Table of Content

20 February 2018, Volume 27 Issue 2

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CONTENTS

Modeled effects of precipitation, temperature, and CO₂ changes on carbon dynamics in grassland and cropland on the Loess Plateau

GUO Ding, GUO Wen-fei, ZHAO Jian, Temuqiletu, LI Xu-dong, FU Hua, LUO Yi-qi

2018, 27(2):  1-14.  DOI: 10.11686/cyxb2017303

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Global climate change usually involves simultaneous and continuous changes under different environmental conditions. However, it is very difficult and expensive to explore those climate change in manipulative experiments. Applying models can help us to understand the responses of ecosystem structure and function to global climate change. To explore the effects of climate change on carbon processes in grassland and cropland on the Loess Plateau, the Terrestrial Ecosystem (TECO) model was applied to identify patterns of ecosystem carbon processes in response to changes in CO₂ concentration, temperature, and precipitation. The results showed that net primary production (NPP) and heterotrophic respiration (Rh) increased with temperature up to +4 ℃ and then declined, except that the highest Rh in cropland ecosystem was at 0 ℃ (ambient conditions). Net ecosystem exchange (NEE) showed the opposite trend with the lowest value at +4 ℃, and the highest C sequestration was at +4 ℃ in both systems. Changes in precipitation and CO₂ concentration affected the responses of NPP, Rh, and NEE to temperature change. The NPP, Rh, and NEE became more sensitive to temperature change with increased precipitation. Changes in precipitation affected the turning points of temperature responses for NPP, Rh, and NEE in the grassland ecosystem, but not in the cropland ecosystem. With increased CO₂ concentration, the patterns of NPP, Rh, and NEE became flatter when temperature change was greater than +4 ℃. The interaction between increased precipitation and warming had the highest relative strength in terms of effects on NPP, Rh, and NEE, with values of 51.0% and 30.0%, 51.3% and 16.6%, and -46.1% and -28.9% in the grassland and cropland ecosystem, respectively. The interaction between increased precipitation and increased CO₂ concentration had the smallest relative strength in terms of effects on NPP, Rh, and NEE, with values of 2.4% and 7.5%, 3.7% and 3.4%, and 8.1% and -9.0%, in the grassland and cropland ecosystems, respectively. Three-factor interactions were not significant for these ecosystems. Our results suggest that carbon dynamics are less sensitive in the cropland ecosystem than in the grassland ecosystem to interactions among climatic factors under climate change.

Floristic quantitative classification and successional characteristics of typical grassland under different ecological restoration methods in the Loess Hilly Region of Ningxia

JIA Xi-yang, MA Hong-bin, ZHOU Yao, ZHANG Rui, SU Ting-ting, ZHANG Shuang-qiao, ZHANG Jun

2018, 27(2):  15-25.  DOI: 10.11686/cyxb2017159

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Restoration measures strongly influence vegetation communities. To design effective restoration measures for the Loess Hilly Region, it is important to classify the flora and study the succession of degraded grassland plant communities on the typical steppe in Ningxia. In this study, we explored the relationship between the plant succession process and soil factors under three ecological restoration measures (enclosure, contour trench, and fish-scale pits) implemented for 0 (1), 3, 6, 10 and 15 years by using Two Indicators Species Analysis (TWINSPAN) combined with a detrended correspondence analysis (DCA). The main results were as follows: (1) According to the TWINSPAN-DCA, the vegetation in the study plot was divided into eight communities. (2) With increasing exclosure time, the vegetation succession sequence was as follows: Stipa bungeana+Thymus mongolicus communities→S. bungeana+Stipa grandis communities→T. mongolicus+S. bungeana communities→S. bungeana+S. grandis communities→S. bungeana+Artemisia sacrorum communities. The succession process from 1 to 15 years in the contour trench grassland was as follows: Astragalus adsurgens+Pennisetum flaccidum communities→Poa annua+Leymus secalinus communities→S. bungeana+T. mongolicus communities→T. mongolicus+L. secalinus communities→S. bungeana+S. grandis communities. The succession process from 1 to 15 years in the fish-scale pits grassland was as follows: A. adsurgens+P. flaccidum communities→P. annua+S. bungeana communities→S. bungeana+T. mongolicus communities→T. mongolicus+S. bungeana communities. In the contour trench grassland and the fish-scale pits grassland, the trend in the dominant vegetation type over time was rhizome type-sparse type-dense cluster type, but there were also non-linear or spiral changes. The coverage of the plant community and aboveground biomass increased over time under all three restoration measures, and the growth rate was fastest in enclosed grassland and slowest in the fish-scale pits grassland. (3) The results of a detrended canonical correspondence analysis indicated that soil bulk density, organic matter, fungi, total phosphorus, and protease activity are the main soil factors affecting the vegetation communities in this area.

