Table of Content

20 February 2023, Volume 32 Issue 2

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Effects of fencing enclosure on interspecific associations in a Savanna grassland community in China’s arid-hot valley region

Guang-xiong HE, Zheng-tao SHI, Bang-guo YAN, Hao-zhou YANG, Yi SUN, Yan-dan WANG, Jian-lin YU, Run-lian HE, Liang-tao SHI, Hai-dong FANG

2023, 32(2):  1-14.  DOI: 10.11686/cyxb2022080

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This research studied the effects of fencing enclosure on interspecific associations in a Savanna grassland plant community. Fencing enclosure and disturbed areas were set up and maintained for 20 years to facilitate investigation of vegetation and water and soil conservation techniques in the arid-hot valley region surrounding the Jinsha River， and 25 dominant species from the two zones were selected as marker plants to calculate interspecific association indexes using the variance ratio （VR） method， chi-square testing， Jaccard index and Spearman rank correlational methods. Findings included the following. Enclosure resulted in obvious changes in the community composition and structure and nurtured the growth of native herbs such as like Cymlopogon goeringii （Cg）， and promoted the establishment of more lignified species such as Barleria cristata （Bc）， Pistacia weinmanniifolia （Pw）and Gaultheria forrestii （Gf）， while inhibiting annual species， weed species and alien species， resulting in the emergence of a plant community dominated by constructive species. The overall interspecific association of Savanna grassland community in arid-hot valley was mainly positive， and enclosure facilitated the formation of more complex interspecific associations within the plant community. In disturbed areas， a strong positive association between annual species， weed species and alien species was strongly evident and a high resource competition or mutual ecological exclusion was stronger among community species， resulting in a single dominant species community represented by Heteropogon contortus （Hc）. Overall the interspecific relationships in the enclosed area showed a significant positive association， with the formation of a positive association among leguminous species， lignified species and native species， while the positive and negative correlations among dominant species was also strengthened after enclosure. These results suggest that fencing enclosure has a significant effect on the relationship between dominant species in Savanna grassland from the arid-hot valley zone， affecting the species composition and functional group structure of the plant community. The resulting enhancement of the interaction between dominant species appears to be ecologically important.

Effects of incorporated and mulched tree branches on arbuscular mycorrhizal fungi in the desertified soil and root of alfalfa in arid areas

Bo WANG, Ru ZHANG, Jing LIU, Zhi-gang LI

2023, 32(2):  15-25.  DOI: 10.11686/cyxb2022248

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Desertification is one of the main land degradation processes in arid and semiarid areas globally. However， there is an abundant supply of woody organic materials， from ecological shelterbelts， farmland shelterbelts， and urban forests which can provide raw materials for amendments for soil restoration in these areas. Trimmed poplar （Populus alba） branches available in Ningxia were used for amendment materials in this study. Four amendment treatments （with five replicates） were set up： Wood chip mulch （M）， wood chip incorporation （W）， wood chip incorporation with branch cover （WB） and zero addition （CK）. Then， soil physio-chemical properties， enzyme activities， aboveground biomass of Medicago sativa， and arbuscular mycorrhizal （AM） fungi colonization rate were determined. Meanwhile， the Illumina Miseq high-throughput sequencing technology was used to measure AM fungal community structure both in soil and roots. Finally， data were analyzed to identify the key driving factors which affect AM fungi colonization and community structure. It was found that all branch amendments improved soil properties and increased the aboveground biomass of alfalfa. Compared with CK， the WB treatment generated the best enhancement effect. Moreover， the WB treatment also significantly increased the colonization of roots by arbuscular mycorrhizal fungi （AMF）， and increased clump abundance， hyphal abundance， vesicle abundance， and soil spore number （P<0.05）. Also， compared with CK， the WB treatment significantly increased the Chao1 and ACE indexes of AM fungi in the root （P<0.05）， although there were no differences among treatments for α-diversity of AM fungi in soil （P>0.05）. In addition， non-metric multidimensional scaling （NMDS） and permutational MANOVA （PERMANOVA） analyses indicated that the WB treatment induced a significant soil and root AM fungal community structure response （P<0.05）. Additionally， correlation analysis and distance-based redundancy analysis （dbRDA） indicated that colonization and community structure of AM fungi were closely correlated with soil properties and alfalfa above-ground biomass. Furthermore， above-ground biomass of alfalfa and inorganic nitrogen were identified as the mutual and key factors affecting AM fungal community both in soil and root. In all， WB substantially improved soil properties and accelerating colonization and activity of AM fungi， so these results provide a scientific basis for promoting the use of forest residues for the improvement and restoration of desertified soil in arid and semi-arid areas.

