Table of Content

20 February 2016, Volume 25 Issue 2

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Orginal Article

Analysis of vegetation and soil characteristics alongside trails in Yak Meadow Park, Jade Dragon Mountain

SHENG Zhi-Lu, HUANG Xiao-Xia, CAI Xing-Yuan, HE Ke-Jian, ZHANG Li-Li

2016, 25(2):  1-9.  DOI: 10.11686/cyxb2015120

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Trails used in tourism are essential for sustainable recreation practices, but they also have impacts on trailside vegetation and soil. There is limited recreation ecology research on the impact of trails in China, and especially on Jade Dragon Mountain, a globally recognized biodiversity site with high scenic value. To quantify the changing pattern of vegetation and soil alongside trails and their variation between different trail types, field investigations have been carried out in the subalpine meadows of Jade Dragon Mountain. Analysis of variance (ANOVA), non-metric multidimensional scaling (NMDS) and regression analysis have been applied to the data collected. The results showed that: 1) With increasing distance to the edge of trail (DIST), vegetation cover, height, species richness, soil organic matter (SOM), total nitrogen (TN) and soil moisture content tended to increase, while soil pH decreased. 2) With increased DIST, the percentage of herbs decreased and grass increased. 3) Vegetation cover, height, SOM, TN and soil moisture content alongside formal trails (created with wooden building materials) were generally higher than those alongside informal trails (unpaved paths), while soil pH alongside formal trails was lower than informal trails. The difference in vegetation characteristics between the two types of trail was obvious to the range of 7 m DIST. 4) The vegetation aggregative index (VAI) within a range of 3 m to the trails was significantly different compared to background sites (P<0.05). The changing pattern of VAI and the soil aggregative index (SAI) indicated that soil changes lag behind vegetation changes. 5) The study indicates that a 7 m range to the edge of formal trails and 12 m to the edge of informal trails are the key spatial areas requiring management for ecological restoration.

Ecological footprint of water resources in the Shiyang River Basin from 2001-2011

JIA Yan, ZHANG Jun, ZHANG Ren-Zhi

2016, 25(2):  10-17.  DOI: 10.11686/cyxb2015125

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Water is an important resource for all human beings and for the sustainable development of ecosystems. The Shiyang River Basin is one of the continental drainage basins in Northwest China where the level of water utilization is very high, and the shortage of water resources is therefore serious. Furthermore, the environment is fragile, and the social and economic development is restricted. This paper studies the water consumption by the human population and the impact on the natural ecological environment. Quantitative indicators of the influence are developed to statistically define data of water resources in the Shiyang River Basin. We introduce a concept of regional water resource carrying capacity. The ecological footprint method is used to build a model of the ecological carrying capacity of water resources for the Shiyang River Basin, and calculate the ecological water resource carrying capacity of the Basin. The average water resource carrying capacity was 1955.5 ha, and the ecological footprint is 43531.04 ha. Therefore the average ecological deficit for 2001-2011 in the Shiyang River Basin was 41575.55 ha. Future water resource management should include appropriate immigration policy, adjustment of industrial activity; planting area should not increase, and public education to enhance awareness of water conservation issues should be implemented.

The effect of nitrogen and phosphorus applications on soil enzyme activities in Qinghai-Tibetan alpine meadows

SUN Ya-Nan, LI Qian, LI Yi-Kang, LIN Li, DU Yan-Gong, CAO Guang-Min

2016, 25(2):  18-26.  DOI: 10.11686/cyxb2015188

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This study investigates the effect of nitrogen and phosphorus applications on soil nutrient cycles, focusing on soil enzyme activities in particular. Enzyme activities and available nutrients have been measured in plots of Qinghai-Tibetan alpine meadow with 4 years of N and P fertilizer application. The study focuses on six soil enzyme activities that represent several significant nutrient cycles (C, N, P, S). The results showed that the contents of available phosphorus and alkaline nitrogen increased under the different treatments. The activities of alkaline phosphatase, urease, chitinase and cellulase vary significantly under the different treatments, while there is no significant difference in the activities of arylsulfatase and sucrase. In soils at a depth of 0-10 cm, nitrogen applications have a positive effect and phosphorus applications a negative effect on alkaline phosphatase activity. Urease activity is repressed in 0-10 cm soils under both nitrogen and phosphorus treatments. In soils at a depth of 10-20 cm, chitinase activity is significantly promoted by nitrogen and phosphorus applications, and especially by phosphorus. Cellulase activity at both soil depths is repressed by nitrogen treatment. The results indicate that nitrogen supply effects the mineralization of P and that phosphorus supply can promote the decrease of N. The relative degree of phosphorus limitation may be higher than nitrogen limitation in Qinghai-Tibetan alpine meadows.

The effect of compound bio-fertilizers on soil physical and chemical properties and soil enzyme activity in Leymus chinensis steppe

QUAN Guo-Ling, XIE Kai-Yun, TONG Zong-Yong, LI Xiang-Lin, WAN Li-Qiang, BI Shu-Yi, WAN Xiu-Fu