Distribution of herbaceous community biomass and its relationship with influencing factors in the Loess Hilly Region

FANG Zhao, ZHANG Shao-kang, LIU Hai-wei, JIAO Feng, ZHANG Jun

2018, 27(2):  26-35.  DOI: 10.11686/cyxb2017152

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Grassland is the main vegetation type in arid and semiarid areas of the Loess Plateau. Herbs, as the dominant community in the grassland ecosystem, have an irreplaceable advantage in the restoration of vegetation and in the conservation of soil and water on the Loess Plateau. In this study, we analyzed the spatial distribution characteristics of aboveground and belowground biomass and their influencing factors in herbaceous plant communities at different latitudes in the Loess Hilly Region. In addition, isokinetic growth was statistically analyzed to provide theoretical guidance for the restoration of vegetation and improvement of ecological management strategies for the Loess Hilly Region. The results showed that: (1) in the range of 35.95° to 38.36° N, the aboveground biomass of the herbaceous plant community in the Loess Hilly Region ranged from 54.60 to 204.32 g·m^-2 (average, 156.968 g·m^-2; coefficient of variation, 27.83%). Belowground biomass ranged from 78.88 to 829.64 g·m^-2 (average, 469.21 g·m^-2; coefficient of variation, 48.87%). The change in the belowground/aboveground biomass of the herbaceous plant community was 0.93-4.49 (average, 2.89; coefficient of variation, 39.18%). The communities were ranked, from highest biomass (belowground+aboveground) to lowest, as follows: forest-grassland belt>grassland belt>forest belt>grassland-desert belt. The aboveground and belowground biomass showed a “single peak” trend along the latitudinal gradient, first increasing and then decreasing with increasing latitude. (2) There was a significant positive correlation between belowground biomass and aboveground biomass (P<0.01; coefficient of determination, 0.59), and this relationship was consistent with isokinetic growth. (3) The belowground biomass of the herbaceous plant community was positively correlated with mean annual precipitation, mean annual temperature, soil organic carbon, soil total nitrogen, and soil total phosphorus. Both climatic factors and soil physico-chemical properties had important effects on belowground biomass. To draw accurate conclusions about the effects of climatic and soil physico-chemical properties on plant communities, further plant biology and eco-physiology research should be undertaken to explore the mechanisms underlying plants’ responses.

Drought resistance of three common slope plants determined in a simulated drought experiment

XU Pian-pian, WANG Jian-zhu

2018, 27(2):  36-47.  DOI: 10.11686/cyxb2017122

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Vetiveria zizanioides, Medicago sativa, and Festuca elata are commonly used as greening plants on engineered slopes. The aim of this study was to determine the effects of drought stress on the seed germination, photosynthesis, and physiological and biochemical indices of V. zizanioides, M. sativa, and F. elata. Analyses of the drought resistance of these three plants will provide a reference for selecting species suited to community reconstruction and/or ecological restoration of engineered slopes (e.g. those created in hydropower schemes). Drought stress was imposed using polyethylene glycol (PEG) at 5%, 10%, 15%, and 20%, and seeds of V. zizanioides, M. sativa, and F. elata were germinated under this range of PEG concentrations. To explore the adaptability of the three plant species to natural soil water stress, their photosynthetic characteristics and physiological and biological indexes were measured under four treatments: normal water (soil moisture content 75%-80% of field capacity), mild soil drought stress (65%-70% of field capacity), moderate soil drought stress (50%-55% of field capacity), and severe soil drought stress (35%-40% of field capacity). The membership function method was used to evaluate the drought resistance of the three plant species. The number of germinated seeds and seedling vigor decreased with increasing drought stress for all three plant species. The higher PEG concentration significantly inhibited seed growth, and reduced the relative germination rate and relative germination index. In contrast, the seed relative germination rate and germination index of V. zizanioides were promoted in the 5% PEG treatment. The net photosynthetic rate (P_n), transpiration rate (T_r), intercellular CO₂ concentration (C_i), stomatal conductance (G_s), and water use efficiency (WUE) of the three species decreased to different degrees under drought stress. The largest decreases in P_n, T_r, and C_i under drought stress were in V. zizanioides, while the largest decreases in G_s and WUE under drought stress were in F. elata. The malonaldehyde (MDA), proline (Pro), and soluble sugars content significantly increased in all three plant species with increasing drought severity. As the severity of the drought stress increased, the largest increase in MDA content was in V. zizanioides and the smallest was in F. elata. The MDA and soluble sugars content in M. sativa leaves significantly increased and showed a strong response to drought stress. The increase in Pro and soluble sugars content in leaves was smaller in V. zizanioides than in the other two species. The drought resistance of the three plant species was evaluated based on their germination rate, germination index, and photosynthetic and physiological characteristics using the membership function method. The most drought resistant species was M. sativa, followed by F. elata, and then V. zizanioides.