Effects of mowing intensity on community characteristics and soil physicochemical properties of Stipa grandis steppe， Inner Mongolia， China

Qi WANG, Jia-hua ZHENG, Meng-li ZHAO, Jun ZHANG

2023, 32(2):  26-34.  DOI: 10.11686/cyxb2022064

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This study investigated the effects of different mowing intensities on plant community characteristics and soil physicochemical properties of Stipa grandis steppe in order to provide a theoretical and scientific basis for establishing an appropriate mowing system in S. grandis steppe. We conducted a field vegetation survey and sampling in an experimental mowing area at Maodeng Ranch， Xilinhot， Inner Mongolia， China in 2020. The experimental mowing area was established in 2014 with no mowing as control （CK） and three treatments of light （LM）， moderate （MM） and heavy mowing （HM）. In this study， we investigated the relationship between community characteristics and soil physicochemical properties by calculating species importance values and diversity indices， and measuring above- and below-ground biomass of plant communities and soil physicochemical properties. It was found that： 1） Compared with no mowing， new species were increased under the various mowing intensities， and the number of species was highest under MM. Compared with no mowing， the mowing treatments significantly increased community richness and the Shannon-Wiener index， and light mowing also significantly increased the Simpson and Pielou indexes， indicating that light mowing was most beneficial to maintaining community diversity. Variation in mowing intensity had no significant effect on productivity of S. grandis steppe. 2） Soil total carbon， total nitrogen and pH were the highest under MM， and under this treatment were significantly higher than under no mowing， indicating that moderate mowing had positive effects on soil nutrient status. 3） Nitrate nitrogen was the main soil factor affecting grassland productivity， and soil water content was the main soil factor affecting grassland community diversity. This study provides important reference information for the study of community structure， species diversity and productivity of S. grandis steppe.

Responses of non-structural carbohydrates and C∶N∶P stoichiometry of Agropyron mongolicum to nitrogen addition

Ai-yun XU, Li-hua ZHANG, Xiao-jia WANG, Chong MA, Yuan-jing LI, Bing CAO

2023, 32(2):  35-43.  DOI: 10.11686/cyxb2022045

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This research investigated the physiological and ecological adaptive mechanisms of Agropyron mongolicum to nitrogen （N） addition. Soluble sugar， starch， carbon （C）， N and phosphorus （P） contents in roots and leaves of A. mongolicum were determined at different levels of nitrogen addition （0， 0.8， 1.6， 2.4 and 4.0 g N·m^-2·yr^-1）. The effects of N addition on the non-structural carbohydrate （NSCs） content and the C∶N∶P stoichiometry in leaves and roots of A. mongolicum were analyzed. The results showed that adding the appropriate amount of N （2.4 g N·m^-2·yr^-1） favoured the accumulation of NSCs and C， N and P contents in the leaves and roots of A. mongolicum， and the responses of different organs were significantly different （P<0.05）. Leaf NSCs content was significantly positively correlated with leaf N， soluble sugar， starch content， C∶P and N∶P； And significantly negatively correlated with leaf P content and C∶N （P<0.05）. Root NSCs content was significantly positively correlated with root C， N content， C∶P， N∶P， soluble sugar and starch content （P<0.05）. Leaf and root N∶P were the main factors affecting the accumulation of soluble sugar； The N content of roots and P content of leaves collectively affected starch synthesis； Leaf P content， root N content and root N∶P were collectively the major factors affecting the accumulation of NSCs in A. mongolicum. In summary， appropriate N addition relieved N limitation， while the addition of large amounts of N produced an imbalance between N and P and exacerbated P limitation. Therefore， optimization of nitrogen fertilizer application and appropriate phosphorus addition should be considered in the establishment and management of artificial A. mongolicum grasslands and in the restoration of degraded grasslandsunder future climate change scenarios.

Effects of nitrogen and phosphorus addition on litter decomposition in Hulunber steppe

Peng-chong DU, Yu-zhen PAN, Shuang-li HOU, Zhi-hui WANG, Hong-yi WANG

2023, 32(2):  44-53.  DOI: 10.11686/cyxb2022038

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Litter decomposition is an important component process in grassland ecosystem energy flows and cycling of carbon （C）， nitrogen （N）， phosphorus （P） and other elements. Litter decomposition rate depends on its initial chemical composition （internal factors） and soil environment （external factors）. N and P as essential macronutrients for plants， are important to regulation of internal and external factors in litter decomposition. Here we report a two-year N and P controlled addition experiment with two N levels （0， 10 g N·m^-2·yr^-1） and 2 P levels （0， 10 g N·m^-2·yr^-1） in their four combinations to define the N×P interaction. There are five replicates. The experiment studied Leymus chinensis， Cleistogenes squarrosa and Thermopsis lanceolata， which have different nutrient utilization patterns and used the net-bag decomposition method to study the effects of N and P addition on litter decomposition. It was found that the litter decomposition process was affected by both internal factors and external factors， with the external factors having a greater effect than the internal factors. In the external factors， nutrient addition promoted the decomposition of all three litter types. With respect to the internal factors， nutrient addition promoted the degradation of C. Squarrosa and T. lanceolata， but inhibited the degradation of L. chinensis. The rate of release of N and P was positively correlated with the contents of N and P in the initial litter and soil environment. This study revealed that the differences of nitrogen and phosphorus nutrient in soil were the main factors affecting litter decomposition and nutrient release. In future studies， more attention should be paid to the influence of external factors on the litter decomposition process.

