Table of Content

20 April 2018, Volume 27 Issue 4

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Effects of fairy ring formation on community vegetation structures and stability in alpine meadows

LI Jia-qi, ZHAO Min, WEI Bin, HU Ting-hua, YU Ying-wen

2018, 27(4):  1-9.  DOI: 10.11686/cyxb2017212

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Fairy rings is a common ecological phenomenon in alpine meadows on the Qinghai-Tibet Plateau and is an important site for vegetation regeneration. In order to explore the effects of fairy ring formation on vegetation change and community stability in the Plateau’s alpine meadows, we studied the vegetation characteristics of different ring zones, functional group biomass composition by economic category, the life form and succession climax component, the Raunkiaer frequency coefficient, succession degree and Spearman rank correlations within the plant community surrounding the fairy ring zone. The results indicated that: 1) fairy ring formation significantly changed species composition. The dominant species on the fairy ring were Elymus nutans and Aneurolepidium dasystachys but there were no clearly dominant species either within and outside the rings; 2) fairy ring formation significantly increased the biomass ratios of grasses, geophytes and decreaser on the fairy ring, but reduced its species diversity; 3) the community on the fairy ring was at a higher successional stage, and the importance value of plant species accorded with their economic category and succession climax component type’s biomass composition; 4) on the fairy ring, the positive to negative associations ratio of the main species-pairs was 0.89, the interspecific association of most species-pairs was not significant and the community was in a lower stable state; while within and outside the fairy rings the ratios were both >1, the association between most species-pairs was stronger and the community was more stable. The respective associated species-pairs occurred mainly between sub-dominant species or companion species and the companion species of fairy ring communities. This research shows that fairy ring formation can encourage alpine meadow succession from sedges/forbs communities to grass/forbs communities, but that they also reduce the stability of alpine meadows.

Monitoring of grassland herbage accumulation by remote sensing using MOD 09GA data in Xinjiang

XUN Qi-lei, DONG Yi-qiang, AN Sha-zhou, YAN Kai

2018, 27(4):  10-26.  DOI: 10.11686/cyxb2017232

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This study focuses on grassland in the Xinjiang Uygur Autonomous Region; in situ measurements of above ground biomass (AGB) and its spatial distribution were recorded during the growing seasons from 2010 to 2014. Regression models using AGB data and the corresponding daily surface reflectance obtained remotely from EOS Terra MODIS were established. Spatial analysis was used to calculate six vegetation indices (NDVI_max, MSAVI_max, PVI_max, NDVI_mean, MSAVI_mean and PVI_mean) using MOD 09GA data and the accuracy of the inversion models analyzed. The spatial distribution and spatial variation of the NDVI_mean, MSAVI_mean and PVI_mean values from 2010 to 2014 were also analyzed. Above-ground grassland biomass and its spatial distribution from 2005 to 2014 were estimated. It was found that NDVI_mean, MSAVI_mean and PVI_mean values gradually decreased from South to North and from West to East, and different grassland types have characteristic biomass differences. The biomass of azonal lowland meadow was highest and alpine desert type lowest among the grassland types included in the study. The trend of NDVI_mean, MSAVI_mean and PVI_mean value from 2010 to 2014 indicates that over 28% of regions in North Xinjiang could be categorized as showing ‘Improvement’, whereas in South Xinjiang these indicators were stable. The grassland of 14 prefectures in Xinjiang, representing 40% of the region, was also stable. The grassland of the Bortala Mongol Autonomous Prefecture, Kumul Prefecture, Tacheng Prefecture and Bayingolin Mongol Autonomous Prefecture showed improvement of over 15%. Over 10% of the grassland in Altary Prefecture, Bortala Mongol Autonomous Prefecture, Ili Kazakh Autonomous Prefecture, Karamay City, Changji Hui Autonomous Prefecture, Kizilsu Kirghiz Autonomous Prefecture, Aksu Prefecture and Urumqi City can be categorized as showing ‘Mild Improved’. The overall trend for grassland vegetation in Xinjiang is positive.

