Table of Content

20 April 2016, Volume 25 Issue 4

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Ecosystem dynamics in the ‘Returning Rangeland to Grassland’ programs, China

ZHANG Hai-Yan, FAN Jiang-Wen, SHAO Quan-Qin, ZHANG Ya-Xian

2016, 25(4):  1-15.  DOI: 10.11686/cyxb2015469

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Grassland in arid, semi-arid and alpine areas has experienced severe degradation in recent decades. To enable restoration of grassland vegetation and sustainable development, the Returning Rangeland to Grassland (RRG) program was initiated in 2003. Based on remote sensing images, meteorological data and ground observed data, this study utilized data fusion, ecological model simulation and scaling transformation to construct the regional macro ecosystem structure, ecosystem quality and dynamics in regions hosting RRG programs. Fractional vegetation cover (FVC), leaf area index (LAI) and net primary production (NPP) were utilised to indicate ecosystem quality. We examined the spatiotemporal characteristics of ecological structure and ecosystem quality in regions where the RRG programs were implemented from 2000 to 2010. Additionally, we analyzed ecosystem evolution characteristics and the driving mechanism of ecosystem change.Grassland ecosystems were dominant in the study area. The ecosystem structure was stable, but grassland experienced local change in farmland, wetland and desert. FVC showed a slight increasing trend for grassland; LAI tended to fluctuate but tended to also increase; NPP increased, ranging from 218.23 g C/(m²·a) in 2000, to 226.30 g C/(m²·a) in 2010, a 3.7% increase. Ecological conditions differed spatially; overall there was improvement but with areas of localized deterioration. The integral level of the sub-region was: the degraded grassland region of eastern Inner Mongolia>the riverhead grassland region of the Qinghai-Tibetan Plateau>the degraded grassland region of Xinjiang>the desert grassland region of western Inner Mongolia-Gansu-Ningxia. The spatiotemporal variation of ecosystems was mainly affected by ecological restoration projects, climate change and human activities. The RRG programs restored degraded grassland and promoted natural grassland protection. The warming-wetting trend observed over this time promoted the restoration of vegetation. Human activities such as overexploitation resulted in conversion of grassland into farmland in some areas.

Temporal and spatial dynamics of grassland fires in Inner Mongolia

ZHOU Huai-Lin, WANG Yu-Hui, ZHOU Guang-Sheng

2016, 25(4):  16-25.  DOI: 10.11686/cyxb2015286

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Analyses of a dataset for grassland fires in Inner Mongolia from 1981 to 2005 showed that there were 3142 grassland fires in the last 25 years. Among them, 68.84% were caused by human activities, 5.19% were caused by lightening, and 25.97% were attributed to unknown causes. Grade Ⅲ and Ⅳ fires accounted for the majority (81.17%) of grassland fires with known causes. The number of grassland fires generally decreased over time, but tended to increase in the early 21st century. Spring and autumn were the main fire seasons, with more human-caused fires in April and more lightning-caused fires in May and June. During the main fire seasons, human-caused fires tended to occur between 9:00 am to 16:00 pm, while lightning-caused fires mainly started between 13:00 pm and 17:00 pm. In terms of geographical distribution, the number of grassland fires in Inner Mongolia decreased from the northeast to the southwest. The areas with the most fires were the Xin Barag Right Banner, the Chenbarhu Banner, and the Yakeshi-Oroqen Autonomous Banner, the total number of fires in these regions ranged from 119 to 187. These results indicate that the grassland fire prevention region in Inner Mongolia should include its central, eastern and northeast regions, and that efforts to detect and control fires should be made in the spring, especially between 9:00 am and 16:00 pm.

Variations in vegetation composition and nutrient characteristics related to aspect in an alpine meadow in the northeast margin of the Qinghai-Tibet Plateau

XU Chang-Lin

2016, 25(4):  26-35.  DOI: 10.11686/cyxb2015481

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Aspect is an important topographical factor that affects illumination, temperature, and soil nutrients, all of which affect the composition and distribution of plant species. In this study, we evaluated the effect of aspect on the soil nutrient characteristics and on the composition and spatial distribution of plant communities in an alpine meadow in the northeast margin of the Qinghai-Tibet Plateau. The dominant and subdominant species in grassland communities were Leymus secalinus, Stipa krylovii, and Koeloria cristata (Gramineae) on sunny slopes and Kobresia humilis and Kobresia capillifolia (Cyperaceae) and Melilotoids ruthenica var. inschanica (Leguminosae) on shady slopes. The herbage height, α-diversity index, and number of plant species in grasslands were greater on shady slopes than on sunny slopes, while the β-diversity indexes of grasslands were similar between shady and sunny slopes. The plant life-form spectrum both on sunny and shady slopes mainly consisted of hemicryptophytes and geophytes, accounting for 89% and 71% of the total number of species, respectively. There were more annual and biennial plants and hemicryptophytes on sunny slopes than on shady slopes, but more hemicryptophytes on shady slopes than on sunny slopes. There were similar numbers of geophytes on sunny and shady slopes. The plant families contributing to total biomass in grassland communities on sunny slopes were Gramineae (78.3%)>Cyperaceae (8.3%)>Asteraceae (6.4%)>others (7%); and to grassland communities on shady slopes were Cyperaceae (54.3%)>Leguminosae (16.4%), Gramineae (14.8%)>Polygonaceae (5.3%), Asteraceae (4.6%), and others (4%). For all of the plant families except for the Asteraceae, the contribution to total biomass differed significantly between sunny and shady slopes, but the contribution to total aboveground biomass was similar between sunny and shady slopes. The nitrogen content in the 0-20 cm soil layer was higher on the shady slope than on the sunny slope, while the phosphorus, potassium, copper, and zinc contents in the 10-20 cm soil layer were higher on the sunny slope than on the shady slope. The soil temperature in the 0-30 cm layer was higher on the sunny slope than on the shady slope, whereas the water content in the 0-40 cm soil layer was higher on the shady slope than on the sunny slope. Together, these results show that aspect plays an important role in the composition of vegetation communities and in the physical and chemical properties of soil in alpine meadows.