Effects of swamp meadow degradation on soil nitrogen invertase activity in wet areas of Gahai

Wen-hua CHANG, Wei-wei MA, Guang LI, Guo-rong XU, Yong-chun LONG

2023, 32(2):  54-64.  DOI: 10.11686/cyxb2022075

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This study explored the effects of degradation of alpine wetlands on soil nitrogen invertase activities. Four swamp meadows exhibiting different degrees of degradation ［non-degraded （ND）， lightly degraded （LD）， moderately degraded （MD） and heavily degraded （HD）］ in the wet areas of the Eastern Qinghai-Tibetan Plateau were selected for study and data on the distribution characteristics of soil nitrogen invertase （protease， urease， nitrate reductase and nitrite reductase） in 0-40 cm soil horizon were collected and their relationship with soil physicochemical properties was ascertained. It was found that： 1） With increasing swamp meadow degradation， the soil moisture content， total nitrogen， ammonium nitrogen and microbial biomass nitrogen content were significantly reduced， but the soil temperature and nitrate nitrogen content were significantly increased. 2） As the degree of degradation increased， the soil urease activity increased and the protease activity decreased in each soil layer， but the changes were statistically significant only in the 20-40 cm soil horizon. The nitrate reductase activity increased and the nitrite reductase activity decreased， and there were significant differences in the 0-20 cm soil horizons. 3） The activities of soil urease， protease， and nitrite reductase for each meadow degradation status category all decreased significantly with increasing soil depth， while the nitrate reductase activity decreased significantly only in HD. 4） The activities of all four soil nitrogen converting enzymes varied with degradation status and soil depth， and a there was a significant interaction between degradation status and soil depth for soil nitrate and nitrite reductase activities. 5） Redundancy analysis showed that soil water content accounted for 67.1% to the change in soil nitrogen invertase activity， and was thus the dominant factor driving changes in soil nitrogen invertase activity across the degradation succession of Gahai. The results of this study provide a theoretical basis for defining the pattern of change in soil enzyme activity at different stages in the degradation of alpine wetland ecosystems.

Physiological responses of female and male Buchloe dactyloides plants to different nitrogen forms

Li-zhu GUO, Hui-zhen MENG, Xi-feng FAN, Ke TENG, Wen-jun TENG, Hai-feng WEN, Yue-sen YUE, Hui ZHANG, Ju-ying WU

2023, 32(2):  65-74.  DOI: 10.11686/cyxb2022035

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The aim of this study was to explore the preference and responses of female and male buffalograss （Buchloe dactyloides） to different nitrogen forms， and provide technical data for optimal management of nitrogen fertilizer for B. dactyloides. Thus we investigated the effects of NO₃^--N （N₁）， NH₄⁺-N （N₂）， NO₃^--N∶NH₄⁺-N=1∶1 （N₃） and a zero nitrogen treatment （CK） on growth traits， biomass， chlorophyll content， leaf nitrogen content and enzymes related to nitrogen metabolism of female and male buffalograss ramets in a glasshouse sand culture experiment. It was found that growth traits， biomass of different parts， aboveground biomass and total biomass of female buffalograss were significantly lower under the N₂ treatment than under N₁ and CK， with the result for N₃ being intermediate between N₁ and N₂ treatment， indicating that treatment with NH₄⁺-N alone may inhibit the growth of female buffalograss. Meanwhile， there was no significant difference between the N₁ treatment and CK in spacer length and diameter of male buffolagrass plants， but values for the N₁ treatment were significantly greater than those under N₂ and N₃ treatments. Additionally， stolon node number， stolon length， root biomass， aboveground biomass and total biomass of male buffalograss were significantly greater under N₁ than other treatments. Chlorophyll A content and total chlorophyll content of female and male buffolagrass were greater under the NO₃^--N treatment than CK. However， there was no significant difference between the three N-form treatments for female buffalograss， but male buffalograss under the N₁ treatment differed significantly from N₂ and N₃ treatments. In the NH₄NO₃ treatment， leaf nitrogen content and three nitrogen metabolism related enzymes activities of female buffalograss were the highest， however， those of male buffalograss were highest under the N₁ treatment. These results indicate that both female and male buffalograss plants prefer nitrate nitrogen； female buffalograss plants were found to be extremely sensitive to NH₄⁺-N as the sole nitrogen source and their growth was inhibited， but mixed supply with ammonium and nitrate nitrogen alleviated or even improved the physiological function of N metabolism of female buffalograss； this response was not observed in male buffalograss. In summary， significant differences in the response of female and male buffalograss plants to different forms of nitrogen were found. This information could form a theoretical foundation for development of a differential nitrogen management of female and male buffolagrass.

