Table of Content

20 December 2014, Volume 23 Issue 6

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Orginal Article

Ecological and productive succession process of a cultivated alfalfa grassland community on Loess Plateau

WANG Shu-zhuan,HAO Ming-de,PU Qiong,WU Zhen-hai

2014, 23(6):  1-10.  DOI: 10.11686/cyxb20140601

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The ecological and productive succession process of cultivated alfalfa grassland communities which were established 31 years ago on the Loess Plateau was studied. The sown alfalfa grassland evolved with time to display more and more characteristics of natural grassland. As the community structure developed, ecological indexes changed significantly and the change process could be divided into three stages. The first stage was alfalfa dominance from 2 to 6 years.The second stage was from 6 to 31 years, during which alfalfa grassland gradually transitioned to Stipa bungeana natural grassland. The third stage was S. bungeana secondary natural grassland after 31 years. The alfalfa grassland exhibited marked retrogressive succession from 6 years after establishment. At this point the alfalfa important value, community diverstiy index, evenness index and dominance index gradually decreased. The community structure tended to complexity, the ecological stability increased and the community characteristics gradually evolved towards those of natural vegetation. The herbage production initially showed an increasing trend, reached a maximum after 6 years, and then gradually declined. The annual biomass production correlated well with alfalfa contribution, while the highest direct path coefficient in a path coefficient analysis linked annual biomass production and the diversity index. As sown alfalfa grassland aged, the correlation between the annual biomass and the diversity index increased and then decreased and 6 years from sowing represented a turning point for productivity and ecological succession. By removing weeds, fertilization, effective use of water and exploring appropriate cultivation practices, the succession to natural grassland and “ecological stability” could be delayed and the productive phase prolonged.

Analysis of net primary production of potential natural vegetation in the upper reaches of the Heihe River basin

WANG Da-wei,ZHAO Jun,HAN Tao,LI Li-li

2014, 23(6):  11-19.  DOI: 10.11686/cyxb20140602

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Understanding the spatial pattern of the potential natural vegetation (PNV) is import for identifying the response of spatial pattern to the climate change and carbon cycling and for predicting net primary production (NPP) distribution of PNV in ecological restoration projects. The dynamic characteristics of spatial distribution, the potential vegetation of NPP, the gross and cumulative NPP and the relationship between NPP and hydro-thermal factors on the upper research of Heihe River were investigated by using meteorological data including rainfall, temperature and accumulative temperature ≥0℃ (1960-2009) in conjunction with the location and altitude record from 12 climate stations in western China covering the period from 1960 to 2009. Based on these data, we used a comprehensive sequential classification system (CSCS) method, validated at regional and global scales, to estimate the NPP variation of grassland ecosystems and the responses to climate change. PNV’s fell into 8 classes based on vertical zones. Increasing altitude in the mountainous region resulted in NPP initially tending to rise but subsequently decline. The predictive distribution of NPP was dependent on hydro-thermal factors. The relationship between NPP and annual accumulated temperature ≥0℃ was negative in cold areas, but was positive in cool temperate areas. There were positive correlations between NPP and humidity in arid, semiarid, sub-humid and humid areas. The spatial pattern of PNV reflected the ability of vegetation to adapt to different habitats and climate change.

Measuring grassland vegetation cover using digital camera images

CHEN Zu-gang,BATU Nacun,XU Zhi-ying,HU Yun-feng

2014, 23(6):  20-27.  DOI: 10.11686/cyxb20140603

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Grassland vegetation coverage is an important parameter for characterizing vegetation condition in ecological research. With the popularization of digital devices, such as digital cameras, vegetation coverage can be measured in automatic or semi-automatic ways by analyzing the digital photographs using image processing platforms. Moreover, the rapid development and popularity of smart mobile devices (such as the iPhone/iPad) means that there is an opportunity to investigate the use of these devices for real-time collection, processing and analyzing of data such as vegetation cover. Five quadrats with different vegetation cover were selected and measured in different lighting conditions. Photographs were taken every 2 h from 6 AM to 6 PM. The RGB threshold value method, RGB decision tree method and HSV discriminant method were selected for calculating vegetation cover. When light intensity was constant, vegetation cover had no effect on the measurement precision of the RGB threshold value method and the HSV discriminant method, but greatly influenced the measurement precision of the RGB decision tree method. The RGB threshold value method and the HSV discriminant method were influenced by light condition; when light intensity increased cover estimates declined. However, there did not appear to be a good relationship between light intensity and cover estimates for the RGB threshold value method. Overall, the measurement precision of the RGB threshold value and HSV discriminant methods were higher than the RGB decision tree method but the latter could identify plant stems and flowers that were not green. Using the current green plant pixel identification methods combined with improved statistical analysis methods such as algorithms able to examine edge pixels further improvement of the precision of this technique could be achieved.

Effect of sampling method on the estimation of soil carbon and nitrogen storages in thicketed semiarid grasslands, Inner Mongolia

CHAI Hua,FANG Jiang-ping,WEN Ding,LI Jie,HE Nian-peng

2014, 23(6):  28-35.  DOI: 10.11686/cyxb20140604

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Large areas of grasslands have been subjected to severe degradation in Inner Mongolia because of long-term overgrazing. Thicketization, associated with an increase in Caragana microphylla, on Inner Mongolian grasslands has resulted in an apparent increase in heterogeneity of the distribution of soil nutrients. Consequently, setting up appropriate sampling points is crucial for accurately evaluating storage of soil carbon (C) and nitrogen (N). In this study we selected three grasslands with different levels of thicketization (different levels of degradation) and analyzed the differences in soil C and N from soil sampled from underneath, the canopy edge, and between C. microphylla shrubs. Soil C and N contents differed at different sampling locations. In lightly thicketed grasslands, carbon storage in the 0-100 cm soil layer varied; soil underneath shrub canopies, the canopy edge and between shrubs contained 8831.26 g C/m², 8174.59 g C/m² and 7716.48 g C/m² respectively. Sample variation was greatest under the shrubs, intermediate at the canopy edge and least between shrubs. Our findings suggest that traditional sampling between shrubs can be used to accurately estimate soil C and N content in thicketed grasslands in Inner Mongolia. However, apparent spatial heterogeneity in soil nutrients was found; soil C and N contents were negatively correlated with shrub size in different grasslands.

Effect of change in semiarid sand dune habitat on aboveground plant biomass, carbon and nitrogen

ZHOU Xin,ZUO Xiao-an,ZHAO Xue-yong,WANG Shao-kun,LUO Yong-qing,YUE Xiang-fei,ZHANG La-mei

2014, 23(6):  36-44.  DOI: 10.11686/cyxb20140605

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This study examined the characteristics of aboveground plant biomass, carbon (C) content, nitrogen (N) content and total C and N of four different habitats; mobile, semi-stable and stable dunes (three stages of sand dune stabilization) and natural grassland at Horqin, Inner Mongolia, in Northern China. The change in sand dune habitat had significant impacts on leaf dry weight, branch dry weight, total biomass, C and N contents and total C and N. Leaf and branch dry weight, total biomass, % C and N and total C and N in the fixed dune were higher than those in mobile and semi-stable dunes. Total biomass, leaf and branch dry weight, total branch C, total biomass C and total branch N in the grassland were lower than those in the stable dune, but higher than those in the mobile dune. The leaf and branch C %, total C % and total branch C in the semi-stable dune were higher than those in the mobile dune, while leaf and branch N % and total N in the semi-stable dune were lower than the mobile dune. Annual plant species separately accounted for 63.99%, 79.28%, 70.86% of the total biomass in the mobile dune, stable dune and grassland respectively, while shrubs accounted for 73.15% of the total biomass in the semi-stable dune. C₃ plant species contributed 39.99%, 90.87%, 96.01%, 82.67% of the total biomass in the mobile, semi-stable and stable dunes and grassland respectively. The biomass, total C and N of annuals and C₃ plants in the stable dune were higher than in the other habitats. In semi-stable and stable dunes and grassland, the C %, total C and N of C₃ plants were higher than those of C₄ plants. The results indicate that total biomass, C and N increase gradually during sand dune stabilization. Plants on the stable dune had greater potential to sequester C and N, mostly contributed by annuals and C₃ species. The C₃ species also provided an important buffer against the decrease in C₄ plant biomass during the sand dune stabilization process.

