Table of Content

20 October 2016, Volume 25 Issue 10

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Orginal Article

Meta-analysis of effects of grazing on carbon pools in grassland ecosystems in different climatic regions

ZHOU Gui-Yao, WU Yan-You

2016, 25(10):  1-10.  DOI: 10.11686/cyxb2015579

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Changes in carbon stocks in grassland ecosystems are an important factor in the global carbon balance. Although many individual studies have been conducted around the world on the effects of grazing on carbon cycling, there is still some controversy regarding the general effects of livestock grazing on different carbon pools. In this study, 105 individual studies on the effects of grazing on carbon cycling were subjected to a meta-analysis. Our results revealed several general trends, which can be summarized as follows. Grazing activities significantly decrease the size of above-belowground and related carbon pools, but increase soil respiration. The types of carbon pools vary significantly among climate types. Grazing activities decrease the size of plant belowground carbon pools and soil carbon pools in semi-humid/humid climate regions (by 15.21% and 15.35%, respectively), but have smaller effects on these carbon pools in arid/semi-arid climate regions. There is no significant relationship between plant aboveground carbon pools and soil carbon pools, but there is a significant positive correlation between plant belowground carbon pools and soil carbon pools. The response ratio of soil carbon pools is positively correlated with mean annual precipitation, and significantly negatively correlated with mean annual temperature. Both mean annual precipitation and mean annual temperature are significantly negatively correlated with the response of plant belowground carbon pools. Grazing activities not only significantly decrease the size of plant aboveground and belowground carbon pools, but also alter carbon distribution in the plant.

Estimation of nitrogen content of alpine grassland in Maqin and Guinan Counties, Qinghai Province, using remote sensing

GAO Jin-Long, MENG Bao-Ping, YANG Shu-Xia, FENG Qi-Sheng, CUI Xia, LIANG Tian-Gang

2016, 25(10):  11-20.  DOI: 10.11686/cyxb2015576

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Using data sourced from a hyper-spectrum imager (HSI) from an environmental mitigation satellite (HJ-1A) and ground observation during 2014 in Maqin and Guinan Counties, Qinghai Province, inversion models were established for estimating the nitrogen (N) content of alpine grassland. The optimal inversion model was selected and the spatial distribution map of grassland N was analyzed in the study area. The results showed that there was a correlation between N and the original spectral reflectance, the first-order differential spectral reflectance and the continuum removed spectral reflectance of the original hyper-spectral image, and significant correlations between grassland N content and absorption feature band one (750.95-791.95 nm) and absorption feature band three (889.03-921.3 nm) were also found. The band depth index BD767.99 was able to estimate N content with the greatest accuracy; the linear model was able to explain over 44% of the variation in N content. The spatial variation of N content in Guinan County was large; generally N content was higher in northwest and southwest than in the northeast. The spatial variation of grassland N content in Maqin County was low and grassland N content was also low.

The spatial differentiation of soil properties under banded vegetation systems on the Loess Plateau

LV Wen-Qiang, DANG Hong-Zhong, WANG Li, DANG Han-Jin, HE Xiu-Dao

2016, 25(10):  21-30.  DOI: 10.11686/cyxb2015484

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In order to explore the effects of banded vegetation on soil properties and their spatial differentiation, an analysis was carried out on the Loess Plateau of the 0-60 cm soil layers of typical banded hedgerows made up of Caragana korshinskii and Armeniaca sibirica. The results showed that: (1) There were significant spatial differences in soil moisture physical properties within the hedgerow systems and these also varied across the different types of hedgerow. Soil bulk density, maximum water holding capacity, non-capillary porosity and total porosity varied significantly under the C. korshinskii hedgerow system (P<0.05), and soil capillary porosity and non-capillary porosity varied significantly under the A. sibirica system (P<0.05). (2) Under the two types of hedgerows, there were significant differences in the contents of water-stable micro-aggregates (<0.25 mm) and small aggregates (0.25-2 mm) (P<0.05). The spatial differentiation of water-stable aggregates with particle sizes less than 2 mm was obviously affected by the hedgerows. (3) There were no significant differences in the contents of soil sand (0.05-2 mm), silt (0.002-0.05 mm) and clay (<0.002 mm) under the two hedgerow systems, although hedgerows can change the relative composition of these three components. (4) There were differences in the content of soil organic matter under the two hedgerow systems. The content of soil organic matter was distributed as follows: for the C. korshinskii system, inner-band (3.57%, grade Ⅱ)>behind band (3.09%, grade Ⅱ)>inter-band (2.72%, grade Ⅲ)>in front of band (2.64%, grade Ⅲ); for the A. sibirica system, inter-band (1.47%, grade Ⅳ)>inner-band (1.41%, grade Ⅳ). (5) Soil sand and water-stable small aggregates showed a significant positive correlation with soil organic matter (P<0.01). Silt and clay showed a significant negative correlation with soil organic matter (P<0.05). There were no significant correlations between soil organic matter and either soil bulk density, water-stable macro-aggregates or micro-aggregates.