Role of glucose-6-phosphate dehydrogenase in the drought tolerance of alfalfa

XIONG Li-li, YAN Shuang, LI Ping, YANG Guo-zhu, YIN Wei, YAN Xiao-xia, ZHANG Han

2018, 27(2):  48-56.  DOI: 10.11686/cyxb2017308

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Glucose-6-phosphate dehydrogenase (G6PDH, EC1.1.1.49) is the first and critical rate-limiting enzyme in the pentose phosphate pathway. It is involved in the synthesis of NADPH and ribose-5-phosphate, and plays an important role in plant responses to biotic and abiotic stresses. The aim of this study was to explore the role of G6PDH under drought stress in alfalfa. First, 7-day-old alfalfa seedlings were treated with different concentrations of polyethylene glycol (PEG), and then plant height and root length, fresh weight and dry weight, and the contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) were determined. These analyses were used to define the concentration of PEG causing drought stress to the seedlings. Then, the activity of G6PDH in alfalfa seedlings was determined under a range of stress-inducing PEG concentrations. The G6PDH inhibitor Na₃PO₄ was applied to alfalfa seedlings under drought stress, and changes in the indexes described above were determined. The results showed that PEG treatment significantly inhibited the growth of alfalfa seedlings. Plant height, root length, fresh weight, and dry weight decreased with increasing PEG concentrations. Compared with non-stressed seedlings, those subjected to PEG-induced drought stress (15% PEG) showed 28.4% and 19.9% higher contents of H₂O₂ and MDA, respectively, and 49.4% lower G6PDH activity. Application of Na₃PO₄ decreased the activity of G6PDH and caused the symptoms of drought stress to become more severe, suggesting that G6PDH is involved in the regulation of oxidative stress induced by PEG.

Characteristics of soil microbial biomass carbon, nitrogen, and phosphorus under Cynodon dactylon vegetation at different altitudes in the hydro-fluctuation belt of the Three Gorges Dam Reservoir

YANG Wen-hang, REN Qing-shui, QIN Hong, SONG Hong, YUAN Zhong-xun, LI Chang-xiao

2018, 27(2):  57-68.  DOI: 10.11686/cyxb2017133

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The full operation of the Three Gorges Dam Reservoir (TGDR) on the Yangtze River, China, has formed a hydro-fluctuation belt with an annual change in water level of almost 30 m and spanning an area of 350 km². These large changes in the water level have led to a direct decline in the plant community within the hydro-fluctuation belt. Revegetation is an environmentally friendly measure to restore the ecological integrity of the hydro-fluctuation zone in the TGDR, and is also crucial for maintaining sound riparian ecosystem function and services. The study site (107°32'-108°14' E, 30°03'-30°35' N) was located in the Ruxi River basin in Gonghe Village, Shibao Township, Zhong County, in the Chongqing municipality of China. We monitored the changes in soil fertility and quality upon revegetation of Cynodon dactylon in the hydro-fluctuation belt of the TGDR. Plots of C. dactylon grassland at three elevations (150, 160 and 170 m above sea level) in Zhong County in the TGDR were sampled and the contents of soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and soil microbial biomass phosphorus (SMBP) were determined. The results showed that: (1) The soil microbial biomass at each elevation was significantly higher in C. dactylon grassland than in unplanted soil, indicating that artificial vegetation restoration had significantly increased the soil microbial biomass; (2) The SMBC and SMBN were significantly higher at 160 m elevation than at 150 m and 170 m elevations, but the SMBP was significantly lower at 160 m elevation than at 150 m and 170 m elevations. Thus, special attention should be paid to the transfer of P into water. (3) At the different altitudes, the ratio of SMBC/SMBN ranged from 5.32 to 15.62, and the ratio of SMBC/SMBP ranged from 7.11 to 19.99. The range of SMBC/SOC (soil organic carbon) was 0.68%-2.57%, the range of SMBN/TN (total nitrogen) was 0.68%-3.33%, and the range of SMBP/TP (total phosphorus) was 1.95%-5.23%. The SMBC/SMBN and SMBC/SMBP ratios were significantly higher in C. dactylon grassland than in unplanted soil, indicating that there was more available nitrogen and available phosphorus in C. dactylon grassland than in unplanted soil. In addition, the soil turnover rate was faster in the C. dactylon grassland than in unplanted soil; (4) Soil microbial biomass was significantly correlated with soil organic carbon, total nitrogen, and soil moisture, but was negatively correlated with soil pH. Our study showed that the physical and chemical properties of soil under revegetating C. dactylon significantly affected the soil microbial biomass. Thus, revegetation of C. dactylon increased the soil microbial biomass and also enhanced soil quality in the hydro-fluctuation belt of the TGDR.

Effects of polyacrylamide and grass root system on shear strength and physical properties of purple soil on barren slopes

LI Tie, WANG Run-ze, CHEN Yun, HE Bing-hui, ZHOU Tao, WU Chen, LIU Xiao-hong

2018, 27(2):  69-78.  DOI: 10.11686/cyxb2017138

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We studied the effects of polyacrylamide (PAM) and the grass root system on the shear strength and physical properties of purple soil on barren slopes. Three different treatments were applied to purple soil on barren slopes: PAM (single application of PAM), grass (single planting of grasses), and grass+PAM. The root parameters were measured using the WinRHIZO (Pro.2004c) root analysis system and soil shear strength of soil samples was determined using a ZJ-type strain-controlled direct shear apparatus. We also determined the basic physical properties of soil samples. The main results were as follows: 1) All three treatments significantly improved the soil water holding capacity. The grass+PAM treatment had the best effects on soil porosity and water content, followed by the grass treatment. 2) All three treatments significantly increased the abundance of microaggregates in the 1-0.25 mm and 0.25-0.05 mm size ranges, and decreased the abundance of those in the smaller size category (<0.01 mm). 3) The average internal friction angle of grass was 37.12% and 36.59% higher in the grass and grass+PAM treatments, respectively, than in the control, and the average soil cohesion in the grass and grass+PAM treatments was increased by 69.47% and 83.64%, respectively. The root surface area density and abundance of roots with diameter between 0.7 mm and 0.9 mm were the main factors affecting the shear properties of soil. 4) The growth of grass roots was markedly affected by PAM, which increased the average root length density, root surface area density, root volume density, and root weight density of Cynodon dactylon soil samples by 15.57%-53.16%, and of Trifolium repens soil samples by 23.02%-80.00%.