Biomass allocation patterns in the temperate meadow steppe in Inner Mongolia

HU Fei-Long, YAN Yan, LU Xiao-Qiang, WU Jun, DING Hui, LIU Zhi-Min

2016, 25(4):  36-44.  DOI: 10.11686/cyxb2015305

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Grasslands are one of the most widespread landscapes worldwide, covering approximately one-fifth of the world’s land surface. Although China’s grasslands cover only 6%-8% of the world’s total grassland area, they store 9%-16% of the total carbon in the world’s grasslands. Many studies have focused on monitoring and understanding the factors affecting carbon partitioning; however, the role of species composition in carbon partitioning is still not fully understood. In this study, we evaluated the biomass distribution patterns and other indexes of vegetation in the meadow steppe of northern China, based on geographic information systems (GIS) tools and field data for different community types. The results showed that the average biomass carbon density was 566.35 g C/m² in the temperate meadow steppe. Among the different plant communities, Sanguisorba officinalis with 460.63 g C/m² had the highest aboveground biomass (AGB), while a tessellated meadow had the highest belowground biomass (BGB). However, there were no significant differences in BGB among other types of plant communities (P>0.05). The temperate meadow steppe contributed 111.20 Tg biomass carbon within an area of 12.90×10⁶ hm², where the AGB was 27.57 Tg and the BGB was 83.63 Tg. The root∶shoot in the temperate meadow steppe was 3.03. There were two types of BGB distribution: the exponential function type, in which BGB was mainly distributed in the first 0-10 cm soil depth, and the quadratic function type, in which the BGB was mainly distributed at soil depths of 0-10 cm and 20-40 cm. The BGB distribution was the exponential function type in the Filifolium sibiricum, Achnatherum splendens, Hordeum agriocrithon, S. officinalis, Stipa baicalensis, Carex tristachya, and the tessellated meadow communities, indicating that this type of BGB distribution was a characteristic of grassland communities. The Calamagrostis epigeios, Caragana microphylla, and Phragmites australis communities showed a BGB distribution that fitted the quadratic function, rather than the exponential function. Evaluation of grassland biomass carbon storage by different grassland communities is meaningful for understanding carbon storage dynamics. The results of this study provide a theoretical basis for developing management strategies and designing research on natural grasslands in northern China.

Plant community characteristics, soil organic carbon and soil biological properties of grassland desertification sites in Northwest Sichuan

SHU Xiang-Yang, HU Yu-Fu, JIANG Shuang-Long, MA Chang, LI Yi-Ding, PU Qin, WANG Qian

2016, 25(4):  45-54.  DOI: 10.11686/cyxb2015523

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Changes in surface vegetation cover, soil organic carbon and soil microorganisms associated with alpine grassland desertification in Northwest Sichuan were explored. We studied the surface vegetation cover, aboveground and underground biomass and the vertical distribution of soil organic carbon and microorganisms in different grassland on sandy soils using repeated sampling. The results showed that with aggravation of desertification, vegetation cover and aboveground and underground biomass decreased sharply. Compared with grassland not undergoing desertification, aboveground biomass of grassland suffering mild, medium, heavy and severe desertification was decreased by 13.0%, 91.8%, 76.5% and 40.6% respectively. Underground biomass decreased by 21.4%, 44.0%, 83.4% and 94.7% respectively. With the increase of the degree of desertification, soil organic carbon and humus carbon fractions showed a declining trend, most obvious in the 0-20 cm soil layer. There were differences among different soil layers but there were no differences between grassland undergoing heavy and severe desertification. The degree of desertification also influenced the number of soil microorganisms (bacteria, fungi, actinomycetes) and microbial biomass carbon and nitrogen; desertification reduced all of these soil traits.

Influence of cutting interval on soil enzyme activity and nutrients in Leymus chinensis meadow

QIN Yan, HE Feng, TONG Zong-Yong, CHEN Bao-Rui, LI Xiang-Lin

2016, 25(4):  55-62.  DOI: 10.11686/cyxb2015549

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Soil enzymes are essential bioactive substances and among the most active components of soil ecosystems closely relation with the nutrient status of soils.This paper focused on the influence of cutting interval on soil enzyme activities and nutrients and their relationships in Leymus chinensis meadow in Hulunber. Soil urease and alkaline phosphorus activity were most sensitive to forage cutting intervals. Compared with the annual cutting, soil urease activity was enhanced 0.4-1.0 times in the top 30 cm compared with forage cutting intervals between 2 and 6 years whereas soil alkaline phosphatase activity decreased by 28.9%-44.2%. Soil nutrients were influenced greatly by cutting. Longer cutting intervals did not result in significant differences in soil total nitrogen, available nitrogen, total phosphorus, available phosphorus and available potassium, but soil organic matter was increased 10.5% in the 0-30 cm soil layer when grassland was cut every 6 years. With increasing cutting interval, variation in soil total nitrogen and organic matter content in the 30-60 cm soil layer were 0.36-0.66 g/kg and 12.26-17.73 g/kg respectively, but available phosphorus and potassium content were reduced. Correlations between soil nutrients and enzyme activities differ with forage cutting interval.It is concluded that annual cutting does not adversely affect soil meaning that cutting L. chinensis meadow annually is a useful strategy for its management.

Inorganic phosphorus in a regosol (purple) soil under long-term phosphorus fertilization

HAN Xiao-Fei, GAO Ming, XIE De-Ti, WANG Zi-Fang, CHEN Chen

2016, 25(4):  63-72.  DOI: 10.11686/cyxb2015509

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The Jiang Bofan-Gu Yichu Inorganic Phosphorus Grading System was used to grade measurements of different inorganic phosphorus forms in the 0-100 cm soil layer under a long term (22 years) fertilizer application trial.Total phosphorus, available phosphorus and inorganic phosphorus all increased in soils receiving long-term application of chemical phosphate fertilizer and treatments combining organic and chemical fertilizer [pig manure+NPK (M+NPK)].Available phosphorus increased by a factor of six while available phosphorus, total phosphorus, and various forms of inorganic phosphorus reduced in soil without fertilizer. In addition the Fe-P and Ca₁₀-P content in the lower soil layers were higher than those in the upper layers; the same trend was apparent in all inorganic phosphorus forms. The distribution profiles for inorganic phosphorus including Ca₂-P, Al-P, Ca₈-P, and O-P were similar, all reduced rapidly between 20-60 cm soil depth but few changes were observed at 80-100 cm depth. The relative contribution of various forms of inorganic phosphorus to soil phosphorus was Ca₂-P(0.9569)>Al-P(0.9265)>Ca₈-P(0.9100)>Fe-P(0.8277)>Ca₁₀-P(0.7449)>O-P(0.7362). Long-term application of organic and inorganic fertilizers to regosol soil could significantly increase the accumulation of phosphorus, suppress phosphorus fixation, enhance phosphorus mobility and improve phosphorus use efficiency.

