Table of Content

20 December 2013, Volume 22 Issue 6

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Multi-scale biomass estimation of desert shrubs: a case study of Haloxylon ammodendron in the Gurbantunggut Desert, China

TAO Ye, ZHANG Yuan-ming

2013, 22(6):  1-10.  DOI: 10.11686/cyxb20130601

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Shrubs are an important component of desert ecosystems. Their biomass allocation and biomass estimation are important indices to study the structure, function, mass, and energy flow of desert ecosystems. However, research on desert shrub biomasses is still limited. The current destructive biomass estimation is unsuitable for use in arid lands where the ecosystem is weak, so it is important to estimate the shrub biomass using models at multiple scales. In this study, the constructive shrub species Haloxylon ammodendron in the Junggar Desert was used as an example. A number of plant morphological parameters were chosen, and the aboveground (AGB) and belowground biomass (BGB) models were established at the individual plant, plot and regional scales using allometric (power function) equations. The biomass estimation was then performed using the same model. Based on the canopy volume (CH), the formula AGB=0.3628×CH^0.9605 accurately reflected the AGB individual accumulation characteristics. The individual BGB was estimated using BGB=0.8737×AGB^0.9394. The total canopy cover (TC) of H. ammodendron was an effective parameter to calculate the total AGB and BGB (TAGB=0.6757×TC^1.1343, TBGB=0.6384×TC^1.0959) in sampling plots with an area of 0.1 hm². On a large, regional scale, the relative canopy cover (RC) had a positive effect on estimating the AGB and BGB densities (DAGB=0.0921×RC^1.1343, DBGB=0.0796×RC^1.0959), from which the total regional biomass storage of H. ammodendron could be obtained. It showed that the issue of scaling was successfully resolved using the RC of the H. ammodendron biomass density. There was no scale limit when RC was used. In future, the RC of H. ammodendron can also be obtained quickly through aerial photography, remote sensing, etc, thus the total AGB and BGB in relevant regions would be estimated accurately using the aforementioned biomass density models.

Differences in the impacts of flooding frequency and duration on riparian vegetation and soil in the Lower Tarim River

FU Jin-yi, XU Hai-liang, ZHAO Xin-feng, BAI Yuan, WANG Xi-yi

2013, 22(6):  11-20.  DOI: 10.11686/cyxb20130602

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To analyse the impacts of frequency and duration of flooding on the regional riparian vegetation and soil, a field survey of riparian vegetation and soil was carried out in selected plots with different flooding frequencies and durations in the Lower Tarim River. 1) The importance values of annual and perennial herbs increased with flooding disturbance. After flooding, perennial herbs dominated instead of shrubs and trees in two sample plots of flooding frequency and in three sample plots of flooding duration. 2) In the flooding frequency plots, the one flooded many times in many years had the richest diversity with values of Simpson index, Shannon-Wiener index and Margalef index of 0.523, 0.979 and 1.023, respectively. 3) In the flooding duration plots, the ones flooded for 10-20 days and 20-30 days had the largest diversity indexes. The former had the largest Margalef index (0.863), and the latter had the largest Simpson index and Shannon-Wiener index (0.451 and 0.777 respectively). 4) Flooding reduced the surface soil conductivity very significantly, and was at a minimum in the sample plots flooded once to twice per year (1.148 ms/cm) and flooded for 10-20 days (1.155 ms/cm). The organic matter of the surface soil increased in the sample plots flooded many times in many years and in those flooded for 5-10 days (values of 11.577 and 8.770 g/kg respectively). The organic matter of other sample plots were all less than that of the control plots. Accordingly, to encourage vegetation restoration in the Lower Tarim River, it is advisable to proceed with flooding many times for many years with a duration of 10-30 days per time.