Relationships between community characteristics and soil nutrients and moisture in abandoned hill country grassland

LIU Hai-Wei, ZHANG Shao-Kang, JIAO Feng

2016, 25(10):  31-39.  DOI: 10.11686/cyxb2016175

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Using comparative analysis and substituting temporal serial with spatial serial data, we analyzed data collected from abandoned farmland with eight different vegetation restoration periods (1-35 years). The interaction between vegetation regeneration, soil moisture and soil nutrients as the vegetation restoration period changed was also investigated. Results; 1) During 35 years of natural restoration the number of species present fluctuated, initially decreasing, increasing and decreasing again. The Margalef richness index and Shannon-Wiener index firstly increased, then decreased, and then increased again. However, the Pielou evenness index showed the opposite trend. 2) With increasing restoration period, aboveground biomass and underground biomass were both significantly positively correlated with restoration duration. 3) As restoration duration increased, soil moisture and soil fertility (except available phosphorus) in different soil layers initially declined and then increased. Available phosphorus decreased. Soil moisture of 20-50 cm, 50-80 cm, 80-100 cm initially declined and then increased; the opposite pattern was observed in the 20cm soil layer. 4) During the restoration process, indices of vegetation traits (except the Pielou index) were significantly positive correlated with soil nutrient content including soil organic matter, nitrogen and phosphorus.

Response of soil aggregate stability and soil organic carbon fractions to different growth years of alfalfa

LUO Zhu-Zhu, LI Ling-Ling, NIU Yi-Ning, CAI Li-Qun, ZHANG Ren-Zhi, XIE Jun-Hong

2016, 25(10):  40-47.  DOI: 10.11686/cyxb2015585

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This study used dry and wet sieving methods to investigate the distribution and stability of soil aggregates, their mean weight diameter (MWD) and the percentage of aggregate destruction (PAD) in land that had been planted with alfalfa (Medicago sativa) for a range of different growth years (3, 10, and 12 years), and compares these results with those for cropland from a long-term experiment. The relationships between soil aggregates and both stability and soil organic carbon fractions were also studied. The results showed that soil aggregates had a “V”-shaped distribution under the different treatments. With dry sieving, the aggregates primarily involved small (<0.25 mm) and large (>5 mm) particle sizes, while with wet sieving they were dominated by <0.25 mm particles. The MWD of the alfalfa soils was significantly higher than that of the cropland soils at 0-10 cm depth. The PAD of alfalfa soils was significantly lower than that of cropland and it decreased with the increasing number of alfalfa growth years. Soil organic carbon fractions diverged greatly in the different treatments. The order of TOC (total organic carbon), HFOC (heavy fraction organic carbon) and ROOC (readily oxidized organic carbon) in 0-10 cm topsoil was 12 yrs>10 yrs>cropland>3 yrs, indicating that improvement in the organic carbon of alfalfa field topsoils is associated with the number of growth years. Correlation analysis returned the highest coefficients between water-stable aggregates and LFOC (light fraction organic carbon) and ROOC, suggesting that LFOC and ROOC rather than TOC play a vital role in maintaining soil aggregate stability on the Loess Plateau.

Influence of fertilizer use on nitrogen transformation in soils of the Leymus chinensis steppe

QIN Yan, HE Feng, TONG Zong-Yong, XIE Kai-Yun, WANG Dong, Gammal, QUAN Guo-Ling, SONG Qian, WANG Hu, ZHANG Wei-Zhen, LI Xiang-Lin

2016, 25(10):  48-55.  DOI: 10.11686/cyxb2015561

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Fertilizer application is a common grassland management technique and plays an important role in the maintenance of grassland productivity and the health of its ecosystems. In this study, five kinds of fertilizer treatment were applied to determine their effects on soil nitrogen forms and transformations in the Leymus chinensis grasslands of Guyuan, Hebei Province. The results showed that, during the whole forage-growing season, the soil nitrate and ammonium nitrogen contents in grassland fertilized with both nitrogen and phosphorus were lower than that in grassland fertilized only with nitrogen. The application of nitrogen fertilizer changed the process of soil nitrogen mineralization. Grasslands with nitrogen fertilization showed stronger soil nitrification than the other treatments during the period from May to August, and higher net nitrogen mineralization during the period from May to July, which accounted for 57.58%-68.97% of total net nitrogen mineralization over the whole forage-growing season. Positive correlations were observed between soil ammonium nitrogen content, soil nitrate nitrogen content, net nitrogen nitrification, net nitrogen mineralization, soil temperature and soil moisture (r=0.491, P<0.01). High levels of nitrogen fertilizer application could increase the loss of nitrate nitrogen by leaching and thus the risk of environmental pollution.