Effects of salt stress on photosynthetic characteristics of Gymnocarpos przewalskii seedlings

Xiao-jin ZHOU, Hai-xia HUANG, Jun-xia ZHANG, Bu-dong MA, Gang LU, Jian-wei QI, Ting ZHANG, Zhu ZHU

2023, 32(2):  75-83.  DOI: 10.11686/cyxb2022041

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This research examined the effect of salt stress on photosynthesis responses in potted seedlings of the annual plant Gymnocarpos przewalskii. Salt stress was simulated using seven NaCl solutions of different concentrations （CK， 0.2%， 0.4%， 0.6%， 0.8%， 1.0% and 1.2%） and changes in leaf gas exchange parameters， light response curves and chlorophyll fluorescence parameters were determined and analyzed. It was found that with increasing salt concentration， leaf net photosynthetic rate （P_n）， stomatal conductance （G_s） and transpiration rate （T_r） all showed a downward trend. At NaCl concentrations ≥0.4%， P_n， G_s and T_r were all significantly lower than in CK plants. Stomatal limit value （L_s） and instantaneous water use efficiency （WUE） showed an initial upward with a maximum value in the 0.4% NaCl treatment， and then a downward trend at higher NaCl concentrations. Intercellular CO₂ concentration （C_i） showed the opposite trend， reaching its minimum value when the NaCl concentration was less than or equal to 0.4%. The decrease in P_n was mainly due to non-stomatal limitation when the NaCl concentration was equal to or greater than 0.6%， at lower NaCl levels， stomatal limitation was the main factor. As the degree of salt stress increased， the maximum net photosynthetic rate （P_nmax）， dark respiration rate （R_d）， light saturation point （L_SP） and the apparent quantum efficiency （A_QY） all gradually decreased， while the light compensation point （L_CP） gradually increased， indicating salt inhibits the ability of seedlings to absorb， utilize and convert light. Leaf PSII potential activity （F_v/F₀）， light energy conversion efficiency （F_v/F_m）， actual photochemical efficiency （Φ_PSII）， electron transfer rate （ETR） and photochemical quenching coefficient （q_p） all showed decreases with increasing salt concentration. The non-photochemical quenching coefficient （NPQ） was significantly increased compared with CK at NaCl concentrations ≤0.4%， but was significantly decreased when the salt concentration was ≥0.8%. At NaCl concentrations in the seedling substrate of 0.2% and 0.4%， the P_n， F_v/F₀， and F_v/F_m values of G. przewalskii leaves did not decrease significantly， relative to CK， and the WUE increased. The PSII system can protect the photosynthetic mechanism by dissipating excess light energy， thus conferring some salt tolerance. However when the salt concentration exceeded 0.6%， the light energy utilization range was narrowed， the photosynthetic apparatus was obviously damaged， and the photosynthetic capacity was significantly inhibited. Therefore， based on these results， 0.6% NaCl is the threshold concentration， above which salt stress injury for seedlings of G. przewalskii is likely to occur.

Effects of stubble height on nitrogen metabolism， yield and quality of Cyperus esculentus

Bian-bian LI, Feng-hua ZHANG, Ya-guang ZHAO

2023, 32(2):  84-96.  DOI: 10.11686/cyxb2022061

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This study investigated the effects of varying stubble heights on the growth of Cyperus esculentus. We evaluated differences in height， chlorophyll content， nitrogen metabolism and related indicators， tuber yield and quality of C. esculentus for different cutting regimes （stubble 50 cm， R₅₀； stubble 40 cm， R₄₀； stubble 30 cm， R₃₀； stubble 20 cm， R₂₀； stubble 10 cm， R₁₀； and uncut， CK） to clarify the effects of different stubble heights on the nitrogen metabolism， yield and quality of C. esculentus， to elucidate the relationship between nitrogen metabolism and yield and quality and to identify the optimal cutting height. It was found that severe clipping （R₁₀ and R₂₀） had an inhibitory effect on the accumulation of plant matter， while moderate clipping （R₃₀ and R₄₀） promoted the growth and development of plants. The chlorophyll content of R₁₀ and R₂₀ treatments was severely reduced， while the R₄₀ treatment （7， 14 and 21 d） promoted increased chlorophyll content. Nitrate reductase （7， 14， 21 and 28 d）， glutamate synthase （five periods）， and glutamine synthetase （7， 21 and 28 d） activities in the R₃₀ treatment were higher than those in other treatments. The content of soluble protein （21 and 28 d） and the activity of glutamine synthetase （1 and 14 d） in the R₄₀ treatment were higher than those in the other treatments. Appropriate clipping height was not only conducive to the regeneration of aboveground organs， but also promoted the growth and development of belowground organs through source-sink regulation. Tuber yield in the R₃₀ （12366.09 kg·ha^-1） and R₄₀ （11506.62 kg·ha^-1） treatments was significantly higher than in the other treatments， but there was no significant difference between R₃₀ and R₄₀. Thousand seed weight （597.53 g） and the content of crude fat （27.85%） in the R₄₀ treatment were significantly higher than those in the other treatments. Total grain number （26.99 million grains·ha^-1）， grains per hole （169 grains·hole^-1）， and the contents of crude protein （8.01%） and total sugar （18.78%） in the R₃₀ treatment were significantly higher than those in the other treatments. A correlation analysis showed that the activity of glutamate synthase in the leaves of C. esculentus was significantly positively correlated with the yield of belowground tubers， and the contents of crude protein and starch in C. esculentus tubers in all five periods after clipping. In summary， R₃₀ and R₄₀ treatments promoted C. esculentus leaf nitrogen metabolism， compared with other treatments， and thus improved the yield and quality of belowground tubers. Based on these results， a stubble height of 30-40 cm is recommended.