The ecological stoichiometry of dominant species in different land uses type of grassland

XU Sha,GONG Ji-rui,ZHANG Zi-yu,LIU Min,WANG Yi-hui,LUO Qin-pu

2014, 23(6):  45-53.  DOI: 10.11686/cyxb20140606

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The stoichiometric elements of three dominant species, namely Stipa grandis, Artemisia frigida and Leymus chinensis were measured in different land use (grazing-exclusion, grazing and mowing) in the temperate grassland in Inner Mongolia. The seasonal variations of stoichiometric characteristic of plants and soil under different grassland uses were discussed. The stoichiometric characteristic response mechanisms of the plants and the nutrient limiting conditions were analyzed. The results show that obvious seasonal variations in C, N, P concentrations and their mass ratio of the three species exist in each grassland use type. Grassland use type, species and their interactions have significant impacts on N, P concentrations and the ratios C∶N, C∶P and N∶P, among which C concentration is relatively stable in the whole growing season and different uses show no significant impact on it. N concentration reduces overall. N and P concentrations in leaves are higher in grazing plot than those in grazing-exclusion and mowing plots. It shows that grazing can increased N and P concentrations. On the whole, plant growth is limited by N. Characteristics of soil nutrients among different grassland uses have certain differences, where comparably more serious N deficiency happens in the enclosed plot and P deficiency in the grazing plot. Generally the organic matter, C, N and P concentrations in the grazing plot are higher than those in the mowing and enclosed plots. It shows that soil nutrients can be increased which can promote plants growth in grazing plot.

Spatial distribution of soil carbon and nitrogen in Jiaozhou Bay estuarine wetlands

XIE Wen-xia,ZHU Kun-jie,CUI Yu-qian,DU Hui-na,CHEN Jian-lei

2014, 23(6):  54-60.  DOI: 10.11686/cyxb20140607

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In order to elucidate the spatial distribution characteristics of soil carbon and nitrogen in Jiaozhou Bay estuarine wetlands, soil TOC, TN, NO₃^--N, NH₄⁺-N, TP, pH, salinity and water content were measured and analyzed in November, 2011. 1) Soil TOC, TN, NO₃^--N, NH₄⁺-N and TP decreased significantly with the increasing soil depth. The coefficient of variation for NH₄⁺-N was higher than that of NNO₃^--N in reed and Suaeda wetlands. 2) The main form of nitrogen was organic. The TOC content in the surface soil of reed wetland was higher than that of Suaeda wetland, while TN and TP contents of Suaeda wetland were higher than those of reed wetland. 3) There was a significant correlation between TN and TP and TOC. Flooding influenced the generation and migration of NNO₃^--N and NH₄⁺-N. 4) Compared with other coastal wetland ecological systems, Jiaozhou Bay estuarine soils were high in TOC, TN, NNO₃^--N and NH₄⁺-N. Surrounding land is the main source of organic matter for these wetlands which are in an advanced stage of humification.

Phosphorus contents in the rhizosphere and bulk soil under Amorpha fruticosa established in different years

LI Jin-hui,LU Xin,ZHOU Zhi-yu,ZHAO Ping,JIN Qian,ZHOU Yuan-yuan

2014, 23(6):  61-68.  DOI: 10.11686/cyxb20140608

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The rhizosphere and bulk soil of Amorpha fruticosa established in different years were studied. Available phosphorus (P), total P and P fractions were analysed using the method of Hedley which was a soil P classification method revised by Tiessen. Available P levels in the rhizosphere were higher than those out of the rhizosphere. The Y₆₀ had the highest inorganic P content than the other except for H₂O-Pi and Conc. HCl-Pi. The NaHCO₃-Pi, NaOH-Pi, NaHCO₃-Po, NaOH-Po, and Conc. HCl-Po in the rhizosphere were higher than those in bulk soil in different aged Amorpha except for NaHCO₃-Po in Y₂₈. Available P in the rhizosphere had a significant relationship with Dil. HCl-Pi and Conc. HCl-Po. H₂O-Pi and total P had a significant relationship. Available P and pH in the rhizosphere and out of the rhizosphere did not have a significant relationship with total P in the rhizosphere.

Effects of different irrigation methods and quantities on soil salt transfer in oasis alfalfa fields

ZHANG Qian-bing,Anwar Ahmat,YU Lei,LU Wei-hua,CHANG Qing

2014, 23(6):  69-77.  DOI: 10.11686/cyxb20140609

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Salination is a major problem in oasis agricultural systems. This study explored the effects of different irrigation methods and quantities on soil salt spatial distribution and transfer in oasis alfalfa crops. A two-factor experiment including two irrigation methods and three irrigation gradients was conducted. Soil electrical conductivity was measured and analyzed during alfalfa growth in the second year of the experiment. With the advancement of crop growth and an increase in irrigation frequency, soil salt content fluctuated significantly but tended to decrease as the growing season progressed. Reduced soil salt levels occurred at 0-40 cm depth under drip irrigation and at 0-30 cm depth under flood irrigation; salt was deposited at 50-60 cm depth under drip irrigation and at 40-60 cm depth under flood irrigation. Increased irrigation resulted in peak soil salinity trending downwards under both irrigation methods. Soil salt content increased with increasing soil depth after irrigation with most salt concentrated at 40-60 cm depth, but the “salt drive” effect was greater under drip irrigation than flood irrigation. The benefits of “salt drive” for crop yield were maximized at irrigation rates of 3000 m³/ha and 5250 m³/ha under drip and flood irrigation, respectively.

Effect of grazing exclusion on soil respiration during the dormant season in alpine meadow grassland ecosystems on the northern shore of Qinghai Lake, China

CHEN Ji,CAO Jun-ji,WEI Yong-lin,LIU Ji-hong,MA Fu-lin,CHEN Di-chao,FENG Jia-yu,XIA Yao,CEN Yan

2014, 23(6):  78-86.  DOI: 10.11686/cyxb20140610

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Dormant season soil CO₂ efflux is a significant component of the ecosystem carbon cycle and it therefore plays an important role in carbon budgets calculated to address global climate change. This study investigates the response of dormant season soil CO₂ efflux to short-term grazing exclusion. It also explores the impacts of soil temperature and moisture on soil respiration using the Li-8100 system. Soil respiration was studied in three blocks-free-range grazing (FG), grazing exclusion for 3 years (GE₃), and grazing exclusion for 5 years (GE₅). Respectively, the average dormant season soil respiration was 0.21, 0.22, and 0.19 times of the annual average soil respiration in each of the three blocks. The carbon released by soil respiration during the dormant season was 117.2, 109.2 and 100.7 g/cm², accounted for 21.2%, 22.3% and 23.2% of the amount of annual carbon released from soil for FG, GE₃ and GE₅, respectively. The Q₁₀ values during the dormant season were lower than both the annual and growing season scores. Soil temperature and moisture almost equally account for the variation in soil respiration, and a certain amount of soil water content is necessary for maintaining the response of soil respiration to soil temperature. Therefore, when considering the carbon budget and cycle of ecosystems, we cannot ignore dormant season soil respiration; and soil moisture plays a considerable role in regulating this process.

