Table of Content

20 April 2017, Volume 26 Issue 4

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Sustainable development of the alpine pastoral region in the eastern Tibetan Plateau based on the emergy ecological footprint model

LI Weng-Long, YU Cui, ZHAO Xin-Lai, LIANG Tian-Gang, ZHANG Jin-Lin, XU Jing

2017, 26(4):  1-14.  DOI: 10.11686/cyxb2016186

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Sustainable development is a shared goal of all countries around the world. The assessment of regional sustainability is becoming an important theoretical basis for policy making. Gannan Tibetan Autonomous Prefecture is a typical alpine pastoral region in China. In this region, sustainable development has become a major issue with the ongoing development of animal husbandry. Therefore, we analyzed the sustainable development of counties and cities in Gannan from 2005 to 2013 based on a modified emergy ecological footprint model. Regional emergy densities are the key of the modified model, which was used to quantify the ecological carrying capacity and the ecological footprint. Therefore, this model can truly reflect the supply capacity of ecosystems and human resource consumption in these areas. The results indicated that livestock products accounted for the largest proportion of the ecological footprint in the study area, and remained stable during the study period. The percentage of electricity and coal consumption increased year by year, while the proportion of farming products and wild firewood decreased. The per capita ecological footprint in Gannan increased from 4.77 ha per capita in 2005 to 7.09 ha per capita in 2013. The per capita ecological carrying capacity fluctuated between 4.64 ha per capita and 5.65 ha per capita. The ecological footprint index of Gannan showed a decreasing trend, and its ecological environment had an unsustainable development status during the study period. The ecological footprint per ten thousand yuan GDP in Gannan dropped from 12.60 ha per ten thousand yuan in 2005 to 4.86 ha per ten thousand yuan in 2013, revealing that the resource utilization efficiency had improved. Among the counties and cities, Hezuo had the highest ecological footprint index, followed by Diebu. There were no significant differences among the other counties. In general, the per capita ecological footprint and ecological carrying capacity were higher in regions of animal husbandry development (Maqu, Luqu, Xiahe, and Hezuo) than in regions with a farming-pastoral ecotone (Lintan, Zhuoni, Zhouqu, and Diebu). During the 9 years, Diebu, Maqu, and Luqu had a sustainable development status while Xiahe, Zhuoni and Zhouqu had an unsustainable development status. Hezuo and Lintan had a seriously unsustainable development status. Based on these findings, we discuss the future sustainable development of Gannan.

Driving forces of Leymus chinensis community differentiation in the Xilin River Basin

WU Ren-Ji, KANG Saruul, ZHANG Qing, REN Hai-Juan, REN Jing, ZHOU Jun-Mei, WANG Zhen, LI Dan, NIU Jian-Ming

2017, 26(4):  15-23.  DOI: 10.11686/cyxb2016184

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The relationship between vegetation and the environment is a key issue in community ecology. There are theoretical and practical reasons to clarify grassland vegetation differentiation under the coupled effects of climate variables and grazing pressure, and to quantify the effects of natural and anthropogenic disturbances on vegetation processes. In this study, we quantitatively explored the effects of climate, altitude, soil, and grazing factors on Leymus chinensis community differentiation in the Xilin River Basin using a detrended canonical correspondence analysis (DCCA) and structural equation modeling (SEM). Our results can be summarized as follows: (1) The first two axes of the DCCA explained more than 67.63% of the variability; the first axis captured mainly the variance caused by grazing and thermal-hydrological conditions, while the second axis captured the variance caused by soil variables; (2) The results of the SEM indicated that sheep density had the largest total impact on vegetation differentiation, followed by climate variables; (3) We detected indirect effects of climate, altitude, and grazing on vegetation differentiation, manifested mainly by changes in soil physical and chemical properties. This work clarified the key role of grazing on L. chinensis community differentiation in the Xilin River Basin, and also revealed the importance of climatic factors in vegetation differentiation on the basin scale. Therefore, these findings will be useful to design grassland management strategies that take into account climate characteristics for the rational use and protection of grassland resources.

Response of CO₂ exchanges to short-term grazing by Euler’s sheep in an alpine meadow in the peak of the growing season

LI Ya-Ting, YI Shu-Hua, HOU Fu-Jiang, CHANG Sheng-Hua, WANG Zhao-Feng, QIN Yu, CHEN Jian-Jun

2017, 26(4):  24-32.  DOI: 10.11686/cyxb2016168

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The aim of this study was to evaluate the effects of grazing on ecosystem respiration and productivity in a meadow grassland on the Qinghai-Tibetan Plateau. We used an LI-8150 Automated Soil CO₂ Flux System and a LED light system to simulate maximum photosynthetic active radiation, and measured ecosystem respiration (Re) and potential net ecosystem productivity (NEP_pot) under three grazing treatments (no grazing, light, and heavy grazing) in a meadow grassland of Maqu County, Gansu Province, on the Qinghai-Tibetan Plateau in August 2014. The results can be summarized as follows: 1) The diurnal NEP_pot peaked at noon in all three treatments, and increased with decreasing grazing intensity (P>0.05). The Re and potential gross primary productivity (GPP_pot) showed similar patterns; 2) The NEP_pot, Re, and GPP_pot decreased from early to middle to late August under all of the different grazing rates during the study period; 3) The aboveground biomass in the light and heavy grazing treatments was significantly reduced by 24.88% and 47.69%, respectively, as compared with the no-grazing treatment in late August; 4) Aboveground biomass was more sensitive to grazing than were GPP_pot, NEP_pot, and Re (P<0.001). NEP_pot, Re, and GPP_pot were significantly positively correlated with average temperature (P<0.001) and significantly negatively correlated with soil moisture at 5 cm depth (P<0.001). Consequently, the NEP_pot, Re, and GPP_pot gradually decreased with increasing grazing intensity and decreasing aboveground biomass.