Rhizosphere microbial functional diversity affected by vegetation restoration in the Hobq Sand Land, Inner Mongolia, China

DAI Ya-Ting, HOU Xiang-Yang, YAN Zhi-Jian, XIE Ji-Hong, WU Hong-Xin

2016, 25(10):  56-65.  DOI: 10.11686/cyxb2015586

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Soil microbial functional diversity is an important indicator of the condition and function of soil microbial communities and is also a useful indicator in the process of ecological restoration. We sought to study the effects of different vegetation restoration techniques on microbial functional diversity during ecological restoration in the Hobq Sand Land. Two types of vegetation restoration were compared; natural restoration of Artemisia ordosica and reintroduction of Caragana intermedia, which began in 1995, using a Biolog micro-plate technique with untreated sandy soil as the control. The results demonstrated that: 1) compared to untreated land, vegetation restoration resulted in increases in the rate of soil microbial carbon source utilization and community metabolic diversity. Between the two restoration types, both soil microbial carbon source utilization rate and community metabolic diversity in the rhizosphere and non-rhizosphere soils were higher in sites restored with A. ordosica than in sites restored with C. intermedia. 2) The carbon sources predominantly used by soil microbes in untreated soil were amino acids, amines, and phenolic acids; these were replaced by carbohydrates, carboxylic acids, and polymers as vegetation recovered; these differences were significant. 3) Principal component analysis demonstrated that there were differences in soil microbial metabolic activity among different vegetation restoration systems, in particular, carbohydrates. 4) Soil nitrogen (N) was strongly correlated with microbial functional diversity. Redundancy analysis (RDA) of microbial communities constrained by different soil factors showed that soil organic matter, total N, available K, available N, pH, and total P were important factors determining the rate of metabolism of carbon substrates. It was concluded that natural restoration of the A. ordosica community was better at fostering soil microbial communities capable of using different carbon sources with enhanced microbial metabolic activity than reintroduction of the C. intermedia and the untreated approach.

Decomposition and nutrient release characteristics of different Vicia villosa green manure applications in red soil uplands of South China

LIU Jia, ZHANG Jie, QIN Wen-Jing, YANG Cheng-Chun, XIE Jie, XIANG Xing-Jia, CAO Wei-Dong, XU Chang-Xu

2016, 25(10):  66-76.  DOI: 10.11686/cyxb2016132

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Vicia villosa is commonly used as a green manure or pasture in north China. In order to provide a scientific basis for its use as green manure in south China, a study has been undertaken in winter-fallowed red soil uplands used for sweet potato crops in Dongxiang County, Jiangxi Province. The decomposition and nutrient release characteristics of Turkmen V. villosa were tested with different application amounts. Nylon net bags (30 cm×20 cm) were used to assess three application treatments: low (90 g fresh grass per bag, equivalent to 15000 kg/ha), medium (135 g fresh grass per bag, equivalent to 22500 kg/ha) and high (180 g fresh grass per bag, equivalent to 30000 kg/ha). The rates of dry matter decomposition and nutrient release were monitored at 10, 20, 30, 60, 90, 120, 150 and 180 days after application. The results showed that all three treatments decomposed rapidly over the first 20 days and then the release speeds slowed. The dry matter decomposition rate reached 60.59%-66.72% after 20 days and 70.19%-84.18% by the end of the experiment. Carbon (C), nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulphur (S), copper (Cu) and zinc (Zn) released rapidly in the first 20 days, reaching 62.1%-68.1%, 71.5%-76.0%, 70.4%-81.8%, 97.3%-97.7%, 75.6%-82.1%, 73.4%-79.0%, 78.6%-81.6% and 84.1%-88.4% respectively. Calcium (Ca) and manganese (Mn) released relatively slowly at first (43.5%-63.8% and 20.6%-35.9% after 20 days), but their release rates reached 86.0%-92.6% and 54.2%-76.7% respectively by the end of the experiment. Iron (Fe) was a significant “enrichment” phenomenon in the early stages but its release rate was ultimately very low. The general rules of decomposition and nutrient release did not change significantly with increasing application amounts. The release rates and speeds of C, N, P and K in the different applications fitted well with both the power function formula y=ax^b (all P<0.001) and the exponential decay model v=v₀e^-kx (all P<0.01). Regression analysis showed that the delay effects of nutrient release caused by increasing application amounts were C and N>P>K, with the full release of these nutrients needing 354-406 d, 791-1358 d, 87-122 d and 16-27 d respectively. The release speeds of C, N, P and K improved significantly over the first 10 and 20 d after application, following which the values remained at extremely low levels. This pattern did not change significantly with higher applications. Therefore, the ability to continuously supply nutrients for following crops by increasing the application amounts of V. villosa is very limited. Optimum application amounts need to be determined by fully considering the fertilizer requirements of the following crops.