Effects of different temperature and moisture conditions on seed germination of Festuca sinensis

WANG Jian-Jun, MA An-Wei, WANG Zhi-Gang, CAI Yu, KUANG Yu, TIAN Pei

2016, 25(4):  73-80.  DOI: 10.11686/cyxb2015301

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The aim of this study was to determine the most suitable moisture and temperature conditions for seed germination of Festuca sinensis. The germination of F. sinensis seeds was evaluated at 15, 20, and 25℃, and under different moisture conditions imposed using various concentrations of polyethylene glycol (PEG). The F. sinensis seeds showed different germination features under different moisture and temperature conditions. The highest germination rate was at 25℃ and the lowest was at 15℃, suggesting that higher temperatures are beneficial for seed germination. At 15 and 20℃, the seed germination rate, germination potential, germination index, and vigor index of seeds were significantly higher in the -0.2 MPa water treatment than in the control and the other treatments (P<0.05). These results indicated that a low PEG concentration can improve F. sinensis seed vigor under low temperatures. However, at 25℃, the germination rate and germination index of seeds were higher in the control than in the PEG treatments (P<0.05) suggesting that PEG inhibited the germination of F. sinensis seeds at higher temperatures. The degree of inhibition increased with increasing PEG concentrations. As the PEG concentration increased, there were decreases in the seed germination rate, germination index, plumule length, radicle length, shoot ratio of seeds, seedling moisture content, and drought resistance. Together, these results show that a low concentration of PEG can promote F. sinensis seed germination whereas high concentrations of PEG can decrease seed vigor.

Growth of Suaeda salsa tin response to salt stress in different habitats

PENG Bin, XU Wei, SHAO Rong, FENG Gong-Neng, SHI Wen-Yan

2016, 25(4):  81-90.  DOI: 10.11686/cyxb2015312

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The influence of salt (0, 200 and 400 mmol/L NaCl; 0, 200 and 400 mmol/L KCl) on growth, ion accumulation, chlorophyll fluorescence and gas exchange in leaves and antioxidant levels was assessed in Suaeda salsa plants from different habitats; intertidal and inland saline. 200 mmol/L NaCl significantly increased shoot fresh weight and dry weight and succulence of S. salsa plants, while 400 mmol/L NaCl and all KCl treatments resulted in reduced growth. The concentrations of Na⁺ and Cl^- were increased by NaCl treatments while the concentration of K⁺ significantly decreased. Similarly KCl treatments resulted in increasing K⁺ and Cl^- concentrations accompanied by a marked reduction in Na⁺ concentration. The 200 mmol/L NaCl treatment had no effect on net photosynthesis, photosynthetic oxygen evolution rate, F_v/F_m and φPSⅡin S. salsa, but KCl treatments resulted in a significant decrease in these traits. In addition, 200 mmol/L NaCl resulted in a significant increase in the SOD activity whereas 400 mmol/L NaCl and all KCl treatments markedly decreased SOD activity. Interestingly, the POD activity in S. salsa was significantly increased by all NaCl and KCl treatments. Shoot fresh weight and dry weight, succulence, net photosynthesis, photosynthetic oxygen evolution rate and ion concentration (Na⁺ and Cl^-) of S. salsa plants from the intertidal zone were lower than that those from an inland saline areas. The salt stress effect of KCl was greater than that of NaCl. Saline stress in S. salsa plants from saline inland habitats was significantly greater than plants from an intertidal zone.

Effect of exogenous 2,4-epibrassinolide on the uptake, transport, and disputation of ions, and photosynthetic characteristics of Medicago sativa seedlings under NaCl stress

KOU Jiang-Tao, KANG Wen-Juan, MIAO Yang-Yang, SHI Shang-Li

2016, 25(4):  91-103.  DOI: 10.11686/cyxb2015289

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The aim of this study was to explore the salt resistance and physiological regulation mechanisms induced by exogenous 2,4-epibrassinolide (EBR) in alfalfa (Medicago sativa) seedlings. The effect of EBR on photosynthetic pigment contents, gas exchange parameters, and ion uptake, transport, and disputation in seedlings of M. sativa cv. Zhongmu No.3 and M. sativa cv. Longzhong under NaCl stress were investigated using a hydroponic method. In the 150 mmol/L NaCl stress treatment, alfalfa seedling leaves showed significant decreases in photosynthetic pigment contents and photosynthetic ability, and disrupted metabolic processes of ion uptake, transport, and disputation. When EBR at 0.1 μmol/L was supplied to seedlings under NaCl stress, the chlorophyll a, b, and a+b contents increased, the chlorophyll a/b increased, and the chlorophyll/carotenoid decreased. Also, the photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, and photosynthetic ability increased after 0.1 μmol/L EBR treatment. These changes would facilitate the accumulation of aboveground and underground biomass. In the NaCl-stressed seedlings treated with 0.1 μmol/L EBR, the Na⁺ and Cl^- contents and the Cl^-/Na⁺ in different organs (leaf, stem, and root) significantly decreased, and the contents of K⁺, Ca²⁺, and Mg²⁺ and the K⁺/Na⁺, Ca²⁺/Na⁺, and Mg²⁺/Na⁺ significantly increased. The transport ratio of inorganic ions and transport selectivity ratio of cations were effectively regulated in the seedlings treated with EBR. Together, these results show that EBR treatment effectively alleviated photo inhibition caused by NaCl stress in alfalfa seedlings, and promoted the synthesis and accumulation of organic matter. Treatment with EBR also improved the selective absorption and transport of inorganic ions, helping to maintain the metabolic ion balance and improve the NaCl-resistance of alfalfa seedlings.

