years after the mixtures were established， the forage yield， land equivalent ratio （LER）， relative forage yield （RY）， relative density （RD）， relative total yield （RYT）， and inter-species competition rate （CR） were evaluated for three different growth periods during the summer. It was found that the forage yield of all mixed sowing combinations was much higher than single species stands at all three harvest dates. Hence the LER of all mixed sowing combinations was greater than 1. RY， RD and RYT also exceeded 1 in most combinations， with the exception of two of the mixtures sown at the 1∶3 ratio. The competition relationship within the different mixtures was also analyzed. When alfalfa mixtures with the three grass species were established at 1∶1 and 1∶2 ratios， there was stable coexistence with benefits distributed to both species in the mixture， and the CR between legume and grass was predominantly greater than 1 （except for the alfalfa-B. ciliatus combination sown at 1∶1） and tended to increase as the proportion of grass in the mixture was increased. Considering both the productivity and stability of the pasture mixtures， an alfalfa-B. ciliatus mixture sown at a 1∶1 or 1∶3 ratio， or alfalfa-E. elongata or alfalfa-P. juncea mixtures established at 1∶1 or 1∶2 ratios were most conducive to the establishment of high-productivity and stable artificial grassland in this area.

Effects of Epichloë endophytic fungi on the germination of grass seeds

Chun-jie LI, Ming-xiao LANG, Zhen-jiang CHEN, Tai-xiang CHEN, Jing LIU, Yuan-yuan JIN, Xue-kai WEI

2022, 31(3):  192-206.  DOI: 10.11686/cyxb2020601

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Seeds are the most basic output generated in agricultural production， and seed germination plays a decisive role in survival and reproduction of species. However， the process of germination is easily affected by various environment factors. It is significant to improve germination quality in stress condition for grass planting. The establishment of the symbiotic relationship in plants with Epichlo? endophyte confers on the symbiosis higher germination rate， stronger resistance to adverse stress， and leads to the occupation of a more favourable ecological niche in the phytocoenosis. Hence， the Epichlo? endophyte has a wide impact in ecosystems， with ramifications affecting animals， plants and microorganisms within an ecosystem. This study reviewed the influence of Epichlo? endophyte infection on host grass germination under different habitats and treatments， with a focus on roles of endophyte in seed germination under natural growth conditions and various stress conditions， including allelopathy. It was found that endophyte promotes seed germination under both natural and stress conditions. However， germination responses were inconsistent in the presence of allelopathic effects. Additionally， the negative effect on germination caused by extended storage time is alleviated by endophyte infection. Building on previous research， we should prioritize research into the physiology and biochemistry of promoting germination and enhancing resistance to biotic and abiotic stresses in grass infected with Epichlo? endophyte， and on defining the mechanism whereby endophyte fungi influence germination， in order to identify excellent endophytic strains and explore novel ways of creating grass germplasm resources using Epichlo? endophyte.

Effect of catechol on the quality and antioxidant activity of Toona sinensis leaf silage

De-kui CHEN, Shuo WU, Xuan ZOU, Wei ZHOU, Xiao-yang CHEN, Qing ZHANG

2022, 31(3):  207-213.  DOI: 10.11686/cyxb2020599

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This study investigated the effect of catechol on the nutritional quality and antioxidant activity of ensiled Toona sinensis leaves （TSL）. The results showed that the protein fraction of TSL silages was preserved well， with the non-protein nitrogen and ammonia concentrations maintained at a low level. Antioxidant activity was decreased slightly by catechol but remained high. Compared with the CK treatment， catechol significantly increased （P<0.05） 1，1-diphenyl-2-picrylhydrazyl （DPPH） free radical scavenging activity and ferric-reducing antioxidant potential （FRAP）. Pearson correlation analysis showed that the antioxidant activity of TSL silage was positively correlated with the total flavonoid content （P<0.01）. The nutritional quality and antioxidant activity of TSL were well preserved by ensiling. With the addition of catechol， the antioxidant activity of TSL silage was significantly improved. TSL silage had high nutritional value and antioxidant activity.