2016, 25(2):  27-36.  DOI: 10.11686/cyxb2015422

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Compound bio-fertilizers have recently been developed to improve the performance of bio-fertilizers. These compounds are a mix of inorganic chemical, organic and bio-fertilizers. In this study, we investigated the effect on Leymus chinensis steppe soil fertility of three kinds of compound bio-fertilizer: humic acid, molasses fermentation and alginic acid. We also measured the effects of a mixed application of these three compounds. Results showed that compared to the control there was a significant reduction in total phosphorus in surface soils under the molasses fermentation and three compound mix treatments. Soil organic matter increased significantly, with these increases being higher for the three compound mix than for the humic acid and molasses fermentation treatments. The other soil physical and chemical properties measured showed no significant change under each treatment. Soil enzyme activities were significantly affected. Compared with the control, hydrogen peroxide enzyme activity in the 0-10 cm soil layer was significantly reduced in all treatments except for the humic acid compound. Phosphatase activity increased significantly in all cases except for the alginic acid treatment. Urease activity was reduced significantly in the humic acid and molasses fermentation treatments. Invertase activity did not change significantly. In 10-20 cm soil layer, hydrogen peroxide enzyme activity increased significantly in the humic acid treatment while it significantly reduced under the other treatments. Invertase activity did not change with the three compound mix but reduced significantly under the remaining three treatments. Urease activity decreased only with humic acid treatment, while phosphatase activity did not significantly change in any of the treatments. Hydrogen peroxide enzyme activity and soil pH were significantly positively correlated, while urease and total nitrogen were significantly negatively correlated. Phosphatase and total phosphorus had a significant negative correlation in topsoil. Invertase activity was significantly positively correlated with organic matter, and was significantly negatively correlated with soil moisture content in the lower soils. In general, soil enzyme activity decreased with increasing depth of soil profile.

Agronomic traits of 15 annual Ixeris polycephala varieties in the southwest of Sichuan Province

BAN Qian, HUANG Lin-Kai, ZHANG Xin-Quan, JIANG Lin-Feng

2016, 25(2):  37-46.  DOI: 10.11686/cyxb2015146

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Agronomic traits of 15 Ixeris polycephala varieties were studied in field trials in Ya’an, in the southwest of Sichuan Province. The growth periods of new lines Chuanxuan No.1 and L5-4 were longer than Longmu (P<0.01). In the two years 2013 and 2014, the yields of new line Chuanxuan No.1 were the highest, with a notable yield advantage at the second defoliation and regeneration. The average hay yield of the new line Chuanxuan No.1 was 5585 kg/ha, a 64.75% (P<0.01) increase, compared with Longmu. With respect to stem∶leaf ratio, the highest leaf content was found in the new line L5-4, and the second ranked was new line Chuanxuan No.1; the stem∶leaf ratios were 0.52 and 0.55, respectively. In terms of nutrients, the new line Chuanxuan No.1 had abundant minerals and high nutritional value, the crude protein was 26.12%, while crude fiber was 12.11%. Thus, the new lines Chuanxuan No.1 and L5-4 with high yields and leaves of high feeding value were suitable for recommendation for planting in the southwest of Sichuan Province.

Effect of different mulching materials and methods on soil moisture and temperature and grain yield of dryland spring wheat in northwestern China

CHENG Hong-Bo, NIU Jian-Biao, CHAI Shou-Xi, CHANG Lei, YANG Chang-Gang

2016, 25(2):  47-57.  DOI: 10.11686/cyxb2015395

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This study determined effects of different mulching materials and methods on soil water, soil temperature, grain yield (GY) and important agronomic parameters of spring wheat in a semi-arid rain fed area of northwestern China. A total of 8 mulching treatments were tested in this study. These included straw mulching, plastic film mulching such as flatten culture and whole mulching, micro-ridge and whole mulching, large ridge and half mulching, compared with a non-covered treatment as control (CK). There were significant differences in soil moisture, soil temperature and GY among the various treatments. Compared to the CK, mulching significantly increased GY by 7.7% to 44.9%, with the maximum yield increase occurring in micro-ridge and whole mulched plastic film treatments. The spikes per unit area (SPUA) were the main factor responsible for difference in GY. There was a highly positive correlation (r=0.788^*) between SPUA and GY. Compared to the CK, mulching increased the average soil moisture in the 0-200 cm soil layer during the entire growth period by 0.3%-1.7%, and the highest soil moisture levels were those of micro-ridge and whole mulched white film (C₁) and large ridge and half mulched black film (D₂). Both mulching with wheat straw (A₁) and large ridge and half mulched black film (D₂) decreased average soil temperature in the 0-25 cm soil layer during entire growth period by 1.4 and 0.9℃, while soil temperatures of the other 6 mulching treatments were increased by 0.3-1.8℃. The maximum warming occurred in flatten culture and whole mulched white film (B₁) treatments. However, more detailed analysis of spatio-temporal differences in soil temperature and soil moisture revealed that the various treatment effects were most strongly seen in different soil layers or in different growth periods. Soil moisture data were recorded at 48 time points in each treatment. Each mulching treatment had 26-40 points with soil moisture higher than the CK, and 8-22 points lower than the CK. During the entire growth period, mulching predominantly increased soil moisture at the flower-filling stage, and decreased soil moisture in the booting stage. Mulching-induced soil moisture increases were most evident in the 20-40 cm soil layer, and mulching tended to decrease moisture in the 60-90 cm soil layer. Soil temperatures were measured and recorded at 25 time points in each treatment, and each of the mulching treatments varied in numbers of points higher (range 0 to 24 points) or lower (range 1 to 25 points) than CK plots. The maximum warming was observed in the 25 cm soil layer.

Soil carbon fraction differences under different grass-crop rotations on the Loess Plateau, Central Gansu

ZHAO Jing-Jing, LUO Zhu-Zhu, ZHANG Ren-Zhi, CAI Li-Qun, LI Ling-Ling, NIU Yi-Ning

2016, 25(2):  58-67.  DOI: 10.11686/cyxb2015292

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Field experiments investigating the effect of continuous lucerne (Medicago sativa) (L-L) and five rotation systems [lucerne-fallow (L-F), lucerne-wheat (L-W), lucerne-corn (L-C), lucerne-potato (L-P), lucerne-millet (L-M)] on total organic carbon (TOC), readily oxidation organic carbon (ROC), light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC) in a typical arid area of the Western Loess Plateau. The results showed that under different rotation systems TOC and soil organic carbon fractions decreased with increasing soil depth (0-200 cm soil depth). The highest TOC, ROC and HFOC values were found in the surface soil layer (0-5 cm) under the L-L rotation system, and the lowest values at mid depths (30-50 cm) under the L-W rotation system. The highest and lowest values for LFOC were found in the surface soil layer (0-5 cm) under the L-P rotation and the bottom soil layer (170-200 cm) under the L-C rotation, respectively. Compared with L-L rotation, the L-W, L-C, L-P and L-M rotations reduced TOC by 17.4%, 9.3%, 18.4% and 9.3%, respectively. Similarly, ROC was reduced by 28.1%, 8.5%, 28.1% and 23.2% and HFOC by 18.8%, 10.1%, 20.5% and 12.5% respectively. However, LFOC increased by 7.4%, 5.3%, 22.2% and 57.4% under L-W, L-C, L-P and L-M rotations, respectively. It was concluded that lucerne-grain rotation systems reduce TOC.