Effect of Salix cupularis plantations on soil stoichiometry and stocks in the alpine-cold desert of northwestern Sichuan

HE Jia, HU Yu-fu, SHU Xiang-yang, WANG Qin, JIA An-du, YAN Xing

2018, 27(4):  27-33.  DOI: 10.11686/cyxb2017414

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Based on their different plantation ages, 6, 18 and 24 yr old Salix cupularis plantations in the alpine-cold desert of Northwest Sichuan were selected to explore the nature of ecological stoichiometry changes in C, N and P under S. cupularis. The results showed that the ratio of C∶N∶P increased with plantation age in the 0-60 cm soil layer. Soil C∶N and C∶P increased with plantation age in the 20-40 cm and 40-60 cm soil layers, but the soil N∶P significantly decreased with plantation age (P<0.05). Soil organic carbon (SOC) stock increased with forest development in the 0-60 cm layers, but total N (TN) and total P (TP) stocks showed the opposite trend. SOC, TN and TP significantly increased in the 0-20 cm soil layer (P<0.05). A two-way ANOVA indicated that soil depth, plantation age and soil depth×plantation age significantly affected soil stoichiometric characteristics and stocks (P<0.01). The exceptions were soil TP contents, which did not significantly differ with plantation age, and soil C∶N and P stock, which did not significantly differ by soil depth×plantation age. The results show that imbalances in soil C∶N∶P occurred with plantation aging due to imbalances of C, N and P input.

Effects of different cultivation patterns on soil moisture, temperature, yield and quality of dryland maize

LI Shang-zhong, FAN Ting-lu, ZHAO Gang, DANG Yi, WANG Lei, ZHANG Jian-jun, TANG Xiao-ming, CHENG Wan-li

2018, 27(4):  34-44.  DOI: 10.11686/cyxb2017418

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The objective of this experiment was to study the effects of mulching time, mulching modes and mulching materials on soil moisture, soil temperature, crop yield and quality of dryland maize, in order to offer recommendations for cultivation of dryland maize of good quality and high-yield. A split-split plot field experiment was designed with the main plot treatment comprising two mulching times (autumn mulching and mulching before sowing), and the split-plot treatment comprising two mulching modes: furrow mulching and plane mulching. Three split-split-plot treatments compared two mulching materials: straw, and plastic film and no mulching. Measurements included determination of the soil moisture for 0-2 m soil depths before sowing and harvest, soil temperature of plough layer, grain yield, water use efficiency and quality of maize. It was found that mulching with either plastic film or straw improved water storage by 42.2 and 43.7 mm, respectively, in the 0-2 m soil layers before sowing in the winter and spring fallow period. Water storage did not differ significantly between plane mulching and furrow mulching. During maize growth periods, compared with no mulching, the average soil temperature under plastic film mulching was increased by 1.4 ℃, and under straw mulching was decreased by 2.9 ℃. The average soil temperature with plane mulching was 23.2 ℃, and in comparison, furrow mulching increased soil temperature by 1.8 ℃. The grain yield and water use efficiency under plastic film mulching were, respectively, 42.8% and 38.2% higher than in plots with straw mulching, and 47.3% and 36.0%, respectively, higher than plots with no mulching. Grain yield and water use efficiency were, respectively, 7.1% and 4.5% higher under autumn mulching than when mulching was carried out before sowing. Yield and water use efficiency of furrow mulching were respectively increased by 6.3% and 5.2%, but the furrow straw mulching and furrow no mulching treatments reduced yield. Compared to mulching before sowing, autumn mulching produced non-significant increasing trends in the harvest volume, weight, fat, protein, and starch contents of maize. Plastic film mulching, compared with no mulching, improved harvest volume, weight, and fat content, and decreased protein content, but had no significant effect on starch content. Straw mulching compared to no mulching increased maize grain fat but decreased grain volume, weight and protein content. Furrow mulching compared to plane mulching increased starch content, but decreased protein content, while the grain volume, weight and fat content did not change significantly. In summary, decisions on the seasonal timing of mulching, mulching mode and mulching material all influence regulation of soil moisture and soil temperature, grain yield and quality, and water use efficiency of dryland maize. The effects ranked in order of size mulching materials>mulching mode>seasonal timing of mulching.

Correlation between rhizobia distribution and the physical/chemical properties in soil of winter wheat intercropped with sweet clover