Effect of rest-grazing on soil microbial community functional diversity in Stipa baicalensis steppe

LI Yu-jie, LI Gang, SONG Xiao-long, ZHAO Jian-ning, XIU Wei-ming, YANG Dian-lin

2013, 22(6):  21-30.  DOI: 10.11686/cyxb20130603

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The changes in soil microbial community functional diversity and microbial biomass under different rest-grazing years (RG_3a, RG_6a and RG_9a) in Stipa baicalensis steppe were investigated and compared with zero rest grazing grassland (RG₀) using the Biolog-ECO micro-plate technique and chloroform fumigation extraction method. The soil microbial metabolic activity significantly increased after rest grazing. The average well color development (AWCD), which represented soil microbial metabolic activity, followed the order of RG_6a>RG_9a>RG_3a>RG₀. The AWCD of RG_6a and RG_9a showed no significant difference, but both were significantly higher than that of RG₀ (P<0.05). RG_3a had no significant difference from RG₀ (P>0.05). The RG_9a had the highest Shannon index (H), substrate evenness (E) and Simpson’s dominance (D) of soil microbial community. The Shannon index (H) of RG_9a was significantly (P<0.05) different from those under other treatments. Substrate evenness (E) was not significantly different from each other; Simpson’s Dominance (D) of RG_9a was not significantly different from those of RG_3a and RG_6a, but significantly different from RG₀. Principal component analysis (PCA) showed that the RG₀, RG_3a and RG_6a had a similar carbon source utilization mode and the metabolic function differed from that of RG_9a. The carbon sources most used by soil microorganisms were carbohydrates, amino acids, and lipids. Soil microbial biomass increased gradually with more rest grazing years. RG_9a had the highest soil microbial biomass C (590.20 mg/kg) and soil microbial biomass N (72.86 mg/kg). Correlation analysis indicated that the AWCD had a significantly (P<0.05) positive correlation with the Shannon index (H) and a highly significantly (P<0.01) positive correlation with Simpson’s dominance (D). The Shannon index had a highly significantly (P<0.01) positive correlation with the Simpson’s dominance (D). The Shannon index (H) and Simpson’s dominance (D) both showed a significantly (P<0.05) positive correlation with soil microbial biomass C and there was also a significantly (P<0.05) positive correlation between the Shannon index (H) and soil microbial biomass N (P<0.05). Therefore, rest grazing enhanced the soil microbial metabolic function which was beneficial to the reproduction of soil microorganisms, thereby promoting an increase of soil microbial biomass carbon and nitrogen content.

Productivity responses of different functional groups to litter removal in typical grassland of Inner Mongolia

WANG Jing, ZHAO Meng-li, Willms W, HAN Guo-dong, GAO Xin-lei, WU Yu-shanhina)

2013, 22(6):  31-38.  DOI: 10.11686/cyxb20130604

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The objective of this study was to determine whether litter removal affected the above-ground biomass, the relation between above-ground biomass and different functional groups, and to find whether litter can change the structure of plant communities in typical grasslands. The experiments were conducted in October 2002 and three ‘removal’ treatments were done in typical grassland after they became frozen. There was no significant effect of litter removal on the total above-ground biomass but there was a tendency for the above-ground biomass to increase as the mass of litter removed increased. The effect of litter removal on every different functional group biomass was shown in the 5th year after the removal treatment. The biomass of perennial forbs under the moderate removal treatment was significantly (P<0.05) higher than that under the heavy removal treatment and in the control plots. Perennial bunch grass under heavy removal treatment had significantly (P<0.05) higher biomass than that under moderate removal treatment, but there was no difference from the control plot. Analyses of the correlation between total above-ground biomass and each functional group under the same treatment showed that under the heavy removal treatment, the correlation between total grass and total biomass was the closest and that of perennial forbs was second. The biomass of perennial rhizome grass under the moderate removal treatment was significant (P<0.05) and had the highest correlation with total above-ground biomass. In the control plots, perennial bunch grass had the highest degree of correlation with total above-ground biomass (P<0.05).