Effects of fertilizer and Rhizobium inoculation on alfalfa growth on mine tailings and the physicochemical properties of iron tailings

YANG He-Bao, LI Ji-Quan, WANG Jun-Juan, LI Yu-Ling

2016, 25(2):  68-76.  DOI: 10.11686/cyxb2015121

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This study was undertaken to determine the effects of fertilizer application (iron tailings and organic fertilizer) and Rhizobium inoculation with different strains on the growth of alfalfa planted in iron mine tailings and the physicochemical properties of the soil-plant system in outdoor pots. Rhizobium inoculation significantly increased height growth, root growth, above ground fresh weight, root fresh weight, total biomass and fresh nodule weight. The most effective Rhizobium was strain No.17676. Inoculated alfalfa also influenced the physicochemical properties of iron mine tailings, but the effect was not significant in the first year of the study. Fertilizer application markedly promoted alfalfa growth. Increasing fertilizer rates increased plant height, above ground fresh weight and total biomass. The N₂ fertilizer treatment produced the greatest increase in root nodule weight. Fertilizer application significantly reduced soil bulk density and pH but increased organic matter, available nitrogen, available phosphorus, and available potassium in the mine tailings soil. These effects were significantly higher for the N₃ treatment compared to lower fertilizer rates.

Optimization of culture conditions of a biocontrol agent Bacillus mojavensis ZA1 to antagonize Phoma foveata

FENG Zhong-Hong, CHANG Tao, YANG Cheng-De, XUE Li, LI Xu, YANG Xiao-Li

2016, 25(2):  77-86.  DOI: 10.11686/cyxb2015142

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This work aimed to identify optimum fermentation shaker-flask culture conditions for Bacillus mojavensis strain ZA1. Various single culture factors were combined according to a Box-Behnken design. The optimum ratio of ingredients for the culture medium for ZA1was found to be: 14.25 g ammonium chloride, 19 g corn flour, and 237 g potato, in 1000 mL distilled water. The optimum cultivation conditions were pH 7.7, temperature 28℃, and shaken at 180 r/min for 36 h. Under these conditions, the viable count of B. mojavensis strain ZA1 was 4.12×10¹⁰ colony-forming units per mL (CFU/mL). Further testing using the central composite design method in a 10 L fermentation tank found the optimum for dissolved oxygen level and shaker rotation speed to be 60% saturation and 180 r/min respectively. Under these conditions, when fermentation time was 36 h in the fermentation tank, the viable count of B. mojavensis strain ZA1 reached 1.59×10¹¹ CFU/mL. The results of this study lay a solid foundation for the development of methodology for large scale production of biocontrol agents.

Response of plateau pika burrow density to vegetation management in an alpine meadow, Maqu County, Gansu

ZHANG Yong-Chao, YUAN Xiao-Bo, NIU De-Cao, WU Shu-Juan, ZHANG Dian-Ye, ZONG Wen-Jie, FU Hua

2016, 25(2):  87-94.  DOI: 10.11686/cyxb2014404

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We analyzed the selection of habitat by plateau pika in degraded alpine meadow in Maqu County through different grassland improvement measures including enclosure, reseeding, fertilization (organic) and cleavage to help reveal aspects of the ecology of plateau pika and to provide theoretical basis for ecologically based management of plateau pika. From May to July 2010, 12 different grassland improvement measures were implemented. The density of active pika burrows was estimated using a stolen hole (mousehole) technique, and the selection of habitat by pika assessed. Compared with the control, the density of active pika burrows under different treatment measures was significantly reduced (P<0.05). All of the grassland improvement measures, especially reseeding, decreased the density of active burrows. The relationship between active burrow density and community structure was analysed using correlation analysis and stepwise regression analysis; the density of active burrows was significantly, negatively correlated with grass layer height (P<0.05). This suggests that grass height is an important factor influencing the density of pika. Using multiple management control factors including reseeding and fertilizer application promoted grass productivity, increasing grass layer height, decreasing active burrow densities (P<0.05). In alpine meadow areas of Maqu, different grassland improvement measures can effectively reduce the density of pika burrows, particularly those which increase the proportion of the grasses in the meadow.

Effects of dietary nitrate dosage on ruminal nitrate disappearance rate, fermentation parameters and concentration of blood methemoglobin of Hu Sheep

CHEN Zhi-Yuan, MA Ting-Ting, FANG Wei, ZUO Xiao-Xin, LIN Miao, ZHAO Guo-Qi

2016, 25(2):  95-104.  DOI: 10.11686/cyxb2015376

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This study investigated the effects of dietary nitrate dosage on ruminal nitrate disappearance rate, fermentation parameters and blood methemoglobin of Hu sheep. The experiment used a randomized block design. Six selected Hu sheep were fed different levels of dietary potassium nitrate (0%, 1%, 2%, 3%, 4%, 5% of DM intake). The concentration of nitrate, nitrite and fermentation parameters in rumen fluid were obtained 0, 0.5, 1.0, 1.5, 2.0, 4.0, 6.0 and 8.0 h after feeding. In addition, the concentration of blood methemoglobin was determined 2.0 h after feeding through blood collection from the jugular vein. The nitrate concentration increased to a maximum value (0.95-2.14 g/L) at 1.0 h after feeding, then reduced rapidly. The nitrite concentration increased to maximum value (0.93-6.22 μmol/L) 1.5 h after feeding. The content of methemoglobin significantly increased with the nitrate addition (P<0.01), to a peak of 0.32% at 5% dietary potassium nitrate. Nitrate addition also significantly increased rumen fluid pH value, ammonia nitrogen concentration and acetic acid/propionic acid 2.0 h after feeding (P<0.01). In conclusion, potassium nitrate addition at over 3% of DM intake was found to reduce the concentration of microbial protein and total volatile fatty acids. Microbial protein synthesis and total volatile fatty acids were highest with 2% potassium nitrate addition, and the dosage of 2% potassium nitrate was beneficial to rumen fermentation.