The production performance of 14 annual ryegrass varieties in the southwest of Sichuan Province

WANG Shao-fei,LUO Yong-cong,ZHANG Xin-quan,HUANG Lin-kai,MA Xiao,LIU Lian

2014, 23(6):  87-94.  DOI: 10.11686/cyxb20140611

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The production performance of 14 varieties of annual ryegrass was studied in Ya’an in the southwest of Sichuan province. The growth rates of the new lines YA03 and YA08 were faster than Jumbo and Aubade. From 2011 to 2013, the yields of the new line YA17 were the highest, and YA03 also had advantages in yields from the first three cuts. The fresh yield of YA03 achieved 12994 kg/ha on average, 11.50% to 15.66% more than Changjiang No.2, Tetragold and Aubade. The hay yield was also greater by 9.47% to 12.82%, achieving 98973 kg/ha. In addition, Aubade and YA03 had very rich leaves. There were no significant differences of the phenology and the main nutrient contents among the 9 tested varieties. Therefore the new lines YA17 and YA03, with their higher yields and richer leaves, are more suitable for planting in the southwest of Sichuan province.

Fermentation and aerobic stability of mixed ration forages in Tibet

WANG Yong,YUAN Xian-jun,GUO Gang,WEN Ai-you,WANG Jian,XIAO Shen-hua,YU Cheng-qun,BA Sang,SHAO Tao

2014, 23(6):  95-102.  DOI: 10.11686/cyxb20140612

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The objective of this study was to identify opportunities to improve the utilization of crop straw and forage resources in Tibet. The experiment was based on the total mixed ration (TMR) typically used in local dairy systems, comprising whole-crop corn and barley straw (TMR-1), comparing substitutes for whole-crop corn; alfalfa (TMR-2), whole-crop oat (TMR-3) or wheat straw (TMR-4) at different ratios. After 45 d fermentation, pH values of TMR-2, TMR-3 and TMR-4 treatments were significantly (P<0.05) higher than that of TMR-1, while corresponding lactic acid contents were lower. Propionic acid and butyric acid were very low in all treatments except TMR-1 and ammonia nitrogen/total nitrogen was <100 g/kg TN, indicating that fermentation was good in all treatments. Water-soluble carbohydrate content in all treatments was significantly lower (P<0.05) after 45 d of fermentation. The dry matter content of all treatments except TMR-1 remained constant,while crude protein, neutral detergent fiber, acid detergent fiber and ether extract increased in all treatments. The crude protein content of TMR-2 and TMR-3 were above 15%, sufficient for dairy production. During aerobic exposure, lactic acid, acetic acid and water-soluble carbohydrate content of all treatments declined. Propionate and butyrate content initially increased after three days of aerobic exposure and then gradually decreased in all treatments. After 9 d of aerobic exposure, the pH increased but the increase was minimal in TMR-3, indicating good aerobic stability. It was concluded that TMR-3 group could be used to produce TMR in Tibet.

Effects of corn flour and lactic acid bacteria on quality of mixed silage made from sweet potato vines, distiller’s grains and rice straw

WANG Hong-ze,WANG Zhi-sheng,KANG Kun,ZOU Hua-wei,SHEN Jun-hua,HU Rui

2014, 23(6):  103-110.  DOI: 10.11686/cyxb20140613

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This study aimed to evaluate the effects of corn flour and lactic acid bacteria addition on the quality of mixed silage of sweet potato vines, distiller’s grains and rice straw during ensiling. The treatments were: control (CK), corn flour added (CF), lactic acid bacteria added (LAB), and corn flour and lactic acid bacteria added (CF+LAB). After ensiling for 60 d at ambient temperature, the silage quality of each treatment was measured. Applications of corn flour and lactic acid bacteria improved the sensory evaluation of silage. Compared with CK, CP content of CF, LAB and CF+LAB silage were significantly higher, while NH₃-N/TN, acetic acid (AA) and propionic acid (PA) contents were significantly lower. The dry matter (DM), crude protein (CP) and lactic acid (LA) contents of CF silage were significantly higher than those of CK silage, while neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of LAB silage were significantly lower than those of CK silage. The DM content of CK+LAB silage was significantly higher than for CF and LAB silage, while NH₃-N/TN, AA contents and pH value were significantly lower. Collectively, applications of corn flour and lactic acid bacteria improved the quality of mixed silage. The effect of adding corn flour on the mixed silage was better than that of adding lactic acid bacteria. Application of corn flour and lactic acid bacteria together in the mixed silage was the best.

Effects of molasses and acetic acid on fermentation and aerobic stability of total mixed ration silage in Tibet

QIU Xiao-yan,YUAN Xian-jun,GUO Gang,WEN Ai-you,YU Cheng-qun,BA Sang,SHAO Tao

2014, 23(6):  111-118.  DOI: 10.11686/cyxb20140614

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An experiment was undertaken to study the effects of acetic acid or/and molasses on the quality of fermented total mixed ration silage. Treatments: silage fermented without additive (control), with acetic acid (0.3% fresh matter basis), with molasses (3% fresh matter basis), or with acetic acid+molasses. There were 20 silos per treatment. All silos were opened 45 d after ensiling; five silos per treatment were analysed to determine fermentation characteristics, the remaining silos were exposed to air for 12 d to evaluate aerobic stability. After 45 dall silages were of good quality having high lactic acid concentration, low ammonia/total nitrogen, low butyric acid and very little propionic acid. During aerobic exposure, lactic acid, acetic acid and water soluble carbohydrate tended to decrease in all silages. The pH of the control and molasses treated silages increased significantly to 5.70 and 6.50 respectively and ammonia/total nitrogen and yeast counts were higher than the acetic acid and acetic acid+molasses treatments after 12 days of exposure. However, adding acetic acid reduced ammonia/total nitrogen compared with the control. Lactic acid content in the acetic acid and acetic acid+molasses silages increased during the early stages of aerobic exposure and then slowly decreased. Undesirable bacteria and yeast counts in the acetic acid treatment remained at low levels during aerobic exposure and the pH remained at about 4.50. It is concluded that adding 0.3% acetic acid maintained fermentation quality and improved the aerobic stability of fermented total mixed ration silage.

Effects of different moisture contents and additives on the quality of baled oat silage

QIN Fang-cuo,ZHAO Gui-qin,JIAO Ting,HAN Yong-jie,HOU Jian-jie,SONG Xu-dong

2014, 23(6):  119-125.  DOI: 10.11686/cyxb20140615

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In order to study the effects of different moisture contents and additives on the quality of baling oat silage, a 2×5 experiment was designed. Baling oat harvested at grain filling stage was wilted to target moisture contents (45%-50% and 65%-70%) and treated with corn flour (4%), urea (0.4%), Synlac Dry (0.002 g/kg), Sila-Max 200 (0.0025 g/kg), or directly baled without additives (CK). After 40 d ensiling, nutrition and fermentation were measured, and microbial counts and community analysis were undertaken by plate-culture. Moisture contents and additives had significant effects on silage quality. Compared with those at 45%-50% moisture content, treatments at 65%-70% moisture content had more stable CP, main organic acids and lactic acid bacteria (LAB), lower acid detergent fiber (ADF), neutral detergent fiber (NDF), water soluble carbohydrate (WSC) and mould and yeast (M&Y) counts, showing a better ensiling effectiveness. In contrast with CK, flour and urea treatments at 65%-70% moisture content had higher NDF, ADF and NH₃-N contents, but lower WSC. Sila-Max 200 led to the lowest NDF and ADF contents (52.12% and 32.14%, respectively), the highest lactic acid and significantly increased LAB, thus inhibiting aerobic microorganisms and achieving the best silage performance. In conclusion, adding suitable additives to oat with 65%-70% moisture content could signficantly improve the oat silage quality.