Impact of enclosure duration on plant functional and species diversity in Inner Mongolian grassland

GAO Kai, ZHU Tie-xia, HAN Guo-dong

2013, 22(6):  39-45.  DOI: 10.11686/cyxb20130605

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Plots in the Leymus chinensis steppe at the Inner Mongolia Grassland Ecosystem Research Station (IMGERS) were fenced in 1979, 1999, and 2004. The effect of enclosure duration on plant functional groups, species diversity and species composition was studied by testing biomass, coverage, density and height. There were differences in species composition, community characteristics and species diversity with increasing enclosure duration until finally a steady state was reached. The cumulative dominance values of perennial grasses, shrub and sub-shrub from the steppes fenced in 1999 and 1979 were significantly (P＜0.05) higher than those fenced in 2004. Similar results were also observed for forbs. The Shannon-Weaver index, richness index and evenness index of the steppes fenced in 1999 and 1979, were remarkably higher than those of 2004. There was no significant difference between the 1999 and 1979 results. The total biomass, and biomass of forbs, perennial grass, shrubs and sub-shrubs of the 1999 and 1979 plots all showed an increasing trend. The total biomass, shrub and sub-shrub biomass of 1999 and 1979 were significantly higher than those of 2004, while the shrub and sub-shrub biomass of 1979 was considerably higher than that of 1999. There was no significant difference in total biomass between the 1999 and 1979 biomasses. There were significant (P＜0.05) differences between the 1999, 1979 and 2004 biomasses and the order was 1979＞1999＞2004. It is concluded that these results will lead to a decrease in grassland use value and grassland degradation for invasion by shrubs and sub-shrubs.

Characteristics of rainfall interception and redistribution for Salix gordejevii in Horqin Sandy Land, Northeast China

YUE Xiang-fei, CUI Jian-yuan, ZHANG Tong-hui, WANG Shao-kun, LIAN Jie, WANG Xin-yuan, YUN Jian-ying

2013, 22(6):  46-52.  DOI: 10.11686/cyxb20130606

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This study aimed to clarify the characteristics of rainfall redistribution in desert shrub areas and the relationship between interception, stemflow and rainfall characteristics (precipitation and rainfall intensity). From May 30 to September 3, 2012, a field experiment was conducted to investigate rainfall redistribution in Salix gordejevii shrub which is one of the typical psammophytes in Horqin Sandy Land, Northeast China. During the experimental period, there were 20 rainfall events, and the cumulative gross rainfall was 135.32 mm. The amounts of throughfall (TF), stemflow (SF) and interception (I) were (112.01±3.76) mm, (1.97±0.20) mm, and (21.33±3.74) mm, respectively, and the proportions of TF, SF and I were 82.78%, 2.19% and 15.03%, respectively. Statistical analysis showed that the correlations between precipitation with TF, SF and I could be fitted by quadratic function, power function and “S” curve, respectively (all P<0.001). TF, SF and I all increased with precipitation increase, but there was an upper limit (1.40 mm) for I. The relationships between precipitation with TF%, SF% and I% might be presented by a logarithmic function, power function and exponential function, respectively (all P<0.001). TF% and SF% increased with a precipitation increase while I% decreased. Moreover, I% decreased with an increased rain intensity, while SF% increased initially then decreased. I% first increased then decreased from May to September, indicating there was an optimum rainfall intensity for SF. Continuous rainfall lowered I%, and raised SF%.

Yield and quality of silage corn (Zea mays) as affected by type and quantity of N fertilization

MA Lei, YUAN Fei, ZHU Ling-ling, WANG Zhong-mei, RONG Yu-ping

2013, 22(6):  53-59.  DOI: 10.11686/cyxb20130607

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To provide a scientific basis and guidelines for improving the production of silage corn (Zea mays) in the Bashang region, Hebei, a complete randomized block design was used to study the effects of nitrogen fertilizer types (available nitrogen, slow-release nitrogen) and quantities (180, 150, 120, 90, 60, 30 and 0 kg/ha) on the yield and quality of silage corn at different growth stages. All fertilization treatments significantly (P<0.05) increased fresh and hay yields of silage corn, and the highest yields was found in the treatment slow-release ⅡC, with hay yields reached to 2.45×10⁴ kg/ha. Each of fertilization treatments had increased the stem-leaf ratio of silage corn. All fertilization treatments had significantly enhanced soil and plant analyzer development (SPAD) values and increased crude protein content compared to no fertilization treatments (P<0.05). In the jointing growing stage, crude protein content was significantly higher in Ⅲ (P<0.05), but in maturity growing stage crude protein content was significantly higher in treatment slow-release ⅡB in than other treatments (P<0.05).Compared to single applications, silage corn had higher stem-leaf ratio, crude protein content, fresh yields, hay yields and lower SPAD values with split fertilization, which was better under rainfed cultivation conditions in this region. Comprehensive consideration of both yield and quality of silage corn, we recommended the slow-release treatment ⅡC as the most suitable fertilization in our study.