A study of SNP molecular marker technology for Leymus chinensis genotyping

HOU Li-Juan, QI Xiao, QI Dong-Mei, CHEN Shuang-Yan, LIU Gong-She

2016, 25(2):  105-113.  DOI: 10.11686/cyxb2015466

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Leymus chinensis, is a widely distributed and often ecologically dominant perennial grass in China, frequently used as research material. Because we know of no previous reports of markers in L. chinensis, we performed single nucleotide polymorphism (SNP) mining of 48 genotypes, based on the transcriptome data in the laboratory and established a method using high resolution melting (HRM) curves for L. chinensis SNP genotyping. A total of 41843 SNPs were detected from the transcriptome data by bioinformatics analysis. Transitions were nearly twice as frequent as transversions. Among 112 pairs of designed SNP primers, 98 SNP primer pairs (87.5%) were able to amplify bright single bands, 72 primer pairs (64.29%) had a suitable amplified band size, and 46 SNP primer pairs (41.07%) were suitable for HRM genotyping. The 48 germplasm genotypes of L. chinensis could be separated by 7 primer pairs and the fingerprint of each identified. The partial HRM genotyping results were verified by sequencing. The results of genotype by sequencing analysis were consistent with the results of HRM genotyping, so confirming that the HRM genotyping was reliable. HRM for SNP genotyping first established in this study can also be used in other breeding work with L. chinensis, including parent selection, gene correlation analysis, molecular marker assisted breeding, development of functional molecular markers and new variety protection.

Cloning and expression analysis of a high-affinity K⁺ transporter gene SsHAK2 in Suaeda salsa

DUAN Hui-Rong, WANG Suo-Min

2016, 25(2):  114-123.  DOI: 10.11686/cyxb2015182

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Suaeda salsa, a typical salt-accumulating halophyte, is capable of absorbing K⁺ with high efficiency, and thus maintains a relatively stable K⁺ level in cells, and grows well, even in highly saline soil. Members of the KT/HAK/KUP gene family have an important role in K⁺ uptake in plants. In this study, we cloned SsHAK2 in S. salsa and analyzed the expression patterns of SsHAK2 when the plants were exposed to different concentrations of KCl and NaCl. Results revealed that SsHAK2 coded for 788 amino acid residues and shared a high homology (80%-92%) with the identified members of KT/HAK/KUP family from other plants. Phylogenetic analysis showed that SsHAK2 belonged to a sub-group of the family known as group II, and formed a clade with AtKUP2 of Arabidopsis thaliana, indicating close relationship. SsHAK2 was highly expressed in roots and leaves, and was induced by widely differing K⁺ concentrations (2.5 and 0.01 mmol/L). Under 2.5 mmol/L K⁺ conditions, the expression of SsHAK2 in roots and leaves was induced by 25 mmol/L Na⁺ application. However, in the medium containing 0.01 mmol/L K⁺, the expression of SsHAK2 in roots was down-regulated by Na⁺ (25 and 150 mmol/L) application, but up-regulated in leaves. The results therefore indicate that SsHAK2 might mediate K⁺ uptake and transport in S. salsa, and functioned differently in roots and leaves.

A maize abscisic acid insensitive 3 gene confers drought and salt stress tolerance in Arabidopsis

YUAN Jin-Cheng, SONG Jin-Hui, MA Hai-Lian, WENG Qiao-Yun, WANG Ling-Yun, ZHAO Yan, LIU Ying-Hui

2016, 25(2):  124-131.  DOI: 10.11686/cyxb2015330

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The abscisic acid insensitive 3 gene (ABI3) has been widely studied in cereals such as wheat, maize and rice however, the functions of ABI3 have not been fully described. In this paper, a novel maize ABI3 like gene was cloned and named ZmABI3-L. This gene was predicted to encode a transcription factor with a distinct DNA-binding B3 domain. The full length of the gene was 1735 bp and with an opening read frame of 1212 bp and encoded 404 amino acids. Alignment of the ZmABI3-L proteins with other plants revealed similarities with ABI3 protein from other species. RT-PCR analysis showed ZmABI3-L was up-regulated in maize by dehydration, salt, cold and ABA stress. Over-expression of ZmABI3-L in Arabidopsis plants could enhance salt and drought stress tolerance compared to the wild type. The results suggest that ZmABI3-L may be involved in salt and drought resistance signaling pathways in maize.