Growth and gas exchange characteristics of Jerusalem artichoke (Helianthus tuberosus) at different growth stages in a semi-arid area

YANG Bin, LV Shi-Qi, KOU Yi-Xuan, SUN Shan, ZHAO Chang-Ming

2016, 25(10):  77-85.  DOI: 10.11686/cyxb2015550

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The aim of this study was to evaluate the growth and gas exchange characteristics of Jerusalem artichoke (Helianthus tuberosus) at different growth stages in a semi-arid area. The growth phenotype and photosynthetic physiology of Jerusalem artichoke high-yield lines (LZJ004 and LZJ119) and low-yield lines (LZJ018 and LZJ188) were evaluated at different growth stages. The results showed that plant height, internode length, leaf number, and leaf area were greater in high-yield lines than in low-yield lines at each stage. Compared with low-yield lines, high-yield lines showed a 44.94%, 8.26%, 12.11%, and 4.79% increase in corolla diameter, receptacle diameter, ligulate petal number, and ligulate petal length, respectively. The net photosynthetic rate (Pn) of high-yield lines was higher than that of low-yield lines. The water use efficiency (WUE) was also higher in high-yield lines than in low-yield lines, except at the rhizome formation stage, and the WUE of high-yield lines did not vary widely among the different growth stages. The sensitivity of Pn, stomatal conductance, and transpiration rate to changes in vapor pressure difference was lower in high-yield lines than in low-yield lines. During the whole growth period, the high-yield lines of Jerusalem artichoke had stronger growth potential and lower sensitivity to drought stress, which ensured highly efficient formation of underground tubers. This information will be useful to accelerate the breeding of high-yield Jerusalem artichoke cultivars.

Effect of drought stress on the photosynthetic characteristics and water use efficiency of three dominant forage grasses in Sinkiang

QIN Feng-Fei, SHEN Yi-Xin, LI Lan-Hai, HU Zeng-Yun, CHENG Liang, MA Xu-Long, CHEN Qing-Qing, WANG Ling-Yue

2016, 25(10):  86-94.  DOI: 10.11686/cyxb2015578

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This paper explores the adaptive mechanisms of three forage grasses (Bromus inermis, Dactylis glomerata and Poa pratensis) that are predominant in Sinkiang natural grasslands. Using pot experiment methods, drought stress was simulated to determine the effects of three different soil water contents levels (80%, 60% and 30% of field water capacity) on leaf photo-physiological characteristics and water use efficiency (WUE). With decreasing soil water contents, the daily average value of intercellular CO₂ (C_i) in the three grasses increased. The daily average values of stomatal conductance (G_s), net photosynthetic rate (P_n), transpiration rate (T_r), the ratio of P_n to C_i and evapotranspiration decreased, but the variation ranges of these characteristics differed across the three grasses. As drought stress increased, the daily average accumulated biomass of P. pratensis significantly decreased (P<0.05), but there was no obvious change in the other two grasses (P>0.05). The net water use efficiency (WUE_ET) and the daily average value of instantaneous water use efficiency (WUE_i) of D. glomerata changed very little (P>0.05), but in the other two grasses both WUE_ET and WUE_i significantly decreased (P<0.05). The WUE_ET of P. pratensis was significantly positively correlated with its daily average values for T_r and evapotranspiration (P<0.05). The WUE_ET of the three forage grasses was significantly positively correlated with their daily average accumulated biomass (P<0.05). The WUE_i and WUE_ET of the three grasses followed different change trends with the decrease in soil water contents. This study suggests that the adaptability of the three forage grasses to arid environments depends not only on their WUE but is also related to their biological characteristics and life history strategies.

Response of root morphology to precipitation change in Reaumuria soongorica seedlings

DUAN Gui-Fang, SHAN Li-Shan, LI Yi, ZHANG Zheng-Zhong, ZHANG Rong, CHONG Pei-Fang

2016, 25(10):  95-103.  DOI: 10.11686/cyxb2015459

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To investigate the effects of precipitation pattern change on root morphological characteristics of Reaumuria soongorica seedlings in arid and semi-arid areas, a controlled experiment with two factors: precipitation [natural precipitation as control (W); W plus 30% (W+); W minus 30% (W-) and precipitation interval (5 days, T; 10 days, T+)], during the growing season. Results; (1): Root morphological indices showed an increasing trend with increasing precipitation with total root length, total root volume and root biomass increasing by 39.2%, 62.5% and 63.2%, respectively. (2): Extended precipitation time interval promoted seedling root indices with increased precipitation. When precipitation interval was 10 days and rainfall was increased 30%, the total root volume and root biomass were increased by 116.3% and 224.4% respectively (P<0.01). (3): Apart from specific root length and specific root area which were highest under natural precipitation and 10 day interval, remaining indices were not affected by the irrigation treatments. (4): Correlation analysis showed that the relationship between different indices differed under different precipitation patterns; total root length, total root surface area, total root volume, mean root diameter and root biomass were significantly positive correlated (r=0.5), indicating that R. soongorica seedling root systems possessed strong morphological plasticity. Both irrigation quantity and time interval significantly affected root morphology and there was an interaction between them, but the effect of rainfall was more important. R. soongorica seedlings showed strong morphological plasticity, being able to adapt to environmental stress by changing root morphological characteristics.