Biomass allocation patterns in the temperate typical steppe of Inner Mongolia

HU Fei-Long, YAN Yan, LIU Li, CAO Yun, MA Yue, CHEN Meng-Meng, LIU Zhi-Min

2017, 26(4):  33-42.  DOI: 10.11686/cyxb2016214

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Grasslands are one of the most widespread landscapes worldwide, covering approximately one-fifth of the world’s land surface. China’s grasslands cover only 6%-8% of total grassland area worldwide, but contain 9%-16% of the total carbon stored in the world’s grasslands. Although some progress has been made in monitoring and understanding the factors affecting carbon partitioning, the role of species composition in carbon partitioning is still not fully understood. In this study, we evaluated the biomass distribution patterns and other vegetation indexes in several different steppes, including the Hulunbuir, Horqin, and Xilinguole Steppes. Unlike the random sampling method used in other studies, our study used a stratified sampling method to sample different communities in the typical steppes of northern China. The average biomass carbon density was 400.56 g C/m² in the typical temperate steppe. Among the different plant communities, Leymus chinensis-cluster (585.18 g C/m²), Artemisia frigida-others (505.68 g C/m²) and Stipa krylovii (501.45 g C/m²) had the highest belowground biomass (BGB). The temperate typical steppe contributed 112.76 Tg biomass carbon with an area of 32.26×10⁶ hm², where the aboveground biomass was 20.42 Tg and the BGB was 92.34 Tg. The root∶shoot ratio in the temperate typical steppe was 4.52, which was higher than those of other grassland types. There were two types of BGB distribution: the exponential function type, in which the BGB was mainly distributed at a soil depth of 0-10 cm; and the quadratic function type. The BGB distribution showed the exponential function type in the Cleistogenes squarrosa, S. krylovii, L. chinensis-cluster, L. chinensis-forbs, S. grandis, and Agropyron cristatum communities. The BGB distribution showed the quadratic function type in the A. frigida-C. squarrosa, A. frigida-others, and A. halodendron communities. Evaluation of grassland biomass carbon storage in different grassland communities can clarify the dynamics of carbon storage. The results of this study provide a theoretical basis for developing management strategies and designing research on natural grasslands in northern China.

Effect of grassland restoration duration on plant-soil ecological stoichiometry characteristics in a typical steppe

RAO Li-Xian, SHEN Yan, NIE Ming-He

2017, 26(4):  43-52.  DOI: 10.11686/cyxb2016317

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To determine the influence of restoration period on the stoichiometry of dominant plant species and soil C, N, P of typical steppe in Ningxia, China, the stoichiometric characteristics of dominant plant species and soil C, N, P in grassland abandoned for periods of 0, 1, 3, 5, 6, 8, 11, 15 and 20 years. The total nitrogen content of individual plants showed that the aboveground portion is greater than the belowground portion; the total nitrogen content of Artemisia scoparia was higher than other species. Similarly the total P content of plants was dominated by the above ground portion with the exception of Leymus secalinus plants. The organic carbon in grassland abandoned for 1 year Setaria viridis and 3 years L. secalinus was greater in the underground portion; for remaining abandonment periods the aboveground portion was greater than underground portion. The highest C∶N, C∶P, N∶P ratio’s in dominant plants in 20 year grassland occurred in S. bungeana and the lowest in L. secalinus and A. scoparia. Abandonment periods between 6 and 20 years resulted in soil organic carbon content layer decreasing from the surface with increasing depth while abandonment periods between 0-6 years resulted in fluctuating changes in soil N. The response of total P to abandonment period was similar to that of total N. The soil C∶N ration varied from 7.08-19.62, C∶P ranged from 6.60 to 35.25, N∶P varied from 0.82 to 2.17; the mean soil C∶N ration ranged from 11.18 to 15.03 in different soil layers, C∶P from 14.09 to 24.55 and N∶P from 1.06 to 1.98; The soil C∶P and N∶P ratio’s were generally lower than those typically found in other regions of China while the C∶N ration was similar to typical values in China. There was no correlation between soil C∶N and soil organic carbon but there was a negative correlation with total N, meaning that C∶N was mainly controlled by N; the C∶P ratio was significantly positively correlated with organic carbon but not with total P. There was a significant positive correlation between soil N∶P and total soil N, indicating this ration is primarily controlled by N. Total soil N showed a fluctuating upward trend with increasing abandonment period. There was a strong correlation between total plant P and total soil P (P<0.01); soil organic C was also correlated with N∶P (P<0.05).