Changes in physiological and biochemical characteristics, contents of bioactive compounds, and antioxidant capacity of Hypericum perforatum during introduction and acclimatization

KANG Xia, GE Li, LI Meng-Fei, GAN Yan-Tai, LI Jing-Yao, WANG Ke-Peng

2016, 25(4):  104-110.  DOI: 10.11686/cyxb2015385

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In this study, we investigated the changes in bioactive compounds in wild and cultivated Hypericum perforatum during introduction and acclimatization. Physiological and biochemical characteristics, bioactive compound contents, and antioxidant capacity were evaluated for H. perforatum plants at the flowering stage. The net photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll content, and root activity were higher in cultivated plants than in wild plants. The flowering date was 7 days earlier in the cultivated plants than in the wild plants, and the dry weight of aboveground parts was 16.67% higher in cultivated plants than in wild plants. The total flavonoid and hypericin contents in the same organ did not differ significantly between the wild and cultivated plants. The total phenolic contents in flowers were higher in wild plants than in cultivated plants, while the opposite trend was observed for total phenolic contents in the leaves. Both wild and cultivated plants had higher total flavonoid and phenolic contents in the flowers and leaves than in the stem, while the highest hypericin content was in the flowers, followed by leaves, and then stems. The antioxidant capacity of the wild and cultivated plants was highest in the flowers followed by leaves, and then stems. There was no difference in the antioxidant capacity of leaf and stem extracts between wild and cultivated plants, while the antioxidant capacity of flower extracts was significantly stronger in cultivated plants than in wild plants. These results indicate that the cultivated plants not only showed strong acclimatization abilities, but also had bioactive compound contents and an antioxidant capacity similar to those of wild plants.

Taxonomy of Pleurospermum (Apiaceae) species in China based on micromorphology of fruit

WEI Xue-Ying, LIU Mei, RU Jian, WANG Yu-Ting, WANG Chao-Qun, GUO Shi-Qi

2016, 25(4):  111-120.  DOI: 10.11686/cyxb2015284

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The micromorphology of the fruits of 21 species of Pleurospermum (Apiaceae) was evaluated for the first time in this study. The wing, exocarp, mesocarp, vascular bundle, secretory duct, commissure, endosperm, and crystals of the fruits of 21 Pleurospermum species were observed under a light microscope. The structure of Pleurospermum fruits varied greatly and the studied taxa could be divided into three groups. In group one (three taxa including P. hookeri) and group two (seven taxa including P. angelicoides), the wing margins were not wavy, the outer walls of the exocarp were flat, and the exocarp was difficult to separate from the mesocarp. Spherical crystals were present in the mesocarp in group one but not group two. In group three (11 taxa including P. franchetianum), the wing margins were wavy, the outer walls of the exocarp bulged, and the exocarp was easily separated from the mesocarp. There were no spherical crystals in the mesocarp of group three. These analyses of the micromorphology of fruits confirmed that the genus Pleurospermum is polyphyletic, that there is a close relationship between P. hookeri and P. yunnanense, and provided evidence to support the placement of P. decurrens, P. franchetianum, and related taxa into the tribe Pleurospermumeae. The results of this study also provide morphological data for further research on this genus and related taxa.

Molecular cloning and characterization in tobacco of LpGCS from perennial ryegrass

WEI Shu-Qiang, SUN Zhen-Yuan, DAI Xiao-Mei, QIAN Yong-Qiang

2016, 25(4):  121-132.  DOI: 10.11686/cyxb2015288

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Degenerate primers were designed using CDS sequences of homologous genes and the γ-glutamylcysteine synthetase gene LpGCS was cloned from perennial ryegrass (Loliumperenne) using RT-PCR and RACE techniques, with leaves of ‘Top hat Ⅱ’ as the test material. The full-length sequence of LpGCS gene was 1674 bp (GenBank accession number: KJ551844) with a complete open reading frame (ORF) of 1125 bp. Amino acid sequence identity, structure and homologous sequences with amino acids of 8 other homologous genes were studied and predicted. The protein molecular weight was 42.86 kDa (unstable protein) and its main secondary structure being an alpha helix. The protein amino acid sequence had relatively high homology with 8 other homologous amino acid sequences and had higher homology with graminaceous plants, such as wheat (Triticum aestivum), stiff brome (Brachypodium distachyon) and Japanese rice (Oryza sativa Japonica Group). In addition, sense and antisense plant expression vector pCAMBIA-Ubi-LpGCS+ and pCAMBIA-Ubi-LpGCS- were successfully constructed and transgenic tobacco obtained by agrobacterium mediated transformation. The transgenic tobacco with LpGCS+ grew faster and flowered earlier than the transgenic tobacco with LpGCS-. Exposed to Cd²⁺ stress (10 days), physiological and biochemical tests of transgenic and wild-type tobacco showed that the MDA content of LpGCS+ transgenetic plants was lower than the wild type, and POD, SOD and CAT activity higher than those of the wild type. In contrast, the MDA content of LpGCS- transgenetic plants was higher than the wild type and POD, SOD and CAT activity lower. In summary, overexpression of the LpGCS gene in tobacco plants could improve resistance to Cd²⁺ stress and lay the foundation for the genetic transformation of perennial ryegrass cultivars able to tolerate heavy metals.

Effects of RNAi expression of the ARF gene on enzyme activity at different developmental stages and storage temperatures in potato

ZHOU Xiang-Yan, ZHANG Ning, LIU Bai-Lin, PEI Rui-Fang, SI Huai-Jun, WANG Di

2016, 25(4):  133-139.  DOI: 10.11686/cyxb2015194

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ADP ribosylation factor (ARF) gene expression interference in a transformed potato cultivar “Gannongshu 2” was evaluated. Real time fluorescence quantitative polymerase chain reaction (qRT-PCR) showed that the relative expression of the ARF gene varied in the transgenic plants at different developmental stages and increased slightly at latter growth stages, indicating that ARF gene interference expression varied with maturity.Enzyme activity in the leaves was effected by ARF gene interference expression. For leaves of transgenic plants at different development stages, PPO activity increased by 11.61%-27.84%, NR activity increased by 21.10%-41.32%, PLD activity decreased 2.88%-57.64% SPS activity increased by 29.00%-39.57% when compared with the control. Relative expression of the ARF gene in stored tubers under different storage temperatures (room temperature and 4℃)showed the same trend; initially decreasing and then increasing. For transgenic tubers stored at room temperature, the activity of PPO increased by 30.44%-56.28%, NR activity increased by 17.41%-40.92%, PLD activity decreased 24.39%-85.11%, SPS activity increased by 30.89%-45.78% when compared with transgenic tubers stored at 4℃. For non-transgenic tubers stored at room temperature, PPO activity increased by 25.11%-70.66%, NR activity increased by 36.07%-89.62%, PLD activity decreased 11.35%-72.64% and SPS activity increased by 27.31%-61.33%.This study investigated the effect of RNAi expression of ARF gene on physiological and biochemical characteristics in potato to provide a theoretical basis for further study of the regulation role of the ARF gene in potato of different growth and stage of development.