The transferability of SSR and EST-SSR markers of different origins in Elymus and Roegneria in the Triticeae (Poaceae)

CHEN Shi-Yong, MA Xiao, ZHANG Xin-Quan, CHEN Zhi-Hua, ZHOU Kai

2016, 25(2):  132-140.  DOI: 10.11686/cyxb2015324

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Elymus and Roegneria, two important genera in the tribe Triticeae, include many important forage grasses, and also carry elite genes for improving cereal crops. However, there is ongoing dispute on the species boundaries and interspecific systematic relationships in the two genera. The biosystematic relationships in the group are of keen interest to agrostologists around the world. Based on known SSR markers in Triticeae, the objective of this study was to screen out the high transferability markers for Elymus and Roegneria, which would provide important information for understanding the biosystematic relationships of the two genera. A total of 230 simple sequence repeats (SSR) and SSR based on expressed sequence tags (EST-SSR) markers from 5 different genera including wheat, barley, Elymus, Pseudoroegneria and Leymus, were used to study the transferability to 23 species containing the St, H, and Y genomes. Among the 230 SSR markers, 163 (70.87%) markers could generate clear bands, which showed a high transferability for those markers. The EST-SSR markers (87.60%) showed a higher transferability than genomic SSR markers (49.50%), but the genomic SSR markers showed a higher polymorphism (85.98%) than the EST-SSR markers (79.37%). A total of 579 bands were amplified from the 163 SSR markers able to generate clear bands, of which 533 bands were polymorphic. The number of amplified bands of each of these 163 SSR markers ranged from 1 to 11 with an average of 3.55 bands. Cluster analysis using the unweighted pair group method with arithmetic average (UPGMA) showed that the species with same or similar genome could be grouped together. Additionally, the H genome showed a rather distant phylogenetic relationship with St genome, and distant phylogenetic relationships were also revealed between the diploid species containing the H genome and other species in the study. The selected SSR markers from 5 genera could be amplified successfully in Elymus and Roegneria. To summarise, a total of 163 high transferability SSR markers were found to be suitable for the further phylogeny analysis, which also revealed the phylogenetic relationships among the species. The results from this study provide important information for improving understanding of biosystematic relationships between Elymus and Roegneria.

The mutagenic effects of colchicine treatment on chromosome ploidy and the leaf epidermal cells of radicles of Medicago sativa cv. Qingshui

LI Yue, SHI Shang-Li

2016, 25(2):  141-149.  DOI: 10.11686/cyxb2015122

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The objective of this experiment was to determine the appropriate colchicine dose levels to produce polyploids of Medicago sativa cv. Qingshui. Three different colchicine concentrations (0.05%, 0.10%, 0.20%) and three treatment durations (4 h, 8 h, 12 h) were used to induce the radicle of gemmiferous seeds and changes were observed in the root tip cell chromosome number and in inclusions in the lower epidermis of leaves. The results showed that colchicine can change chromosomes in the root tip cells of alfalfa seedlings, producing a variety of different mutant types (4x<2n<8x, 2n=8x and 2n>8x). The appropriate dose and treatment period of colchicine to induce a higher proportion of octaploid cells (2n=8x) is 0.1%+8h, with a mutation rate of 13.3%. Increasing levels of colchicine were associated with increases in the size (length, width, length/width) of guard cells and in the number of chloroplasts in the leaves’ lower epidermis, while the density of stomata decreased. The size of guard cells and number of chloroplasts were largest in the 0.1%+8h, 0.1+12h and 0.2%+4h treatments, where stomatal densities were also relatively the smallest. The largest mutagenic effects were observed under the 0.1%+8h treatment.

Effects of Eupatorium adenophorum extracts on seed germination and seedling growth of pasture species

WANG Ya-Qi, JIAO Yu-Jie, CHEN Dan-Mei, YUAN Ling, HUANG Yue, WU Ye-Kuan, DU Ru-Wan

2016, 25(2):  150-159.  DOI: 10.11686/cyxb2015393

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Eupatorium adenophorum is a serious grass weed, among the 16 most invasive plant species in China, widespread in pasture, agricultural land and forests in Southwest China. The potential allelopathic effects of this grass and mitigation strategies were investigated. Trifolium fragiferum, Lolium perenne and Medicago sativa, widely distributed in Liangshan, Sichuan, were used to investigate seed germination and seedling growth by comparing the extracts of composted and fresh E. adenophorum (extract of composted E. adenophorum, ECA; extract of fresh E. adenophorum, EFA) to determine the effects of E. adenophorum on pasture species and to develop a composting technique. Soaking seed in EFA depressed seed germination and young seedling growth to some extent; the effect was greater at higher concentrations. Seedling roots grew away from the EFA solution and some root tips blackened and died when growing in 100 mg/L EFA solution. After composting with a complex agent consisting of Pseudomonas putita sp. and Clostridium thermocellum sp., ECA increased the rate of seed germination by 21.1%, increased seedling height growth by 24.1% and seedling biomass by 22.5%. The results suggest the decomposition of toxicants in E. adenophorum during the composting process promoted seed germination and seedling growth. EFA inhibited hydrolysis of starch, protein and inositol phosphates in embryos,decreasing free amino acids, soluble sugars and soluble phosphorus in seedlings. Chlorophyll content and activities of roots and nitrate reductase were also decreased by EFA in contrast to ECA. Physiological changes in seedlings could be considered as a key reason for the inhibition of seed germination and seedling growth by EFA or promotion by ECA. Composting probably resulted in decomposition of toxins in E. adenophorum, offering a technique for managing the harmful effects of E. adenophorum while providing a large organic fertilizer resource for agriculture.

Effects of Epichloё endophyte and seed hydro-priming on the germination of Festuca sinensis under NaCl stress

KUANG Yu, NAN Zhi-Biao, TIAN Pei

2016, 25(2):  160-168.  DOI: 10.11686/cyxb2015143

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This study investigated the germination and vigor of Festuca sinensis seeds infected (E+) and uninfected (E-) with Epichloё endophyte and under different levels of NaCl stress after hydro-priming. The results showed that NaCl stress treatments significantly reduced seed germination rate, interim germination, the germination index, the length of embryo and radicle and the dry weights of both E+ and E- F. sinensis seeds. Compared with E-, infection with Epichloё endophyte can significantly improve germination and seedling growth of F. sinensis seeds under different concentrations of NaCl. There were interaction effects between seed hydro-priming and the Epichloё endophyte. The highest levels of interaction were with 20 mins seed hydro-priming, when the germination indices and seedling growth rates were significantly higher than for all the other treatments. Correlation analysis showed that F. sinensis seed germination rate, interim germination, germination index, the length of embryo and radicle and dry weight were all significantly positively related to each other.