Effects of different nitrogen fertilizer types and humic acid (HA) on chemical composition, yield and quality of flue-cured tobacco traits in typical ecological zones of Shaanxi province

ZHANG Xi-feng, ZHANG Li-xin, GAO Mei, WEI Cheng-cai, MA Ying-ming, WANG Ping-ping, GENG Wei

2013, 22(6):  60-67.  DOI: 10.11686/cyxb20130608

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To provide a theoretical and practical basis for cultivation of flue-cured tobacco with high yield and better quality, a field experiment was conducted in three different ecological growing-tobacco regions in Shaanxi province. The effects of different types of nitrogen (N) fertilizers and combinations with humic acid (HA) on chemical composition, yield and quality characters of flue-cured tobacco were investigated. Both N fertilizers and combinations with HA increased contents of nicotine and N, but decreased reducing sugar content. Their effects on contents of potassium (K) and chlorine (Cl) were varied due to different ecological conditions. The combined application of N and HA more effectively modulated the content of chemistry components than single N treatment. Yield of tobacco leaves followed the order of Longxian>Luonan>Xunyang, however, the output value showed that Longxian was similar to Xunyang, and both of them were less than Luonan. Both N fertilizers and combinations with HA enhanced yield and quality of flue-cured tobacco in three ecological regions, and their positive effects were different in the three regions. Suitable N fertilizer forms were amide-N in Longxian, but combined-N with ratio of amide∶ammonium∶nitrate 1∶1∶1 in Luonan, and nitrate-N in Xunyang. The effects of N fertilizers combined with HA in Longxian and Luonan were greater than that of a single N application, and similar effects were obtained in Xunyang. It is suggested that different suitable N fertilizers should be applied in the various ecological regions, and N fertilizers combined with HA could more effectively promote growth and development, coordinated chemical components of tobacco leaf, and improved yield and quality of flue-cured tobacco than single N fertilizer in these ecological growing-tobacco regions.

Effects of different nitrogen forms on nutrient uptake, yield formation and quality of cabbage

NIU Zhen-ming, ZHANG Guo-bin, LIU Zhao-fan, JIA Hao-yu, YU Ji-hua

2013, 22(6):  68-76.  DOI: 10.11686/cyxb20130609

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This study determined the effects of different nitrogen forms on nutrient uptake,yield formation, and quality of spring cabbage (Brassica oleracea var. capitata). A field experiment was conducted at Yuzhong (104°12′ E, 35°85′ N), China in 2012, where eight different N forms and various ratios of different N forms were applied to the crop in a completely randomized block design with three replicates. The results showed that the application of NO₃^--N∶NH₄⁺-N in 3∶7 was conducive to the improvement of the stem diameter of cabbage. The fertilization with single NH₄⁺-N could increase the numbers of leaves. The use of NH₄⁺-N improved the content of N and use of NO₃^--N improved the content of K, but the P content varied with N sources in different organs of cabbage. Cabbage supplied with the ratios of NO₃^--N∶NH₄⁺-N ranging from 3∶7 to 7∶3 was conducive to improve the contents of nitrogen, phosphorus and potassium in leaves, head and roots of cabbage, and could improve photosynthesis of leaves. Compared with single nitrogen fertilizer forms, the combined application of NH₄⁺-N and NO₃^--N could obviously improve the yield of cabbage. The application of NO₃^--N: NH₄⁺-N ranging from 3∶7 to 5∶5 had the better effect on increasing yield, and the ratio of NO₃^--N∶NH₄⁺-N 5∶5 was the best. The fertilization with single NO₃^--N increased the accumulation of nitrate, and reduced Vc content in cabbage. Cabbage supplied with the ratios of NO₃^--N∶NH₄⁺-N ranging from 3∶7 to 7∶3 reduced the accumulation of nitrate and increased the content of soluble sugars, and the application of NO₃^--N∶NH₄⁺-N in 5∶5 had the best results. The application of (NH₂)₂CO-N or NH₄⁺-N was conducive to the improvement of Vc content in the leaves of cabbage. We concluded that the ratios of NO₃^--N∶NH₄⁺-N ranging from 3∶7 to 7∶3 significantly improved the yield and quality of cabbage, and the application of NO₃^--N∶NH₄⁺-N in 5∶5 had best effect.