Effects forages on nitrogen and phosphorus loss from sloping land draining into the Three Gorges Reservoir

GOU Tao-Ji, GAO Ming, WANG Zi-Fang, LIU Bin-Bin, HUANG Rong

2017, 26(4):  53-62.  DOI: 10.11686/cyxb2016350

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The research was conducted in a small catchment, Wangjiagou, draining into the Three Gorges Reservoir. We combined field experiments and laboratory analysis; corn was used as the control (T₁), which was compared to Lolium perenne (T₂), Purus frumentum (T₃) and Sorghum bicolor (T₄). Samples of the surface runoff after rainfall from May to August in 2015 were collected and analysed for nitrogen (N) and phosphorus (P) allowing losses to be calculated. The results showed that all three forages significantly reduced N and P losses both in the runoff and the sediment. The most effective species was P. frumentum; N and P losses caused by natural rainfall occurred mainly in sediment which accounted for 76.34%-79.97% and 81.69%-83.90% of total N and total P losses, respectively. The fresh and dry biomass yields of L. perenne and P. frumentum were higher than corn, the mean advantage being 4.45 and 1.52 times, and 4.89 and 1.53 times that of corn, respectively. The nutrient sequestration effect of the four crop types were ranked T₂, T₃>T₄>T₁. The nutrient sequestration and feed economic benefits of P. frumentum indicate that it has the greatest potential as a substitute for corn in Three Gorges Reservoir catchments, followed by L. perenne.

Effect of biochar amendment on purple and yellow soil

ZHANG Xu-Hui, LI Zhi-Ling, LI Yong, WANG Yang-Qing

2017, 26(4):  63-72.  DOI: 10.11686/cyxb2016367

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Purple soil was collected from the National Monitoring Base for Purple Soil Fertility and Fertilizer Efficiency in Beibei, Chongqing and yellow soil from Jinyunshan National Forest Park and used in a greenhouse pot experiment with rapeseed (Brassica napus). Rice husk biochar was applied at 0, 0.8%, 2.0% and 4.0% of the soil weight in each pot; CK, CT₁, CT₂ and CT₃ respectively. The soil nutrient content, soil enzyme activity, microorganism density and plant growth indices were measured after 180 days. The results indicated that both soils were significantly improved by the addition of biochar, the best treatment being CT₃. The organic matter content, total N, P, K, available N, P, K in CT₃ were 1.3, 1.2, 4.0, 1.1, 0.9, 33.1 and 18.0 times those of the CK for yellow soil respectively and 1.4, 1.0, 1.5, 1.1, 0.9, 3.8 and 6.0 times the CK in the purple soil respectively. Compared with the CK, the application of biochar significantly increased the pH in both the purple and yellow soil. Biochar significantly increased the number of two species of soil bacteria, including actinomycetes, and promoted the growth of fungi in the purple soil. The numbers of bacteria and actinomycetes in the CT₃ treatment were increased by 677% and 395% in the yellow soil, while the numbers of bacteria, actinomycetes and fungi in the purple soil were increased by 20%, 88% and 82%, respectively. Invertase and catalase activity were significantly increased by 106% and 30% in the CT₃ treatment, respectively. Similarly, urease and catalase activity were increased by 150% and 130% respectively. Plant heights and biomass of rapeseed in the CT₁ treatment were 4.6 times and 11.4 times of those of the CK in the yellow soil respectively, and 17% and 8% higher than those in CK in the purple soil respectively; other treatments suppressed growth. It was concluded that rice husk biochar could be used as amendment for yellow soil and purple soil in southwest region of China at appropriate application rates.

Mechanisms research on how pH affects nitrification in purple soils of Southwest China

MENG Yao, WANG Zhi-Hui, LUO Hong-Yan, JIANG Xian-Jun

2017, 26(4):  73-79.  DOI: 10.11686/cyxb2016164

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Nitrification processes are highly sensitive to soil pH but the mechanisms through which pH affects soil nitrification are not fully understood. In the present study, three types of purple soils with different pH values were identified from the same parent material in southwest China (acid purple soil pH=5.7, neutral purple soil pH=7.3, calcareous purple soil pH=8.0). These soil types were used to investigate the long-term effects of soil pH on nitrification and ammonia oxidizers and the short-term effects of soil pH on nitrification and the activities and abundance of ammonia oxidizers. Tests were undertaken by artificially adding acid (H₂SO₄) or alkali (NaOH) to change soil pH. The results showed that short-term pH changes had no significant effect (P>0.05) on nitrification in acidic and calcareous purple soils whereas they had a significant effect (P<0.05) on nitrification in the neutral purple soil. The gene amoA of ammonia-oxidizing archaea (AOA) was expressed much more fully in the acid soil (3.04×10⁸/g dry soil, AOA/AOB=31.8), whereas ammonia-oxidizing bacteria (AOB) were more adapted to the calcareous purple soil environment (2.35×10⁸/g dry soil, AOA/AOB=0.07). These results indicate that soil pH can significantly affect nitrification in purple soils and that different pH levels have different mechanisms. The activities and community of nitrifying microorganisms were the dominant factors for nitrification in acidic and calcareous purple soils, while substrate concentration was the dominant factor in neutral purple soil. The key factor affecting the activity and community of nitrifying microorganisms is the long-term stable soil pH, while short-term pH changes mainly influence the substrate availability of nitrification.

