Table of Content

20 April 2015, Volume 24 Issue 4

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Nutrient content of soils under artificial grass vegetation in the urban hydro-fluctuation belt of the Three Gorges Reservoir Region

YANG Yu-Jing, LI Chang-Xiao, MA Peng

2015, 24(4):  1-11.  DOI: 10.11686/cyxb20150401

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A study has been undertaken to explore the dynamics of soil chemical properties under different water-logging durations following re-vegetation in the urban hydro-fluctuation belt of the Three Gorges Reservoir Region. The study also aimed to determine the potential impact of vegetation reconstruction on water quality. Soil samples were taken from Hemarthria compressa, Cynodon dactylon and Saccharum spontaneum communities, and from non-vegetated areas in a hydro-fluctuation belt located in downtown Chongqing, in June 2012, March 2013, May 2013, July 2013 and September 2013. Analysis was undertaken of soil pH, organic matter (OM), alkali hydrolysable nitrogen (AN), available phosphorus (AP), available potassium (AK), total nitrogen (TN), total phosphorus (TP) and total potassium (TK). Results showed that vegetation type significantly influenced soil pH values and AN, AP and TP contents. No significant differences were found in the tested properties between soils without vegetation and those beneath the three types of artificial grasses. However, there were significant soil differences under different water-logging durations. pH values and OM contents fluctuated throughout the experiment. Soil pH ranged from 6.5 to 8.5. AN contents were relatively higher in March and September 2013, when the water level dropped, while maximum AP contents were found in June 2012. At that time, AP contents under bare areas, H. compressa, C. dactylon, and S. spontaneum were (2.62±0.30), (3.92±0.34), (1.08±0.16), and (1.24±0.06) mg/kg respectively. TP and TK contents increased in the later phases of the experiment. The study also showed that, besides vegetation and hydrological factors, other factors such as urban sewage discharge, human disturbance and point or non-point source pollution caused by surface runoff influenced soil pH and nutrients. For the Yangtze River in Chongqing urban areas of the Three Gorges Reservoir Region, the potential risk of water eutrophication caused by artificial grasses might be lower.

Soil properties of Tibetan Plateau alpine wetland affected by grazing and season

HE Gui-Yong, SUN Hao-Zhi, SHI Xiao-Ming, QI Wei, DU Guo-Zhen

2015, 24(4):  12-20.  DOI: 10.11686/cyxb20150402

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The seasonal characteristics of soil physical and chemical properties under different grazing patterns (annual grazing, winter grazing, no-grazing) were studied on an alpine wetland of the eastern Tibet Plateau. The main results were: soil moisture and soil organic carbon content at the surface(0-15 cm)and sub-surface (15-30 cm) layers were highest under non-grazing and lowest under annual grazing. 2) For all treatments, soil moisture, organic carbon, total nitrogen, total phosphorus and available nitrogen significantly declined with increasing soil depth, however, available phosphorus was not affected by soil depth. 3) The surface soil organic carbon content of all treatments showed the same seasonal pattern; September>May>July and soil total nitrogen and total phosphorus content were generally higher in September. 4) Total nitrogen content in both soil layers were significantly positively correlated with soil organic carbon content in July and September. It is concluded that annual grazing increases carbon, nitrogen and phosphorus cycling and increases nutrient losses, leading to decreased soil fertility and declining grassland quality.

The influence of hydrothermal factors on soil respiration and soil temperature sensitivity of Stipa krylovii steppe, Inner Mongolia, China

GU Rui, CHAO Luo-Meng, ZHANG Li-Xin, SU Li-De, WAN Zhi-Qiang, YAN Yu-Long, CHEN Ya-Li, GAO Qing-Zhu

2015, 24(4):  21-29.  DOI: 10.11686/cyxb20150403

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The grasslands of the Inner Mongolian Stipa krylovii steppe make an important contribution to animal production in China. Soil respiration is an important component of the carbon cycle on the steppe and the main source of soil carbon losses. In this study, typical grassland dominated by S. krylovii, located in Maodeng Ranch, Xilinhaote, Inner Mongolia was selected as the study area. An open top type growth chamber was used to simulate the response of soil respiration to temperature and precipitation from 2011 to 2013. The Automated Soil CO₂ Flux System (LI-8100, LI-COR, NE) was used to observe the soil respiration in the study area during the growing season (May to September). Air temperature, soil temperature and soil moisture were measured using the EM50 Data Collection System (Decagon Devices, Inc., NE, USA). Soil samples were collected, soil nutrients and microbial numbers were determined and correlation analysis used to explore associations between soil respiration rate and environmental factors. Soil respiration was significantly affected by air temperature and soil water content (P<0.01). Under warm and warm-moist conditions respectively soil respiration rates were 2.60 μmol/(m²·s) and 1.96 μmol/(m²·s) (2012) and 3.38 μmol/(m²·s) and 2.09 μmol/(m²·s) (2013); differences between years were significant (P<0.05). Increased air temperature and decreased soil water content both inhibited soil respiration. During the 2013 growing season additional environmental factors including soil organic carbon, total nitrogen and soil microbial mass may also have affected soil respiration. The Q₁₀ temperature coefficient was significantly increased by warm-moist conditions. It was concluded that soil respiration is mainly influenced by hydrothermal conditions; increased air temperature and reduced soil moisture content inhibit soil respiration. The relationship between environment factors and soil respiration on the Inner Mongolian steppe is complex and requires further research.