Arsenic absorption characteristics and relationships between arsenic absorption and nutrient accumulation in stems and leaves of two ryegrass species under arsenic stress

LI Jin-bo, LI Shi-gang, SONG Gui-long, PUYANG Xue-hua, XUE Bo-han

2018, 27(2):  79-87.  DOI: 10.11686/cyxb2017290

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Ryegrass is tolerant to heavy metals and has a strong capacity to accumulate them from the soil. Therefore, it is a promising plant for phytoremediation of soils polluted with heavy metals. One of the toxic effects of heavy metals is to disturb the nutrient balance of plants. The aims of this study were to explore the arsenic- and nutrient-absorption characteristics of ryegrass under arsenic stress and to analyze the relationships between As absorption and nutrient accumulation in the stems and leaves. An annual ryegrass (Lolium multiflorum) and a perennial ryegrass (Lolium perenne) were grown in soil without or with As (100 mg·kg^-1) in a pot experiment. After 2 months of growth, the plants were harvested and separated into five parts: old leaves, functional leaves, young leaves, stems, and roots. Then, the As and nutrient contents were determined in each part. The results indicated that annual ryegrass was more As-resistant than perennial ryegrass; the shoot length and root length of annual ryegrass were reduced by 13.3% and 3.3%, respectively, by As. The dry weights of all five parts of both ryegrass species were lower in the As treatment than in the control, but the decrease was not significant for the old leaves of perennial ryegrass and the roots of annual ryegrass. In both ryegrass species, the As concentration was highest in the roots, followed by the old leaves, stems, functional leaves, and then young leaves. The As-absorption capacity of perennial ryegrass was higher than that of annual ryegrass. In both ryegrass species, the nitrogen, phosphorus, and potassium absorption was highest in young leaves, followed by functional leaves, and then old leaves. The calcium, magnesium, and manganese absorption capacity was highest in old leaves, followed by functional leaves, and then young leaves. There was a highly significant negative correlation between As and Mg content in leaves. The correlation between As and other nutrients varied among plant parts in the two ryegrass species.

Effects of Eupatorium adenophorum compost on soil characteristics and yield and quality of grape

SUI Zong-ming, LIU Hai, YIN Jie, GUO Ming-quan, WANG Yong, YUAN Ling

2018, 27(2):  88-96.  DOI: 10.11686/cyxb2017127

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Eupatorium adenophorum, the most harmful invasive plant in China, has huge negative impacts on agriculture, forestry, animal husbandry, and the ecological environment in Southwest China. It is important to control the spread of this invasive plant and to utilize the plant residues produced during its elimination. In this study, therefore, fresh E. adenophorum plants were pulled out and composted at the same site, and then the compost was used as an organic fertilizer in combination with chemical fertilizers at different proportions for grape plants cultivated in an orchard. The yield and quality of table grape and selected characteristics of soil (microorganisms, nutrient contents, and enzyme activities) in the orchard were analyzed. The results indicated that there was no significant variation in grape yields among the fertilizer treatments, but there were differences in grape quality. The grapes were larger, heavier, with higher contents of soluble solids and sugars, and a higher sugar/acid ratio in the M₇₅ (25% chemical fertilizer+75% organic fertilizer) treatment than in the chemical fertilizer only treatment. The vitamin C content in grapes increased and the nitrate concentration decreased with increasing amounts of organic fertilizer. Although soils in the M₅₀ (50% chemical fertilizer+50% organic fertilizer) and M₇₅ treatments had similar microbial carbon and nitrogen contents, the microbial carbon content was 23.2% and 29.4% higher, respectively, and the microbial nitrogen content was 17.5% and 20.8% higher, respectively, than those in the chemical fertilizer only treatment. There were more culturable bacteria, fungi, and actinomycetes in soils treated with organic fertilizer than in soils treated with chemical fertilizer only. Furthermore, application of organic fertilizer alleviated soil acidification. The activities of catalase, urease, and invertase in soils varied among grape growth periods and were synchronized with the nutrient requirements of grape plants. Application of organic fertilizer in combination with chemical fertilizer at appropriate proportions stimulated soil enzyme activities. Therefore, E. adenophorum compost had positive effects on grape quality and soil fertility. Composting E. adenophorum plants could be an effective way to turn this harmful weed into a beneficial product and to utilize an abundant resource.