Effects of cover cropping and organic fertilizer on soil nutrients in a pear orchard

SUN Ji-Ping, ZHANG Yu-Xing, WU Zhao-Hui, LI Ying-Li, WANG Guo-Ying, ZHANG Jiang-Hong

2017, 26(4):  80-88.  DOI: 10.11686/cyxb2016362

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To promote grass sward management in orchards in China, this paper discusses the effects of planting herbage species combined with the application of organic fertilizer on soil mineral composition in a high producing and efficient pear orchard. The ‘xueqing’ pear orchard with 4-year and 8-year old inter-row herbage ground cover located on the Jizhong Plain, Hebei, was compared with a neighbouring pear orchard using inter-row tillage to control vegetation. Stratified sampling was carried out in each 10 cm layer of 0-80 cm soil layers in all pear orchards. Soil organic matter and mineral element content in each soil layer were measured. The results showed that the available nutrient content was highest in the 0-50 cm soil layers after planting herbage. Compared to tillage a herbage regime of 4 years combined with the application of organic fertilizer, soil alkaline hydrolytic nitrogen, available P and Zn content in 0-10 cm layer and the available K and Fe in 0-20 cm layer were clearly higher. Eight years of managed herbage combined with the application of organic fertilizer resulted in significantly improved soil organic matter and alkaline hydrolytic nitrogen content in the 0-10 cm layer, available Mn and Fe in the 0-20 cm layer, available P and Cu in the 0-30 cm layer, available Zn in the 0-40 cm layer and available K in the 0-50 cm layer. However soil pH was reduced. After 8 years of herbage management and application of organic fertilizer the available P, K and Zn in the 0-50 cm soil layer accounted for 92%, 82% and 88% of the 0-80 cm soil layer, respectively; soil fertility was improved and negative environmental effects such as nutrient losses reduced, improving the overall sustainability of the production system.

Morphological characteristics of six kinds of mucilaginous seeds and their response to digestion in the rumen of sheep

WANG Shu-Lin, Narkes Wali, LU Wei-Hua, WANG Wei-Qiang, WANG Chuan-Jian

2017, 26(4):  89-98.  DOI: 10.11686/cyxb2016185

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An experiment has been undertaken to compare the morphological characteristics of mucilaginous seeds from six plant species (Plantago lessingii, Seriphidium transiliense, Malcolmia africana, Descuminia sophia, Diptychocarpus strictus and Cardaria draba) and to study their digestion in the rumen of sheep. After determining their morphological characteristics, seeds were put into nylon bags which were then placed in the rumen of sheep through a fistula. The bags were removed at different times and then the mucilage percentage, water absorption rate and sand adherence rate of the seeds were determined. The results were compared with seeds that had not been digested. The results showed that mucilage on the seed surface of all six species was digested by the rumen fluid of sheep. The seeds became dark after digestion. The seed wings of D. strictus consisted primarily of mucilage. As a result, the width of D. strictus seeds changed significantly as digestion time increased (P<0.05). In contrast, the length and thickness of D. strictus seeds were not significantly affected by digestion time (P>0.05). Digestion time had no significant effects on the length, width and thickness of seeds of the other five plant species (P>0.05). The mucilage percentage, water absorption rate and sand adherence rate decreased as digestion time increased. The relationship between mucilage percentage and digestion time is expressed as the equation y=-1.98+48.26e^-x/8.40, where x is time in hours (R²=0.95441, P=0<0.01). The relationship between water absorption rate and digestion time is expressed by the equation y=90.04+428.03e^-x/4.43 (R²=0.75934, P=0<0.01). The relationship between sand adherence rate and digestion time is expressed as the equation y=-0.71+342.76e^-x/5.05 (R²=0.81124, P=0<0.01). Seed germination rates decreased significantly after digestion (P<0.05), with the largest decreases occurring when digestion time was >12 h. Although seed germinability decreased after passage through the rumen, the survival of some seeds indicates that grazing sheep are a possible pathway for seed dispersal.

Effects of feeding high concentrate diets on lactation indicators and antioxidant levels in the mammary glands of lactating goats

TIAN Ping, SUN Li-Li, DONG Hai-Bo, TIAN Jing, DUANMU Yong-Qian, TAO Shi-Yu, NI Ying-Dong

2017, 26(4):  99-105.  DOI: 10.11686/cyxb2016283

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The effect of feeding high concentrate diets for extended periods on lactation indicators and antioxidant potential in the mammary glands of lactating goats, 12 health multiparous guanzhong goats in mid lactation were randomly allocated to two groups; one group receiving diets with low concentrate (concentrate∶roughage 35∶65) as the LC group (n=6), and another receiving high concentrate diet (concentrate∶roughage 65∶35) as the HC group (n=6). The experimental lasted for 12 weeks. At the end of the experiment, goats were slaughtered after overnight fasting. All goats were killed with neck vein injections of xylazine and pentobarbital. Mammary glands and other tissues were sampled and quickly placed in liquid nitrogen and stored at -70 ℃ for gene and protein expressions analysis. The results showed that milk production was significantly increased by feeding a high-concentrate diet and the percentage of milk lactose, protein and fat was significantly increased with lactation time. The expression of sterol regulatory element-binding protein 1 (SREBP1) and Glucose transport 1 (GLUT1) mRNA was significantly decreased (P<0.05), and AKT1 protein levels tended to be lower (P=0.08) in the HC group compared to the LC group. The HC diet moderately reduced the activity of T-AOC the enzyme (P=0.06) and GSH (P=0.08). These results suggest that feeding high concentrate diets reduced the antioxidant ability and significantly decreased the percentage of milk fat as well as down-regulated SREBP1 and p-AKT expression in the mammary glands.