Influence of different nutrition levels on the digestion metabolism and beef quality of Holstein culling cows

LI Qiu-feng,LI Chun-fang,CAO Yu-feng,LI Jian-guo,YIN Yuan-hu,LI Wei

2014, 23(6):  126-135.  DOI: 10.11686/cyxb20140616

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The study aimed to investigate the influence of different nutrition levels on the digestion metabolism and beef quality of Holstein culled cows. Thirty-two healthy cows were randomly divided into four groups (n=8) in a single-factor design. Four experimental diets were used at different levels of energy and protein, namely group Ⅰ (low nutrition), group Ⅱ (medium nutrition), group Ⅲ (high nutrition) and group Ⅳ (higher nutrition). The experiment included two stages. With the increase in nutrition levels, the apparent digestibility of crude protein and crude fat were significantly different. The apparent digestibility of crude protein and fat in group Ⅲ were the highest (72.47% and 80.64%). Compared with group Ⅰ, the back fat thickness of group Ⅳ increased by 73.33%. The meat cooking rate, fat content and fatty acid content were significantly affected by nutrition levels. The cooking rate of group Ⅲ was 49.73% higher than those of groups Ⅰ, Ⅱ and Ⅳ by 6.03%, 7.87% and 4.30% respectively. The fat content of beef increased by 70.10% compared to groups Ⅳ and Ⅰ. The polyunsaturated fatty acid (PUFA) content of group Ⅳ was the lowest (3.67%) and it was the highest in group Ⅱ (5.93%). Compared with groups Ⅰ and Ⅳ, PUFA content of group Ⅲ was clearly higher. Therefore, the suggested values of nutritional level for finishing Holstein culling cows in the 410-470 kg live weight range are 11.03-11.53 kg/d dry matter intake, 147.86-150.05 MJ/d digested energy intake and 1.57-1.66 kg/d crude protein intake.The values for cows in the 470-530 kg live weight range are 10.76-11.23 kg/d DMI, 149.18-151.21 MJ/d DE and 1.53-1.62 kg/d CPI respectively.

Effect of urea fertilizer on growth and performance of Cleistogenes songorica turfgrass

LI Xin-yong,WANG Yan-rong,JIA Cun-zhi

2014, 23(6):  136-141.  DOI: 10.11686/cyxb20140617

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The effects of different urea application rates (0, 2, 5 and 8 g/m²) on turf color, plant height, leaf width, relative leaf water content, nitrogen content and green period of Cleistogenes songorica turfgrass were studied. Urea fertilizer promoted the growth rate of plants and leaves, increased N and relative leaf water content, improved turf color, enhanced turf quality and prolonged the green period significantly. Turf quality under 5 and 8 g/m² treatments was significantly greater than that under 0 and 2 g/m² treatments, and the main contributing factors were improved turf color during the growth period and extension of the green period for 18 d at least. Compared with the 0 g/m² treatment, the 8 g/m² treatment increased the cut grass 6 times, which more than doubled lawn management costs while the 5 g/m² treatment only increased the cut grass 2 times, which would reduce costs of lawn management. Hence, the optimum rate of urea fertilizer was 5 g/m² for this turfgrass species.

Sodium compound fertilizer improved growth and drought tolerance of Zygophyllum xanthoxylum seedlings under drought stress

ZHOU Xiang-rui,YUE Li-jun,WANG Suo-min

2014, 23(6):  142-147.  DOI: 10.11686/cyxb20140618

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In this study, the effect on growth and drought tolerance of the succulent xerophyte Zygophyllum xanthoxylum under drought stress of a Na compound fertilizer that contains appropriate amounts of nitrogen, phosphorous and sodium was studied in a pot experiment. Compared with control and diammonium phosphate treatments, the application of Na compound fertiliser increased plant height by 30% and 12%, leaf area by 97% and 40%, leaf relative organic weight by 10% and 7%, dry weight by 57% and 38%, water content by 347% and 55%, net photosynthetic rate (P_n) by 145% and 24%, primary light energy conversion of PSⅡ by 6% and 4%, photosynthetic electron transport rate by 16% and 8%, quantum yield by 14% and 5%, but decreased leaf malondialdehyde concentration by 58% and 18%, and penetrability of membranes by 50% and 26% respectively under drought stress. Meanwhile, the application of Na compound fertilizer significantly increased water use efficiency by 4%, compared with control pots. These results suggested that Na compound fertilizer could promote growth and enhance drought tolerance of Z. xanthoxylum, and the effectiveness was greater than diammonium phosphate.

Response of alfalfa and smooth brome to nitrogen fertilizer in monoculture and mixed grasslands

XIE Kai-yun,LI Xiang-lin,HE Feng,WAN Li-qiang,WANG Dong,QIN Yan,YU Qun

2014, 23(6):  148-156.  DOI: 10.11686/cyxb20140619

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It is essential to understand the effect of nitrogen (N) fertilizer in maintaining stable biomass production in mixed legume-grass grasslands. In this study, the effects of three N levels (0, 75 and 150 kg N/ha; denoted as N₀, N₇₅ and N₁₅₀) on the biomasses of smooth brome and alfalfa in mono-culture and mixed-culture were investigated in greenhouse cultivation conditions. In mono-culture, N fertilizer significantly improved smooth brome biomass but had no significant effect on alfalfa biomass. In mixed-cultures, applying N significantly improved smooth brome biomass and indirectly inhibited the growth of alfalfa. In mixed-cultures, the biomass of smooth brome and alfalfa fell between the mono-culture values but was higher on average. The biomass of a single plant of smooth brome was significantly higher in mixed grassland than in mono-culture. The biomass of single alfalfa plants was significantly higher in mono-culture than in mixed grasslands. The study thus suggests that in mixed grasslands nitrogen positively stimulates smooth brome and suppresses alfalfa. In mixed grasslands, the growth of smooth brome and alfalfa changed dynamically and was regulated by inorganic N levels in the soil.

Taxonomic values for leaf structure in the tribe Vicieae (Leguminosae) in northeastern China

SHI Chuan-qi,LIU Mei,WANG Chen,ZHANG Xin-xin,CHENG Xin-yu

2014, 23(6):  157-166.  DOI: 10.11686/cyxb20140620

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The leaf morphological structure of 22 species, 2 varieties and 1 form of the tribe Vicieae in northeastern China were studied in depth using SEM, leaf transparency and GMA methods. The leaf is an even pinnate compound, with one to several pairs of leaflets which are usually ovate in shape. The anticlinal walls of leaf epidermal cells are usually sinuate. The anisocytic stoma is the main type of Lathyrus and Pisum, and the anomocytic type mainly occurs in Vicia. Unicellular, non-glandular hairs and multicellular, glandular hairs occur on the leaves of many species of Vicieae. The petiole is hastate in transverse section and has a groove on the adaxial side. There are several vascular bundles which are arranged in V-shaped, heart-shaped or round patterns in the petiole. This study provides morphological data for distinguishing between the different groups of Vicieae in northeastern China. It also provides the morphological basis for systematic and phylogenic studies of the family Leguminosae.

Effects of cadmium stress on accumulation ability, microstructure and physiological property in leaves of Trifolium repens

HAN Bao-he,ZHU Hong

2014, 23(6):  167-175.  DOI: 10.11686/cyxb20140621

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Cadmium (Cd) toxicity was investigated in Trifolium repens using accumulation ability microstructure physiological. T. repens were treated with Cd²⁺(0, 100, 200, 300, 400, 500 μmol/L) for 7 days. Cd accumulation in different organs of T. repens gradually increased with the increase in the concentration of Cd. The accumulation content of different organs followed the sequence: roots>leaves>stems. Meanwhile, Cd accumulation in the leaves produced certain toxicity: cell walls of mesophyll cell stained deepening, the shape, size, and density were also changed. In response to Cd²⁺, more MDA and ROS contents were produced in leaves than untreated of T. repens. Compared with untreated, the photosynthetic pigments contents decreased significantly (P<0.05). After Cd²⁺ treated, the content of MDA generally increased, and there is a dose-response relationship between the concentration of Cd. Throughout the process of stress, SOD, POD, CAT activity increased initially and then decreased. Correlation analysis showed that: the content of Chl a and Chl b were significantly negatively correlated with Cd²⁺ concentration. While the content of MDA was highly significant positively correlated with Cd²⁺ concentration. The activity of SOD, POD and CAT were highly significant positively among each other. Above three play synergistic role to reduce injury. These physiological indicators reflect T. repens adaptability to Cd²⁺ stress.