Effect of potassium application rate on uptake and distribution of potassium and grain yield in oil flax

SUN Xiao-Hua, XIE Ya-Ping, NIU Jun-Yi, LI Ai-Rong

2015, 24(4):  30-38.  DOI: 10.11686/cyxb20150404

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This study aimed to identify the effect of different potassium supply levels on transportation and distribution of potassium and on grain yield in oil flax. Using the oil flax cultivar “Baxuan No. 3”, a field experiment was conducted with four potassium fertilizer application rates: control (K₀: 0 kg K₂O/ha), low potassium (K₁: 18.75 kg K₂O/ha), medium potassium (K₂: 37.5 kg K₂O/ha) and high potassium (K₃: 56.25 kg K₂O/ha) from 2011 to 2012 at Zhangjiakou, in Hebei Province, China. Significant differences in potassium accumulation of different organs, including root, stem, leaf and grain, were observed. However, the changes in K content of each organ during the whole growing period were basically consistent and closely related to the rate of potassium fertilizer. The potassium accumulation in root, stem, leaf and grain was greatest during the reproductive stage of growth, and accounted for 41.28%-64.09% of the accumulated potassium over all growth stages. Potassium uptake took place in all three organs: the root, stem and leaf. Compared with control (K₀), the potassium uptakes in root, stem and leaf under low potassium K₁ (18.75 kg K₂O/ha), medium potassium K₂ (37.50 kg K₂O/ha) and high potassium K₃ (56.25 kg K₂O/ha) treatments were increased by 35.60%, 29.06% and 43.75%, respectively. The potassium transportation rates from root, stem and leaf to grain were 17.78%-24.85%, 14.82%-23.00% and 39.40%-46.20%, respectively, and the contribution of transported potassium to the total amount of grain potassium in oil flax was 6.71%-14.12%, 11.24%-23.97% and 17.26%-50.83%, respectively. Meanwhile, compared with the control (K₀) treatment, grain yield increased by 14.90%-24.12%, 29.93%-30.11% and 15.65%-23.13%, respectively, under the 3 potassium treatments, K₁, K₂ and K₃. Considering potassium accumulation, transportation, distribution and crop grain yield, the optimal potassium fertilizer fertilization for oil flax was 37.5 kg K₂O/ha (K₂) under the climatic conditions of the experimental area.

The synergy effects of water and fertilizer supply on a rotational system of spring wheat and peas under different tillage practices in a loess hilly region

YAN Li-Juan, LUO Yong-Zhong, LI Guang, WANG Qi, LUO Zhu-Zhu, GAO Zhen-Ni, LI Yue, YAN Zhen-Gang, LIU Qiang, NIE Zhi-Gang

2015, 24(4):  39-47.  DOI: 10.11686/cyxb20150405

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Research has been undertaken using the validated Agricultural Production System Simulator Model (APSIM) to explore the synergy effects of water and fertilizer supply on grain yields of crops under different tillage practices in the loess hilly region of Dingxi City, Gansu Province. The model was used to simulate yields of rotational systems of wheat (Triticum aestivum) and pea (Pisum sativum) under three different tillage practices: traditional tillage (T), no tillage (NT) and no tillage mulched with straw within 35 years (NTS). Multiple regression analysis was used to investigate the synergy effects of precipitation at the growing stage (X₃), fallow period (X₂) and when nitrogen was applied (X₁). Results showed that the order of relevance to grain yields was X₃>X₂>X₁. For X₃ and X₂, the contribution rate differed in the order of NTS＞NT＞T. Nitrogen application has an oppositive U-shaped quadratic relation with wheat and pea yield. The optimum nitrogen quantities were 65.0, 65.5 and 44.5 kg/ha for spring wheat and 17.9, 18.5 and 23.8 kg/ha for peas under T, NT and NTS respectively. The contribution of nitrogen to the grain yields of each rotational system followed the order NTS＞NT＞T for spring wheat and NTS＞NT＞T for peas. Precipitation was therefore the key factor for the grain yields of spring wheat and pea in this region, especially in the case of NTS. Nitrogen application had different effects on yield under the three different tillage practices.