ZHAO Tao, MA Chun-hui, WANG Dong, JING Yong-yuan, XI Lin-qiao

2018, 27(4):  45-55.  DOI: 10.11686/cyxb2017219

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The correlation between rhizobia distribution and the physical/chemical properties in soil of winter wheat intercropped with sweet clover in the Aksu region of Xinjiang was determined. Rhizobia numbers were counted by dilution plate method. Soil physical and chemical properties including pH, soil bulk density, total salt, organic matter, total nitrogen, alkali-hydrolyzale nitrogen, available phosphorus and available potassium were also measured. The results showed that the number of rhizobia was highest at 10-20 cm soil depth compared with 0-10 cm and 20-40 cm from sowing to cutting of sweet clover. The number of rhizobia was highest at 0-20 cm depth (6.89 lg cfu·g^-1) in July and at 20-40 cm soil depth in August (6.46 lg cfu·g^-1). Soil pH and total salt decreased 0.23%-1.40% and 3.45%-37.69% between September and April, respectively. At 0-40 cm soil depth, organic matter, total nitrogen, available nitrogen and available phosphorus decreased from April to August. However, compared with September (sweet clover harvest) organic matter and total nitrogen in August was increased 7.65%-26.98% and 16.67%-44.12%, respectively. Alkali-hydrolyzable nitrogen at 0-20 cm was increased by 20.27%-160.68%, available phosphorus by 167.74% at 10-20 cm and available potassium by 10% at 0-20 cm soil depth. The correlation between total salt and the number of rhizobia at 0-40 cm soil depth was strong and negative (r=-0.81, P<0.05. The correlations between moisture content and rhizobia numbers at 0-20 cm soil depth were also strong and negative (-0.81≤r≤-0.73, P<0.05). There was also a strong negative correlation between total nitrogen content and rhizobia numbers at 20-40 cm soil depth(r=-0.88, P<0.05). Path coefficients for total salt, organic matter and total nitrogen were generally strongly correlated with rhizobia numbers, and organic matter was positively correlated (P₅=0.56) but total nitrogen and total salt negatively correlated (P₆=-0.50, P₄=-0.64). Organic matter had the greatest positive influence on rhizobia, whereas total nitrogen and total salt reduced rhizobia.

Inhibition activities and control efficiency of extracts from Ligularia virgaurea against 4 fungal diseases of greenhouse peppers

LI Jing, LI Na, DING Pin, YANG Hai-xing, LIU Jin-xia, WU Jian-rong, DU Wen-jing,ZHANG Jian-jun

2018, 27(4):  56-68.  DOI: 10.11686/cyxb2017204

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Because of frequent occurrence of, serious damage from, and difficulty controlling 4 fungal diseases of greenhouse-grown peppers and the desirability of identifying safe and efficient biological rather than chemical technologies for control of these fungal diseases, the effects of Ligularia virgaurea extracts against 4 the fungal pathogens were investigated. The mycelium growth rate, spore germination count, microdilution, seed germination and pot experiment methods of assessing biocontrol were all used. The extracts from L. virgaurea had significant inhibitory activity on Botrytis cinerea, Fusarium oxysporum, Fusarium solani and Phytophthora capsici, and the inhibitory activity was positively correlated with concentration. The EC₅₀ for mycelium inhibition was, respectively, 11.93, 51.25, 19.93, and 13.84 g·L^-1, while the corresponding EC₅₀ values for inhibition of spore germination rate were 15.05, 55.26, 57.86, 16.50 g·L^-1, the minimum inhibitory concentration was 0.83-1.75 g·L^-1, and the minimum bactericidal concentration was 2.50-11.67 g·L^-1. The extracts from L. virgaurea exhibited visually obvious control efficacy on B. cinerea, F. oxysporum, F. solani and P. capsici. The preventive effect of a 100-fold diluent of the initial L. virgaurea extract was 75% of that noted above, while the control effect was up to 70%, and was similar to the effect of commonly used chemical fungicides. However, to some extent, the extracts from L. virgaurea also inhibited pepper seed germination and establishment. The inhibition of seed germination was above 52% when concentration was higher than 20.00 g·L^-1, and the seedling height, root length, and biomass all showed significant reduction compared with the control (P<0.05). These results show that extracts from L. virgaurea provide broad-spectrum control against frequently-occurring fungal diseases of peppers. Prospects for development of a commercial product are good.

Effect of various crop residues on growth and disease resistance of Angelica sinensis seedlings in Min County

JIN Yan-bo, GUO Feng-xia, CHEN Yuan, BAI Gang, YUAN Hong-chao, LIANG Wei

2018, 27(4):  69-78.  DOI: 10.11686/cyxb2017329

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Traditional seedling nursery methods relying on uncultivated land for Angelica sinensis have caused serious soil erosion and debris flow. A study has been undertaken to explore the use of crop stubble land for the production of A. sinensis seedlings. Using the stubble fields of Triticum aestivum, Astragalus membranaceus, Solanum tuberosum and A. sinensis crops in Min county of Gansu province, seedlings were cultivated and their growth and resistance indicators measured. Index weights were calculated using principle component analysis and the membership function method was also used to explore the effect of crop stubbles on the seedling nursery. Results showed that the aboveground growth of seedlings varied significantly with different crop stubbles. Seedlings cultured in wheat and Astragalus residues showed the strongest growth indicators, with strong roots and growth power resulting in excellent individual plant quality with a low root incidence rate and disease index. Seedlings produced under potato and Angelica residues were highly affected by seasonal variations, resulting in high death rates and elongation of the growth period. The oldest and smallest seedlings occurred in the continuous cropping system and the potato residue, which had over 36.7% disease rates. According to the comprehensive index, the residues were ranked as Astragalus (0.7840)>wheat (0.7816)>Angelica (0.4731)>potato (0.1656). Seedlings produced in potato residue showed the highest death rate and seedlings in Angelica residue exhibited the highest incidence rate. These results suggest that the residues of wheat and Astragalus crops provide the most suitable soil resources for cultivating Angelica seedlings in Min county.