Cadmium tolerance and accumulation in four cool-season turfgrasses

XU Pei-xian,FEI Ling,CHEN Xu-bing,WANG Zhao-long

2014, 23(6):  176-188.  DOI: 10.11686/cyxb20140622

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Tall fescue, Kentucky bluegrass, perennial ryegrass and creeping bentgrass are hyper-tolerant grasses to soil cadmium (Cd) contamination. However, little information is available on their physiological responses and accumulation capability for Cd. These four cool-season turfgrasses were exposed to Cd at different levels (50, 100, 200, 400 mg Cd/kg) for 60 d. The effect of Cd stress on the physiological responses and Cd concentrations in the shoots and roots were investigated. Tall fescue was most tolerant to Cd stress, followed by perennial ryegrass, Kentucky bluegrass and creeping bentgrass. Leaf relative growth rate and root biomass were more sensitive than other parameters. The concentration and accumulation of Cd in both shoots and roots increased with Cd dose. At the same level of Cd treatment, the highest shoot concentration of Cd was found in Kentucky bluegrass, followed by tall fescue and creeping bentgrass, while the lowest shoot concentration of Cd was found in perennial ryegrass. The highest root concentration of Cd was in perennial ryegrass. Under 50-400 mg Cd/kg treatments, Kentucky bluegrass had the highest translocation factor and phytoextraction rate, whereas perennial ryegrass had the lowest translocation factor and phytoextraction rate. In summary, under the same level of Cd treatment, accumulation of Cd in shoots of Kentucky bluegrass was higher than for the other three species, while the accumulation of Cd in the root of creeping bentgrass was lowest among the four grass species and this may be linked to its low root biomass. Our study provides data on Cd tolerance and accumulation capability of the four grass species, and indicates their potential for phytostabilizing Cd contaminated soils.

Responses of primary root and antioxidase system to exogenous Ca²⁺ in pea under H₂O₂ stress

LIU Hui-jie,LI Sheng,MA Shao-ying,ZHANG Pin-nan,SHI Zhen-zhen,YANG Xiao-ming

2014, 23(6):  189-197.  DOI: 10.11686/cyxb20140623

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In order to explore methodology for improving the resistance of pea primary roots to H₂O₂ stress, physiological characteristics of pea primary roots were studied using a pea variety “Longwan 1” treated with Ca²⁺ under H₂O₂ stress. Several physiological indexes like the curvature rate and root activity of pea primary roots were measured using physiological and biochemical methods. Some other indexes like the relative membrane permeability of primary roots, the concentration of malondialdehyde (MDA) in primary roots, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) enzymes were also measured. The normal growth of pea primary roots under 80 mmol/L H₂O₂ stress was obviously inhibited. However, the inhibitory effect on root growth was reduced and the root activity was restored after treating with Ca²⁺. The MDA content decreased 37.32% compared to controls after treatment with 10 mmol/L exogenous Ca²⁺. The activities of four enzymes including POD, SOD, CAT and APX were enhanced and reached 51.946 U/(mg·min), 865.174 U/g FW, 1.9739 mmol/(L·g·min) and 2.569 μmol/(L·g·min), respectively. In summary, Ca²⁺ (10 mmol/L) significantly alleviated the damage to pea primary root cell membranes caused by H₂O₂ stress, reduced membrane permeability and promoted the antioxidant capacity of pea primary roots for stress resistance.

Effect of shading on photosynthetic and chlorophyll fluorescence characteristics of soybean

LI Rui,WEN Tao,TANG Yan-ping,SUN Xin,XIA Chao

2014, 23(6):  198-206.  DOI: 10.11686/cyxb20140624

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This study investigated the photosynthetic response of soybean seedlings under different shading conditions. Simulating the field maize/soybean relay-cropping pattern, two soybean cultivars, “Nandou 12” and “Guixia 3”,were utilized to analyze changes in the pigment content, photosynthetic rate and chlorophyll fluorescence parameters at different growth stages under shading and during light recovery stages. Five shading treatments were set; no shading, 30% partial shading, 50% partial shading, 70% partial shading and 50% full shading. Shading increased the pigment content and original fluorescence intensity while the chlorophyll a/b ratio decreased. Photosynthetic rate, maximal photochemical efficiency, photochemical efficiency and photochemical quenching initially increased and then decreased, while non-photochemical quenching initially decreased before increasing. The soybean seedlings grew strongly under 50% partial shading but growth was poor under 50% full shading. Shading had a marked effect on seedlings at the four-trifoliolate leaf stage; when shaded, seedlings accommodated the weak light environment by changing the pigment composition or promoting photosynthetic electron transport. “Nandou 12” showed better shade tolerance and higher photo chemical efficiency than “Guixia 3”. “Guixia 3” was unable to dissipate excess light energy under light recovery resulting in severe damage to the photosynthetic system.

Effect of exogenous spermidine on salt tolerance in Kentucky bluegrass seedlings under salinity stress

AN Meng-ying,SUN Shan-shan,PUYANG Xue-hua,HAN Lie-bao

2014, 23(6):  207-216.  DOI: 10.11686/cyxb20140625

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Salinity stress significantly harms the normal growth of turfgrasses and limits their wide establishment. This is especially so for Kentucky bluegrass, which is more sensitive to salinity than other turfgrasses. An experiment was carried out on two different cultivars of Kentucky bluegrass seedlings (‘Kenblue’ and ‘Midnight’) in order to explore the effect of 1 mmol/L exogenous spermidine (Spd) on the salt tolerance of the seedlings, which were cultured in a MS medium supplemented with 200 mmol/L NaCl. Under salinity stress, exogenous Spd alleviated both shoot and root growth inhibition and significantly increased the antioxidant activities of APX, CAT, POD, SOD and proline content. It also significantly decreased the membrane permeability and the content of H₂O₂, O2-· and MDA. Furthermore, exogenous Spd maintained ion balance by reducing Na⁺ content and increasing the contents of K⁺, Ca²⁺ and Mg²⁺, improving proper intracellular ion compartmentalization and stabilizing the membrane’s structure. We conclude that exogenous Spd can improve salt tolerance in the two cultivars of Kentucky bluegrass and provides a profitable approach for reducing the impact of salinity on widely planted turfgrasses.

Effects of water extracts from Solidago canadensis on the growth of maize seedlings and the underlying photosynthetic mechanisms

YE Xiao-qi,WU Ming,SHAO Xue-xin,LIANG Lei

2014, 23(6):  217-224.  DOI: 10.11686/cyxb20140626

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Although hormesis is commonly observed with the effects of plant allelochemicals on plant growth, the mechanisms underlying this phenomenon are not clearly understood. Allelochemicals may affect plant growth via either plant resource investment in leaf tissue or photosynthesis capacity per unit leaf area. In this study, the effects of Solidago canadensis water extracts on maize seedling growth, photosynthesis capacity and biomass allocation to the total assimilation tissue were studied. The maize seedlings were cultivated in silica sand in an incubator with controlled conditions. Shoot water extracts with concentrations of 0-0.25 g/mL were applied to the maize seedlings. After 9 days treatment, plant growth (plant height, total root length, leaf length, leaf area and biomass of root, stem and leaf), photosynthesis capacity (light saturated photosynthesis rate, P_max), apparent quantum yield (AQY), dark respiration rate (R_d) and biomass allocation (LMR, leaf mass ratio, SLA, specific leaf area and LAR, leaf area ratio) were measured. The water extracts had significant effects on growth of the maize seedlings. Compared to the control (0 g/mL), the treatments with concentrations within 0.02-0.11 g/mL promoted growth, while the treatments with 0.143-0.250 g/mL inhibited growth. The water extracts had similar hormesis effects on SLA and LAR, but no significant effects were found for LMR. The P_max of plants treated with the concentrations of 0.02 and 0.20 g/mL, which caused the largest growth promotion and inhibition effects separately, did not differ significantly from the control treatment. The R_d of the 0.02 g/mL treatment was higher than that of the 0.20 g/mL treatment, although it was not significantly different from the control. Therefore, changes of the respiration rate could not explain the differentiated growth. Final biomass accumulation was significantly correlated with SLA and LAR, but not with LMR. These results indicate that the promotion or inhibition effects of S. canadensis water extracts on maize seedlings growth were not caused by changes in photosynthesis capacity per unit leaf area, but by changes of leaf area ratio and specific leaf area.