Analysis of the calcium-dependent protein kinase RtCDPK16 response to abiotic stress in Reaumuria trigyna

Jie ZHANG, Kai CHENG, Ying-chun WANG

2023, 32(2):  97-109.  DOI: 10.11686/cyxb2022198

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Calmodulin kinase is a crucial component of calcium-binding proteins， which read and decode calcium signals and activate downstream target proteins to initiate stress responses in plants after stress stimulation. Reaumuria trigyna， a rare and uncommon salt-producing plant found only in east Alxa and west Ordos， is very resilient to environmental challenges including drought and salinity. Based on transcriptome information， the open reading frame （ORF） of RtCDPK16 was cloned in this study. The ORF shared 78.46% similarity with Arabidopsis thaliana and 80.97% identity with CDPK16 in Vitis vinifera， according to amino acid sequence alignment and evolutionary analyses. RtCDPK16 was found to be expressed in roots， stems， and leaves， with roots expressing it at the highest level. Stress conditions such as sodium chloride （NaCl）/macrogol （polyethylene glycol， PEG）/cold stress （cold）/abscisic acid （ABA） and other environmental stresses and calcium chloride （CaCl₂） were shown to greatly increase RtCDPK16 expression levels. Construction of plant expression vector and transformation of A. thaliana. Drought， salt and abscisic acid stress were applied to wild type Arabidopsis （WT） and overexpression Arabidopsis （OE） strains. The results showed that root length， fresh weight， chlorophyll content and other phenotypic indicators of OE strain were significantly higher than WT under stress treatment， indicating that the overexpression of RtCDPK16 made the transgenic strain obtain stronger stress tolerance. Physiological and biochemical indexes showed that， in each strain under stress treatment， the activities of antioxidant enzymes such as superoxide dismutase （SOD）， Peroxidase （POD）， catalase （CAT） and the content of osmotic regulators such as proline （Pro） and soluble sugar （SS） were significantly induced， and the OE strain was significantly higher than WT， while the accumulation of hydrogen peroxide （H₂O₂）/superoxide anion （O₂^-） was significantly lower than WT. Quantitative real-time （RT-PCR） detection found that the genes related to antioxidant enzymes， ABA synthesis and key elements of signal pathway， and proline synthesis genes of OE strains were significantly induced under stress. The above results indicate that the overexpression of RtCDPK16 in Arabidopsis can promote the osmotic balance and ROS （reactive oxygen species） homeostasis by regulating the genes expression of antioxidant enzyme and osmotic regulation in transgenic plants， and thus improve the stress tolerance of transgenic plants. This process may be achieved through ABA signal dependent approaches.

Variation in ear characteristics and estimation of photosynthetic contributions to oat ear development using techniques of ear shading and glume removal

Lu-ping WEI, Qing-ping ZHOU, Fang LIU, Ji-zhen LIN, Yuan ZHAN, Hui WANG

2023, 32(2):  110-118.  DOI: 10.11686/cyxb2022238

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Exploiting photosynthetic capacity of non-leaf organs such as the ear in cereals has received investigative attention， as the method of improving the whole photosynthetic capacity of crops has been investigated. In this study， six oat （Avena sativa） cultivars （Meida， Beile， Monika， Shezhengwang， Taike and Tianyan 60） were sown in Chengdu Plain in autumn. Two experimental treatments were set up， ear shading and glume removal， to compare the differences in ear characteristics， ear photosynthetic contribution rate， glume photosynthetic contribution and photosynthetic matter transfer rate in stem in the six oat varieties. It was found that the photosynthetic contribution of the ear to grain fill in the six oat varieties ranged from 28.56%-49.05% and Tianyan 60 （T60） had the highest contribution rate. The photosynthetic contribution of glumes ranged from 11.03%-36.88% and contribution of stored photosynthetic matter translocated from stems ranged from 6.65%-35.81%. The ear made the major photosynthetic contribution to grain fill. When ear photosynthesis was limited， the single seed weight and the seed numbers per ear were significantly decreased， especially the number of double seed spikelets.

Effects of exogenous hydrogen sulfide on amino acid metabolism in naked oat leaves under saline-alkali stress