Exogenous H₂O₂ improves alkali resistance of oat seedlings by regulating active oxygen metabolism and osmolyte accumulation

LIU Jian-xin, OU Xiao-bin, WANG Jin-cheng, LIU Xiu-li

2018, 27(2):  97-104.  DOI: 10.11686/cyxb2017137

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Hydrogen peroxide (H₂O₂) is a signaling molecule with diverse physiological functions in plants. The objective of this study was to determine whether exogenous H₂O₂ could improve the alkali tolerance of oat (Avena nuda) seedlings. Seedlings of oat cv. Dingyou No.6 at the three-leaf stage were irrigated with 75 mmol·L^-1 NaHCO₃ solution containing dimethylthiourea (DMTU, a quencher of H₂O₂) or ascorbate (ASA, a scavenger of H₂O₂), and the leaves were sprayed with 0.01 mmol·L^-1 H₂O₂. Seedlings irrigated with water served as the control. After 7 days of treatment, seedling growth, chlorophyll content, active oxygen metabolism, and osmotic accumulation in leaves were measured. The results showed that treatments with exogenous H₂O₂ remarkably relieved the growth inhibition caused by NaHCO₃ stress, and significantly decreased the contents of O2·-, H₂O₂, malondialdehyde, soluble sugars, free amino acids, proline, and activities of catalase and peroxidase. Treatments with exogenous H₂O₂ also increased the activities of superoxide dismutase and ascorbate peroxidase, and increased the contents of ascorbic acid, glutathione, organic acids, and chlorophyll in leaves of oat seedlings. However, none of the treatments affected the soluble protein content. The regulating effects of exogenous H₂O₂ on alkali stress could be reversed by treatment with DMTU or ASA. A comprehensive evaluation based on principal components and subordinate function analyses revealed that foliar spraying with H₂O₂ could improve the alkali stress adaptability of oat seedlings, and the promoting effect of H₂O₂ could be reversed by DMTU or ASA. Together, the results showed that H₂O₂ can increase alkali resistance in oat seedlings by regulating active oxygen metabolism and osmotic accumulation in leaves oat plants under alkali stress.

Transcriptome analysis of Leymus chinensis under different mowing intensities

ZHAO Jin-bo, HOU Xiang-yang, WU Zi-nian, REN Wei-bo, HU Ning-ning, GUO Feng-hui, MA Wen-jing

2018, 27(2):  105-116.  DOI: 10.11686/cyxb2017143

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Mowing is an important part of grassland management. The height of stubble left after mowing directly influences grassland productivity and community structure, which have important implications for forage production. To investigate the transcriptional responses of Leymus chinensis under different mowing intensities, the transcriptome of the regenerative blades from L. chinensis mowed to different stubble heights (0, 2, 4, 8, and 12 cm) were sequenced using the Illumina HiSeq-PE150 high-throughput sequencing platform. In total, 139767803 reads and 41.94 Gb raw data were generated. After filtering, quality control, and de novo assembly, we obtained 270207 transcripts with a total length of 191.6 Mb. After comparisons with various databases, we obtained 48097 unigenes. We detected 2579 differentially expressed genes (DEGs) between the mowed group and the non-mowed control group. The DEGs were classified into several functional categories and metabolic pathways including carbohydrate metabolism, response to wounding, hydrogen peroxide catabolism, and plant hormone signal transduction. A cluster analysis was used to identify genes showing changes in transcript abundance with increasing mowing intensity. These genes were enriched in peroxisome, photosynthesis, and other metabolic pathways. Research on the transcriptome of L. chinensis under different mowing intensities provides valuable data resources for molecular research on herbaceous plants. Our findings will be useful for analyzing the molecular mechanism of mowing responses and for mining genes related high performance of L. chinensis after mowing.

Cloning and expression analysis of LpAGD14 from Lilium pumilum

WANG Wang, TIAN Zhong-ping, SU Xiao-xia, YANG Liu-hui, ZHOU Yun-wei

2018, 27(2):  117-123.  DOI: 10.11686/cyxb2017317

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A gene encoding an ArfGAP protein was cloned from the cDNA library of Lilium pumilum. Its ORF sequence encoded a 640-amino acid polypeptide with a typical C4 ArfGAP conserved domain. The relative molecular mass of the putative ArfGAP protein was 69.43 kDa, the theoretical isoelectric point was 8.95, and it was predicted to be a hydrophilic protein with no transmembrane structure. At the amino acid sequence level, the L. pumilum ArfGAP showed 59% homology to ArfGAP-domain proteins (AGDs) in Elaeis guineensis, and more than 50% homology to AGDs in Musa acuminata subsp., Phoenix dactylifera, and Ananas comosus. Therefore, the gene was named LpAGD14. Transcript analysis by qRT-PCR showed that the transcript levels of LpAGD14 increased to reach the highest value after dormancy release. Subcellular localization assays showed that LpAGD14 localized to the cell membrane. Ultrastructural observations showed that the layers of the Golgi body increased with prolonged cold storage. These results indicated that LpAGD14 is involved in the dormancy release of L. pumilum and plays a role in vesicle transport. This study lays the foundation for further research on the function and regulation of this gene and its product.