Compensatory effects of drought stress and rewatering on growth of Hemarthria compressa

ZHANG Wei-Hua, JIN Jun-Ying, WANG Ming-Xing, HUANG Jian-Guo

2016, 25(10):  104-112.  DOI: 10.11686/cyxb2015584

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The aim of this study was to evaluate the effects of drought stress and compensatory rewatering on Hemarthria compressa, to provide a scientific basis for water management during the cultivation of this plant. Four treatments (normal water supply, light drought, medium drought, and heavy drought) were established in a pot experiment. Light drought did not significantly affect the growth of H. compressa. On day 12 after rewatering, the four treatments could be ranked, based on the biomass of plants, as follows: light drought>normal water supply≈medium drought>heavy drought. The biomass of plants under light drought was 11.47% greater than that of plants with a normal water supply. Also, the nitrogen content in H. compressa was significantly higher in plants under light and medium drought than in those with a normal water supply, and was similar in control plants and drought-stressed plants on day 12 after rewatering. These results showed that appropriate drought and rewatering barely affected or even improved the yield and protein content of H. compressa. Drought increased the root/shoot ratio and potassium and proline contents in H. compressa. However, medium and heavy drought led to decreases in nitrate reductase activity, root activity, and phosphorus, potassium, and nitrogen uptake. After rewatering of drought-stressed plants, the relative water content of leaves, proline content, and nitrate reductase activity recovered quickly to levels similar to those in the control, and the chlorophyll content increased gradually. The root activity of drought-treated plants on day 12 after rewatering was significantly higher than that in the control. The recovery of root activity was helpful for nitrogen assimilation, nutrition uptake, and photosynthesis, which restored normal metabolism and growth. These results implied that mild drought and rewatering could not only save water and mitigate drought damage, but also improve the yield and quality of cultivated H. compressa.

Genetic diversity assessment of tetraploid and octoploid switchgrass using EST-SSR and IT-ISJ molecular markers

ZHONG Ming, ZHOU Si-Fan, ZHANG Xin-Quan, HUANG Xiu, YAN Hai-Dong, ZHANG Ai-Ling, LUO-Qian, HUANG Lin-Kai

2016, 25(10):  113-123.  DOI: 10.11686/cyxb2015554

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Switchgrass is an important bioenergy plant. In this study, the genetic diversity of 65 samples of tetraploid Alamo and mutated octoploid Alamo (using colchicine) was assessed using expressed sequence tag-simple sequence repeat (EST-SSR) and intron-targeted intron-exon splice junction (IT-ISJ) markers. The results showed that EST-SSR primers amplified 245 fragments; the percentage of polymorphic loci was 99.59%, the number of alleles (Na) was 1.9878, the effective number of alleles (Ne) was 1.1718, Nei’s gene diversity (H) was 0.1308, and Shannon’s information index (I) was 0.2388. These genetic parameters for the tetraploid Alamo were as follows: 226 fragments; 88.93% polymorphic loci; Na, 1.8816; Ne, 1.1823; H, 0.1349; and I, 0.2398. These values were higher than those obtained for octoploid Alamo: 217 fragments; 92.24% polymorphic loci; Na, 1.9184; Ne, 1.1652; H, 0.1228; and I, 0.2234. The IT-ISJ primers amplified 165 fragments and the percentage of polymorphic loci was 96.36%, Na was 1.9878, Ne was 1.5777, H was 0.3354, and I was 0.4999. These parameters for tetraploid Alamo were as follows: 145 fragments; 94.55% polymorphic loci; Na, 1.9333; Ne, 1.6366; H, 0.3602; and I, 0.5280. These values were higher than those obtained for octoploid Alamo: 139 fragments; 84.24% polymorphic loci; Na, 1.7515; Ne, 1.4337; H, 0.2573; and I, 0.3864. A clustering analysis with the unweighted pair-group method with arithmetic means did not clearly separate 68 samples of tetraploid Alamo and octoploid Alamo, which had a low level of genetic differentiation. An analysis of molecular variance showed that 94.78% and 80.76% of genetic diversity occurred within ploidy levels, while 5.22% and 19.24% of genetic diversity occurred between ploidy levels.

An effective transformation method mediated by Agrobacterium in chicory (Cichorium intybus)

LI Xiao-Dong, CAI Lu, LI Shi-Ge, MO Ben-Tian, HAN Yong-Fen, WANG Xiao-Li

2016, 25(10):  124-131.  DOI: 10.11686/cyxb2016097

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Transgenic technology plays an important role in gene function analysis and crop germplasm innovation. However, transgenic studies are relatively recent in chicory. In this study we sought to improve tissue culture and genetic transformation methodology in chicory. Cotyledons grown in the dark were collected as explants. After transformation mediated by Agrobacteria, these explants were grown under illuminated conditions. The cotyledon cells divided rapidly when they were transferred from dark to light. The emergence rate of regenerated seedlings was greater than 90%, similar to that of previous studies however, the germination rate could be improved by 80%-90% if the explants were not pre-cultured. Our results were time, money and labor-saving. We also found that during callus induction, plant differentiation and root growth, decreased intensity and concentration of cytokinin significantly reduced the vitrification of callus and regenerated plantlets. Compared with continuously applied cytokinin our method decreased vitrification of callus and regenerated plantlets by about 9% and 16% respectively.