Effect of the Epichloё endophyte on the soil nematode community in the rhizosphere of Achnatherum inebrians

GUO Chang-Hui, LI Xiu-Zhang, LIU Li, CAO Jian-Xin, LI Chun-Jie

2016, 25(4):  140-148.  DOI: 10.11686/cyxb2015308

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The aim of this study was to determine the effect of the Epichloё endophyte on soil nematodes and their community characteristics in the rhizosphere of Achnatherum inebrians. Soil nematodes were isolated and identified from the rhizosphere of A. inebrians plants grown with (E+) or without (E-) the Epichloё endophyte. A total of 11889 soil nematodes were collected, belonging to 37 genera, 22 families, six orders, and two classes. The individual density of soil nematodes was higher in soil of E+ plants than in soil of E- plants. The generic number, Shannon-Wiener index, Pielou index, and Margalef index were lower in E+ soil than in E- soil, whereas the diversity index did not differ significantly between the two treatments. The results suggested that the Epichloё endophyte had a limited effect on the diversity of soil nematodes of A. inebrians. The maturity index (MI) of soil nematodes was significantly higher in the E+ soil than in the E- soil, whereas the plant parasite index (PPI) and PPI/MI were significantly lower in the E+ soil than in the E- soil. The presence of the Epichloё endophyte had a significant effect on MI, PPI, and PPI/MI. These results show that the Epichloё endophyte can change the composition of functional groups of soil nematodes, especially that of plant-parasitic nematodes.

Resistance of Roegneria kamoji (Poaceae: Triticeae) populations to stripe rust and powdery mildew

ZHAO Fu-Qiang, ZHANG Hai-Qin, SUN Zong-Hua, JIAO Zhen-Fei, LIU Xiao-Yan, CHEN Wei-Huan, CHEN Guo-Yue, ZHOU Yong-Hong

2016, 25(4):  149-158.  DOI: 10.11686/cyxb2015309

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Disease-resistant grasses can serve as a germplasm resource to breed resistant varieties of wheat and forage grasses. The aim of this study was to screen populations of Roegneria kamoji for their resistance to two common pathogens, stripe rust (Puccinia striiformis) and powdery mildew (Blumeria graminis). Adult plants of 34 populations of R. kamoji (33 wild germplasms, and one cultivated variety) from domestic regions or introduced from overseas were evaluated to determine their resistance to the two pathogens in field trials. The degree of disease resistance differed among the 34 populations. Among the 34 populations of R. kamoji infected by stripe rust, the disease severity ranged from 11.49% to 50.46%, the disease incidence ranged from 19.85% to 74.24%, and the disease index ranged from 2.63-37.60, with a coefficient of variation of 30.01%, 26.54%, and 49.67%, respectively. The infection type range and occurrence degree index range were 1-4 and 1-5, respectively. The disease indexes were significantly positively correlated (P<0.01). In cluster analyses based on the above indexes, the 34 populations of R. kamoji clustered into four groups: highly resistant (HR), moderately resistant (MR), moderately susceptible (MS), and highly susceptible (HS). The proportion of the 34 populations in the HR, MR, MS, and HS groups was 17.65%, 11.76%, 50.00%, and 20.59%, respectively. In the powdery mildew field trial, the range of infection type, disease severity, and ratio of diseased plants for the 34 populations of R. kamoji was 0-4, 0%-60% and 0%-100%, respectively. The proposed resistance classifications were as follows: 12 populations for HR, 5 populations for MR, 11 populations for MS, and 6 populations for HS (35.29%, 14.71%, 32.35%, and 17.65% of the populations, respectively). These results show that the accessions ZY 1007 and Pr 87-88 344 are resistant to both stripe rust and powdery mildew. Therefore, these accessions would be excellent resources for breeding disease-resistant wheat crops and forage grasses.

Effect of alfalfa flavonoids on bovine mammary epithelial cell cultures in vitro under heat stress

ZHAN Jin-Shun, WEI Ming-Ji, SU Xiao-Shuang, ZHAN Kang, LIU Ming-Mei, ZHANG Chun-Gang, ZHAO Guo-Qi

2016, 25(4):  159-165.  DOI: 10.11686/cyxb2015317

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The aim of this study was to evaluate the effect of alfalfa flavonoids on in vitro bovine mammary epithelial cells under heat stress. Bovine mammary epithelial cells were cultured on media with different concentrations of alfalfa flavonoids (0, 25, 50, 75, and 100 μg/mL) at 37℃ with 5% CO₂ for 72 h. Then, the cultured cells were subjected to a heat-shock treatment (42℃ for 1 h) before being returned to 37℃ with 5% CO₂ for 12 h. The cell activity, antioxidant index, and gene transcript levels were evaluated. The results showed that the cell activity was significantly higher in the 25 μg/mL treatment group than in the 0 and 50 μg/mL treatment groups (P<0.05), but cell activity did not differ significantly among the other groups. Compared with the control group (0 μg/mL) the 50, 75, and 100 μg/mL treatment groups showed significantly higher glutathione peroxidase activity (P<0.01) and significantly lower lactate dehydrogenase activity and malondialdehyde contents (P<0.01 and P<0.05, respectively). The catalase activity did not differ significantly among the five groups. Compared with the control group (0 μg/mL), the 50 and 75 μg/mL treatment groups showed reduced transcript levels of Caspase3 and Socs3, and the 25 μg/mL group showed significantly increased transcript levels of P53, Stat1, and Socs1 (P<0.01 or P<0.05). The transcript levels of Bcl-2 and Fas did not differ significantly among the groups. Together, these results show that alfalfa flavonoids can increase cell activity and antioxidant capacity and inhibit cell apoptosis, and that the optimal concentration of alfalfa flavonoids is 75 μg/mL.