Effect and mechanisms of soil cadmium stress on Dianthus chinensis seedling growth

DING Ji-jun, PAN Yuan-zhi,LIU Shi-liang, HE Yang, WANG Li, LI Li

2013, 22(6):  77-87.  DOI: 10.11686/cyxb20130610

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The toxicity mechanisms of soil heavy metal cadmium (Cd) were investigated on seedling growth of Dianthus chinensis and its ascorbic acid-glutathione (AsA-GSH) cycle using concentrations of (0, 0.3, 1, 3, 10, 30 and 50 mg/kg Cd) in the soil in a greenhouse pot experiment. Seedling tiller number, height and biomass exhibited significantly ‘low promoting/suppression’ phenomena. This was because the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), and some other antioxidant enzymes increased gradually against increased reactive oxygen species in seedling leaves at low concentrations of soil Cd and at the beginning of the stress. With an increase in Cd concentration and prolonged stress time, the activities of SOD, APX, MDAR, DHAR and GR decreased. This led to the accumulation of excessive reactive oxygen species that could not be removed in an effective way, thus resulting in an outbreak of the superoxide anion (O₂^-·), hydrogen peroxide (H₂O₂), and some other reactive oxygen species, eventually causing membrane lipid peroxidation and stress damage. This work also demonstrated that APX was an important enzyme for H₂O₂ removal, and GR was an important enzyme to generate GSH. It was the main way to renew AsA in the AsA-GSH cycle and restore MDAR to MDHAR.

Effect of sod cultivation on mineralization of soil organic carbon in nectarine orchards

WANG Yi-xiang, WANG Feng, WENG Bo-qi, HUANG Yi-bin, WANG Cheng-ji, YE Jing

2013, 22(6):  86-92.  DOI: 10.11686/cyxb20130611

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The red soil located at Yuchi village, Fujian province, was sampled to investigate the effect of sod culture on mineralization of soil organic carbon (SOC) using laboratory incubation and field measurements. There was a similar diurnal fluctuation in soil respiration rate under the treatments of sod culture and clean tillage. In addition, there were highly significant correlations between soil respiration and soil temperature, C/N, and significant correlations between soil respiration and soil moisture, humic acid (HA), fulvic acid (FA), HA/FA values and total SOC. The average soil mineralization rate under sod cultivation treatment was 22.890 mg/(kg·d), was increased by 62.13％ and 33.83％ compared with those under longitudinal clean tillage and landings clean tillage treatments, respectively. When compared with those under the longitudinal clean tillage and landings clean tillage, soil respiration rate, potential mineralizable SOC (C₀), easily mineralizable SOC content (C₁) and initial potential mineralization rate (C₀k) under sod culture treatment were significantly higher, showing that sod cultivation in orchards can increase soil respiration and soil organic carbon turnover, and be conducive to the transformation of soil carbon and nitrogen and the improvement of soil fertility. It also showed that there was no significant increase in the ratio of C₀ to SOC in sod cultivation compared with the clean tillage treatments. This suggests that orchard sod cultivation is also conducive to the accumulation of organic carbon in the soil.

A study on the shade tolerance of Lauraceae obtusiloba

LIU Qing-chao, LIU Qing-hua, MA Zong-xiang, WANG Kui-ling

2013, 22(6):  93-99.  DOI: 10.11686/cyxb20130612

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The plant morphogenesis and photosynthetic characteristics of potted Lauraceae obtusiloba were studied under different shade treatments. Fifty percent shading improved the growth and accelerated the morphological building of L. obtusiloba, and the synthetical evaluation of the growth index reached 0.91. Under natural sunlight and 95% shading, the growth indexes were 0.29 and 0.20 respectively. Under different shading treatments, the total chlorophyll content, chlorophyll a content and chlorophyll a/b showed significant differences, but there was no obvious linear relationship with light intensity. The chlorophyll b content increased gradually with the extent of shading. Under different shading treatments, the diurnal change curves of Pn varied significantly, but there was no significant linear relationship with the biomass. With adequate illumination, the diurnal change curve of Pn showed double peaks, and the photosynthesis had a significant midday depression. The light compensation point of L. obtusiloba was 12.98 μmol/(m²·s), the light saturation point was about 200-400 μmol/(m²·s), and the apparent quantum efficiency was 0.0366 mol/mol, which showed the capability of L. obtusiloba to use weak light.