The filling dynamics and germination traits of Rheum tanguticum seeds

CAO Shi,GUO Feng-xia,CHEN Yuan,YANG Yu-feng,GUO Ai-wei

2014, 23(6):  225-232.  DOI: 10.11686/cyxb20140627

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Flowers of four-year-old Rheum tanguticum plants were labeled with cards on Flourish-blossom Day in Zhuoni county in the Gannan Tibetan autonomous prefecture, Gansu province. The cards were hung on inflorescences with consistent development signs. Seed filling dynamics were measured once every three days during filling duration, starting 10 days after the experiment’s launch. Germination traits were measured after air drying in order to explore the relationship between seed filling dynamics and germination, providing a theoretical and technical basis for standardizing seed harvesting. The 100-seed dry weight fitted to a logistic equation, with rapid increases during 12-39 days after blossoming and finishing on the 60^th day. The seeds’ water content decreased during the seed filling process. Seeds harvested on the 22^nd day following blossom showed low germination ability. Following this point in time, germination quality significantly improved and remained stable until 49 days after blossom. Water content in the seeds decreased to below 10% from 55 days after blossom. Germination quality indicators were significantly and positively related to the 100-seed dry weight and seed filling duration, but were negatively related to the water content in seeds. The seed filling rate was significantly affected by the weather. The study thus showed that seed maturity affects germination quality. The best harvest time is 55-60 days after blossom (in late July and early August), when seed water content is approximately 10%.

Genome-wide identification and investigation of the MADS-box gene family in Medicago truncatula

ZHANG Jun,SONG Li-li,GUO Dong-lin,GUO Chang-hong,SHU Yong-jun

2014, 23(6):  233-241.  DOI: 10.11686/cyxb20140628

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MADS-box genes encode important transcription factors in plants that are involved in many processes during growth, development and reproduction. A Pfam domain search of the Medicago truncatula genome revealed 138 putative MADS-box genes. These genes were classified into two classes, type I (92 members) and type II (46 members), based on multiple alignment and phylogenetic analysis. There were 134 MADS-box genes present on all chromosomes in M. truncatula, while four were located on the super-contigs. Like Arabidopsis and rice MADS-box genes, those MADS-box genes expanded through gene duplication events in M. truncatula, especially the type I genes. There were many duplicate gene clusters, where MADS-box genes with high degrees of similarity were clustered across the M. truncatula genome. Analysis of RNA-seq data from different tissues in M. truncatula revealed that MADS-box genes are expressed in seedpod, flower and other tissues. This expression pattern suggests that the MADS-box genes play an important role in tissue differentiation, development and reproduction process in M. truncatula.

Transcriptome characteristics of Paspalum vaginatum analyzed with Illumina sequencing technology

JIA Xin-ping,YE Xiao-qing,LIANG Li-jian,DENG Yan-ming,SUN Xiao-bo,SHE Jian-ming

2014, 23(6):  242-252.  DOI: 10.11686/cyxb20140629

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The transcriptome of Paspalum vaginatum leaf was sequenced using an Illumina HiSeq 2000 platform, which is a new generation of high-throughput sequencing technology used to study expression profiles and to predict functional genes. In the target sample, a total of 47520544 reads containing 4752054400 bp of sequence information were generated. A total of 81220 unigenes containing 87542503 bp sequence information were formed by initial sequence splicing, with an average read length of 1077 bp. Unigene qualities for several aspects were assessed, such as length distribution, GC content and gene expression level. The sequencing data was of high quality and reliability. The 46169 unigenes were annotated using BLAST searches against the Nr, Nt and SwissProt databases. All the assembled unigenes could be broadly divided into biological processes, cellular components and 48 branches of molecular function categories by gene ontology, including metabolic process, binding and cellular processes. The unigenes were further annotated based on COG category, which could be grouped into 25 functional categories. The unigenes could be broadly divided into 112 classes according to their metabolic pathway, including the phenylalanine metabolism pathway, plant-pathogen interaction, plant hormone biosynthesis and signal transduction, flavonoid biosynthesis, terpenoid backbone biosynthesis, lipid metabolism, and RNA degradation. There were 22721 SSR in 81220 unigenes and in the SSR, A/T was the highest repeat, following by CCG/CGG and AGC/CTG. This study is the first comprehensive transcriptome analysis for Paspalum vaginatum, providing valuable genome data sources for the molecular biology of this grass.

Effect of paclobutrazol on drought resistance of six turfgrass cultivars during the seedling stage

WANG Jing-hong,DUO Duo

2014, 23(6):  253-258.  DOI: 10.11686/cyxb20140630

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The wide use of turfgrass in urban landscaping has resulted in an increased water requirement for maintenance and management. A pot experiment was conducted to determine the physiological effects of different concentrations of paclobutrazol (PP333) on drought resistance of six turfgrass cultivars: two each of perennial ryegrass (Bomber and Esquire), red fescue (Beifang and Rubra) and kentucky bluegrass (Kentucky and Merit). Different concentrations of PP333 significantly increased the RWC, chlorophyll content and SOD activity, but decreased leaf relative electrical conductivity and proline content 30 d after drought stress, indicating that PP333 could effectively enhance the vitality and drought resistance of the six turfgrass cultivars. The optimal concentration of PP333 to increase the drought resistance was 100 mg/L for Esquire, Beifang and Rubra, 200 mg/L for Bomber and Kentucky, and 300 mg/L for Merit.

Control of herbicide resistant Echinochloacrusgalli indirect-seeded rice crops

MA Guo-lan,BAI Lian-yang,LIU Du-cai,LIU Xue-yuan,TANG Tao,PENG Ya-jun

2014, 23(6):  259-265.  DOI: 10.11686/cyxb20140631

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Barnyardgrass (Echinochola crusgalli) is one of the more problematic grass weeds in Chinese rice paddies. Continuous application of the herbicide quinclorac since 1990 has resulted in barnyard grass developing resistance to quinclorac. The efficacy of six herbicides; penoxsulam, bispyribac-sodium, pyribenzoxim, flucetosulfuron, metamifop and cyhalofop-butyl for controlling resistant barnyardgrass was determined using pot and field based experiments. The pot trial showed that all six herbicides had good biological activity against quinclorac resistant barnyardgrass. The field trial revealed that 2.5% penoxsulam OD and 10% metamifop EC, applied at 22.5 g/ha and 120 g/ha respectively produced control efficacies of more than 95.0% 20 and 40 d after application. The control efficacy of 10% bispyribac-sodium SC (30 g/ha) was greater than 90.0% while the efficacy of 5% pyribenzoxim EC (40 g/ha) was greater than 85.0% after 20 and 40 d. However 10% cyhalofop-butyl EC (90 g/ha) and 10% flucetosulfuron WG resulted in less than 85.0% control efficacy. The results indicate that penoxsulam and bispyribac-sodium effectively controlled barnyardgrass resistant to quinclorac.