Responses of old world bluestem root systems to changes in soil water conditions

LI Shuai, ZHAO Guo-Jing, XU Wei-Zhou, GAO Zhi-Juan, WU Ai-Jiao, XU Bing-Cheng

2016, 25(2):  169-177.  DOI: 10.11686/cyxb2015171

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Root morphological characteristics are important parameters for evaluating plant adaptability to environmental stress. To clarify the relationship between the root morphological characteristics of old world bluestem (Bothroichloa ischaemum) and soil water conditions, pot experiments were conducted to investigate root biomass, total root length, root surface area, average root diameter, specific root length and specific root area under three soil water regimes: (1) sufficient water supply (HW, 80% field capacity), (2) moderate water stress (MW, 60% field capacity), and (3) severe water stress (LW, 40% field capacity). Moreover, soil water contents were improved from MW to HW, LW to HW and LW to MW at the three main growth periods (jointing, flowering and maturing). At the end of the growth period, root biomass and morphological characteristics under the different water treatments were measured and analyzed. The results showed that old world bluestem root growth was closely related to soil water conditions. Root biomass, total root length and root surface area were also significantly higher with continuous sufficient water supply than under the other treatments (P<0.05). Water stress inhibited the root growth of old world bluestem but there were no significant differences in average root diameter between the different water treatments. Positive linear relationships were found between root biomass and total root length as well as with root surface area. The roots exhibited strong morphological plasticity in response to changes in soil water conditions. Higher levels of water content improvement significantly improved root biomass, total root length and root surface area, especially during the jointing period. These results suggest that old world bluestem has strong water stress tolerance and that the growth response of its roots to soil water change is related to the plant growth period as well as to the degree of water stress prior to improvements in soil water content.

Cadmium uptake and root morphological changes in Medicago sativa under cadmium stress

LI Xi-Ming, SONG Gui-Long

2016, 25(2):  178-186.  DOI: 10.11686/cyxb2015401

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This study used pot experiments to investigate the cadmium (Cd) uptake potential of alfalfa (Medicago sativa) and to explore the possible mechanisms involved in root adaptation under various levels of cadmium stress (0, 10, 25, 50 mg/kg). Alfalfa shoot biomass, root biomass, total root length, root surface-area, root volume, average root diameter and root number were all significantly smaller under the three Cd stress treatments than in the normal Cd condition (P<0.05). Shoot biomass was 87.8%, 56.5% and 14.3%, and root biomass was 96.1%, 63.3% and 16.2% respectively. The highest Cd content was observed in fine roots (root diameter below 1.0 mm) and the Cd content in shoots was higher than that in roots with diameters above 1.0 mm. The Cd content in three parts (shoot, fine root, coarse root) increased significantly with increasing Cd exposure. The highest Cd accumulation was recorded in shoots (7.715 μg/plant) at a concentration of 25 mg/kg Cd. Compared to the control, root length, root surface-area and the root volume of different diameter classes decreased significantly with increases in Cd concentration, except for the proportion of roots with diameters below 0.5 mm, which increased. It can be concluded that alfalfa is suitable for remediation of Cd polluted soil when Cd concentrations are less than 25 mg/kg and the response characteristics of root systems to Cd show dynamic equilibrium.

Effects of Vetiveria zizanioides roots on soil properties in the Purple Soil Area of China and the role of different root diameter classes

CHEN Yun, HE Bing-Hui, LIAN Cai-Xia, LIU Zhi-Peng

2016, 25(2):  187-197.  DOI: 10.11686/cyxb2015189

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The aim of this study was to determine the effects of Vetiveria zizanioides plants and their roots on soil properties, and define the role of different root diameter classes. The research was conducted in the Purple Soil Area of China. The experiment compared bare control plots with plots planted in V. zizanioides. Soil and root samples were collected regularly from 0-10 cm, 10-20 cm, 20-30 cm soil layers. Contents of soil organic matter, total and available nitrogen, phosphorus, and potassium were measured by conventional methods. Roots were divided into 10 diameter classes measured by a Root Analysis System (WinRHIZO, Pro. 2004c). It was found that: 1) V. zizanioides substantially enhanced the accumulation of soil organic matter, the longer the planted time the greater the effect. V. zizanioides also promoted the accumulation of soil total nitrogen, but the effect was weak compared with organic matter. Both available phosphorus and potassium were depleted in all V. zizanioides plots. 2) The levels of organic matter, available phosphorus, total potassium and available potassium showed topsoil accumulation in all V. zizanioides plots; i.e. over time their levels in the 0-10 cm soil layer increased significantly more than in the 10-20 cm and 20-30 cm soil layers (P<0.05). 3) The root diameter range (d) 0.00 mm<d≤2.00 mm was dominant in affecting soil organic matter. root length density (RLD), Root surface area density (RSAD), and root volume density (RVD) of all diameter classes in this range were significantly and positively correlated with soil organic matter content (P<0.01), with the highest correlation being the 0.00 mm<d≤0.50 mm diameter range and the next highest being the 1.50 mm<d≤2.00 mm range. 4) Root diameters of d=2.00 mm and d=4.50 mm were important classification divisions. When 0.00 mm<d≤2.00 mm, RLD, RSAD, and RVD of all diameter classes showed significant differences between all soil layers and were significantly and negatively correlated with soil layer depth. The maximum correlation coefficient occurred in roots of the 0.50 mm<d≤1.00 mm diameter range. When 2.00 mm<d≤4.50 mm, all root parameters of all diameter classes were uncorrelated with any measured soil parameter. 5) The maximum RLD, RSAD, and RVD occurred in the 0-10 cm soil layer, and RLD differed significantly among all soil layers in the same year or between 2011 and 2013 in the same soil layer.