A comparison of photosynthesis responses to light of four Elymus species

QI Juan, SHI Shang-li, XU Chang-lin, YAN Wei-hong, ZHANG Xiao-jiao

2013, 22(6):  100-107.  DOI: 10.11686/cyxb20130613

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The net photosynthetic rate (P_n), transpiration rate (T_r), water use efficiency (WUE), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and vapor pressure deficit (V_pdl) of four Elymus species were determined under simulated photosynthetic radiation (SPR) and the apparent quantum yield (AQY), light saturation point (LSP) and light compensation point (LCP) were calculated. The P_n and T_r increased with an increase in SPR in all four species. Under the same light intensity, E. tangutorum had the highest P_n of the four species, while E. dahuricus was medium, and the other two species had almost the same P_n. The T_r of E. tangutorum and E. excelsus were significantly higher than those of E. sibiricus and E. dahuricus. The WUE also increased with an increase in SPR, and the order of WUE for the species was E. sibiricus＞E. dahuricus＞E. tangutorum＞E. excelsus. The G_s increased with an increased SPR. The G_s of E. tangutorum and E. dahuricus were significantly higher than those of the other two species. The C_i decreased with increases in SPR and P_n. The V_pdl first dropped with an SPR increase from 0 to 500 μmol/(m² · s), and except for E. dahuricus, the other two species then showed an increase in the V_pdl with an SPR increase. Overall, the V_pdl of E. tangutorum and E. excelsus were significantly higher than those of the other two species. In addition, E. sibiricus and E. tangutorum had lower LCPs than the other species, indicating their higher ability to use light under low-light conditions. Both E. tangutorum and E. dahuricus had a high LSP among, showing their better ability to use strong light. In conclusion, E. tangutorum and E. dahuricus had a relatively higher capacity for light utilization than E. sibiricus and E. excelsus; that is, they had higher photosynthetic efficiency whether under high or low-light conditions.

Effect of extended exposure to NaCl stress on the growth, ion distribution and photosynthetic characteristics of malting barley (Hordeum vulgare)

LI Xian-ting, CAO Jing, WEI Xiao-juan, DONG Li-ping, DAI Li-lan

2013, 22(6):  108-116.  DOI: 10.11686/cyxb20130614

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The adaptation mechanism of malting barley (Hordeum vulgare) growth response and ion distribution elicited by extended exposure to NaCl stress were investigated by simulating the formation process of soil salinisation in arid and semi-arid irrigated regions. The objective was to provide the theoretical basis for increasing the yield of malting barley and rationally employing the salt-affected arable land in irrigated agricultural systems. Seedlings of malting barley were treated by adding NaCl to the growth medium to gradually increase the concentration in 17.1 mmol/L increment every week during the vegetative period until a concentration of 154.9 mmol/L was reached. Nine harvests (7 d after treatment) were analysed to examine plant growth, root growth parameters, ion contents, and photosynthetic characteristics. The growth rate of barley seedlings was inhibited by extended exposure to NaCl. Under salinity stress the shoot biomass and height decreased significantly in comparison with the control, but the root biomass and root/shoot ratio increased significantly with extended exposure to NaCl. In addition, root length increased at lower salt concentrations with a short incubation period. At higher NaCl concentrations (≥85.5 mmol/L NaCl), salt stress seriously inhibited the growth of the seedlings and the water content of malting barley was seriously decreased. Furthermore, with an increase in salt stress level, photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and transpiration rate (T_r) were significantly reduced. This was strongly dependent on the appearance of non-stomatal limitation to photosynthetic characteristics imposed by long-term induced salinity stress. Under extended exposure to NaCl stress, Na⁺ and Cl^- content in shoots increased significantly, whereas in roots, Na⁺ content increased but Cl^- content decreased with the extension of incubation days. Compared with the controls, the K⁺/Na⁺ in shoots significantly decreased as NaCl concentration increased. Malting barley accumulated much more Na⁺ in shoots by selectively absorbing K⁺ under intense salt stress. The selective absorption and transportation of K⁺ were the key adaptive mechanism of high salt-tolerance of malting barley.