Development of microsatellite primers in Potentilla anserina by magnetic beads enrichment

FU Gui, LI Jun-qiao, BAO Jin-yuan, BAI Shi-jun, WEI Mei-qin

2018, 27(2):  123-134.  DOI: 10.11686/cyxb2017144

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Simple sequence repeat (SSR) markers have been used extensively in studies on the heredity of flora and fauna because they are widely distributed throughout the genome, codominant, stable, and polymorphic. The genomic DNA of Potentilla anserina was digested with the restriction enzymes EcoRⅠ and MseⅠ and the digested fragments were hybridized with biotinylated (AG)₁₅ and (GT)₁₅ probes. The fragments containing SSR genomic loci were adsorbed onto magnetic beads coated with streptavidin. Then, by elution, PCR amplification, cloning, and sequencing, a collection of SSRs was obtained. A total of 236 effective clones was acquired. Eighty sequences were randomly selected for sequencing, and 68 of them (85%) were found to be single sequences. Forty sequences including SSR loci were selected and 40 primers were developed using primer design soft (Primer 5). Finally, 20 pairs of primers with rich polymorphism and stable amplification were obtained through preliminary screening. The success rate of amplification was 50%. A preliminary analysis using the 20 pairs of primers amplified 338 polymorphic sites, with an average of 17 sites per primer pair. The mean values of effective allele number (Ne), polymorphism information content (PIC), Nei’s gene diversity (H), and Shannon-Weaver index (I) were 1.2440, 0.8996, 0.1768, and 0.3078, respectively. These 20 pairs of SSR primers provide novel molecular markers for research on the genetic diversity of P. anserina.

Study on the combination effect of Pennisetum purpureum and Pennisetum sinese

WU Zheng-min, WANG Zhi-jing, WU Hao-hao, LI Zheng, LI Wen-wei, ZHUANG Gui-feng, YIN Fu-quan, ZHAO Zhi-hui

2018, 27(2):  135-145.  DOI: 10.11686/cyxb2017302

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The study investigated the effects of the combination of Pennisetum purpureum and Pennisetum sinese in different proportion on goats rumen degradation rate by using in vitro gas production technique so as to provide theoretical basis and data support for scientific application of roughage resources in South China. According to the ratio of dry substance, P. purpureum and P. sinese were mixed in the ration of 100∶0, 75∶25, 50∶50, 25∶75, 0∶100 and divided into group Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ respectively, which were cultured for 4, 8, 12, 24 and 48 hours by using in vitro gas production respectively. Three replicates in each time point. We stopped fermentation and determined liquid pH, NH₃-N concentration and the amounts of DM (dry matter), CP (dry matter) and NDF (neutral detergent fiber) in fermentation residue. The results showed as follows: 1) Combinations of P. purpureum and P. sinese influenced rumen pH and NH₃-N concentration while pH decreased significantly (P<0.05) as the increase of the proportion of P. sinese, which was significantly lower than single P. purpureum group (P<0.05); The concentration of NH₃-N firstly decreased and then increased (P>0.05) with their normal fluctuation range, which was beneficial to rumen fermentation. Rumen TVFA (total volatile fatty acids) concentration increased gradually with the increase of P. sinese ratio. Ⅲ, Ⅳ and Ⅴ was significantly higher than that of single P. purpureum group (P<0.05) in 8-48 h. 2) The degradation rate of DM, NDF and CP increased significantly with the increase of the proportion of P. sinese, which was significantly higher than single P. purpureum group (P<0.05), and 75% P. sinese group was higher than those of the other groups as the better proportion. 3) The combined effects of P. purpureum and P. sinese were positive. The maximum combination effect (P<0.05) of DM degradation rate and positive combination effect of NDF degradation rate was obtained in 50% P. sinese group; The maximum combination effects (P<0.05) on the degradation rate of NDF in 75% P. sinese group was obtained at 12 hours; The combined effects on CP degradation rate were positive in P. sinese group at 4 and 48 h. We concluded that the combination of P. purpureum and P. sinese may improve the degradation rate of DM, NDF, CP and positive combination effect while better proportion of P. purpureum and P. sinese was 25∶75.

Problems associated with continuous cropping of Lilium davidii var. unicolor

HUANG Yu-fang, ZHANG En-he, ZHANG Xin-hui, WANG Hui-zhen, WANG Qi, LIU Qing-lin, SHI Yu-qian

2018, 27(2):  146-155.  DOI: 10.11686/cyxb2017153

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To explore the negative effects of continuous cropping on the growth of Lanzhou lily (Lilium davidii var. unicolor), we conducted a pot experiment using soil containing fresh Lanzhou lily stubble and soil from fields where Lanzhou lily had been cultivated for 2 or 4 years. The growth indexes, photosynthetic characteristics, and antioxidant enzyme activity of Lanzhou lily plants were evaluated, and the types and contents of autotoxic substances in soil from fields continuously cropped with Lanzhou lily for 2 or 4 years was analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the growth of Lanzhou lily was inhibited by continuous cropping at the seedling stage, bulb enlargement stage, and maturity stage, and the inhibitory effect increased with increasing number of continuous cropping years. At the same growth stage, with increased number of continuous cropping years, the activity of catalase and superoxide dismutase decreased, the activity of peroxidase increased and then decreased, the malondialdehyde content increased, the total chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate decreased gradually, and the intercellular CO₂ concentration increased. We identified 9 compounds in soil containing stubble, and 15 and 17 compounds in soil where Lanzhou lily had been continuously cropped for 2 and 4 years, respectively. These compounds included 2, 3-butanediol, dioctyl isophthalate, 2, 2'-methylenebis-(4-methyl-6-tert-butylphenol), and dioctyl terephthalate. The highest contents of dioctyl terephthalate were in soil where Lanzhou lily was continuously cropped for 2 and 4 years (33.24% and 41.43%, respectively). Continuous cropping inhibited the growth of Lanzhou lily by affecting its photosynthetic capacity and disrupting the metabolic balance of antioxidant enzymes, ultimately leading to reduced performance under continuous cropping. The autotoxicity of several secondary metabolites that accumulated under continuous cropping was one of the main causes of the reduced performance of Lanzhou lily.