Construction of the AFLP linkage map and QTL analysis of powdery mildew resistance in red clover

PU Xiao-jian, TIAN Jiu-sheng, TIAN Xin-hui, DU Wen-hua

2018, 27(4):  79-88.  DOI: 10.11686/cyxb2017213

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In this study, F₁ generation red clover plants, obtained from crossing red clover varieties resistant (Gannong PR1, and Sensation and Renegade from Australia) or sensitive (Minshan) to powdery mildew, were artificially inoculated with powdery mildew and used as a quantitative trait locus (QTL) mapping population. AFLP markers were used to construct the genetic linkage map and the interval mapping method was used to locate the QTL for resistance to powdery mildew. This study will establish foundation to gene location and transgenosis of red clover. It was found that the linkage map based on 149 AFLP markers included 7 linkage groups (LG1, LG2, LG3, LG4, LG5, LG6 and LG7). The map covers a total distance of 640.5 cM. LG1 was found to be the largest (140.6 cM with the average distance between two markers being 9.4 cM), while LG4 was found to be the smallest yet with the highest marker density of any LG (55.2 cM in length with 1.8 cM on average between markers. Five QTLs (qrp-1, qrp-2, qrp-3, qrp-4 and qrp-5) related to powdery mildew resistance, and located on LG4 and LG5, were detected. The phenotypic variance explained by the 5 QTLs for powdery mildew resistance ranged from 29% to 90%, with the largest contribution being from qrp-1.Therefore, qrp-1 was identified as the main gene controlling powdery mildew resistance in red clover.

Expression of type 1 metallothionein gene from Medicago sativa and analysis of its function in stress tolerance

XU Chang, HE Hao, LI Guo-liang, JIN Shu-mei

2018, 27(4):  89-97.  DOI: 10.11686/cyxb2017230

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A gene sequence was obtained from Medicago sativa “Nongjing No. 1” cDNA via PCR amplification using specific primers designed from the cDNA sequence of Type 1 Metallothionein gene (MET1, GenBank accession number: AF189766.1) in M. sativa. This gene is assigned as MsMT1. The total length of this gene fragment is 228 bp and it encodes 75 amino acids. The nucleotide sequence of MsMT1 has 99% homology with MET1. Multiple sequence alignment and the phylogenetic tree showed a high similarity between the MsMT1 and the MT1 in other plants. MsMT1 gene expression was analyzed in different organs of M. sativa by qRT-PCR, with higher quantities found in roots and cotyledons. MsMT1 gene expression was examined in M. sativa seedlings under different concentrations of salt solution and pH values. The results revealed that the expression quantity of MsMT1 gene changed with the saline or alkaline solution concentration, indicating that MsMT1 is associated with stress tolerance. The MsMT1 gene was transformed into M. sativa plant through Agrobacterium tumefaciens-mediated method. The positive transformation was further confirmed by the kanamycin resistance test and the Northern blot test confirmed that MsMT1 was successfully expressed in the transgenic M. sativa. Wild type and transgenic M. sativa seedlings were treated with different concentrations of NaCl or NaHCO₃ which revealed that the transgenic plants had higher stress tolerance than wild type plants. The results of this study highlight the MsMT1 gene can increase plants tolerance to stress.

Cloning and function analysis of RtSOD gene in the rare recretohalophyte Reaumuria trigyna

SUO Ya-fei, DU Chao, LI Ning-ning, WANG Yan, WANG Ying-chun

2018, 27(4):  98-110.  DOI: 10.11686/cyxb2017227

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Reaumuria trigyna, a highly xerophytic halophyte, shows strong adaption to the high saline and hyper-drought environments. Superoxide dismutase (SOD) plays an important role in withstanding these abiotic stressors. In this study, primers were designed using the known sequence of a SOD gene in the transcription database of R. trigyna. The open reading frame of the SOD gene with a size of 663 bp and encoding 220 amino acids was cloned by PCR and identified as RtSOD. The molecular weight of the protein was predicted to be 55.90 kDa and the theoretical isoelectric point was pH 5.11. The results of multiple sequence alignment analysis showed that the protein belongs to the Cu/Zn SOD family and had high homology with the SOD protein of other plants. Real-time fluorescence quantitative PCR analysis showed that NaCl, 4 ℃ temperature, polyethylene glycol, H₂O₂ and abscisic acid could induce the expression of the gene. Construction and transfer into Arabidopsis thaliana of a eukaryotic expression vector enhanced the growth rate of A. thaliana, compared to that of the wild type. In addition, antioxidant enzyme activities (SOD, peroxidase, catalase) and the content of proline were significantly higher than in wild type A. thaliana, and the contents of H₂O₂ and malondialdehyde were significantly lower than those of wild type A. thaliana under salt and drought stress. qRT-PCR analysis indicated that the expressions of stress-related genes in transgenic Arabidopsis were significantly higher than those of the wild type. The above results indicate that overexpression of RtSOD could increase the stress tolerance of transgenic plants, and further demonstrated that the RtSOD gene is involved in the response to the abiotic stress of R. trigyna and is an important component in the plant antioxidant system.