Kinetics of in situ degradation of Leymus chinensis stems in the dairy cow rumen and changes in cellulolytic bacteria in digesta

XU Jun, HOU Yu-Jie, ZHAO Guo-Qi, LUO Lin-Guang

2016, 25(4):  166-171.  DOI: 10.11686/cyxb2015298

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In this study, we investigated the degradation characteristics of Leymus chinensis stems in the dairy cow rumen and evaluated the changes in cellulolytic bacteria during the degradation process. L. chinensis stems were cut and packed into six nylon bags, which were incubated for 6, 12, 24, 48, and 72 h in the rumen of a dairy cow. Changes in the ultra-structure of L. chinensis stems during digestion in the rumen were evaluated by scanning electron microscopy. L. chinensis stems incubated for 0.5, 2, 6, 12, 24, 48, and 72 h in the rumen were evaluated to determine their neutral detergent fiber (NDF) digestibility. The cellulolytic bacteria in these digesta samples were also analyzed. The results showed that the non-lignified parenchymal tissue and phloem were quickly degraded and the vascular bundle was released from the plant tissues after degradation of the parenchymal tissue. The main bacterial species attached to the stem tissues were Fibrobacter succinogenes>Ruminococcus albus>Ruminococcus flavefaciens. The numbers of these bacteria peaked at 24 h (10⁹/g dry matter for F. succinogenes and 10⁵/g for R. flavefaciens) or 12 h (10⁸/g DM for R. albus) of digestion in the rumen. The numbers of cellulolytic bacteria in digesta remained constant after 24 h, while the disappearance of NDF from the L. chinensis stems showed a linear increase up to 72 h of digestion. These results suggest that the disappearance of NDF from the L. chinensis stem is not synchronized with changes in the populations of cellulolytic bacteria in digesta, and may instead be related to a delayed increase in the activities of fibrolytic enzymes.

Effect of starter supply age on the morphology of the rumen and small intestine in lamb

WANG Xiao-Juan, LIU Ting, LI Fa-Di, LI Chong, WANG Wei-Min, TANG De-Fu, LI Bao-Sheng, WANG Guo-Xiu, TIAN Hua-Qin, XI Rui

2016, 25(4):  172-178.  DOI: 10.11686/cyxb2015187

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The age at which starter is supplied to lambs can affect the development of the intestinal tract. To determine the effect of the age of starter supply on the morphology of the rumen and small intestine of lambs, 72 healthy male Hu lambs (two lambs per litter, birth weight 3.51±0.52 kg) were randomly divided into two groups: one group was supplied with starter at 7 days after birth and the other at 42 days after birth. Six lambs were selected at random for slaughter on day 14, 28, 42, 56, 70, and 84, respectively. The results showed that the rumen papillae in the dorsal sac and the ventral sac were significantly longer in the 7-day group than in the 42-day group at 42 days (P<0.05). Also, the rumen papillae in the ventral sac tended to be wider in the 7-day group than in the 42-day group at 42 days (P=0.053). The rumen muscle layer in the dorsal sac was thicker in the 7-day group than in the 42-day group at 42 days (P<0.05). The villus length, and the ratio of villus length to crypt depth of the duodenum and ileum were significantly greater in the 7-day group than in the 42-day group at 42 days (P<0.05). The depth of the ileum crypt was smaller in the 7-day group than in the 42-day group at 42 days (P<0.05). Together, these results show that supplying starter from 7 days of age could improve the development of the rumen epithelium before 84 days and the small intestinal mucosa before 42 days.

Effect of substituting hulless barley straw for tall fescue on early fermentation quality and aerobic stability of mixed-ration silage in Tibet

JIA Chun-Wang, YUAN Xian-Jun, XIAO Shen-Hua, LI Jun-Feng, BAI Xi, WEN Ai-You, GUO Gang, SHAO Tao

2016, 25(4):  179-187.  DOI: 10.11686/cyxb2015325

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The objective of this study was to evaluate the effects of substituting hulless barley straw for tall fescue at different ratios on the early fermentation quality and aerobic stability of total mixed ration silage in Tibet. The experiment consisted of the control (TH₀) and three treatments (TH₅, TH₁₀, and TH₁₅). The silos containing these treatments were opened at 14 days after the start of ensiling and the fermentation quality, chemical composition, and microbial communities were analyzed. The aerobic stability of silage samples on the 2nd, 5th, and 8th day of exposure to air was evaluated using an online multi-channel data logger temperature recorder. The results showed that the pH, and the contents of lactic acid, acetic acid, total volatile fatty acids (TVFA), and alcohol did not differ significantly between TH₅ and TH₀ (P>0.05). The pH of TH₁₀ was similar to that of TH₀ (P>0.05), but the lactic acid, acetic acid, TVFA, and alcohol contents differed significantly between TH₁₀ and TH₀ (P<0.05). The lactic acid, acetic acid, propionic acid, butyric acid, TVFA, and alcohol contents were significantly lower in TH₁₅ than in TH₀ (P<0.05), while the pH of TH₁₅ was markedly higher (P<0.05) than that of TH₀. The ammonia nitrogen/total nitrogen and lactic acid/acetic acid ratios did not differ significantly (P>0.05) between all treatments and the control. Lactic acid fermentation was dominant in all silages and they all had good fermentation quality. During exposure to air, pH and the ammonia nitrogen/total nitrogen increased in all treatments and the control continued to increase after the 2nd day of exposure to air. However, the contents of lactic acid, acetic acid, and water soluble carbohydrates decreased during exposure to air, and the numbers of yeasts and aerobic bacteria increased. The temperatures in TH₅ and TH₁₀ silages began to increase at 35 h after opening the silos, while the temperature increase was delayed, and was smaller, in TH₁₅. Together, these results showed that TH₁₅ had the best aerobic stability. Taking into account the fermentation quality, aerobic stability, and maximum use of hulless barley straw, the TH₁₅ treatment was the most suitable choice for silage production.