Stomatal structures of the Apiaceae subfamilies Mackinlayoideae and Azorelloideae and their taxonomic value

WANG Chao-Qun, GUO Shi-Qi, LIU Mei, RU Jian, WANG Jing-Ru, CHENG Xin-Yu

2016, 25(10):  132-141.  DOI: 10.11686/cyxb2015557

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The stomatal structures of the leaves (stems or fruits) of 48 species representing 34 genera of the Apiaceae subfamilies Mackinlayoideae (9 genera) and Azorelloideae (21 genera) and their relative taxa were studied in detail for the first time. Three types of stomata - anomocytic, anisocytic and paracytic - were observed. In Mackinlayoideae, the stomata are mostly paracytic and the minority are anomocytic. In Azorelloideae, stomata are mostly anomocytic and the minority are anisocytic. Cell walls in the Bowlesia clade are deeply waved while they are usually straight in the other clades of Azorelloideae. This stomatal study provides morphological evidence for the two subfamilies and the Bowlesia clade that have been established by molecular research. It also provides evidence to support moving Apiopetalum, Mackinlaya and Stilbocarpa from Araliaceae to Mackinlayoideae and Azorelloideae, and against placing Homalosciadium, Platysace, Hermas and Klotzschia in either of these subfamilies.

Effects of additives on the mixed silage quality of corn stover and asparagus lettuce leaves

REN Hai-Wei, DOU Jun-Wei, ZHAO Tuo, LI Xue-Yan, LI Zhi-Zhong, LI Jin-Ping, SUN Wen-Bin, HUANG Juan-Juan

2016, 25(10):  142-152.  DOI: 10.11686/cyxb2015519

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In this study, the effects of different additives on the mixed ensiling fermentation characteristics of dry corn stover (DCS) and asparagus lettuce leaves (ALL) were investigated under laboratory conditions. Four different treatments were measured: control (CK), formic acid (final concentration of 3.0 mL/kg material, fresh weight, FA), Lactobacillus delbrueckii (final concentration of 1×10⁵ cfu/g material, LD) and a combination of formic acid and L. delbrueckii (FA+LD). Silages were prepared in 1.5 L laboratory-scale glass silos at ambient temperature for 50 days. Ensiling samples were removed from the sealed containers for analysis every 10 days. The results showed that for the FA treatment, the pH value, cellulose, hemicellulose and lignin content, and the ammonia nitrogen to total nitrogen ratio (AN/TN) decreased significantly during the ensiling process (P<0.05), while lactic acid (LA) content increased (P<0.05). After ensiling for 50 days, the highest LA content, the lowest pH, AN/TN and dry matter (DM) loss were found in the FA treatment, indicating good fermentation quality. The DM loss and AN/TN of the LD treatment were significantly higher than the control (P<0.05). The pH value of the LD treatment was higher than 4.2. The silage quality the LD+FA treatment was higher before 30 days than at 40 and 50 days; the AN/TN increased substantially after 40 days and was 10% higher than the recommended value for good quality silage. Based on these results, it is suggested that formic acid can be used as an ensiling additive to improve silage fermentation quality and to prolong the preservation of DCS. However, it is also necessary to consider the cost of formic acid.

Effects of potassium application rates on carbohydrate content and resistance to thrips (Thripidae) in alfalfa

ZHANG Xiao-Yan, WANG Sen-Shan, LI Xiao-Long, LI Ya-Juan, HU Gui-Xin

2016, 25(10):  153-162.  DOI: 10.11686/cyxb2016144

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The aim of this research was to investigate the effects of potassium on alfalfa growth and its resistance to thrips. Two alfalfa varieties were chosen for the study; Gannong No.9 (thrip-resistant) and Gannong No.3 (thrip-susceptible). Potassium (K₂O) was applied to field-grown plants at five different levels (0, 6, 9, 12, and 15 g/m²) during the peak thrip damage period, and then the damage index, the potassium and carbohydrate contents in leaves, and yield were evaluated. The results showed that the yields of both alfalfa varieties increased significantly with increasing K₂O levels. The potassium, soluble sugars, starch, and lignin contents in old and heart leaves increased with increasing K₂O levels, and the thrip damage index decreased significantly. The lowest damage index values were in the 9 g/m² K₂O treatment (decreased 47.60% and 46.11% for Gannong No.9 and Gannong No.3 with the control, respectively). The damage index, yield, and potassium, soluble sugars, starch, and lignin contents at the second cutting showed similar trends to those at the third cutting. The damage index at the third cutting was decreased 30.78% and 23.27% for Gannong No.9 and Gannong No.3 with the control, respectively. Correlation analyses indicated that the potassium content of plants at the second and third cuttings was significantly negatively correlated with the damage index when the K₂O application rate was lower than 9 g/m², but not significantly correlated with the damage index when the K₂O application rate was higher than 12 g/m². The damage index was lower in Gannong No.3 treated with potassium than in Gannong No.9 without potassium application. These results indicate that potassium can enhance the resistance of alfalfa to thrips by promoting the synthesis of carbohydrates (especially soluble sugars and starch) and plant growth. Therefore, potassium management is an effective method to increase the tolerance of alfalfa to thrips in the field. The most economical fertilizer application rate was 9 g K₂O/m² in this experiment.