DNA fingerprinting of Ixeris polycephala varieties based on EST-SSR and SRAP markers

BAN Qian, XIE Cai-yun, FAN Guo-hua, HUANG Lin-kai, ZHANG Xin-quan

2018, 27(4):  111-122.  DOI: 10.11686/cyxb2017072

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Ixeris polycephala is a member of the Asteraceae family with an annual growth habit and excellent forage quality. In order to construct DNA fingerprinting of 14 I. polycephala varieties, 24 EST-SSR primers and 32 SRAP primers were screened for clear bands and high polymorphic imformation. A total of 270 bands including 223 polymorphic bands were amplified from the 24 EST-SSR primers, and the polymorphism information content values were up to 0.834. The Nei’s gene diversity (H) values ranged from 0.2464 to 0.4288, and values for Shannon’s information index (I) ranged from 0.3597 to 0.6148, while the number of distinguished varieties ranged from 3 to 14. For the 32 SRAP primers, 367 polymorphic bands were detected, and the average polymorphism information content was 0.826. The Nei’s gene diversity (H) values ranged from 0.2006 to 0.3898, and values for Shannon’s information index (I) ranged from 0.3167 to 0.5716, while the number of distinguished varieties ranged from 2 to 12. Nine varieties produced unique bands from 7 primers. With more detailed consideration of each genetic diversity index, a total of 40 polymorphic bands were obtained from 5 core primers (IpSSR102, IpSSR80, IpSSR91, Me10+Em5, Me9+Em17), and for DNA fingerprinting of the 14 I. polycephala varieties each variety had a specific molecular or DNA fingerprint.

Variation of C, N and P stoichiometry in dominant understory plants during stand development in Salix cupularis plantations in alpine grassland in Northwestern Sichuan, China

SHE Shu-feng, HU Yu-fu, SHU Xiang-yang, YAN Xing, LI Zhi, WANG Qin, HE Jia, JIA An-du

2018, 27(4):  123-130.  DOI: 10.11686/cyxb2017220

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In order to understand the stoichiometric relationships of C, N and P in tissues of understory plants of Salix cupularis at different stand ages, we collected three species of dominant understory plants (Artemisia wellbyi, Heracleum millefolium and Oxytropis falcata) from under 6, 18 and 24 year old S. cupularis stands in Northwestern Sichuan, China. Then the carbon (C), nitrogen (N) and phosphorus (P) concentrations, as well as their ratios in plant organs (leaf and root) were analyzed. The C concentration of the understory plants and the N concentrations of their roots decreased with increase in plantation age, while conversely, the N concentration of leaves increased with plantation age. No significant variation in P concentration was found. The C∶N ranged from 1.92 to 12.86 and the C∶P ranged from 29.18 to 196.88. There were significant differences in N∶P of the understory plants at different plantation ages, but the results suggested that understory plants were mainly limited by P nutrient status. The finding that growth of plantations in this region is mainly limited by P nutrient supply indicates that attention to the adequate addition of P nutrients is needed.

Effects of lead stress on growth and physiology of Pogonatherum crinitum

HAN Hang, CHEN Shun-yu, XUE Ling-yun, HOU Xiao-long, CAI Li-ping, LIU Ai-qin, ZHOU Chui-fan

2018, 27(4):  131-138.  DOI: 10.11686/cyxb2017357

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In order to understand the response mechanisms of Pogonatherum crinitum growing in contaminated mining areas, a pot culture experiment was carried out to study the physiological indexes of P. crinitum under varying Pb stress concentrations. Low Pb concentration (1000 mg·kg^-1) had promotional effects on POD activity, soluble protein content in leaves and ASAFR activity, and on soluble sugar content and proline content in roots, allowing P. crinitum plants to maintain their overall antioxidant capacity at a high level and promoting plant height, leaf length and biomass. Increasing Pb concentrations (2000, 3000 mg·kg^-1) inhibited shoot height, leaf length, leaf area and biomass, but increased the MDA content of plants. P. crinitum’s adaptability to high Pb concentration treatments was evident as increasing POD and CAT activities in leaves and roots to enhance antioxidant activity, as increasing soluble protein and soluble sugar content to maintain the normal operation of cells, and as the promotion of root development and root∶shoot to keep T-AOC at a high level. These findings indicate that P. crinitum can adapt to Pb stress by adjusting its antioxidant system and enhancing its osmotic adjustment substance contents, suggesting that the plant has application potential for the remediation of Pb polluted soil.