Effects of mixed silage modes on the fermentation quality and in vitro gas dynamics of a sorghum-sudangrass hybrid (Sorghum bicolor×Sorghum sudanense)

LIANG Huan, LIU Gui-Bo, WU Jia-Hai, ZENG Bing, LI Yuan, YOU Yong-Liang, ZHAO Hai-Ming

2016, 25(4):  188-196.  DOI: 10.11686/cyxb2015271

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The fermentation quality of sorghum-sudangrass hybrids (Sorghum bicolor×Sorghum sudanense) is poor because of their high moisture contents. In this study, we analyzed the effects of different storage modes on the fermentation quality of a sorghum-sudangrass hybrid. A sorghum-sudangrass hybrid was mixed different types of hay (corn stalk, wheat straw, and alfalfa hay) at different proportions (12.5, 25.0, 37.5 and 50.0 kg/t). Then, the nutritive value, fermentation quality, 72 h dry matter digestibility, and gas dynamics were measured using an in vitro system that simulated rumen fermentation. The results showed that the silage produced from the sorghum-sudangrass hybrid had a high butyric acid content, and a poor Flieg evaluation ranking. The addition of all types of hay significantly improved the fermentation quality of stored silage. The addition of wheat straw resulted in the best fermentation quality, while the addition of alfalfa hay resulted in the best nutritive value. The addition of alfalfa hay resulted in the highest values for IVDMD (in vitro dry matter digestibility), c (gas production speed), and AGPR (speed when gas production was one-half of the maximum). There was no significant difference in GP_72h (accumulated gas production in 72 h), A (ideal maximum gas production), and lag (lag time of gas production) among silages produced with the three types of hay. In terms of the amount of hay added, the addition of 25.0 kg/t resulted in the best fermentation quality and the highest half-time content, and the addition of 50.0 kg/t resulted in the best nutritive value and the highest IVDMD. The addition of 37.5 kg/t hay resulted in the highest c and AGPR values. The amount of hay added did not significantly affect GP_72h, A, or lag. Considering the nutritive value and fermentation quality, the best mixed silage was produced by adding 37.5 kg/t wheat straw. The addition of 50.0 kg/t alfalfa hay gave the highest IVDMD content, the addition of 37.5 kg/t alfalfa hay gave the highest gas production rate, and the addition of 50.0 kg/t wheat straw resulted in the highest GP_72h and A.

Screening of cellulose-degrading bacteria and evaluation of silage performance of Pennisetum

HUANG Qin-Lou, ZHONG Zhen-Mei, HUANG Xiu-Sheng, CHEN Zhong-Dian, FENG De-Qing, XIA You-Guo

2016, 25(4):  197-203.  DOI: 10.11686/cyxb2015290

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Cellulose-degrading bacteria play important roles in improving forage quality and increasing forage utilization. In this study, a variety of cellulose-degrading bacteria were screened to identify strains with high enzyme activity. Three strains (designated as No.11, No.21, and No.36) were selected from the screening experiment and used to produce silage from hybrid Pennisetum. The four treatment groups consisted of treatment 1 (control, CK; hybrid Pennisetum without broth), and treatments 2, 3, and 4 (hybrid Pennisetum with broth of strain No.11, 21, and 36, respectively). The addition of cellulose-degrading bacteria into silage of hybrid Pennisetum increased the lactic acid content. The lactic acid contents of treatments 2, 3 and 4 were 19.42% (P<0.05), 38.35% (P<0.05), 4.85% (P>0.05) higher, respectively, than that in CK. The neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose (HC) contents of silage were lower in treatments 2, 3, and 4 than in CK and in the Pennisetum mixtures before ensiling. The silage produced in treatment 3 had the lowest NDF, ADF, and HC contents. The three strains screened from many cellulose-degrading bacteria improved silage quality, and degraded cellulose to different degrees. Among the three strains, No.21 showed the best performance in degrading cellulose of hybrid Pennisetum and produced silage with the best nutritional quality.

Effect of lactic acid bacteria on corn silage quality and stability after aerobic exposure

WAN Xue-Rui, WU Jian-Ping, LEI Zhao-Min, HE Yi-Qun, WU Run

2016, 25(4):  204-211.  DOI: 10.11686/cyxb2015397

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To investigate the effect of lactic acid bacteria (LAB) with antibacterial activity on the number of LAB, aerobic bacteria, yeasts and molds and pH of whole corn silage during fermentation and aerobic exposure, 5 LAB strains collected from corn silage across Gansu were added to whole corn silage. The results showed that the number of LAB was significantly increased by adding LAB to silage and the number of aerobic bacteria, yeasts and molds significantly reduced and pH reduced after addition of Leuconostoc mesenteroides subsp. Mesenteroides B1-7, Pediococcus pentosaceu B2-3, Lactobacillus plantarum B3-1, Enterococcus faecium B5-2 and Lactobacillus fermentum E2-3 compared with the control (no LAB added). At the beginning of fermentation the number of LAB in B1-7 and B5-2 treatments was highest. After aerobic exposure (7 to 30 days),the number of LAB was highest, aerobic bacteria, yeasts and molds lowest, and pH lowest in the B3-1 strain treatment. These results indicate that all added LAB had a potential role in improving the quality of silage and aerobic stability but L. plantarum B3-1 was the most effective.

The evolutionary causes of rodent group-living: Hypotheses

WEI Wan-Rong, MA An-Wei, HE Kai, ZHANG Wei-Guo

2016, 25(4):  212-221.  DOI: 10.11686/cyxb2015520

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This paper describes 7 hypotheses concerning group-living rodents which are accepted by most researchers. The resource-defense hypothesis believes that group-living individuals may become more efficient in obtaining and protecting resources than solitary-living conspecifics when resources (food, water, shelter) are non-uniformly distributed. The predatory risk hypothesis states that sociality should prevail in riskier habitats because group-living can reduce the risk of predation. The social thermoregulation hypothesis suggests that group-living could reduce the energy consumption in relatively cold habitats. The aridity food-distribution hypothesis believes that rodents living in arid habitats live in groups to share burrows or minimize the cost of burrow construction. The life-history constraint hypothesis thinks that rodents with smaller size, lower fat reserves, and low rate of postnatal growth are forced to live in groups to be able to successfully foster offspring. The burrow-sharing hypothesis states that rodents are forced to live in groups to share burrow use or minimize the cost of burrow construction. The parental investment hypothesis believes that, because of the continuing investment in offspring, group-living resulted from delay dispersion of offspring. Finally the paper discusses the future research focus on rodent group-living.