Temporal variation of water soluble carbohydrate in Seriphidium transiliense under different mowing intensities and it how to transfer during seasonal change

HOU Yu-Rong, AN Sha-Zhou

2015, 24(4):  48-56.  DOI: 10.11686/cyxb20150406

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Seriphidium transiliense is one of a common constructive species of sagebrush desert in Xinjiang, which is responsible for livestock recovery body fat, lambing, nurture young in spring pasture and storage next generation in autumn pasture. The paper analyzed the water-soluble carbohydrate dynamic change in roots, stems, and leaves of S. transiliense in different mowing intensities based on the sagebrush desert and field positional sampling. Meanwhile, based on the analysis for data, the beginning stage of nutrient storage and consumption of S. transiliense made clear, but also, the relevance was judged between water-soluble carbohydrate storage amount in autumn root and plant consumed carbohydrate for germination in coming year. The results showed that, the content of water-soluble carbohydrate in roots finished the accumulation on Oct. 15. When the plants are beginning turning green in the coming year, water-soluble carbohydrate stored in roots transferred from belowground back to aboveground automatically, which providing nutrients to turning green and regrowth. Water-soluble carbohydrate of C₂ treatment was different comparing to others, it not only had a highest sugar accumulation in autumn and maintained a higher content after plants turning green and regrowth in coming year, water-soluble carbohydrate content of C₀ treatment always the lowest one regardless of in autumn or in spring, metabolism was mild recession in plants body and maintaining its life reluctantly. Non-mowing is not the best recovery method, this explained that moderate mowing is advantageous to forage grass growth and recycling. But C₀ even presented inferior strength and the death.

Simulation study of nutrient leaching from soils irrigated with biogas slurry under different environmental temperatures

ZHANG Zhen, TANG Hua, GUO Yan-Jun

2015, 24(4):  57-65.  DOI: 10.11686/cyxb20150407

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Biogas slurry is widely used in agriculture due to its high nutrient utilization rate in soil. However, temperature might influence nutrient leaching from the slurry by affecting the physical and chemical characteristics of soils. In this study, nutrient leaching under different environmental temperatures was analyzed using the soil column simulation method, with the aim of providing advice for slurry use in different seasons. Three simulations were investigated: 300 mL water as control, 40 mL slurry plus 260 mL water, and 80 mL slurry plus 220 mL water, with application rates equaling to 0, 130 and 260 kg N/ha respectively. 300 mL of each solution were applied per soil column (7.5 cm, height 20 cm) with irrigation periods of 30 min. Leached solutions were collected until no further leaching was observed. The soil columns were cultured under 20 and 30℃ conditions and leached every 6 days for 5 times in total. The leached solution was analyzed to determine levels of total nitrogen, NO₃-N, NH₄-N, total potassium, total phosphorus, available phosphorus and electric conductance. Results showed that NO₃-N, NH₄-N, total phosphorus, total potassium and electric conductance decreased with increased leaching times only for the water control. Compared to the control, slurry applications increased the amounts of leached nitrogen, phosphorus and potassium. With the 40 mL solution, total nitrogen, total potassium and total phosphorus increased on average by 73%, 880% and 388% respectively. The amount of leached nutrient increased with increased slurry application rates and with higher environmental temperatures. Compared with 20℃, the 30℃ leached solutions showed increased total nitrogen, total phosphorus and total potassium by 14.7%, 33.6%, and 24.1% respectively. Higher environmental temperatures thus increase the amount of nutrient leaching from soils irrigated with biogas slurry. It is thus suggested that application times should be reduced in summer and increased in spring and autumn. However, the total amount of biogas slurry should be less than 130 kg N/ha to avoid excessive leaching and pollution of surrounding environment.

Trichomes and fruit structures of Angelica and related genera of the family Apiaceae and their taxonomic significance

WANG Yu-Ting, LIU Mei, CHENG Xin-Yu

2015, 24(4):  66-75.  DOI: 10.11686/cyxb20150408

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Trichomes and fruit structures of Angelica and seven related genera (Archangelica, Coelopleurum, Czernaevia, Heracleum, Levisticum, Ostericum, and Peucedanum) were studied. Differences in the trichome and fruit structures (e.g. wing, vitta, vascular bundle, mesocarp, endocarp, commissural side, and crystals) were found to provide useful characters to distinguish between Angelica and related taxa. Angelica austro-yunnanensis and A. oncosepala should be moved to the genus Heracleum, and other taxa of the Angelica group could be divided two groups, one with a wide and the other narrow commisure. In the former the fruit structures of the taxa are similar to those of Peucedanum, and differ from those of Heracleum and in the latter they are similar to those of Archangelica, Coelopleurum, Czernaevia, Levisticum, and Ostericum. This study supports the findings from molecular research that as currently defined the Angelicaceae is not a natural group. Angelica and Peucedanum should be placed in an Angelica clade and Heracleum in a Heracleum clade. The fruit structures of Ostericum differ from the other genera in the wing without mesocarp cells, and the rib duct presenting inside of the vascular bundles. On this evidence, the genus Ostericum is not very close to the genera Coelopleurum, Czernaevia, and Levisticum.