Effects of a potato/maize intercropping system on physiological characteristics and total yield with two potato varieties at different row ratios

HUANG Cheng-jian, ZHAO Si-yi, WANG Ji-chun, WANG Long-chang, ZHAO Yong, CAI Ye-mao, TENG Yan, YANG Guo-cai

2013, 22(6):  117-128.  DOI: 10.11686/cyxb20130615

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The intercropping of potato (Solanum tuberosum) and maize (Zea mays) is a traditional cropping pattern in southwest China. Potato/maize intercropping trials were carried out to determine the dynamic changes of photosynthetical active radiation (PAR), soluble protein content (SPC), proline content (Pro), malondialdehyde content (MDA), superoxide dismutase (SOD), peroxide dismutase (POD), and catalase activities (CAT) from the tuber initiation stage to the tuber expansion stage. The yield was also studied using monocropped potato as the control. Two potato varieties: Zhongshu 5 (early-maturing variety with erect branches) and Mira (mid-late maturing variety with spread branches)were employed as well as two potato to maize ratios. The ratio 2∶2 meant two rows of potato to two rows of maize and 3∶2 meant three rows of potato to two rows of maize. Gradual decreases in PAR and SPC were observed from the tuber initiation stage to tuber expansion stages in both Zhongshu 5 and Mira. However, there were gradual increases in Pro, MDA, CAT and a decrease in SOD in Zhongshu 5 but decreases in MDA, CAT and a similar SOD activity in Mira. POD activity in Zhongshu 5 and Pro and POD activity in Mira had different trends due to row ratios. In addition, intercropping led to lower SPC and higher Pro, SOD and POD in the two potato varieties. Lower PAR, higher MDA, and lower CAT at the tuber initiation stage and higher CAT at the tuber expansion stage in Zhongshu 5 were also detected, as was a higher PAR and lower MDA and CAT in Mira compared with the monocropped plants. Moreover, higher PAR and CAT in the 3∶2 intercropping system than in the 2∶2 intercropping system were observed, as well as a similar SPC. Other parameters changed differently due to growth stages. Nonetheless, intercropping reduced the light environment in the Zhongshu 5/maize system but improved it in the Mira/maize system. A better light environment was found in the 3∶2 than in the 2∶2 systems. Mira was more tolerant to shade than Zhongshu 5 while both Mira and Zhongshu 5 were more tolerant to shade in the 3∶2 combination than in the 2∶2 one. In summary, a varied light environment in intercropping led to substantial changes in physiological characteristics of potato and a reduction in tuber yield at harvest. LERs were 0.88 and 1.00 in the 2∶2 intercropping potato/maize system for Zhongshu 5 and Mira, respectively, while it was 1.24 and 1.40 in the 3∶2 system. It is suggested that there is no intercropping advantage in a 2∶2 potato/maize system but an obvious advantage in the 3∶2 system with better production in the latter.

A study on the filling dynamics and germination characteristics of Gentiana straminea