Physiological response of Chamaecrista rotundifolia to cadmium exposure

HE Li-Xiang, HUANG Yun-Xiang, HUANG Chu-Yu, LIU Li-Shan, LONG Xiang, LUO Lin

2016, 25(2):  198-204.  DOI: 10.11686/cyxb2015158

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Chamaecrista rotundifolia, introduced from Australia in the 1980s is a leguminous forage widely cultivated in subtropical regions. The effects of cadmium (Cd) exposure on the growth and physiological characteristic of C. rotundifolia were studied at different Cd concentrations (0, 1, 2, 4, 8 mg Cd/kg dry soil) using a pot experiment. When C. rotundifolia was exposed to a Cd concentration of 1-2 mg Cd/kg soil, the protective enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were all produced and C. rotundifolia growth was normal. There was no significant decrease in underground or aboveground biomass, compared with the controls. When C. rotundifolia was exposed to 4 mg Cd/kg soil, SOD activity was reduced, while the content of the oxidative stress marker malondialdehyde (MDA) increased. However, the enzymes POD and CAT were activated. Therefore, there was some alleviation of Cd stress. Although no tissue death was observed, at the Cd concentration of 4.0 mg/kg, the values for underground and above ground biomass were reduced by 59.69% and 63.77%, respectively, compared with the control. When C. rotundifolia was exposed to 8 mg Cd/kg soil, the MDA content increased significantly, the cell protective enzyme system was imbalanced, and all plants were dead when harvested. The synthesis of chlorophyll a, chlorophyll b and carotenoids was inhibited by Cd exposure, and the inhibitory effect increased with increasing Cd concentration. The Cd accumulated mainly in the underground organs of C. rotundifolia, and the translocation factor was only 0.152-0.234. In this experiment were available Cd was added to soil, C. rotundifolia tolerated Cd concentrations below 2.0 mg/kg. C. rotundifolia has potential as a remediation plant to restore soil contaminated with Cd by mining operations in China’s south red soil region.

Effect of low temperature on phytohormones and carbohydrates metabolism in Bermuda grass

YANG Yong, LOU Yan-Hong, YANG Zhi-Jian, XIANG Zuo-Xiang, XU Qing-Guo, HU Long-Xing

2016, 25(2):  205-215.  DOI: 10.11686/cyxb2015133

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To investigate the effects of modulated cold acclimation on the leaf membrane stability, chlorophyll content, endogenous hormones (ABA, IAA, GA₃, tZR), and carbohydrate (soluble sugars, starch, fructan, total nonstructural carbohydrates) metabolism, five Bermuda grass cultivars, Tifway, Tifgreen, Tifsport, Tifeagle and Baoding were selected and treated under a range of temperatures: optimum (30℃/25℃), suboptimum (18℃/12℃), chilling (8℃/4℃) and freezing (4℃/-4℃) in growth chambers. The results demonstrated that leaf electrolyte leakage, abscisic acid (ABA) content and carbohydrates (soluble sugars, starch, fructan, total nonstructural carbohydrates) increased while chlorophyll content, endogenous hormones auxin (IAA), gibberellin (GA₃) and cytokinin (tZR) content decreased with low temperature stress, but the changes varied with cultivar. Tifeagle, Tifsport and Tifgreen were ranked highest, Tifway was ranked intermediate while Baoding ranked lowest. Accumulating or maintaining relatively higher levels of phytohormones and carbohydrates, associated with cellular osmotic homeostasis and membrane stability, delayed leaf senescence. Cold resistance genes or protein induction may contribute to the higher cold tolerance in Bermuda grass under low temperature.

The physiological mechanisms through which exogenous H₂O₂ increases the resistance of Avena nuda to salt stress

LIU Jian-Xin, WANG Jin-Cheng, WANG Rui-Juan, JIA Hai-Yan

2016, 25(2):  216-222.  DOI: 10.11686/cyxb2015128

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Soil salinity is a major limiting factor for plant growth and productivity globally. Hydrogen peroxide (H₂O₂) is an important signaling molecule in plants that regulates many important physiological and biochemical processes and induces tolerance to different stresses, including salt stress. A study has been undertaken in order to further understand the operation of these regulatory mechanisms in oat seedlings (Avena nuda). A new oat cultivar, ‘Dingyou No. 6’, was selected to investigate, using greenhouse nutrient solution cultivation, the effects of exogenous H₂O₂ on plant growth, osmotic adjustment substances accumulation and active oxygen metabolism in seedlings under salt stress. The results showed that 150 mmol/L NaCl exposure significantly inhibited seedling growth. It enhanced the production of free amino acid and proline and decreased the contents of glutathione (GSH) and soluble sugar in leaves. Foliar spraying of 0.010 mmol/L H₂O₂ significantly alleviated the inhibitory effect of NaCl stress on seedling growth. Exogenous H₂O₂ increased the contents of soluble protein, soluble sugar and proline, and decreased free amino acid content in leaves. Under 150 mmol/L NaCl stress, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) activities all increased, along with excessive production of O2·-, H₂O₂ and malondialdehyde (MDA) in seedling leaves. Spraying the stressed seedlings with 0.010 mmol/L H₂O₂ treatments significantly increased the activities of SOD, CAT, POD and APX and GSH content, but decreased O2·- production rate and the contents of H₂O₂ and MDA in leaves. These results indicate that exogenous H₂O₂ could enhance anti-oxidative ability and decrease membrane lipid peroxidation injury in oat seedlings under NaCl stress. Exogenous H₂O₂ enhanced seedlings’ salinity tolerance by regulating osmotic adjustment substances accumulation and active oxygen metabolism in plant leaves.