Analysis of the ecological structure of angiosperm composition in Juglans cathayensis in the Nature Conservation Area of Xinjiang, China

ZHANG Wei, NUER Mai-Mai-Ti, JIAO Zi-Wei, YANG Yu-Fei, LI Jian-Dong

2015, 24(4):  76-86.  DOI: 10.11686/cyxb20150409

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289 sample quadrats of Juglans cathayensis were set up in the Nature Conservation Area in Xinjiang and the ecological structure of their angiosperm composition has been analyzed. The 193 species of angiosperm observed belong to 49 families, 6 growth forms of plant, 4 growth forms of root, 6 life forms, 5 ecological types of water and 6 forage value types. The most common species is Cornpositae (17.1%), followed by Gramineae (11.4%) and Rosaceae (7.3%). In terms of plant growth form, 33.7% are of the erect type, 28.0% the tuft type and 14.5% the half bottom of lotus seed type. With regard to root growth form, most species belong to tap root type (69.9%), followed by rhizome (19.7%) and brush root (8.8%). Most angiosperm belong to the hemicryptophyte life form (33.2%), followed by geophyte (23.3%) and therophyte (21.2%). Mesophyte are the most common ecological type of water (73.1%), followed by xerophytic (10.9%). In terms of forage value, excellent and good quality species predominate (67.3%), with coarse, poisonous and inedible types making up only 11.4%. This study shows that in the Nature Conservation Area of J. cathayensis, plants and roots take on the typical hemicryptophytic and xerophytic characteristics of a temperate plant community and most species possess high forage value.

Effects of nitric oxide on Medicago sativa seed germination under imbibitional chilling

ZHAO Meng, WEI Xiao-Hong

2015, 24(4):  87-94.  DOI: 10.11686/cyxb20150410

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Seeds of Medicago sativa were used to study the effects of 0.1 mmol/L sodium nitroprusside (SNP), as a source of nitric oxide, on seed germination and antioxidant capacity under imbibitional chilling at 4℃. Four treatments: control, chilling, SNP and chilling+SNP were replicated three times. The results indicated that after imbibitional chilling for 12 h and germination at 25℃ for 84 h, the vigor and germination of M. sativa seeds were increased by SNP treatment. The activities of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) increased 149.3% to 60.4% by SNP treatment. The radical clearance rate tended to decline with SNP treatments and chilling for 12, 24 and 48 h. At 12 h chilling the radical clearance rate reached a maximum of 97.5%. Imposing exogenous nitric oxide can promote germination, enhance antioxidant enzyme activities and reduce the reactive oxygen damage in M. sativa seed.

Effect of natural saline soil on organic acid accumulation in the stem and leaf of Chloris virgata and analysis of stress factors

LV Jia-Qiang, LI Chang-You, YANG Chun-Wu, HU Rui

2015, 24(4):  95-103.  DOI: 10.11686/cyxb20150411

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Chloris virgata is a native forage grass with strong salt-alkali resistance. Samples of 45 natural populations of C. virgata were randomly chosen from the saline meadows in Changling County, Jilin Province. Soil electrical conductivity, pH and buffering capacity were measured in each sample area to assess the degree of soil salinization and associated plant stress. Organic acid contents in C. virgata stems and leaves were measured as plant physiological response indexes. A regression analysis was conducted incorporating incorporating both plant and soil data. C. virgata accumulated large amounts of organic acids including citric acid, malic acid and oxalic acid in response to strong salt-alkali stress, and there was a significantly positive correlation between the accumulation of citric acid, malic acid, oxalic acid and total organic acids and the three soil indexes. By contrast, the level of amber acid was less under saline stress and was negatively correlated with the three soil indexes. Further multiple regression analysis showed that soil electrical conductivity was more strongly correlated with the accumulation of the plant organic acids (except succinic acid) than pH and buffering capacity. In conclusion, soil electric conductivity can be used as a reliable indication of stress intensity faced by C. virgata plants exposed to salt-alkali stress in natural saline environments.