Aerobic stability and microbial populations in sweet sorghum silages during aerobic exposure

ZHOU Fei-Ran, ZHANG Su-Jiang, WANG Ming, XIAO Dan, GUO Xue-Feng

2017, 26(4):  106-112.  DOI: 10.11686/cyxb2016304

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In order to promote the exploitation and utilization of sweet sorghum silage, three kinds of silages (high sugar sweet sorghum silage, HSS; low sugar sweet silage, LSS; maize silage, MZS) were used to analyze the changes in dry matter (DM), water soluble carbohydrates (WSC), pH, temperature and microbial populations during aerobic exposure over 0, 5, 10, 15, 20 and 25 days. The results showed that HSS had a lower pH and higher LAB (lactic acid bacteria) population and higher temperature compared with LSS and MZS (P<0.05) in the early stage of aerobic exposure (0-5 d). The numbers of yeast, mould and aerobic bacteria in HSS were higher than that in LSS and MZS (P<0.05), while temperature and pH were lower in LSS than those in HSS and MZS (P<0.05) in the latter stages of aerobic exposure (15-25 d). HSS had the highest WSC and LSS had the lowest dry matter content (P<0.05) over all exposure periods. Overall, LSS had the greatest aerobic stability with less yeast, mould and aerobic bacteria which were highest in HSS which had the lowest aerobic stability; bacteria numbers and aerobic stability were intermediate in in MZS. The results of this study suggest that it is necessary to use additives when making HSS to assure quality because it is more prone to secondary fermentation under aerobic exposure.

Dynamics of soluble sugar and nitrogen contents in the stem and grain of soybean under relay intercropping and monoculture conditions

LIU Qin-Lin, LI Jia-Feng, FAN Yuan-Fang, DENG Chuan-Rong, YONG Tai-Wen, LIU Wei-Guo, YANG Wen-Yu, YANG Feng

2017, 26(4):  113-119.  DOI: 10.11686/cyxb2016174

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Carbon and nitrogen metabolisms play critical roles in plant growth and development and are closely related to crop yield and grain quality. The stem plays an important role in transporting and storing sugar and nitrogen in a plant. Two typical genotypes of soybean, Nandou 12 and Nandou 20, were used as experimental materials in monoculture and relay intercropping patterns. Under intercropping, soybean was alternatively sown with maize at wide-narrow intervals. The dynamics of soluble sugar and nitrogen contents in the soybean stem and seed were analyzed at different growth stages. In the stem, soluble sugar and nitrogen contents changed in a ‘low-high-low’ trend with stem growth. However, the ratio of soluble sugar to nitrogen contents appeared as a ‘low-high’ trend under monoculture and relay intercropping conditions. Significant differences in stem soluble sugar, nitrogen contents and their ratio under monoculture and intercropping were measured from seedling to full bloom stages (P<0.05), while after that stage no significant differences were measured in either planting pattern (P>0.05). In addition, there were significant correlations between soluble sugar, nitrogen contents and the ratio between the stem and seed from full bloom to seed filling stages, notably for nitrogen content and the ratio, where the maximum correlation coefficient was 0.85. This study thus shows that carbon and nitrogen metabolisms after full bloom stage are closely related to crop yield and grain quality under relay intercropping and monoculture conditions, providing theoretical support for a better understanding of plant transportation of carbon and nitrogen from stem to seed and guidance for effective planting under relay intercropping systems.

Effect of boron on migration and colonization by rhizobia and seedling growth in Medicago sativa

MIAO Yang-Yang, ZHOU Tong, SHI Shang-Li, KANG Wen-Juan, ZHANG Yun-Ting

2017, 26(4):  120-133.  DOI: 10.11686/cyxb2016340

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The effect of boron on the migration and colonization of rhizobia in Gannong No.5 alfalfa (Medicago sativa Gannong No.5) tissues and subsequently seedling growth were investigated by root drenching using two cyan fluorescent protein (CFP) tagged rhizobia; Ensifer meliloti 12531f (12531f) and Ensifer meliloti GN5f (gn5f) containing different boron concentrations. The results showed that the best supplementation levels were less than 1 and 100 mg/L boron for 12531f and gn5f respectively. The optimum boron level enhanced the colonization of both rhizobia in alfalfa roots; colonization densities of 2184.99 and 58307.11 cfu/g were achieved by using 100 mg/L boron co-inoculated 12531f and 0.5 mg/L boron co-inoculated gn5f, respectively. Rhizobia were able to migrate to the aerial tissues and colonize lower stems and leaves through application of 1 mg/L boron co-inoculated 12531f and 100 mg/L boron co-inoculated gn5f, respectively. No fluorescent tagged rhizobia were detected in the control treatment. Individual plant root nodule number, nodule weight, leaf number, plant height, root length, aerial fresh weight, aerial dry weight, root fresh weight and root dry weight were increased by 21.31%-909.28% for the 1 mg/L boron co-inoculated 12531f treatment compared with control and zero boron innoculation. These traits were increased by 15.07%-1424.24% for the 100 mg/L boron co-inoculated gn5f treatment compared with control and zero boron inoculation treatments. Leaf chlorophyll content was reduced by 12531f without boron whereas 1 mg/L boron co-inoculated 12531f significantly increased the leaf chlorophyll content by 18.31% and 36.86% compared with the control and zero boron inoculation, respectively (P<0.05). Boron supplemented gn5f enhanced the leaf chlorophyll content; 100 mg/L boron co-inoculated gn5f increased leaf chlorophyll content by 24.41% and 12.92% compared with control and zero born inoculation, respectively (P<0.05). The results suggest that 1 mg/L boron co-inoculation with 12531f, 100 mg/L boron co-inoculation with gn5f promoted the migration and colonization of rhizobia in alfalfa seedlings, enhancing growth, indicating possible benefits for alfalfa cultivation.