Analysis of grassland farming systems’ economic benefit based on the short-term production model

LIU Yun-Heng

2016, 25(2):  223-230.  DOI: 10.11686/cyxb2015223

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“Input-output” research of farming systems can assist the development of appropriate agricultural structures in China. Such analysis can assist grassland systems to optimize farmland resources and to make better use of the multiple cropping index. In this paper, we use economic theory’s short-term production model, focusing on the marginal product and the law of diminishing marginal returns, to systematically compare traditional grain crops monoculture with grassland farming systems. Our analysis concludes that the grassland system has clear advantages. It can readily adjust variable factors, offsetting a single variable input in order to reduce the adverse effects of negative marginal outputs and production. Grassland systems also have substantial effects on the recovery of soil fertility and increased crop output, thereby increasing actual economic benefits for farmers. They play a significant role in the optimal use of land resources, agricultural water and soil conservation and also the development of animal husbandry. In conclusion, grassland farming systems help to increase both farmer incomes and the ecological protection of agricultural environments.

Effects of moisture and additives on the quality of pepper straw silage

ZHOU Juan-Juan, WEI Wei, QIN Ai-Qiong, CHEN Ben-Jian

2016, 25(2):  231-239.  DOI: 10.11686/cyxb2015181

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The objectives of this research were to determine the effects of moisture and additives on the quality of pepper straw silage and to identify new approaches for feed conservation. Pepper straw was wilted to three different target moisture contents (approx. 75%, 65% and 55%) and treated with (1) formic acid (1.5% FW, FA); (2) propionic acid (1.5% FW, PA); (3) corn flour (100 g/kg DM, CF); (4) potato dregs (30% FW, PD); (5) direct ensiling without additives (CK). After 45 days of ensiling with PE (polyethylene plastic vial, 100 mL), the fermentation quality and nutritional traits were analysed. The results showed that moisture and additives had significantly influenced silage quality (P<0.05). Dry mater and pH increased while lactic acid (LA), acid detergent fiber (ADF) and neutral detergent fiber (NDF) declined with decreasing moisture content. ADF was lowest at 75% moisture content while LA was highest and NH₃-N/TN (total N) lowest. In contrast with CK, FA treatment had significantly increased pH and NH₃-N/TN (P<0.05), lowered LA and water soluble carbohydrate (WSC); PD and CF treatments provided sufficient fermentation substrate; DM and WSC increased (P<0.05). The results indicated that a silage moisture content of 75%+FA produced the best quality silage followed by 65%+PD. In conclusion, the most suitable moisture for pepper straw silage is approximate 75%; adding PD may be advantageous at lower moisture contents.

Effects of simulated warming and precipitation enhancement on photosynthesis of Stipa krylovii

YAN Yu-Long, ZHANG Li-Xin, WAN Zhi-Qiang, GU Rui, SU Li-De, YANG Jie, GAO Qing-Zhu

2016, 25(2):  240-250.  DOI: 10.11686/cyxb2015163

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This study was conducted to examine the interactive effects of climate warming and changing precipitation on photosynthetic parameters of Stipa krylovii to evaluate the effects of future climate change on a typical steppe environment. Open top chambers (OTCs) were used to simulate warming +2℃, based on the local temperature increase from 1961 to 2010 (IPCC, 2007) and precipitation enhancement of +20%, based on the local average monthly precipitation from 1961-2010. The photosynthetic parameters were measured by a portable gas exchange system (LI-6400) in the growing season of 2012. Warming significantly reduced the photosynthetic rate (P_n) and stomatal conductance (G_s) of S. krylovii, and there was a clear seasonal trend. Warming reduced P_n 17% and 27% and reduced G_s by 24% and 32% in July and September, respectively. Warming also reduced the transpiration rate (T_r), chlorophyll content, the maximum ribulose 1,5-bisphosphate (RuBP) carboxylation rate (V_cmax), RuBP regeneration capacity (J_max), apparent quantum efficiency (AQE) and the maximum photosynthetic rate (P_nmax) of S. krylovii. Conversely, water use efficiency (WUE) increased by 16.5%. Precipitation enhancement produced compensatory effects on photosynthesis responses to warming. Precipitation enhancement promote P_n, G_s, T_r, chlorophyll content, V_cmax, J_max, AQE and the P_nmax of S. krylovii but had did not affect WUE. The effects of temperature and precipitation on photosynthesis and WUE of S. krylovii was caused by stomatal and non-stomatal factors. Under warm conditions and precipitation enhancement, G_s influenced both P_n and T_r. No interactive effects were observed.

Initial response of light use efficiency to experimental warming in an alpine meadow in the Northern Tibetan Plateau

ZHOU Nan, FU Gang, SUN Wei, LI Shao-Wei, SHEN Zhen-Xi, HE Yong-Tao, ZHANG Xian-Zhou, WANG Jiang-Wei

2016, 25(2):  251-257.  DOI: 10.11686/cyxb2015150

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Light use efficiency (LUE) is an important eco-physiological variable and the quantification of LUE at a variety of spatial and temporal scales would be advantageous for global carbon cycle and climatic change research. In order to assess the initial response of LUE to climatic warming, a field experiment was conducted in an alpine meadow in Northern Tibet beginning late June, 2013. Open-top chambers (OTC) with two different warming magnitudes (top diameter 0.60 and 1.00 m, labeled as OTC2 and OTC1, respectively) were used to increase temperatures. Daily LUE was estimated by using daily minimum air temperature and daytime mean vapor pressure deficit, based on a Moderate-Resolution Imaging Spectroradiometer (MODIS) algorithm, between July and September in 2013. Compared to the control, OTC2 and OTC1 significantly increased average vapor pressure deficit by 0.60 and 0.20 kPa, respectively. Compared to the control, OTC2 significantly increased average daily minimum air temperature by 0.66℃, whereas OTC1 did not produce a significant increase (0.25℃). OTC2 and OTC1 significantly reduced LUE by 12.9% (i.e. 0.06 g C/MJ) and 3.1% (i.e. 0.01 g C/MJ), respectively. Our findings suggested that climatic warming will probably decrease LUE in alpine meadow ecosystems and that the negative effect of experimental warming on LUE may increase with the magnitude of warming on the Northern Tibetan Plateau.