Quality of mixed naked oats (Avena nuda) and alfalfa (Medicago sativa) silage

GE Jian, YANG Cui-Jun, YANG Zhi-Min, BAI Xue-Mei, ZHAO Hai-Xiang, LIU Gui-He

2015, 24(4):  104-113.  DOI: 10.11686/cyxb20150412

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Using sun-dried or fresh alfalfa and naked oats as materials, five silages, including alfalfa silage, naked oats silage, three mix silage, (alfalfa∶naked oats =1∶1, alfalfa∶naked oats =1∶2 and alfalfa∶naked oats =2∶1), were prepared. After 60 days ensiling, the sensory score, fermentation quality and nutrition composition of silages were evaluated. The results revealed that silage made of fresh alfalfa showed a common performance in the sensory score and V-Score and Kaiser-Score evaluation system, while both silage made of sun-dried materials and mixed silage had a improved silage score. Sun-drying and mixing process had effect on silage quality, such as decreasing pH value, acetic acid (AA), propionic acid (PA), butyrate acid (BA) and ammonia nitrogen /total nitrogen (AN/TN) (P<0.01 or P<0.05) content of silages, significantly increasing lactate (LA) content (P<0.01or P<0.05) of silages. Among which, mixed silage of alfalfa and naked oats with a ratio of 2∶1 showed a biggest increasing and decreasing describe above. The sun-drying process had a significantly effect on the dry matter (DM), water-soluble carbohydrate (WSC) and crude ash (Ash) content of silage, while had no effect on remaining nutrients. Notably, mixing process had significant effects on most of fermentative indexes, such as the content of crude protein (CP), water-soluble carbohydrate (WSC), neutral detergent fiber (NDF) (P<0.05 or P<0.01), whereas had no effect on other nutrient indexes. In conclusion, the interaction of sun-drying process to silage materials and mixed ratio can improve silage quality, while had no effect on nutrient composition of silages. According to the sensory score, fermentation quality, and nutrient content, the mixed and sun-dried materials can produce better silages than sole and fresh material, and silage made of naked oats and alfalfa with a ration of 2∶1 was the best.

Effect of feeding grape pomace on nutrient digestibility, body weight gain, and carcass quality in lambs

LU Zhen-Zhen,ZHENG Chen, LI Fa-Di, LI Chong,TANG De-Fu, WENG Xiu-Xiu,LIU Ting, MA Zhi-Yuan, MA Dong-Fang

2015, 24(4):  114-120.  DOI: 10.11686/cyxb20150413

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A total of 60 hybrid 3-month-old Dorper (♂) × Small Tail Han sheep (♀) F1 male lambs were randomly allocated to 4 groups with 15 animals per group to determine the effect of different levels of grape pomace on nutrient digestibility, body weight gain, and carcass quality. The control group (groupⅠ) was fed a base diet without grape pomace, while the trial groups were fed diets with grape pomace added to the base diet at 8%, 16% or 24% on a dry weight basis (groups Ⅱ, Ⅲ and Ⅳ), respectively. The condensed tannin (CT) levels in the diets for each group were 0, 1.5, 3.0 and 4.5 g/kg, respectively. The apparent digestibility of acid detergent fiber (ADF) and N of the control group were significantly higher than group Ⅳ(P<0.05). In contrast, the lambs in trial groups had significantly higher average daily feed intake, average daily gain, carcass weight, dressing out rate and GR values (carcass fat cotent) (P<0.05), as well as a higher N retention rate (P<0.01), than the control group. The feed conversion rate (P<0.01) and carcass net meat content of group Ⅱ were significantly higher (P<0.05) than for the control group. With increase of CT content in the diet, apparent digestibility of N, ADF and neutral detergent fiber (NDF) gradually decreased. However, apparent N retention increased. In conclusion, dietary supplementation with 8%-16% of grape pomace had a positive effect on feed conversion efficiency, average daily body weight gain, carcass characteristics and nutrient utilization.

Detection of pathogenic organisms in Medicago sativa in Zhangye, Gansu Province

WEN Zhao-Hui, NAN Zhi-Biao

2015, 24(4):  121-126.  DOI: 10.11686/cyxb20150414

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Two Medicago sativa plants with severe leaf mosaic symptoms were collected from alfalfa fields in Linze County, Gansu Province, in July 2011. The two samples were tested by enzyme-linked-immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR). The tested specimens were negative for Cucumber mosaic virus, Tobacco streak virus, Watermelon mosaic virus, Potato virus X, Potato virus Y, Tobacco ringspot virus, Tomato ringspot virus and Bean yellow mosaic virus. However, Tomato mosaic virus (ToMV) and Alfalfa mosaic virus (AMV) were detected. The 687 and 351 bp fragments obtained from PCR with appropriate species-specific ToMV and AMV primers showed 99% nucleotide similarity with published ToMV CP and AMV CP gene sequences. A 805 bp PCR products was obtained using genus-specific Tobamovirus primers and the presence of ToMV was confirmed by RT-PCR-RFLP. To the best of our knowledge, this is the first report of ToMV in alfalfa.