Pathogen identification and occurrence regularity of a novel disease——Angelica anthracnose

BIAN Jing,CHEN Tai-xiang,CHEN Xiu-rong,WANG Han-qi,YANG Xiao-li,WANG Yan

2014, 23(6):  266-273.  DOI: 10.11686/cyxb20140632

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A suspected anthracnose disease on Angelica stems was found in the main producing areas in Gansu province in 2012 and 2013. The major damage of this disease is to the plant stem. In the initial stages of the disease, many light brown spots appear on stems, and then expand to dark brown rectangular lesions, leaf chlorosis and wilting. Stems gradually dry up from outside to inside, abundant black acervuli appear on the spots, and then the plant dies. Through pathogenicity testing, morphology and ITS sequence analysis we determined that the pathogen of Angelica anthrax is Colletotrichum dematium. As far as we know, this study is the first report for this disease. An inoculation test using potted plants indoors shows that puncturing, root-irrigation and spraying with conidial suspension all can cause disease. Puncturing caused the most severe symptoms. Spraying with suspension induced the lightest symptoms. C. dematium can infect Angelica through wounds, roots and aerial parts. This disease first appears in mid or late June, and incidence peaks in late August or early September. Field temperature and relative humidity are significantly positively correlated with disease incidence and severity, suggesting that high temperature and high humidity promote progress of the infection.The impact of humidity on disease development is greater than temperature. This study provides a basis for developing prevention and control methods for Angelica anthrax.

Phosphate dissolving capability and the affect of phosphate-dissolving bacteria in the rhizosphere on Sorghum bicolor

LEI Xue-jun,WU Yi,HUANG Xin,CAI Jian-bo,LI Zhuo,WU Lin-shi

2014, 23(6):  274-278.  DOI: 10.11686/cyxb20140633

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Phosphorus is the second of the most necessary elements for plant growth.The phosphorus nutrients needed by plants are mainly sourced from rhizospheric soil, and phosphorus deficiency in the soil is an important limiting factor for agricultural production in many developing countries. Some micro-organisms can convert insoluble phosphate to soluble forms and research on such organisms therefore has considerable practical significance. Five bacterial strains were screened from Mengjinna inorganic mediums. The phosphate-solubilizing characteristics and IAA secretion ability of these strains of bacteria were studied using both the Molybdenum antimony resistance colorimetric method and Salkowski colorimetric method. There were notable differences in the micro-organisms’ phosphate dissolving capability. Phosphate-dissolving capability was 107.26-233.95 μg/mL. All the strains had the ability to produce IAA and IAA capability was 15.23-27.79 μg/mL. In comparison with the control, every strain showed significant benefits to Sorghum bicolor height, stem diameter and dry weight. In summary, strains WD₅₁ and WD₂₀ showed strong capability for phosphate dissolving and IAA secretion and could be used as potential strains for biofertilizer manufacture.

Nitrogen cycling in grassland ecosystems in response to climate change and human activities

YAN Zhong-qing,QI Yu-chun,DONG Yun-she,PENG Qin,SUN Liang-jie,JIA Jun-qiang,CAO Cong-cong,GUO Shu-fang,HE Yun-long

2014, 23(6):  279-292.  DOI: 10.11686/cyxb20140634

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As an important component of proteins, nucleic acids, enzymes and chlorophyll nitrogen (N) is a crucial element for ecosystem function. Many large research programs undertaken by the International Geosphere and Biosphere Program (IGBP) and the Intergovernmental Panel on Climate Change (IPCC) have included the N cycle as part of their core research. Globally, grassland ecosystems play an extremely important role in maintaining global and regional ecological balance. To date, few studies on the response of the N cycle to global changes have been conducted. There is some urgency to determine the effect of elevated atmospheric CO₂ and temperature, precipitation change, nitrogen deposition and human activities (grazing, cultivation, fire, etc.) on the N cycle in grasslands. This paper reviews research progresses in China and globally on the effects of global change and human activities on the key N cycle processes in grassland ecosystems. Additionally, issues requiring research emphasis are identified.

Advances in genetic engineering for drought tolerance in plants

XU Li-ming,ZHANG Zhen-bao,LIANG Xiao-ling,LU wen,ZHANG Chen-lu,HUANG Feng-zhu,WANG lei,ZHANG Su-zhi

2014, 23(6):  293-303.  DOI: 10.11686/cyxb20140635

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Drought is a major abiotic stress that significantly reduces crop yield. The use of high throughput screening techniques has accelerated the identification of the gene series that are involved in drought tolerance. Some of the more important genes have already been transferred into plants by genetic transformation in order to activate specific or broad pathways related to drought tolerance. More recent advances have improved our understanding of drought-resistant regulation by controlling the expression pattern of drought-tolerant genes. We now better understand the complex regulatory network that regulates drought stress response and so are able to develop practical approaches for engineering drought tolerance in plants. This article reviews these advances in genetic engineering, including such factors as identifying the genes encoding signaling molecules, transcription factors, small RNA and the gene expressions involved in osmotic substances biosynthesis, polyamines biosynthesis and ROS scavenging. Current problems and future applications are also discussed.

Research progress in the quantitative trait loci (QTL) and genomic selection of alfalfa

KANG Jun-mei,ZHANG Tie-jun,WANG Meng-ying,ZHANG Yi,YANG Qing-chuan

2014, 23(6):  304-312.  DOI: 10.11686/cyxb20140636

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Although tetraploid alfalfa is one of the most practically important forage legumes, its genetic mapping and the QTL identification of its significant traits are lagging behind other diploid crops due to its complex genetic background. High-density genetic and physical mapping of diploid alfalfa was initiated several years ago and these studies have laid the theoretical foundation for the genetic mapping and QTL identification of tetraploid alfalfa. This new work on tetraploid alfalfa will be greatly accelerated by the rapid development of third generation molecular markers and sequencing technology. On this basis it will be possible to increase the efficiency of alfalfa breeding programs, especially by using marker-assisted selection. This paper reviews the genetic map construction and QTL analysis of alfalfa. It outlines research progress and the prospects of association mapping and genomic selection in the future.

Plant community structure and soil moisture in the semi-arid natural grassland of the Loess Plateau

ZHANG Zhi-nan,WU Gao-lin,WANG Dong,DENG Lei,HAO Hong-min,YANG Zheng,SHANGGUAN Zhou-ping

2014, 23(6):  313-319.  DOI: 10.11686/cyxb20140637

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Climate change has resulted in altered hydrothermal conditions and variation in soil moisture content which affects plant community structure and function on the Loess Plateau. The effect of soil water on the plant community in the semiarid natural grassland of the Loess Plateau was investigated using a large scale randomized design trial. Key results were: 1) Above-ground biomass and litter biomass were significantly positively correlated with soil water content. 2) Plant diversity and species richness were significantly positively correlated with soil moisture. 3) Plant functional groups were also affected by soil water content; both grass and legume species increased significantly with increase in soil water content, whereas forbs decreased significantly. It was concluded that soil moisture is one of the most important factors limiting community productivity and plant species diversity. Additionally, grass species may be able to indicate or reflect soil moisture status. Soil moisture changes may be driving plant community succession in semi-arid grassland.

Variation in the biodiversity of montane shrub grassland communities along an altitudinal gradient in a Lhasa River basin valley

LUO Li-ming,MIAO Yan-jun,WU Jian-shuang,PAN Ying,TU Yan-li,YU Cheng-qun,ZHAO Yan,ZHAO Guan-feng,WU Jun-xi

2014, 23(6):  320-326.  DOI: 10.11686/cyxb20140638

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A field survey was carried out to measure the variation in the biodiversity of montane shrub grassland communities along an altitudinal gradient in the Xincang village valley, Taktse County in the Lhasa River basin. Community assembly and functional trait diversity were assessed using the Rao index. The aboveground biomass and total coverage of shrubs initially increased and then decreased with increasing altitude. Variation in aboveground biomass (49.18±19.17 g/m²) or total coverage (71%±14%) for alpine meadows among plots along the altitudinal gradient was not high. Species composition indices varied along the altitudinal gradient; Kobresia pygmaea (0.591±0.034) and Carex moorcroftii (0.326±0.061) were the two most dominant species. Species diversity of the shrub-grassland community revealed a unimodal variation pattern along the altitudinal gradient; both species richness and the Shannon-Wiener diversity index initially increased and then decreased from 3992 to 4940 m. Conversely, the Rao index for plant height decreased with increasing altitude. Being the most important factor in the ecological security of the Lhasa river basin, montane shrub grassland should be afforded more scientific attention, particularly the interactions between and the mechanisms underlying species richness, functional traits and ecological processes.