Comparison of the root morphology of oilseed rape and winter wheat during the seedling period using a rhizotron tube method

GAO Song-Juan, CAO Wei-Dong, THORUP-KRISTENSEN Kristian

2017, 26(4):  134-142.  DOI: 10.11686/cyxb2016208

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Fast and accurate methods for determining root growth in situ are important tools. In the present study, a rhizotron tube method was trialed as a means to more conveniently observe the dynamic development of roots under conditions similar to those encountered in the field. Crops were planted in transparent tubes covered with photomask to ensure a dark environment in the tube. This method can also be used in field studies of deep root development in crops by changing the length and diameter of the tube. Combined with root scan technology, we investigated the dynamics of root growth in oilseed rape and winter wheat at the seedling period from 16 days after germination. The results showed that winter wheat had a larger root and shoot dry weight than oilseed rape at both 7 days and 16 days. For winter wheat and oilseed rape, the root to shoot ratios at 16 days after germination were 0.513 and 0.372 respectively; the ratios of root length to total root length in the top soil layer (0-16 cm) were 62.60% and 67.76% respectively. The total surface, total volume and number of first class lateral roots of the two crops both had larger percentages in the top soil layer, indicating that most of the roots were distributed in the top 16 cm soil layer at 16 days. At 7 days after germination, the total length, total surface, total volume and number of first class lateral roots in winter wheat were higher than those in oilseed rape, while there were no differences between the two crops for the total length and total surface of roots at 16 days, suggesting that the root growth of oilseed rape was slow in the beginning but fast thereafter. The average root diameter in top soil was smaller than that in the deep soil layer, and the average root diameter of oilseed rape was smaller than that of winter wheat, which was typically between 0-0.50 mm. In terms of root growth, there were more and more thinner lateral roots, meaning that average root diameter became smaller. At 16 days after germination, the root elongation rate of winter wheat was 1.83 cm/d, larger than that of oilseed rape (1.51 cm/d). In conclusion, the root growth of winter wheat at the seeding stage was faster than that of oilseed rape, and the root of oilseed rape grew slowly at the beginning but faster thereafter. The rhizotron tube method introduced in this research is recommended as an effective method for root study in situ.

The morphological and physiological responses of the soil and water conservation plant Neyraudia reynaudiana to acid stress

CHEN Xue-Jiao, HAN Hang, HOU Xiao-Long, LIU Ai-Qin, CAI Li-Ping, ZHOU Chui-Fan, MA Xiang-Qing

2017, 26(4):  143-149.  DOI: 10.11686/cyxb2016170

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Soil acidification is one of the main limitation factors affecting vegetation restoration in mining wastelands. Neyraudia reynaudiana can grow normally in the wasteland of rare earth mines with extremely serious soil acidification, indicating that it has specific morphological and physiological mechanisms. In order to reveal these mechanisms, a one-pot acid stress experiment was designed with four different pH levels (3.5, 4.5, 5.0 and 5.6) and the growth indices, biomass, antioxidant enzymes and MDA content of N. reynaudiana were measured. The results showed that N. reynaudiana grows normally in soil with pH 3.5, suggesting a strong resistance to acid stress. With the increase of soil pH, growth indices such as plant height, leaf length, number of leaves, tiller number, root length, root volume, root surface area and root diameter at first increased and then decreased, demonstrating that the low acid stress had a promotion effect on N. reynaudiana growth. In addition, all the growth indices for N. reynaudiana reached their peak under the pH 4.5 treatment, suggesting that this is the most suitable soil pH level for the species. N. reynaudiana adapts to acid stress by accelerating the root diameter growth rate and increasing the biomass allocation of the root. Our research also indicated that the antioxidant enzymes of N. reynaudiana were inhibited under acid stress.