Factors influencing pathogenicity of Uromyces striatus

LI Yue, YUAN Qing-Hua

2015, 24(4):  127-131.  DOI: 10.11686/cyxb20150415

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Uromyces striatus is the causal organism of alfalfa rust. The effects of humidity, temperature and time on disease severity and the effects of incubation temperature on the latent period of alfalfa rust were investigated using growth chamber and greenhouse experiments, respectively. Alfalfa plants were inoculated with U. striatus and incubated at 19℃ with 100% relative humidity (RH) for different periods before being transferred to 25℃ conditions for 15 days. Subsequently, spore densities on the leaves of inoculated plants were assessed. The results showed that spore density of treatments incubated at 19℃ for 12 h to 48 h was significantly higher than those incubated for 4 h to 8 h. Plants were also inoculated and incubated at 19℃ with 100% RH for 24 h and then transferred to different temperature environments; 15, 20, 25, 30 and 35℃. Plants transferred to 35℃ conditions did not display any alfalfa rust symptoms. The disease latent period on inoculated plants grown at 15, 20, 25 and 30℃ was 11, 10, 7 and 7 days, respectively. The spore density on leaves in the 25 and 30℃ treatments was significantly higher than the 15 and 20℃ treatments. There was no relationship between incubator temperature and disease latent period.

Selective abortion and fruit-set pattern of Vicia unijuga in Gannan Tibetan region

SHEN Zi-Wei, NAN Zhi-Biao

2015, 24(4):  132-139.  DOI: 10.11686/cyxb20150416

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Vicia unijuga is a valuable forage species in Gannan Tibetan region, and its seed production is important for planting and popularizing of V. unijuga in this region. Fruit-set patterns and selective abortion of flowers of V. unijuga in Gannan Tibetan region were studied. The results showed that: 1) In terms of time, the highest fruit set was observed for the two-year-old population (28.8%) at the full-bloom stage and for the five-year-old population (41.6%) at the early flowering stage. For both populations, the lowest fruit set (3.0% and 1.1%) was found at the end of flowering stage. There was no appreciable difference (P>0.05) in the seed number per pod between the early flowering and full-bloom stages for the two populations, and the seed number per pod at the end of flowering stage was zero; 2) On an inflorescence, the highest fruit set was in the middle of the inflorescence for both populations. The two-year-old population was 43.9% and the five-year-old population was 41.6%. However, the seed number per pod exhibited no significant difference (P>0.05) in each part of the inflorescence for the two populations; 3) The ovules closing to the stigma and pedicel were more likely to abort. The ovules in the 2^nd, 3^rd, 4^th and 5^th positions starting from the side of the stigma would have higher possibility to form mature seeds and showed alternating abortion patterns; 4) The number of fruit per inflorescence was lower than eight, which was not affected by the number of flowers on the inflorescence. It may indicate that the selective abortion of the fruit and seed is caused by the resource limitations, or is a reproductive strategy of V. unijuga that the redundant flowers are selectively aborted by the plants, suggesting that the actual seed yield of V. unijuga will be influenced by the selective abortion.

The antioxidant enzyme activities and gene expression induced by spermidine in leaves of white clover

WANG Xiao-Juan, LI Zhou, PENG Yan

2015, 24(4):  140-147.  DOI: 10.11686/cyxb20150417

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A pharmacological experiment was designed to investigate the function of nitric oxide (NO) in the spermidine-induced antioxidant enzyme activities and gene expression in white clover (Ladino). Treatment with exogenous spermidine (Spd) at 20 μmol/L significantly improved (P<0.05) the nitrate reductase (NR) and nitric oxide synthase (NOS) activities in leaves of white clover and NO content reached a maximum after 2 h of Spd treatment. However, treatments that included 50 μmol/L bovine hemoglobin (Hb) (NO-scavenger), 5 mmol/L partial sodium vanadate (NaVO₃) (a NR-inhibitor) and 200 μmol/L NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) (a NOS-inhibitor) inhibited the accumulation of NO in Spd-treated white clover. Exogenous Spd treatment can also enhance the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbic acid peroxidase (APX) and the relevant gene expression in leaves. Hb, NaVO₃ and L-NAME inhibited the Spd-induced enzyme activities of SOD, POD, CAT, APX and gene expression to different degrees. These results suggest that Spd induced NO by enhancing antioxidant enzyme activities and expression of related genes in white clover, and that NO production is probably regulated from the NR and NOS pathways.

Effects of spermidine on proline metabolism, antioxidant enzyme activity and gene expression in white clover leaves under water stress

LI Zhou, PENG Yan

2015, 24(4):  148-156.  DOI: 10.11686/cyxb20150418

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The effects of spermidine (Spd) on relative water content, reactive oxygen, membrane lipid preoxidation, antioxidant enzyme activity and proline metabolism were studied in white clover (Trifolium repens) leaves, cultivar ‘Ladino’. The expression patterns of four different antioxidant enzyme genes were analyzed using semi-quantitative RT-PCR under different water stress. Under water stress, relative water content gradually declined whereas reactive oxygen and malondialdehyde (MDA) content increased. Exogenous Spd significantly improved relative water content and effectively reduced the accumulation of reactive oxygen and MDA. Exogenous Spd changed antioxidant activities and gene expression pattern under different water stress regimes and increased expression of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) genes to improve antioxidant enzyme activities, reducing water stress injury. Exogenous Spd accelerated proline catabolism and biosynthesis from the glutamate pathway during water stress although it had no effect on the ornithine pathway of proline biosynthesis. The results suggested that exogenous Spd can effectively improve water stress tolerance of white clover associated with the improving antioxidant enzyme activities, enhancing expression of genes encoding antioxidant enzymes and accelerating proline metabolism.