Effects of soil adhesive on seed germination and seedling growth of Paspalum wettsteinii under different temperatures

WANG Yu-zhen, HUANG Xiao, CAI Li-ping, ZHENG Hui-xin, HOU Xiao-long, ZHOU Chui-fan, ZOU Xian-hua

2018, 27(4):  139-149.  DOI: 10.11686/cyxb2017393

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In order to explore the optimum conditions for seed germination and seedling growth beneficial to vegetation restoration in areas suffering from soil erosion, this study investigated the effects of temperature and soil adhesive on seed germination and seedling growth of Paspalum wettsteinii. An experiment was carried out using the topsoil from an eroding area in Changting County as substrate with 4 different temperatures (15, 20, 25 and 30 ℃) controlled by an artificial climate incubator and 4 different soil conditions created by different soil adhesive-PAM concentrations (0, 0.5, 1.0 and 2.0 g·L^-1) which were added to the soil. The results showed that the initial seed germination time of P. wettsteinii was advanced from the 10th day to the 3rd day and the terminal seed germination time was advanced from the 26th day to the 9th day after seeding as temperature increased from 15 to 30 ℃. The seed germination rate and germination energy of P. wettsteinii under 20 and 25 ℃ were higher than other temperatures. The germination index, vigor index, seedling growth, and biomass at 20, 25, 30 ℃ were significantly higher than that at 15 ℃. The addition of soil adhesive increased the seed germination and prolonged germination and growth of P. wettsteinii. The seed germination rate, germination energy, germination index and vigor index were increased by adding low concentrations of adhesive (0.5 or 1.0 g·L^-1) to soil, seed germination was restrained by high soil adhesive concentration (2.0 g·L^-1). The results of this research provide a useful scientific reference and technical insight for vegetation restoration using P. wettsteinii.

Variations in seed mass, shape and adaptation characteristics in Seriphidium desert

JIN Gui-li, LU Wei-hua, WANG Shu-lin, CHEN Yi-shi, WANG Chuan-jian, MA Chun-hui

2018, 27(4):  150-161.  DOI: 10.11686/cyxb2017358

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Seriphidium desert grassland is widely distributed across the northern Xinjiang region and is known for its abundant plant diversity. We collected the seeds of 88 plant species from this grassland and measured seed mass, shape index and life form. We also analyzed the phylogenetic signal of seed mass and the shape index using phylogenetic comparative methods, in order to identify seed adaptation types for desert and semi-desert environments. Results showed that the seed mass of plants can be divided into four classes: A (0.01-0.10 mg), B (0.10-1.00 mg), C (1.00-10.00 mg) and D (10.00-50.00 mg), with classes B and C being dominant in quantity. The plant species divided into six life forms, of which the dominant are annual, perennial and ephemeral herbaceous. The shape index of seeds was determined by the variance of three dimensions (length, width and height), with the index scores ranging between 0.00 and 0.20. The shape of 42 species was close to sphericity while the remaining 46 species were flat or enlongated. There were significant differences in seed size and shape between families and between species of the same family, as well as seed heteromorphism within the same species. We found that seed mass had no significant phylogenetic signal and showed stability. However, seed shape had a significant phylogenetic signal and showed instability. Most seeds evidenced very strong adaptability to the extreme environment through seed heteromorphism, mucilaginous diaspore, appendages for seed dispersal, specialized life forms and endozoochorous dispersal by animals.

Effects of lactic acid bacteria preparation and bran on corn stover silage quality