Effects of straw pellets on rumen function and live weight gain of beef cattle

HU Jiang, WANG Yi, ZHAO Fang-Fang, LIU Xiu, QUAN Jin-Peng, NIU Xiao-Liang, HAN Xiang-Min

2016, 25(10):  163-170.  DOI: 10.11686/cyxb2016129

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The effects of different corn straw pellets on rumen function, apparent digestibility, rumen fermentation and weight gain of beef cattle were determined to assess the potential for increased use of straw in feed processing. Thirty 18-month old Simmental cross cattle with similar body weight were randomly divided into a control group and two groups fed straw, groupⅠ and group Ⅱ. Ten animals were allocated to each group. The control and groupⅠ groups were fed crushed corn straw and corn straw pellets at 50% of dietary fibre, respectively. Group Ⅱ was fed straw-concentrate pellets providing the same corn fibre intake as the groupⅠ diet. The results showed that ingestion, rumination and chew time of cattle fed straw pellets were shorter than that those fed crushed straw, and chew time per food ball of cattle fed straw pellets and ingestion time of group Ⅱ animals were significantly lower than the control group (P<0.05). There were no differences in apparent digestibility of diets in any group except for NDF (neutral detergent fiber) digestibility in groupⅠ which was significantly lower than the control group (P<0.05). Rumen fermentation differed among the three groups; groupⅠ had lower pH value and butyrate content in rumen gastric juice than the control group (P<0.05), but had higher acetate content and acetate/propionate ratio(P<0.05). There were significantly decreased butyrate content and increased acetate/propionate ratio and NH₃-N content in rumen gastric juice from group Ⅱ than that the control group(P<0.05). Higher daily weight gain and feed conversion rate were observed in groupⅠ and group Ⅱ animals(P<0.05); daily weight gain increased by 0.36 kg and 0.38 kg and feed conversion increased by 27.9% and 29.1% compared with the control group, respectively.

Effects of pelleted rape straw feed on productive performance, rumen fermentation parameters, and blood biochemical indexes of Hu sheep

ZHANG Yong, GUO Hai-Ming, TANG Zhi-Hong, CAO Kai, WANG Yang-Po, YE Jun-An

2016, 25(10):  171-179.  DOI: 10.11686/cyxb2015548

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An in vivo experiment was conducted to study the effects of granulated rape straw feed on the productive performance, nutrient utilization, rumen fermentation parameters, and blood biochemical indexes of Hu sheep. Thirty 6-month-old healthy Hu sheep (32.33±1.65 kg) were equally divided into two groups based on their body weights. One group was fed on pelleted peanut vine feed (control group), and the other was fed on pelleted rape straw feed. The total feeding period lasted 52 days. The average daily weight gain, feed conversion ratio, rumen fermentation parameters, feed apparent digestibility, and blood biochemical indexes were measured. The results showed that, compared with the control group, the group fed with pelleted rape straw showed a significantly lower (P<0.05) dry matter intake (1.37 kg versus 1.47 kg), but similar average daily weight gain (147 g vs. 143 g). The pelleted rape straw feed increased the levels of total volatile fatty acids (102.27 mmol/L vs. 90.44 mmol/L) (P<0.05), propionate (17.08 mmol/L vs. 13.79 mmol/L) (P<0.01), butyrate (11.97 mmol/L vs. 10.31 mmol/L) (P<0.01), and NH₃-N (15.90 mg/dL vs. 11.33 mg/dL) (P<0.01), and decreased the acetate to propionate ratio (3.96 vs. 4.33) (P<0.01). The apparent total tract digestibility of neutral detergent fiber (P=0.09) showed an increasing trend in the group fed with pelleted rape straw (54.75% vs. 51.50%). The pelleted rape straw feed significantly increased the concentration of glucose (3.77 mmol/L vs. 2.97 mmol/L) (P<0.05), and decreased the concentrations of blood urea nitrogen (11.01 mmol/L vs. 12.80 mmol/L) (P<0.01), free fatty acids (133.07 umol/L vs. 144.50 umol/L) (P<0.05), alanine aminotransferase (14.85 U/L vs. 19.23 U/L) (P<0.05), and high-density lipoprotein (0.92 mmol/L vs. 1.05 mmol/L) (P<0.05). The cost per kg weight gain was 5.87 yuan lower in the experimental group than in the control group. In summary, feeding growing Hu sheep with pelleted rape straw had no adverse effects on their health and reduced feed costs, and could therefore improve breeding efficiency. Rape is a rich forage source in the areas where Hu sheep are farmed, and the use of rape straw as feed is a promising strategy to reduce regional rape straw pollution.