Jian-xin LIU, Rui-rui LIU, Xiu-li LIU, Xiao-bin OU, Hai-yan JIA, Ting BU, Na LI

2023, 32(2):  119-130.  DOI: 10.11686/cyxb2022044

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The mechanism where by hydrogen sulfide alleviates saline-alkali stress in plants has attracted much attention. This experiment investigated the mechanisms underlying exogenous hydrogen sulfide effects on the amino acid metabolism of plants under saline-alkali stress in potted plants of the naked oat variety ‘Dingyou 9’ grown in soil. There were four treatments： a 2×2 factorial combination of no saline-alkali or 3.00 g·kg^-1 saline-alkali （molar ratio NaCl∶Na₂SO₄∶Na₂CO₃∶NaHCO₃=12∶8∶1∶9） added to the soil in the pot， and the leaves were sprayed with distilled water or 50 μmol·L^-1 sodium hydrosulfide （a hydrogen sulfide donor， NaHS） solution at the heading stage. Effects of exogenous hydrogen sulfide on the total amino acid and malondialdehyde contents in leaves and on the grain yield of naked oats under the four treatments were studied. Liquid chromatography and mass spectrometry were used for chemical analysis， and data were analyzed by principal component analysis of levels of the 22 amino acids that make up the protein， in order to determine the regulatory effect of exogenous hydrogen sulfide on amino acid metabolic pathways. It was found that： homocysteine was not detected in the leaves of naked oat. There was no significant decrease in total amino acid content in naked oat leaves under saline-alkali stress as a result of spraying NaHS， but NaHS significantly alleviated the increase in malondialdehyde content in leaves and the decrease in grain yield induced by saline-alkali stress. The results of principal component analysis showed that under saline-alkali stress， spraying NaHS solution significantly down-regulated the contents of ornithine （α-ketoglutarate family） and asparagine （oxaloacetate family）， and significantly up-regulated the contents of glutamine， proline， arginine （α-ketoglutarate family）， leucine （pyruvate family）， and tyrosine （aromatic family） in leaves， but had no significant effect on the contents of glycine， serine （3-phosphoglycerate family）， tryptophan， phenylalanine acid （aromatic family）， alanine， valine （pyruvate family）， 4-aminobutyric acid， histidine， glutamic acid （α-ketoglutarate family）， isoleucine， threonine， methionine， lysine and aspartic acid （oxaloacetic acid family）. The above results indicate that exogenous hydrogen sulfide is involved in the regulation of amino acid metabolic pathways in naked oat under saline-alkali stress， and that NaHS can alleviate the oxidative damage and inhibition of assimilate accumulation caused by saline-alkali stress.

Comparison of rumen epithelium morphology and function in dairy cows with differences in susceptibility for subacute ruminal acidosis

Tao ZHANG, Ying-yu MU, Wang-pan QI, Ji-you ZHANG, Sheng-yong MAO

2023, 32(2):  131-139.  DOI: 10.11686/cyxb2022065

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This experiment was conducted to compare the morphology and function of rumen epithelium in dairy cows with differences in susceptibility to subacute ruminal acidosis （SARA）. Twelve multiparous fistulated Holstein cows in mid lactation were housed in individual stalls and fed a diet with a concentrate to forage ratio of 4∶6 throughout the experimental period. Based on the ruminal pH， cows with relatively lower and higher mean ruminal pH were assigned， respectively， to susceptible （SUS， n=4） and tolerant （TOL， n=4） groups. The examination of ruminal epithelial morphology and function revealed that the cells in the spinous process and basal layer of ruminal epithelium were thicker in the SUS than in the TOL group （P<0.05）. In the SUS group， the expression levels of PAT1， MCT4， and DRA genes involved in volatile fatty acid （VFA） absorption were significantly lower （P<0.05）， while the NHE1， NHE2， NHE3， vH⁺ ATPase， and Na⁺/K⁺ ATPase levels were significantly higher than in the TOL group （P<0.05）. The results of gene expression for ruminal VFA metabolism showed that PDHA1 and SREBP2 in the SUS group was higher （P<0.05）， while the expression of HMGCL-2 was significantly lower （P<0.05）. In addition， the expression levels of genes involved in the proliferation and apoptosis of rumen epithelial cells， such as CDK2， CDK6， Cyclin D1， Bad and Caspase-9 in the SUS group were higher in the SUS group than in the TOL group （P<0.05）. In summary， under the same diet， there was a lower expression of genes associated with free fatty acid absorption and a higher expression of genes related to non-free fatty acid absorption in rumen epithelial cells of SUS cows. This results in free fatty acid accumulation and reduced ruminal pH in the SUS group， and increased the risk of SARA in these cows.

A comparative study of slaughter and meat quality for sheep fed indoors or grazed with supplementary feed in the hill and gully region of the Loess Plateau