Effects of active allelochemicals from feral Gentiana straminea on the seed germination and seedling physiological properties of forages

DING Chun-Fa, WEI Xiao-Hong, WANG Fang-Lin

2017, 26(4):  150-161.  DOI: 10.11686/cyxb2016181

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Gentiopicroside and flavonoids were extracted from feral Gentiana straminea using ultrasonic extraction methods and then the extracts were applied at different concentrations to three forages, Medicago sativa, Trifolium pratense and T. repens. The forages’ seed germination and seedling physiological properties (seedling height, root length, fresh weight and the activities of SOD, POD and CAT) were measured to analyze the allelopathy and antioxidation effects of feral G. straminea. In general, the gentiopicroside and flavonoid extracts showed allelopathic inhibitory effects on seed germination and seedling growth in the selected forages. The exception was gentiopicroside at 2.52 mg/mL, which increased seedling height in T. repens. The effects of gentiopicroside and flavonoid extracts on the activity of anti-oxidative enzymes varied with extract concentration. Specifically, both POD and CAT activities in seedlings of the three forages peaked when the concentrations of gentiopicroside and flavonoid extracts were 6.30 and 1.95 mg/mL respectively. When the concentrations of gentiopicroside and flavonoid extracts were 12.60 and 3.90 mg/mL respectively, SOD activity in M. sativa seedlings reached their maximums (22.971 and 25.013 U/g respectively), while in T. pretense and T. repens these activities peaked when the concentrations of gentiopicroside and flavonoid extracts were 6.30 and 1.95 mg/mL respectively. In conclusion, the sampled plants differ in their tolerance to allelopathic stress and M. sativa shows a greater tolerance than either T. pretense and T. repens.

Effect of altitude on fruit characteristics, bioactive compounds and antioxidant capacity in Podophyllum hexandrum

LI Meng-Fei, YAO Yuan-Yuan, DING Yao-Lu, GE Li, CAO Xiao-Lu, LI Jie, YANG De-Long

2017, 26(4):  162-168.  DOI: 10.11686/cyxb2016212

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This study investigated the effect of altitude on fruit characteristics and the accumulation of bioactive compounds in the fruit of Podophyllum hexandrum, with the aim of better protecting and utilizing this wild resource. The experiments were conducted at different altitudes (2400-2500 m and 2900-3000 m), with measurements taken of fruit characteristics, bioactive compound content and antioxidant capacity. Differences in altitude showed very strong effects on fruit characteristics and the accumulation of bioactive compounds in fruit tissue. The duration from flowering to fruit ripening stages at lower altitudes was 111 d, 5 d longer than that at higher altitudes, and the duration of the ripening stage increased by 13 d. The length, diameter, dry weight, seed number and thousand-seed weight per fruit were greater at lower than at higher altitudes, while the ratio of length-diameter was lower. The contents of soluble sugar, total flavonoid and phenolic in both peel and pulp at lower altitudes were significantly higher than those at higher altitudes. The inhibition percentages (I%) and ferric reducing/antioxidant power (FRAP value) of 70% and 10% ethanol extracts from the peel and the FRAP value of 70% ethanol extracts from the pulp at lower altitudes were significantly higher than those at higher altitudes. At the same altitude, the content of soluble sugar in the pulp was significantly greater than that in the peel, while the contents of total flavonoid and phenolic were lower. The I% and FRAP value of 70% and 10% ethanol extracts from peel were significantly greater than those from pulp at lower altitudes, while at higher altitudes only the FRAP value of 70% ethanol extracts from the peel was significantly greater than that from the pulp. In conclusion, this study indicates that low altitude is conducive for fruit growth and development and for the accumulation of soluble sugar, total flavonoid and phenolic contents in the fruit of P. hexandrum.

Effects of salt treatments on growth and osmoregulatory substance accumulation in sugar beet (Beta vulgaris)

WU Guo-Qiang, FENG Rui-Jun, LI Shan-Jia, WANG Chun-Mei, JIAO Qi, LIU Hai-Long

2017, 26(4):  169-177.  DOI: 10.11686/cyxb2016192

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In this study, the effects of NaCl at different concentrations (0, 50, 100 and 150 mmol/L) on the growth and osmoregulatory substance accumulation in 60-day-old sugar beet (Beta vulgaris) plants were investigated in pot experiments. The addition of 50, 100, and 150 mmol/L NaCl promoted the growth of sugar beet plants and maintained water conditions well. Compared with the control (0 mmol/L), various concentrations of NaCl significantly increased the fresh weights and dry weights of the leaf blade, leaf petiole, and storage root of B. vulgaris plants (P<0.05). Compared with the control, the high-salt treatment (150 mmol/L) resulted in marked increases in Na⁺ concentrations in the leaf blade and leaf petiole (4.4- and 4.9-fold, respectively; P<0.05), and decreased the relative distribution of Na⁺ in storage roots and lateral roots (by 44% and 53%, respectively; P<0.05). The high-salt treatment also reduced the K⁺ concentrations in the leaf blade and lateral root by 39% and 55%, respectively (P<0.05), and increased the relative distribution of K⁺ in the leaf petiole and storage root by 35% and 80%, respectively (P<0.05). The salt treatments reduced sucrose contents by 44%-50% (P<0.05) and fructose contents in the storage root by 31%-36% (P<0.05), whereas glucose contents were unaffected. The high-salt treatment increased the proline concentration in the storage root by 93%, compared with the control (P<0.05). These results suggested that sugar beet plants can adapt to saline conditions by accumulating the large quantities of Na⁺ in the leaf blade and leaf petiole, by maintaining K⁺ homeostasis, and by enhancing the accumulation of proline in storage roots.