Textual research of the relationship between Zhang Qian and the introduction of alfalfa to China during the Han Dynasty

SUN Qi-Zhong, LIU Qian, TAO Ya, XU Li-Jun

2016, 25(10):  180-190.  DOI: 10.11686/cyxb2015413

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Alfalfa (Medicago sativa) was introduced to China during the Han dynasty. There is divergence of opinion as to whether or not alfalfa was introduced by Zhang Qian. The relationship between Zhang Qian and alfalfa introduction was analyzed from the motivation, experience and influence of Zhang Qian during exploration of the Western Regions and the possibility that Zhang Qian brought back alfalfa’s seeds. There are four opinions regarding the idea that Zhang Qian introduced alfalfa to China. They are: (1) Zhang Qian introduced alfalfa; (2) Zhang Qian didn’t introduce alfalfa; (3) Zhang Qian transferred information on alfalfa; (4) Introduction of alfalfa was attributed to Zhang Qian in commemoration of his exploration of Western Regions. Although there is no direct historical evidence to prove that Zhang Qian introduced alfalfa to China during the Han dynasty, it is clear that there was a close relationship between Zhang Qian’s activities and alfalfa introduction to China. Information about Zhang Qian bringing alfalfa to China from Western Regions was the basis of the saying that the Chinese brought alfalfa seed and the emperor planted alfalfa. During the time alfalfa was being introduced to China, Zhang Qian provided useful information on its culture; “It was known that during the Han dynasty that alfalfa was planted in Dawan. Alfalfa was important forage for Ferghana horses.” Zhang Qian’s activities played a major part in the introduction of alfalfa to China.

Research progress on signal transduction and regulation mechanisms in plant-nematode interactions

YE De-You, QI Yong-Hong, LI Min-Quan

2016, 25(10):  191-201.  DOI: 10.11686/cyxb2015574

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Plant parasitic nematodes pose a serious threat to agricultural production and result in significant economic losses in crops worldwide. A key factor in crop production is plant resistance or susceptibility to nematodes; therefore, this has been an important subject for researchers in the areas of crop genetics and breeding. Understanding the mechanisms of plant resistance or susceptibility to nematodes is of great theoretical significance and practical value to guide the breeding of nematode-resistant crops. In this paper, the mechanisms underlying plant resistance or susceptibility to nematodes are reviewed, including specific plant resistance genes or proteins, plant hormone synthesis and signaling pathways, and reactive oxygen signals that are generated in response to nematode attack. In recent years, many researchers have suggested that plant resistance or susceptibility to invading nematodes and nematode-secreted effectors is mainly determined by the coordination of different signaling pathways. Many studies have shown that crosstalk among various nematode resistance-related elements represents an integrated signaling network regulated by transcription factors and small RNAs at the transcriptional, posttranscriptional, and translational levels. Ultimately, the outcome of this highly controlled signaling network determines the resistance or susceptibility of the host plant to nematodes. These above-mentioned results lay the foundation for further research on the signal transduction and regulation mechanisms involved in the plant-nematode interaction, and thus, provide a theoretical basis for the development of new strategies to prevent and control plant nematodes.

Spatial distribution patterns and environmental interpretation of plant species richness in the Lhasa Valley, Tibet

La-Duo, ZHANG Yan-Jie, LIU Jie, CUI Ling-Ling, PANG You-Zhi

2016, 25(10):  202-211.  DOI: 10.11686/cyxb2015566

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Spatial distribution patterns of species richness and potential influencing factors are important aspects of species diversity research and biodiversity conservation. However, little biodiversity research has been carried out in the Lhasa valley. Based on vegetation types, 47 plots with 141 quadrats were established to investigate the spatial distribution of species richness and its relationship with environmental factors. The study showed that a total of 247 species of vascular plant species, belonging to 47 Families and 134 different Genus, were recorded in this study. Climatic data for each plot was calculated using the Cokriging method. Moran's eigenvector maps (MEM) and variation partitioning were generated to explore the influence of spatial structures and environmental factors on the distribution of species richness, and generalized additive model analyses (GAM) were performed to examine the influence of environmental factors and vegetation cover on species richness. De-trended correspondence analysis (DCA) was utilised to detect and analyze the distribution of species richness and its relationships with environment. The results of MEM and variation partitioning indicated that spatial structure was important to the distribution of species richness but environmental factors also played an important role in spatial structure. GAM of environmental factors and transformed species richness (TSR) suggested that distribution patterns of plant species richness are significantly related to longitude, latitude, altitude, AP (annual precipitation), AET (actual evapotranspiration), MAT (mean annual temperature), PET (potential evapotranspiration), MI (moisture index). DCA also supported this result, indicating that these environmental factors influenced the distribution patterns of species richness. Other important factors influencing biodiversity include disturbance and humidity.