Chromosomal composition and forage production potential of Yuqilin 58

LI Hua-Xiong, CHENG Ming-Jun, SU Yue-Gui, LI Zhi-Long, JIANG Wei-Ming, ZHANG Hong-Fen, ZHENG Ming-Min, RONG Ting-Zhao, ZHOU Shu-Feng, WU Yuan-Qi, CAO Mo-Ju, TANG Qi-Lin

2015, 24(4):  157-163.  DOI: 10.11686/cyxb20150419

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Multi-color genomic in situ hybridization (McGISH) was employed to identify the chromosomal composition of Yuqilin 58 (MTPP-58), derived from the tri-generic hybridization of Zea mays, Zea perennis and Tripsacum dactyloides. GISH (Genomic in situ hybridization) showed that MTPP-58 is an aneuploid with 58 chromosomes; 11, 28 and 17 chromosomes came from Z. mays, Z. perennis and T. dactyloides respectively. Translocation of chromosomes between Z. mays and Z. perennis accounted for the balance. Assessment of forage yield, forage quality, over wintering rate and reproductive characteristics showed that the fresh and dry hay yield of MTPP-58 were 93.845 t/ha and 22.083 t/ha respectively, in the first year, and 82.851 t/ha and 14.394 t/ha respectively, in the second year. The crude protein content of the forage was 10.48% with a leaf/stem ratio of 0.71. Winter survival rate was 100%. MTPP-58 displayed a number of desirable characteristics including good growth, a well-developed root system, good tillering ability and good reproductive potential suggesting it has good potential for ongoing development.

Analysis of DNA methylation of tall fescue in response to drought based on methylation-sensitive amplification polymorphism (MSAP)

TANG Xiao-Mei, WANG Yan, MA Dong-Wei, CHENG Hai-Yang, YANG Hong, DAI Ya, TAO Xiang, MA Xin-Rong

2015, 24(4):  164-173.  DOI: 10.11686/cyxb20150420

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DNA methylation is one of the most important mechanisms in the epigenetic regulation in eukaryotic cells. DNA methylation affects gene expression and plays an important role in plants adapting to adverse environments. Tall fescue (Festuca arundinacea), a gramineous monocot, has superior resistance to cold and heat. It is widely used for sports turf, erosion control, and as a forage grass. However, the distribution and yield of tall fescue is constrained by drought stress. In this paper, the growth was measured and the DNA methylation profile of tall fescue (cv. Barlexas) evaluated using methylation-sensitive amplification polymorphism (MSAP) after 15 d drought treatment. The growth of the plants was seriously restricted under water-deficit challenge. Genome-wide, a total of 475 CCGG sites were detected by MSAP using 10 selective primer pairs in tall fescue seedlings. Among these sites, 131 sites (27.58%) showed drought-induced methylation and demethylation. The total methylation level was 43.16% in control and 42.11% in drought-treatment, which indicates a 1.05% decrease when exposed to drought. The sequences of 13 amplified fragments were successfully obtained, representing the differential types of methylation changes. Homologous analysis showed that most of the fragments were relevant to stress. Two sequences (Fa6 and Fa7) with enhanced methylation induced by drought were homologous to a retrotransposon of Triticum aestivum and Hordeum vulgare, respectively, showing drought induced methylation of the retrotransposons. The methylation of transposons is vital in maintaining DNA stability. In summary, drought stress decreased the total DNA methylation level in the tall fescue genome, and the altered methylation in response to stress was probably involved in environmental stress acclimation.

Research progress and prospects for controlling plant diseases using Pseudomonas fluorescens

SUN Guang-Zheng, YAO Tuo, ZHAO Gui-Qin, LU Hu, MA Wen-Bin

2015, 24(4):  174-190.  DOI: 10.11686/cyxb20150421

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Biological control agents, especially Pseudomonas fluorescens, have become one of the most important and useful options for plant disease management. This study reviews the culture characteristics of P. fluorescens, including the morphological characteristics, physiological and biochemical characteristics, culture conditions and the similarities or differences with other bacteria also isolated from various plant groups to control diseases. The disease control efficiency of P. fluorescens when used alone or together with other bacteria or treatment preparations is summarized. The modes of action of both P. fluorescens and bio-active substances used for controlling plant diseases are elucidated. Hazards of P. fluorescens in medicine, agriculture and environmental protection are discussed. The outlook and prospects for biological control in the field are also evaluated and a field risk assessment presented.