Dry matter production and nitrogen accumulation of rice genotypes with different nitrogen use efficiencies

JI Lin,YANG Huan,LI Ting-xuan,ZHANG Xi-zhou,YU Hai-ying

2014, 23(6):  327-335.  DOI: 10.11686/cyxb20140639

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Nitrogen plays an important role in promoting plant growth and development. The purpose of this study was to investigate the characteristics of dry matter production and nitrogen accumulation for rice genotypes with different nitrogen use efficiencies (NUE) and to analyse the relationship between grain yield and NUE. A soil culture pot experiment was carried out at Sichuan Agricultural University, Sichuan province, China in 2009. The grain yield of high NUE genotypes was 1.74-2.37 times higher than that of low NUE genotypes, while NUE of high NUE genotypes was 23.97%-70.55% higher than that of low NUE genotypes. Dry matter weight of high NUE genotypes was significantly higher than that of low NUE genotypes at all growth stages, which were 1.12, 1.49 and 5.85 times higher than that of low NUE genotypes at tillering-to-jointing stage, jointing-to-heading stage and heading-to-maturity stages respectively. The peak dry matter weight of high NUE genotypes occurred at heading-to-maturity stage, while that of low NUE genotypes occurring at tillering-to-jointing stage. Nitrogen accumulation rate of high NUE genotypes increased faster in the early stages, and achieved a maximum 30-50 d after transplanting, then slowed down. Maximum nitrogen accumulation rates of Meigugu, IR31892-100-3-3-3 and IRIT216 were 11.32, 12.36 and 15.83 mg/(d·plant), which were respectively 1.22, 1.33 and 1.70 times higher than Jiazao 935; and, respectively, 1.56, 1.70 and 2.18 times higher than IR32429 with low NUE respectively. High NUE genotypes can maintain higher rates of nitrogen accumulation for longer, with an average duration of 49 d from tillering to heading stages. Low NUE genotypes had a development period 12 d shorter than that of high NUE genotypes. Dry matter weight and nitrogen accumulation at the heading-to-maturity stage were associated, respectively, with 62.65% and 47.42% differernce in rice yield, with 14.51% and 8.77% variation in nitrogen grain production efficiency, and 22.14% and 15.90% variation, respectively, in nitrogen harvest index. In summary, rice dry matter accumulation and nitrogen accumulation were closely related to yield and NUE at the heading-to-maturity stage. Tillering-to-heading is a critical stage for rice nitrogen nutrition management.

Effects of simulated acid rain and Cd on the membrane lipid peroxidation and morphological characteristics of Hosta ventricosa

WANG Cheng-cong,GAO Su-ping,HUANG Li,LIN Xiao,ZHANG Shuo,LEI Ting

2014, 23(6):  336-341.  DOI: 10.11686/cyxb20140640

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In order to better understand how acid rain and heavy metals work together to influence the membrane lipid peroxidation and morphological characteristics of Hosta ventricosa, in a soil culture experiment, different pH (6.5, 5.5, 4.5, 3.5 and 2.5) of acid rain and different concentrations (0, 10, 30, 50 and 100 mg/kg) of Cd were set to test how they influence morphological characteristics, lipid peroxidation and antioxidant activity of the plants. Compound pollutants had more influence on plants than with single pollutants. There was significant interaction between the acid rain and Cd. H. ventricosa showed some tolerance to low pH acid rain and low concentrations of Cd. However, acid rain combined with Cd caused a synergistic effect. The Cd influenced H. ventricosa more than acid rain, and as appeared to be a primary cause of plant damage. The CAT activity was more sensitive to Cd than SOD. Visible injury to plants was observed at 30 mg/kg of Cd and pH 3.5 of acid rain. All the indices indicated that H. ventricosa can be selected as the appropriate plant to remediate soils contaminated with Cd or affected by acid rain.

Effects of moisture content and lactic acid bacteria additive on the quality of Italian ryegrass silage

LI Jun-lin,ZHANG Xin-quan,YU Zhu,GUO Xu-sheng,MENG Xiang-kun,LUO Yan,YAN Yan-hong

2014, 23(6):  342-348.  DOI: 10.11686/cyxb20140641

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The effects of moisture content and lactic acid bacteria additive on the quality of Italian ryegrass silage were investigated. Italian ryegrass (booting stage) was ensiled in plastic drums for 42 d with application of lactic acid bacteria at 0, 10⁵, 10⁶ and 10⁷ cfu/g fresh weight at three different moisture contents: 85.23%, 74.70% and 65.70%. Ensiling at 65.70% moisture produced good quality silage with or without addition of lactic acid bacteria but the highest quality silage resulted from the application of lactic acid bacteria. Silage quality was also good at 74.70% moisture but only with the addition of lactic acid bacteria; higher bacteria application rates improved silage quality. It is concluded that ensiling at 65.70% moisture with the addition of lactic acid bacteria (10⁷ cfu/g fresh weight) produced the highest quality silage.

Biological activities of eight herbicides against four grass weeds of wheat fields

GAO Xing-xiang,LI Mei,FANG Feng,ZHANG Yue-li,QI Jun-shan

2014, 23(6):  349-354.  DOI: 10.11686/cyxb20140642

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Pyroxsulam, flucarbazone-Na, pinoxaden, tralkoxydim and clodinafop-propargyl are newly registered herbicides in China. A glasshouse experiment was conducted to evaluate the efficacy of these herbicides, compared with several commonly used herbicides, on four grass weed species in wheat fields. Key results were: 1) The acetolactate synthase (ALS) inhibiting herbicide pyroxsulam achieved 93.06% control on Poa annua and 82.82%-86.89% control on Puccinellia distans, Lolium multiflorum, Polypogon fugax (all herbicides applied at recommended field dose rates). 2) Other ALS inhibiting herbicides flucarbazone-Na and mesosulfuron-methyl achieved 61.27%-86.71% control on P. annua, but only 10.47%-29.43% control of P. distans, L. multiflorum and P. fugax. 3) In contrast, the acetyl coenzyme A carboxylase (ACCase) inhibiting herbicides pinoxaden, tralkoxydim and clodinafop-propargyl showed 85.41%-100.00% control on P. distans, L. multiflorum and P. fugax, and 19.08%-60.69% on P. annua. 4) The other ACCase inhibiting herbicide fenoxaprop-p-ethyl showed 99.60% control of P. fugax, 72.00% and 55.00% of P. distans and L. multiflorum, and 16.18% control of P. annua. 5) The plant photosystem Ⅱ inhibiting herbicide isoproturon also controlled P. annua, P. distans and P. fugax (88.15%-96.53% control), but showed poorer control of L. multiflorum (67.43%).

Development of a plant regeneration system via tissue culture in Puccinellia tenuiflora

WANG Xue-fang,WANG Chun-mei,ZHANG Jin-lin,DUAN Li-jie,WANG Suo-min

2014, 23(6):  355-360.  DOI: 10.11686/cyxb20140643

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The effects of husk-off treatment and various hormone ratios on callus induction and differentiation were investigated using mature seeds of Puccinellia tenuiflora as explants. Finally, a plant regeneration system via tissue culture was established. The husk-off treatment increased seed germination rate and deceased contamination rate significantly. The optimal medium for callus induction was MS medium supplemented with 5.0 mg/L 2,4-D with the highest callus induction rate of 55.2%. The optimal medium for bud differentiation and rooting was MS medium supplemented with 1.0 mg/L 6-BA+0.5 mg/L NAA with the highest bud differentiation rate of 31.7%, the highest rooting rate of 81.7% within a period of two weeks. The rooting rate of regenerated plants was up to 100% on half strength MS medium and their transplant survival rate in soil was also up to 100%. The whole process of plant regeneration via tissue culture lasted for about 16 weeks totally. The establishment of plant regeneration system via tissue culture in P. tenuiflora has laid a foundation for further exploring the molecular mechanism of its salt tolerance.