Interactions between additives and ensiling density on quality of Medicago sativa silage

WANG Mu-chuan, YANG Yu-xi, YU Yi-dong, YU Zhu

2018, 27(2):  156-162.  DOI: 10.11686/cyxb2017161

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Medicago sativa (alfalfa) was used to make silage, with and without addition of additives. Alfalfa plants were freshly harvested at the initial blooming stage, when their dry matter content was about 400 g·kg^-1 (fresh matter basis). The effects of additives and ensiling density on the quality of alfalfa silage were investigated in an experiment with eighteen treatment levels. The quality of silages was analyzed after 45 days of fermentation. The results showed that silage treated with S (sucrose), S+LP (sucrose+Lactobacillus. plantarum) and S+LC (sucrose+Lactobacillus. casei) had lower pH, butyric acid content, NDF neutral detergent fiber content, and acid detergent fiber content than silages without these additives. Treatments with CE (acremonium cellulose), LP+CE, and LC+CE did not significantly improve the quality of silage. Treatments with additives resulted in higher quality alfalfa silage than treatments without additives (P<0.05). Preparing silage with higher density did not significantly improve its quality but significantly increased its DM (dry matter) content and ammonia nitrogen/total nitrogen ratio (P<0.05). The additive×density interaction was not a significant factor for silage quality (P>0.05).

In vitro study on the effect of supplementing an alfalfa diet with straw or shells of fennel, sunflower, and cotton, and their associative effects

YUAN Jiu, WAN Xin-jie

2018, 27(2):  163-172.  DOI: 10.11686/cyxb2017121

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We investigated the effects of supplementing an alfalfa diet with fennel straw, fennel shells, sunflower straw, sunflower plates, cotton straw, and cotton shells, and their associative effects (AE), in an in vitro experiment. The concentrate∶straw/shell∶alfalfa ratios were 30∶70∶0, 30∶63∶7, 30∶56∶14, 30∶49∶21, 30∶42∶28, 30∶35∶35, 30∶28∶42, 30∶21∶49, 30∶14∶56, 30∶7∶63, 30∶0∶70 in diets with a concentrate∶roughage ratio of 30∶70. Gas production (GP) was recorded at 0, 2, 4, 6, 9, 12, 24, 36, 48, 72, and 96 h. The AE was defined as the difference between the observed in vitro GP and the predicted value from the individual feed fermented alone. In total, there were 74 groups that included straws or shells: (11×6)+8=74. The AEs of the groups with 14%, 7%, and 0% fennel straw were 58.74%, 54.18%, and 77.91%, respectively, significantly higher than the AEs of the groups with 70%, 63%, and 56% fennel straw (P<0.01). The AEs of all groups with fennel shell were positive. The AEs were also high for the groups containing 7%, 14%, 21%, and 28% sunflower straw, with the highest AE (124.84%) for the group containing 7% sunflower straw. The AE of all groups containing sunflower plates were positive, and the highest AE was in the group with 7% sunflower plates (143.84%). The AE of the groups containing 0%, 70%, and 7% cotton straw were 77.91%, 57.76%, and 54.56%, respectively. The highest AE among the groups containing cotton shells was 139.05% in the group containing 7% cotton shell. The AE of the groups containing 14%, 21%, and 0% cotton shells were 100.09%, 86.22%, and 77.91%, respectively. We conclude that addition of straw or shells at 7%, 14%, or 21% is an effective strategy to extend alfalfa.

Effects of mixing ratio and additives on ensilage efficiency of mixed chicory and silage maize

LIANG Xiao-yu, JI Yang, YI Jun, FU Mao-zhong, HU Yuan-bin

2018, 27(2):  173-181.  DOI: 10.11686/cyxb2017132

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We evaluated the effects of different mixing ratios and additives on the quality of silage made from mixtures of chicory and maize, to provide guidelines for producing high-quality silage. The ratios of maize and chicory by weight were 0∶1, 1∶3, 1∶1, 3∶1, and 1∶0 (0C1M, 1C3M, 1C1M, 3C1M, 1C0M). There were three additive treatments for each mixing ratio: no additive, 5 g·t^-1 lactic acid bacteria (LD) + 5 g·t^-1 cellulose (LX), and 10 g/t LD + 5 g·t^-1 cellulose (2LX). The nutrient composition and fermentation traits were measured after 60 days of ensilage to identify the optimal treatment. For sensory characters, the 0∶1 and 1∶1 mixing ratios of chicory and maize resulted in better silage quality scores than the other three mixing ratios, especially in the treatments with additives. Silage made from mixtures of chicory and maize showed improved nutritional quality and additives facilitated the fermentation process. The nutritional value increased significantly with an increasing proportion of chicory, while the fermentation quality decreased substantially if the proportion of chicory was greater than 1∶1. In summary, silage made from a 1∶1 mixture of chicory and maize had the best quality among all the mixing ratios tested. The silages treated with 1C1M/2LX had the best nutritional quality, with lower levels of neutral detergent fiber and acid detergent fiber, a low ratio of ammonia nitrogen to total nitrogen, and higher crude protein and lactic acid contents than those of the silages without additives.