Stability of alfalfa and wheatgrass pasture under dry farming in a pastoral agronomy area

WANG Bo-Jie, TANG Hai-Ping, HE Li, LIN Guo-Hui, ZHAO Shi-Jie, ZHAO Ming-Xu

2016, 25(4):  222-229.  DOI: 10.11686/cyxb2015287

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We conducted a 3-year field experiment to analyze the stability of alfalfa (Medicago sativa) and wheatgrass (Agropyron cristatum) pastures under dry farming in Duolun County, Inner Mongolia. The structural and functional stability of pastures were studied by analyzing yield, competition, proportion of weeds, quality, and soil nutrient contents. The results showed that the yields of monocultures and a mixed culture were significantly higher than those of natural grassland, except in the year of establishment. The highest yields were in year 2, and the lowest yields were in year 1. Interspecific competition between alfalfa and wheatgrass in the mixed culture weakened the stability of the pasture because wheatgrass was more competitive than alfalfa. Weeds were controlled in the first and third year; therefore, it would be effective to conduct weeding in year 2. The quality of forage was significantly better in mixed cultures than in monocultures. The contents of soil organic carbon and nitrogen increased in the wheatgrass monoculture, providing adequate nutrition to support pasture stability.

Analysis of soil nutrient characteristics under different land use patterns in the northern piedmont of Yinshan Mountain

GAO Jun-Liang, LUO Feng-Min, GAO Yong, YUAN Wei-Jie, WANG Huai-Liang, DANG Xiao-Hong

2016, 25(4):  230-238.  DOI: 10.11686/cyxb2015311

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The aim of this study was to illustrate differences in the nutrient characteristics of soil under different land use patterns in the northern piedmont of Yinshan Mountain. Soil nutrient characteristics were evaluated under four different land use patterns (enclosed grassland, grazed grassland, farmland, and abandoned land) in field studies, by analyses of field samples, in laboratory analyses, and by mathematical models. The contents of organic matter, total nitrogen (N), total phosphorus (P), and total potassium (K) in soil samples were (25.12±6.56), (0.63±0.08), (0.76±0.10), and (31.99±1.07) g/kg, respectively. The contents of soil available N, available P, and available K were (39.87±9.14), (6.72±3.75), and (175.83±105.45) mg/kg, respectively. The soil pH value was (7.74±0.14). The type of land use pattern significantly affected soil organic matter, total N, total P, available P, and available K (P<0.01), but did not significantly affect the available N, total K, or pH (P>0.05). The total soil nutrient contents and the pH value in the 0-25 cm soil layer showed little variation, but the contents of available soil nutrients and organic matter decreased at deeper soil depths. Based on a comprehensive evaluation of soil fertility, the four plots were ranked from most to least fertile as follows: enclosed grassland (0.506)>grazed grassland (0.417)>farmland (0.361)>abandoned land (0.357). The soil fertility of enclosed grassland and grazed grassland was evaluated as medium, while that of farmland and abandoned land was classified as low. These results suggested that grassland is more beneficial than farmland for maintaining soil fertility. In conclusion, the soil fertility was low in these studied areas, and the contents of total N and available N were especially low.

Cloning and expression of ZjNAC from Zoysia japonica

ZHANG Yin-Bing, SUN Xin-Bo, FAN Bo, HAN Lie-Bao, ZHANG Xue, YUAN Jian-Bo, XU Li-Xin

2016, 25(4):  239-245.  DOI: 10.11686/cyxb2015453

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Proteins in the NAC family (including NAM, ATAF1/2, and CUC2 proteins) are plant-specific transcription factors that play critical roles in plant development. To explore and exploit the excellent resistance-gene resources of zoysia (Zoysia japonica), a gene encoding a NAC transcription factor (ZjNAC) was cloned by blasting the Zoysia transcriptome database. The biological function of the cloned ZjNAC gene was explored by a phylogenetic analysis with OsNACs of rice (Oryza sativa) combined with protein and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analyses. The bioinformatics analysis showed the cloned ZjNAC gene was 1496 bp long, and contained a 1332 bp open reading frame (ORF) encoding 449 amino acids with a NAM domain. In a phylogenetic analysis, the cloned ZjNAC gene showed the highest homology to OsNAC036 from rice, and so the cloned gene was designated as ZjNAC036. The qRT-PCR analysis showed that ZjNAC transcript levels increased under drought stress, reaching peak levels (approximately 50-fold that in the control) after 8 h of drought stress. The transcript levels of ZjNAC did not show obvious variations under salt stress or cold stress. Together, these results show that the protein encoded by ZjNAC036 may play an important role in the drought stress response, rather than the salt or cold stress responses.

Botanical characteristics and medicinal value of five Glycyrrhiza species cultivated in the Hexi region of Gansu

CHEN Xiao-Na, QIU Dai-Yu, LIN Hai-Ming

2016, 25(4):  246-253.  DOI: 10.11686/cyxb2015225

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We evaluated the ecological adaptability and medicinal value of five Glycyrrhiza species (G. uralensis, G. inflata, G. glabra, G. pallidiflora, and G. euycarpa) cultivated in the Hexi region of Gansu, China. The botanical characteristics were analyzed and the contents of glycyrrhizic acid and liquiritin in roots were determined. The botanical characteristics differed among the five species. G. pallidiflora had the highest values for plant height, number of blades, and fresh weight of above-ground parts, and G. eurycarpa had the lowest values for these attributes. The root of G. uralensis was significantly longer than those of other four species, but its fresh weight was not significantly different from those of G. glabra, G. inflata, and G. pallidiflora. The contents of glycyrrhizic acid and liquiritin in roots were significantly higher in 3-year-old plants than in 2-year-old plants. The lowest glycyrrhizic acid content was in roots in 3-year-old plants of G. pallidiflora, but the glycyrrhizic acid content in roots reached the standard of the Chinese Pharmacopoeia in the other four species. Only G. uralensis roots had a liquiritin content that reached standard of the Chinese Pharmacopoeia. Considering these agronomic traits and comprehensive indexes, Glycyrrhiza species show good ecological adaptability and can be cultivated in the desert area of Gansu, and G. pallidiflora can be grown as a windbreak and sand-fixing plant in the Hexi region of Gansu.