WANG Jian-fu, LEI Zhao-min, CHENG Shu-ru, JIAO Ting, LI Jie, WU Jian-ping

2018, 27(4):  162-169.  DOI: 10.11686/cyxb2017229

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To elucidate the effect of lactic acid bacteria and bran on the quality of corn stover silage at two treatment times (harvest and harvest+3 days), the effect of three inoculants (Sila-Max, Sila-Mix and bran) on the nutritive value and fermentation parameters of ensiled corn stover was studied using 20 L self-made mini-silos for 45 d under ambient environmental conditions. The results demonstrated that all treatments made good quality corn silage in the mini-silos. In the uninoculated group, delaying ensiling time by 3 d significantly (P<0.05) increased the acetic acid, ammonia nitrogen, crude protein, acid detergent fiber, lignin, calcium and dry matter loss by 22.05%, 50.00%, 10.34%, 5.19%, 10.92%, 20.51% and 48.37%, respectively, while decreasing dry matter content by 7.37%. For the harvest time treatment, Sila-Max+bran significantly (P<0.05) increased lactic acid, ether extract and crude protein by 22.98%, 12.46% and 5.57%, respectively, while decreasing dry matter loss by 39.27%; Sila-Max significantly (P<0.05) increased dry matter by 6.41%, decreased dry matter loss by 45.80%, and bran decreased crude protein by 9.17%. For the 3 d delayed ensiling, Sila-Max significantly (P<0.05) increased the acetic acid and lignin by 10.94% and 9.14%, respectively, decreased ether extract by 11.29%, while bran increased acetic acid by 10.94% and decreased ether extract by 11.29%. Sila-Max+bran significantly (P<0.05) increased acetic acid, lignin and dry matter by 9.67%, 12.13% and 6.23%, respectively, while decreasing ether extract and dry matter loss by 15.81% and 26.73%. All treatments were similar (P>0.05) for 48 h in vitro dry matter digestibility. In conclusion, delayed ensiling decreased dry matter and fermentation quality, enhance aerobic fermentation, increase dry matter loss. Sila-Max+bran enhanced corn silage fermentation quality and decrease nutrient loss when ensiled immediately but had no effect on fermentation quality when ensiling was delayed by 3 d.

Effects of complex enzyme on rumen fermentation and milk production in early lactation dairy cows

CHEN Ya-kun, WANG Jian-ping, BU Deng-pan, LIU Ning, LIU Wei

2018, 27(4):  170-177.  DOI: 10.11686/cyxb2017222

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Two experiments were conducted to evaluate the effects of different levels of complex enzyme on rumen fermentation and milk production in early lactation dairy cows. The first experiment evaluated rumen fermentation in vitro with total mixed ration (TMR) as substrate. There were four treatments, with complex enzyme supplementation at concentrations of 0, 0.10%, 0.15% and 0.20%. Each treatment had 9 replicates and each replicate consisted of 0.500 g accurately weighed substrate. The degradation rate of nutrients in the substrate and in vitro fermentation parameters were determined with an in vitro fermentation gas automatic recording device within 48 h. Results showed that the complex enzyme significantly increased total volatile fatty acids and acetic acid in fermentation fluids (P<0.05). The degradation rates of neutral detergent fiber (P<0.05) and crude protein (P<0.01) in the supplemented treatments were significantly higher than in the control. The second experiment was conducted using a randomized complete block design with thirty-six Holstein dairy cows of similar body weight, parity, days in milk and milk yield. Complex enzyme was supplied to four treatments at concentrations of 0, 0.10%, 0.15% and 0.20% respectively. Each treatment had 9 replicates and the experiment lasted for 8 weeks. Milk yield, milk composition content and 3.5% fat-corrected milk were measured. The results showed that complex enzyme significantly increased 3.5% fat-corrected milk (P<0.05). For the 3.5% fat-corrected milk, the 0.10%, 0.15% and 0.20% treatments were 3.88, 4.27 and 2.26 kg·d^-1 more than the control respectively. The milk fat rate in the 0.15% treatment was significantly higher than the control (P<0.05), with a 12.7% increase. In conclusion, adding complex enzyme can affect rumen fermentation and production performance. The results suggest that the optimal compound enzyme level in TMR is 0.15%.

Research progress in nitrogen and phosphorus resorption from senesced leaves and the influence of ontogenetic and environmental factors

LU Jiao-yun, DUAN Bing-hong, YANG Mei, YANG Han, YANG Hui-min

2018, 27(4):  178-188.  DOI: 10.11686/cyxb2017223

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Nutrient resorption of a plant is a fundamental process in which the nutrients, i.e. nitrogen and phosphorus, in older tissues or organs are partly retranslocated into other vital parts before the tissues or organs senesce and fall. This process can retain nutrients within the plant that would otherwise be lost and enhance the nutrient use, thus reducing the dependence of a plant on soil nutrient availability. Resorption is an important strategy for adaption to adverse environments and for promotion of competitive ability. This review summarizes findings on the effects of environmental factors (i.e. soil fertility and water) and ontogenetic influences (i.e. growth stage and leaf lifespan) on nitrogen (N) and phosphorus (P) resorption from senesced leaves. Nutrient resorption varies among plant life forms or functional groups (e.g. N₂-fixing and non-N₂-fixing). Fertilizer application and irrigation can change nutrient availability in soils, influencing nutrient resorption. Plants sense and absorb nutrients differently at different growth stages, leading to ontogenetic changes in patterns of nutrient resorption. Resorption is not confined to leaves and may occur in other plant organs. In summary, nutrient resorption is influenced by multiple factors including ontogenetic and environmental signals. Improved knowledge about nutrient resorption may help understanding of how plants adapt to adverse environments and provide theoretical knowledge to support the development of more sustainable agricultural production practices.