Effects of adding oat hay to the diet on in vitro ruminal fermentation

ZHANG Bi-yang, ZHAO Gui-qin, JIAO Ting, CHAI Ji-kuan, GOU Zhi-qiang, XU Xing-ze, YAN Che-tai

2018, 27(2):  182-191.  DOI: 10.11686/cyxb2017377

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The aim of these experiments was to investigate the effects of including oat hay in the diet on in vitro ruminal fermentation. Ruminal fluid was collected from six cross breed sheep (Merino×Mongolian) with similar body condition and body weight (70.32±2.14 kg). The three diets had different ratios of oat hay and corn silage (dry matter basis), i.e., C₁ (concentrated feed+100% corn silage), C₂ (concentrated feed+50% oat hay+50% corn silage) and C₃ (concentrated feed+100% oat hay). In all the diets, the ratio of concentrate to roughage was 35:65. The results indicated that: 1) adding oat hay to the diet significantly increased gas production and methane production (P<0.05). Gas production was slightly higher in the C₂ group than in the other groups, while methane production in the C₂ group was lower than that in the C₃ group but higher than that in the C₁ group. 2) Adding oat hay to the diet did not affect pH, but it significantly increased the NH₃-N content (P<0.05). The NH₃-N content was slightly higher in the C₂ and C₃ groups than in the C₁ group. Adding oat hay to diets did not affect the proportion of propionic acid, but significantly increased the proportion of total volatile fatty acids, acetate acid, and butyric acid, and the acetate/propionate ratio (P<0.05). 3) Adding oat hay to the diet significantly increased the in vitro dry matter degradation rate and in vitro protein degradation rate, and promoted degradation of rumen nutrients. 4) The highest multiple-factors associative effects index was in the C₂ group, followed by the C₁ group. In conclusion, in a 35∶65 concentrate: roughage ratio diet, the C₂ diet (1∶1) could improve the rumen environment, and achieve the maximum combined effect.

Responses of ciliate community structure to degradation of the Gahai alpine wetland

LIU Han-cheng, PU Xiao-jian, LIU Jing, DU Wen-hua

2018, 27(2):  192-205.  DOI: 10.11686/cyxb2017126

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The structural features of ciliate communities can be used to evaluate environmental quality. The aim of this study was to explore the responses of ciliates to environmental change in alpine wetlands and to try to estimate the environmental quality of the Gahai alpine wetlands based on the structural characteristics of the ciliates communities. Species diversity, characteristics of the ciliates community, seasonal distribution of ciliates, and functional-trophic groups were studied and analyzed using the non-flooded Petri dish method, live observations, and a silver staining method from January 2015 to October 2015. In total, 162 species of ciliates were identified, including 30 unnamed species. These 162 species belonged to 66 genera, 46 families, 13 orders, and 3 classes. In this habitat, Kinetofragminophorea was the dominant class with 78 species, accounting for 48.15% of the total number of ciliate species. The next most dominant glass was Polyhymenophorea with 51 species. The number of ciliate species was significantly associated with the temperature and soil moisture content at each site (P<0.05), and more species were detected in summer and autumn than in spring and winter. Analyses of functional-trophic groups of ciliates showed that Bactivores-detritivores was the main group with 118 species, accounting for 72.84% of the total. Some members of this group consumed both algal and debris and others consumed only algal debris. Algivores were the next most dominant group with 51 species, accounting for 31.48% of the total. The main predators were raptors, and nonselective omnivores also fed on ciliates. The results showed that the diet of ciliates in the Gahai alpine wetland is a typical pyramid-type and the community structure of ciliates is stable.

Effect of precipitation patterns on litter decomposition in three annual herb species in the Horqin Sandy Land

LUO Yong-qing, YUE Xiang-fei, LI Yu-qiang, ZHAO Xue-yong, DING Jie-ping, YAN Zhi-qiang

2018, 27(2):  206-212.  DOI: 10.11686/cyxb2017141

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The effect of precipitation patterns on both aboveground and belowground litter decomposition in three annual herb species in the Horqin Sandy Land was investigated by the litter-bag method. Precipitation patterns, which were designed according to historical precipitation characteristics, included high-, medium-, and low-frequency precipitation, but the total amount was the same in each treatment. The results showed that precipitation patterns and depth of litter burial were the two main factors affecting the litter decomposition rate. The aboveground litter decomposition rate was significantly slower than the belowground litter decomposition rate. The belowground litter decomposition rate was faster at deeper depths than at shallower depths, especially for Setaria viridis. The decomposition rate of S. viridis litter belowground was significantly (P<0.01) faster at the 10-20 cm depth than at the 0-10 cm depth. The aboveground litter decomposition rate was significantly (P<0.01) slower under the low-frequency precipitation pattern than under the other precipitation patterns. There was a significant interaction between precipitation pattern and litter burial depth for litter decomposition. The influence of precipitation pattern on litter decomposition decreased with increasing depth. The litter decomposition rate differed among the three plant species. The belowground litter decomposition rate for both S. viridis and Artemisia sacrorum significantly differed among precipitation patterns at the 0-10 cm burial depth, while the aboveground litter decomposition rate differed significantly (F=48.42, P<0.001) among precipitation patterns only for Chenopodium acuminatum.