Chao PENG, Zi-jian LI, Hu-cheng WANG, Qiang FENG, Yu-ying SHEN

2023, 32(2):  140-147.  DOI: 10.11686/cyxb2022046

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Cultivated grassland production systems have both advantages and disadvantages. This study compared the slaughter and meat quality performance of mutton sheep either fed indoors or grazed with supplementary feeding with the aim of identifying a system for the efficient production of high-quality sheep meat. Eighty small-tailed Han lambs aged from 6 months and in similar body condition were selected and randomly divided into two groups of 40 （an indoor feeding group and a group for grazing with supplementary feeding）. The House-fed （HF） group was provided ad libitum access to a total mixed ration feed. Feed supply for the HF sheep was such that 10% of the feed was left over. The grazing group with supplementary feeding （GS） were grazed in a sainfoin （Onobrychis viciifolia） stand during the day， and then penned at night with supplementary feed provided in the pen. The supplementary feed was the same as that provided to the HF sheep. After 90-days differential feeding， 6 sheep closest to the average weight of the group from both HF and GS groups were slaughtered. The study found that the small-tailed Han sheep pre-slaughter live weight， carcass weight and drip loss rate did not differ significantly between the HF and GS feeding regimes （P>0.05）. The muscle fiber diameter and muscle fiber area of ??the longissimus dorsi muscle of the GS group were significantly greater than those of the HF group （P<0.01）. Compared with the HF group， the total unsaturated fatty acid （TUFA） and total saturated fatty acid （SFA） contents of meat of the GS group did not differ significantly （P>0.05）. The content of linolenic acid （C18：3n-6） in the GS group was higher than that in the HF group （P<0.05）. The content of valine in the longissimus dorsi sheep from the HF group was lower than that in the GS group （P<0.05）， and there was no significant difference in the content of other amino acids （P>0.05）. In summary， compared to HF feeding， the GS treatment had no effect on the slaughter performance and meat quality of the trialled small-tailed Han sheep， and some indicators were improved. Grazing of sheep with supplementary feeding sheep production in agricultural areas has both ecological and economic benefits and should be promoted.

Effects of dietary rumen-protected cysteine on growth performance， nutrient apparent digestibility and serum biochemical indexes of sika deer during weight gain

Qian-long YANG, Qian-qian WEI, De-hui ZHAO, Xiao-lan GUO, Tie-tao ZHANG, Xiao-xu WANG, Kun BAO, Kai-ying WANG

2023, 32(2):  148-159.  DOI: 10.11686/cyxb2022053

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This experiment was conducted to study the effects of dietary rumen-protected cysteine （RPCys） on growth performance， nutrient apparent digestibility and serum indexes of sika deer during weight gain. A single factor experimental design was adopted. Twelve 7-month-old healthy sika deer were divided into 4 groups with 3 replicates per group and 1 deer per replicate. There was no significant difference in body weight between groups （33.63±0.73 kg） at the start of the experiment. The control group （Group Ⅰ） was fed a basal diet， and the experimental groups were the fed basal diet supplemented with RPCys （active ingredient 51.70%） at 1.25 （Group Ⅱ）， 2.50 （Group Ⅲ） and 5.00 g·kg^-1 （Group Ⅳ）. Following a pre-trial period of 15 days， the trial period lasted for 112 days. It was found that， compared to Group Ⅰ： 1） Dietary RPCys significantly increased total weight gain and average daily gain of Group Ⅲ （P<0.05） and significantly increased the feed conversion efficiency in this group （P<0.05）. 2） Dietary RPCys significantly increased the apparent digestibility of crude protein， calcium and phosphorus of all groups （P<0.05）， and significantly increased the apparent digestibility of dry matter and organic matter of Group Ⅲ （P<0.05）. 3） Dietary RPCys significantly increased the apparent digestibility of glycine in Group Ⅱ and Group Ⅲ （P<0.05）， and significantly increased the apparent digestibility of cysteine， methionine， serine， lysine， threonine， valine， isoleucine， leucine， arginine， phenylalanine， histidine， aspartic acid， tyrosine， glutamate， alanine and proline of all groups （P<0.05）. 4） Dietary RPCys significantly increased the total protein content in Group Ⅲ （P<0.05）. 5） Dietary RPCys significantly increased the catalase activity in Group Ⅲ （P<0.05）， and significantly reduced the malondialdehyde content of all groups （P<0.05）. 6） Dietary RPCys significantly reduced serum cysteine concentration of Group Ⅲ （P<0.05）， and significantly increased concentration of taurine， serine， aspartic acid and glutamic acid of Group Ⅲ （P<0.05）. In summary， dietary RPCys significantly increased the total gain， average daily gain and feed conversion efficiency of sika deer during weight gain， significantly increased the apparent digestibility of crude protein， crude ether extract， calcium， phosphorus， organic matter， dry matter and amino acid， significantly increased serum total protein content and antioxidant function of the body， significantly increased concentration of serum taurine， serine， aspartic acid and glutamic acid， and significantly reduced serum cysteine concentration. Under the conditions of this experiment， the appropriate dietary supplementation level of RPCys was 2.50 g·kg^-1， or 1.29 g kg^-1 active ingredient.

Advances and perspectives in forage oat breeding

Xue-ling YE, Zhen GAN, Yan WAN, Da-bing XIANG, Xiao-yong WU, Qi WU, Chang-ying LIU, Yu FAN, Liang ZOU