Effect of salt stress on proline accumulation and the activities of the key enzymes involved in proline metabolism in Medicago ruthenica seedlings

ZHONG Hua, DONG Jie, DONG Kuan-hu

2018, 27(4):  189-194.  DOI: 10.11686/cyxb2017464

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In order to study the effects of salt stress on proline accumulation and the activities of the key enzymes involved in proline metabolism a pot experiment was conducted using wild Medicago ruthenica stressed under different NaCl and Na₂CO₃ solutions; 0, 50, 100, 200, 300, 400 and 500 mmol·L^-1. The result showed that, under salt stress, proline content and P5CS and δ-OAT activity gradually increased while ProDH activity declined with increasing salt concentration. The initial accumulation of proline was a major reason for the reduced damage from NaCl and Na₂CO₃ stress in M. ruthenica seedlings. The Glu and Orn pathways were synergistic to the accumulation of proline, with the Orn pathway playing a leading role. This study suggests that the concentration of NaCl and Na₂CO₃ should not exceed 400 mmol·L^-1 for M. ruthenica.

The effects of ryegrass and biochar on soil nutrient distribution in Karst area

SONG Dan-dan, HE Bing-hui, LUO Song-ping, WU Yao-peng

2018, 27(4):  195-201.  DOI: 10.11686/cyxb2017239

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This study explored the effects of biochar addition and ryegrass growth on the nutrient distribution in yellow soil in Karst area, of Bozhou County, Guizhou Province, China. The experiment was conducted over a period of 45 days with twelve treatments, including a bare land control (CK), only planting of ryegrass (R), only addition of biochar at various rates (BLB₁, BLB₃, BLB₅, BLB₇, BLB₉; subscripts indicate % biochar added to soil weight∶weight), and ryegrass planting together with addition of biochar at various rates (RB₁, RB₃, RB₅, RB₇, RB₉). The soil organic matter (SOM), pH, total phosphorus (TP), available phosphorus (AP), total potassium (TK) and available potassium (AK) were tested after 45 days. The results indicated that the treatments BLB and RB were the most effective way to increase the content of all nutrients. The rate of biochar addition was significantly positively correlated with the content of all nutrients (P<0.01), and the smallest correlation coefficient was 0.78. The R treatment was the treatment in which the content of SOM, TP, TK and AP were decreased, as the nutrient consumption of ryegrass was higher than the nutrient return to the soil. Compared with BLB treatments, RB treatments decreased the nutrient except the 7% treatment. However, considering the optimum pH value for ryegrass growth and the soil erosion situation in Karst area, the treatment RB₇ can be recommended because it both improved the soil nutrient status and texture in this yellow soil. This study provided scientific data comparing options for ameliorating the nutrient limitations of nutrients in Karst region yellow soil.

Effect of ascorbic acid priming on the vigor of oat seeds under NaCl stress

DONG Qiu-li, XIA Fang-shan, LI Xiao-yu, WANG Ming-ya, MAO Pei-sheng, ZHU Hui-sen,TONG Li-rong, DU Li-xia

2018, 27(4):  202-208.  DOI: 10.11686/cyxb2017324

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An experiment was undertaken to study the effects of ascorbic acid (AsA) priming on oat seed germination and seedling growth under salt stress conditions. Oat seeds were primed with different AsA concentrations (0, 0.5, 1.0, 1.5 and 2.0 mmol·L^-1) and then germinated in different concentrations of NaCl stress (0, 50, 100 and 200 mmol·L^-1). Changes in germination percentage (G_p), germination index (G_i) and mean germination time (MGT) were analyzed. Results showed that the G_p, G_i and MGT of oat seeds declined significantly under NaCl stress. With increasing AsA concentrations, G_p at first increased and then decreased under NaCl stress at 100 and 200 mmol·L^-1. However, the seeds’ G_i declined with increasing AsA concentrations, while their MGT increased. The effects of different concentrations of AsA and NaCl and their interaction on G_p, G_i and MGT were highly significant (P<0.01). The level of oat seed vigor was decreased by NaCl stress. However, priming with exogenous AsA promoted the vigor of salt-stressed seeds and this effect was closely related to the concentrations of AsA and NaCl. Optimal effects were reached at AsA concentrations of 1.0 mmol·L^-1 under NaCl stress at 100 and 200 mmol·L^-1. However, the germination time of oat seeds was prolonged by AsA priming under NaCl stress.