The important role of arbuscular mycorrhizal fungi in carbon storage in grassland ecosystems

ZHANG Feng, NAN Zhi-Biao, YAN Fei-Yang, LI Fang, DUAN Ting-Yu

2015, 24(4):  191-200.  DOI: 10.11686/cyxb20150422

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Grassland ecosystems occupy an important position in global carbon storage. Arbuscular mycorrhizal fungi (AMF) exist widely in these grasslands and play a significant role in the ecosystem’s ability to act as carbon sinks. This paper summarizes this role from the perspective of the fungi’s functional diversity. It reviews, 1) the impact of AMF on the net primary productivity of grassland ecosystems, 2) their impact on variation in the soil carbon pool, 3) the response of AMF to elevated atmospheric CO₂ and increased anthropogenic nitrogen deposition, and 4) how grazing management practices could affect AMF and therefore the carbon cycle of grassland systems. This review is undertaken in order to provide references for evaluating carbon sinks, calculating carbon fixation rates, predicting carbon storage and coping with global climate change.

Shrub-mediated “fertile island” effects in arid and semi-arid grassland

QU Wang-Long, YANG Xiao-Peng, ZHANG Cun-Tao, WEI Bing

2015, 24(4):  201-207.  DOI: 10.11686/cyxb20150423

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Shrubs can change the local ecological environment, which in turn impacts on the surrounding plant biomass, plant composition, plant chemical composition, and macro- and micronutrient elements in the nearby soil. Shrubs can change the local micro-environment in ways which affect the spatial distribution and circulation of nutrients, and may concentrate nutrients under the shrub canopy or enhance moisture retention. Such patches displaying enhanced moisture and nutrient retention and shade effects relative to the surrounding space are known as the shrub fertile islands. Here we discuss the ecological impact of shrubs in natural arid and semi-arid grassland areas and their role in the desert grassland restoration process, reduction of soil erosion and associated grassland productivity decline. The importance of shrubs and their ecological significance for vegetation succession and restoration and reconstruction is discussed, and a theoretical basis for prevention and control of land degradation in ecologically fragile regions is provided.

Decay and nutrient release in Vulpia myuros grasses, a species suitable for soil conservation in temperate zone orchards

YANG Hong-Xiao, ZHOU Mei-Hua, LI Jun-Liang, LIANG Bin, SUI Fang-Gong

2015, 24(4):  208-213.  DOI: 10.11686/cyxb20150424

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The grass species Vulpia myuros has a September-to-June growth period and can enhance orchard soils and prevent water loss and soil erosion. However, orchard managers are often concerned by the species’ presence as a competitor for nutrients with fruit trees. This paper reports an investigation of the decomposition and nutrient release rates of V. myuros in the Qingdao area of northern China, which has a humid climate. Dead V. myuros was collected in late June 2012 and buried at the depth of 10 cm in soils with three moisture content levels (65%, 75% and 85%). Decay rates and the release rates of carbon, nitrogen, phosphorus and potassium were measured every ten days between July and October. Results showed that V. myuros has a very fast decay rate, with approximately 30% decomposed within 80 days. This decay releases carbon, nitrogen, phosphorous and potassium, principally during the first 20-40 days. Potassium had the fastest release rate, followed by phosphorous, while nitrogen and carbon were the slowest. Soil moisture had a significant effect on decomposition. The decay rate is accelerated when moisture levels are raised from 65% to 85%. The study concludes that V. myuros can supply nutrients to fruit trees and does not compete with them, as previously thought. Thus V. myuros can be used in the temperate hilly regions in northern China in order to enhance nutrient cycling in orchard ecosystems.

Effect of soil bulk density on root morphology and biomass of vetiver grass seedlings

LIU Wan-Gou, LI Liang-Xian, XIE Hai-Rong, HE Yong-Yi, LIU Jin-Xiang

2015, 24(4):  214-220.  DOI: 10.11686/cyxb20150425

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Vetiver grass (Vetiveria zizanioides) has an extensive root system and is consequently used worldwide for water and soil conservation. However, soil compaction resulting in high soil bulk density negatively influences root growth. In order to understand the adaptation of vetiver grass to soil compaction, the effects of soil of different bulk density, 1.20 g/cm³ (D_1.20), 1.35 g/cm³ (D_1.35) and 1.58 g/cm³ (D_1.58), on the root morphology and biomass of vetiver seedlings were investigated using soil columns. The results showed that shoot and root dry weight, root:shoot ratio, root surface area, root length density and root volume density decreased with increasing bulk density, but that average root diameter increased. High bulk density influenced the spatial distribution of roots; more roots grew in the upper (0-6 cm) and lower (18-24 cm) soil horizons under the D_1.20 and D_1.35 treatments, suggesting that vetiver typically produces a deep root system but that root growth is inhibited by high soil bulk density, confining roots to the upper soil horizon (0-6 cm). The average root diameter in the D_1.20 and D_1.35 treatments decreased but increased in D_1.58 with increasing soil depth. It is concluded that vetiver grass could tolerate moderately compacted soil.