Nitric oxide is involved in regulating antioxidant enzyme activity and expression of their encoding genes in white clover under PEG osmotic stress

WU Xing, WANG Xiao-Juan, PENG Yan

2017, 26(4):  178-187.  DOI: 10.11686/cyxb2016190

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The aim of this study was to evaluate the role of endogenous nitric oxide (NO) in regulating antioxidant enzyme activity in white clover (Trifolium repens cv. Ladino) under osmotic stress. We investigated endogenous NO fluorescence, dynamic changes in NO content, antioxidant enzyme activity, and the transcript levels of genes encoding antioxidant enzymes in white clover treated with an NO scavenger or NO synthesis inhibitors, and also evaluated the mitigating effects of the exogenous NO donor, sodium nitroprusside (SNP). Leaves of white clover were subjected to osmotic stress (15% PEG-6000). Compared with the leaves in the control, those in the osmotic stress treatment showed higher NO-dependent fluorescence, increased NO content, enhanced activity of antioxidant enzymes, and higher transcript levels of genes encoding antioxidant enzymes. Under osmotic stress, bovine hemoglobin (Hb), sodium vanadate (NaVO₃), and LNG-nitro-L-arginine methyl ester hydrochloride (L-NAME) inhibited the accumulation of NO, leading to inhibition of antioxidant enzyme activity and reduced transcript levels of their encoding genes. The NO donor SNP (50 μmol/L) significantly alleviated the decline in the relative water content (RWC), reduced electrolyte leakage, decreased malondialdehyde accumulation, and promoted antioxidant enzyme activities under osmotic stress. These results suggested that NO is an important signaling molecule in response to osmotic stress, and that it plays a role in regulating gene expression and antioxidant enzyme activity to reduce peroxidation injury in white clover.

Cross-species markers developed from genome sequencing in Medicago truncatula, Medicago lupulina and Medicago polymorpha

REN Hai-Long, WEI Zhen-Wu, CHEN Xiang

2017, 26(4):  188-195.  DOI: 10.11686/cyxb2016400

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Medicago truncatula is another whole genome sequenced species next to Arabidopsis thaliana and Oryza sativa. Studying genomics and genetics using cross-species markers developed from M. truncatula has become an important strategy for species with more complex genomes or for legumes with less well understood genome. M. lupulina and M. polymorpha are the most important annual medics in China. However, limited by molecular marker, little research has been done on genome scales in these species. Specific length amplification fragment sequencing (SLAF-seq) possesses significant advantages including development of markers with high throughput, high accuracy, low cost and time saving which has been successfully used in single nucleotide polymorphism (SNP) development in many species. In this study, 28.04×10⁶ reads were obtained from a collection of twelve of M. truncatula, M. lupulina and M. polymorpha accessions using SLAF-seq. The average sequencing depth was 17.44, and 276432 high-quality SLAFs were developed, among which 58748 SLAFs were polymorphic. Further 189133 cross-species SNPs were identified from these polymorphic SLAFs with minor allele frequencies (MAFs)>0.05. These SNPs can be used in genetic diversity, genetic linkage mapping and QTL mapping of important agronomic traits in annual medic. They will also convey benefits for the study of genome orders, system evolution, and comparative map construction.

Signaling in the mutualistic symbiotic interaction between endophytes and their hosts

TIAN Pei, NAN Zhi-Biao

2017, 26(4):  196-210.  DOI: 10.11686/cyxb2016176

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Symbioses between fungi and plants have occurred naturally and widely during long-term evolution. This relationship makes both fungi and plants more adaptable to environmental changes. Endophytes form symbiotic associations with temperate grasses including Festuca and Lolium spp. The establishment and maintenance of these mutualistic associations involves mutual communication between the endophyte and the host. The growth of these endophytes is strictly intercellular and tightly regulated, and is synchronized with the growth of the host. Using this unique growth pattern, the endophyte does not trigger the host defense response and establishes a precise communication and regulatory pathway with the host. This communication will likely involve many well-known signaling pathways. Mitogen-activated protein kinase (MAPK) cascades and second messenger signaling pathways involving cAMP and calcium are the main pathways for signal transduction. Here, we review the endophyte growth pattern in the host, and discuss research on the genes involved in signaling pathways between the endophyte and host using modern molecular technologies. The information gained so far can be used to predict the possible functions of these pathways in endophyte associations, and provides a reference for further in-depth analyses of the communication network between the endophyte and the host.

Effect of fertilizer on the yield and forage quality of Glycine max

HUANG Yan, DUO Tian-Qi, YU Yao, YAO Feng-Jiao, JI Jing, KUANG Xiao, CUI Guo-Wen, HU Guo-Fu

2017, 26(4):  211-217.  DOI: 10.11686/cyxb2016201

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Using a “3414” optimal regression design, this study set three factors of nitrogen, phosphorus and potassium and four fertilizer levels (N: 0, 20, 40, 60 kg/ha; P₂O₅: 0, 35, 70, 105 kg/ha; K₂O: 0, 25, 50, 75 kg/ha) to investigate effects on the yield and forage quality of Glycine max. The results showed that during the seed-filling stage and with N₂P₂K₂ fertilizer level (N 40 kg/ha,P₂O₅ 70 kg/ha,K₂O 50 kg/ha), G. max had the best nutrient quality. At N₂P₂K₂ fertilizer level, the fresh and hay yields were at their highest levels, which were 39238.09 and 16209.12 kg/ha respectively, representing increases of 24.47% and 36.17% compared with the control, crude protein and crude fat content were the highest (18.40% and 2.60%), 37.02% and 73.61% higher than the control respectively. Crude fiber content was the lowest, reducing by 18.46% when compared with the control.