2023, 32(2):  160-177.  DOI: 10.11686/cyxb2022263

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Oat （Avena sativa） is an annual crop belonging to the Poaceae family with resistance to salinity， drought， cold stress， and adaptability to a wide range of environmental conditions including lower soil fertility. Oats are widely grown in temperate regions north of 40° N latitude in Europe， North America， and Asia. Oats also have a high forage yield， high nutritional value， good palatability， high digestibility， and the crop is suitable for silage and hay production. Therefore， oat is a versatile grain crop useful for food and forage purposes. Oat cultivars can be classified as naked or hulled oats depending on whether the grains readily separate from the husk or lemma at threshing. Hulled oats retain their husk. Naked oats without husks are mostly grown in China and are commonly used for food， while hulled oats which retain their husks are mainly grown in other countries， and are often used for feeding livestock. With the rapid development of animal husbandry in China in recent years， the available forage oat varieties are currently in need of improvement. Our country has formulated and implemented a series of policies that include “grass-based livestock husbandry”， “grain to forage” and “planting grass in fields”， which have promoted the rapid development of the forage oat industry. Under the strong support and guidance of these national policies and industry need， the planting area of forage oats has continued to expand， and the demand for new varieties has become increasingly urgent， which also points to higher requirements for the breeding of forage oats. In this study， we reviewed： 1） Collection， sorting， identification， and evaluation of germplasm resources of forage oats at home and abroad； 2） Four development stages of conventional breeding； and 3） The application of molecular technology in scientific research and breeding of oats. Based the above review， the current breeding objectives of forage oats are clarified， and the key points， difficulties， and immediate issues of forage oat breeding are discussed and analyzed， thus providing an important resource to underpin further developments in forage oat breeding.

Research progress relating to stelar K⁺ outward rectifier （SKOR） channels in plants

Pan-pan REN, Guo-qiang WU, Ming WEI

2023, 32(2):  178-190.  DOI: 10.11686/cyxb2022078

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Maintaining K⁺ homeostasis is one of important physiological component processes in plant resistance to abiotic stress. Stelar K⁺ outward rectifier （SKOR） is one of the outward rectifier K⁺ channels located in the plasma membrane of pericycle cells in plant roots. This channel is involved in mediating K⁺ efflux from cytoplasm and K⁺ loading in xylem. On the one hand， SKOR regulates intracellular K⁺ homeostasis； while on the other hand， it maintains the K⁺ balance between root and shoot by controlling K⁺ flow in xylem. SKOR plays a crucial role in plant response to salt， drought and nutrient deficiency. Therefore， research into SKOR function and regulation and its application is of great significance for crop production and stress resistance enhancement. In this study， the discovery， structure， nomenclature， biological function， gene expression regulation， and response to abiotic stresses of the SKOR family are reviewed， and directions for future research into functioning of this channel are proposed. This review contributes theoretical understanding and knowledge of gene resources for the genetic improvement of crop quality and stress resistance.

Research status and suggestions for grassland carbon sequestration and emission reduction in China

Zi-jing LI, Cui-ping GAO, Zhong-wu WANG, Guo-dong HAN

2023, 32(2):  191-200.  DOI: 10.11686/cyxb2022049

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With rapid economic development， and continuing increase in the emission of greenhouse gases， coupled with intensification of human use of natural resources， the carbon sequestration capacity of the global ecosystem has weakened， and the concentration of greenhouse gases in the global atmosphere has reached a new high. This has become a major global issue of general concern to the international community. China’s grassland carbon sink resources are unique， and the development of the grassland carbon sink economy has become an important vehicle for fulfilling international commitments， creating a new carbon sequestration economy and building a beautiful China with regenerative food production systems. This study reviews the current status of grassland carbon sequestration and emission reduction in China and the factors influencing sequestration， including research into grassland carbon sink capacity and reduction of emissions linked to livestock production now that there is a background of climate change and establishment of sown artificial grassland construction. Our review proposes a plan for the development of grassland carbon sequestration and emission reduction in China and provides a theoretical basis for contribution to carbon neutrality， and carbon sequestration and emission reduction in China’s grasslands.

Research status and development prospects of dual-purpose crops （grain and forage）

Liu-xing XU, Yuan-yan MENG, Chang-fen LUO, Qi-wang QI, Jin-jing ZHENG, Ji-wang ZHANG, Li LIU, Xiao-long ZHANG, Yu-feng TANG, Dan WU, Rong-jin CAI

2023, 32(2):  201-209.  DOI: 10.11686/cyxb2022055

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With population expansion， acceleration of urbanization processes and increase in household income， food consumption patterns have gradually changed. However， the development of animal husbandry is usually restricted by the availability of feed stocks. The reliable supply of high-quality animal feed is vital to the development of animal husbandry. Dual-purpose crops （grain and forage） alleviate the shortage of winter feed， and make an important contribution to agricultural production systems in regions with integrated agro-pastoral production in some countries. In this study， the current status and development trends in domestic and foreign research on dual-purpose crops is reviewed. Coverage includes： 1） Background of dual-purpose crops； 2） Concept of dual-purpose crops； 3） Representative areas； 4） Forage and grain yields and economic benefits； and 5） Animal utilization and livestock products. In addition， the problems faced and countermeasures implemented in the current dual-purpose crop production system are overviewed， including： 1） Selection of sowing time and sowing rate； 2） Nitrogen fertilizer management after grazing or mowing； 3） The appropriate crop growth stage for grazing or mowing； 4） Selection of germplasm resources. Overall， improper management of dual-purpose crops production （including grazing time， nitrogen application rate， seeding rate， and grazing intensity， among others） increases the risk of reduced grain yield. However， based on the benefits to agricultural production systems， it is profitable to manage crops in a dual-purpose mode.