MI Yong-wei, CHEN Yuan, GUO Feng-xia, YANG Yu-feng, CHEN Xiang

2013, 22(6):  129-135.  DOI: 10.11686/cyxb20130616

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Flowers were labeled with cards on flower-blossom days of Gentiana straminea plants cultivated in Zhuoni county, Gannan prefecture, Gansu. The seed weight and germination in capsules of the plants were measured once every three days after flower-blossom. Filling dynamics and germination characteristics of the plant seeds were studied to provide a theoretical and technical basis for determining the best time to harvest seeds. The fresh weight increased and reached its maximum on the 34th day following blossom, and then rapidly decreased to a level near its dry weight. This fitted a Logistic equation with a rapid increase during 13-34 d after blossom and finished changing on the 60th day. The grain filling rate showed a ‘slow-fast-slow’ pattern with two slow times because of rain. The seeds dehydrated increasingly faster as filling duration increased and the water content decreased to the end of this process. The seed germination rate was highest 43 d after blossom and showed a relatively stable value with prolonged filling, except for rain and cloudy conditions. The germination quality indicators were significantly and positively related to the grain dry weight and the seed filling duration respectively, and were positively related to the seed dehydration rate but negatively related to the water content in the seeds. All the above revealed that the seed filling process was mostly affected by weather and seed maturity affected the germination quality. The best harvest time should be 52-55 d after blossom (early-middle September), during which time the water content in seeds should be about 10% and the plants showing non-dissilient capsules. The seeds should be picked by stages with cloth or nylon bags on sunny days.

Research on allelopathy of aqueous extract from Astragalus strictus

HU Yuan-bin, CHEN Jun, XIAO Tian-hao, HU Tian-ming, XU Yue-fei

2013, 22(6):  136-142.  DOI: 10.11686/cyxb20130617

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Aboveground parts of Astragalus strictus distributed in the Tibet autonomous region, was used to prepare aqueous extracts to test the allelopathic effects on Avena sativa, Amaranthus retroflexus, Trifolium repens and Capsella bursa-pastoris using Petridishs with filter papers. Allelopathic effects of aqueous extract were tested on seed germination, root length, seedling height and fresh weight of four species of Astragalus. The malondialdehyde (MDA) content, and the activities of superoxide dismutase (SOD), and peroxidase (POD) of A. sativa and T. repens were investigated to reveal the allelopathic potential of A. strictus, and thereby to provide a theoretical basis for further development and use of A. strictus resources. The aqueous extract inhibited seed germination and seedling growth of A. sativa, and the inhibition was enhanced with an increase in extract concentration. Seed germination of A. retroflexus, T. repens and C. bursa-pastoris were also inhibited by the aqueous extract, and the effects on seedling growth presented an obvious ‘concentration effect’, promoting growth at the lower concentrations and inhibiting growth at the higher ones. A. retroflexus seed germination was inhibited completely when the aqueous extract concentration was 100 mg/mL. The activities of SOD, POD and MDA contents of A. sativa and T. repens were affected by different concentrations of aqueous extract. SOD, POD activities and MDA content markedly increased at 50 mg/mL aqueous extract, whereas at 100 mg/mL, the extract increased MDA content and reduced the enzyme activity in the seedlings of A. sativa and T. repens. Therefore, A. strictus shows a great allelopathic potential.

Utilization of harvested aquatic plants as a mulch

YU Hong-bing, ZHANG Shu-nan, XIAO Run-lin, YANG Zhi-jian, LIU Feng, WEI Jia-bin

2013, 22(6):  143-149.  DOI: 10.11686/cyxb20130618

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Aquatic plants not only absorb a lot of nitrogen and phosphorus pollutants, but after harvest they may also be used for nutrient mulching, recycling utilization and ground cover in tea plantations. 1) A covering of aquatic plants in tea plantations could improve the physical and chemical properties of the soil. It increased the contents of organic material, total nitrogen, total phosphorus, alkali-hydro nitrogen and available phosphorus in the 0-20 cm soil layer, and, increased the contents of soil microbial biomass nitrogen and phosphorus. The soil nutrient declined with an increase in depth. 2) A covering of aquatic plants in the tea plantation could prevent the domination by weed species by significantly reducing weed density and biomass, thus reducing the competition between weeds and tea trees. 3) A covering of aquatic plants in the tea plantation could improve the growing and ecological conditions of tea gardens and promote the quality and production of tea.

Screening, identification and solubilizing properties of the endophytic phosphate-solubilizingbacteria isolated from Anaphalis lactea

LI Zhen-dong, CHEN Xiu-rong, YANG Cheng-de, LI Peng

2013, 22(6):  150-158.  DOI: 10.11686/cyxb20130619

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To screen and identify endophytic phosphate-solubilizing bacteria, endophytic bacteria were isolated from Anaphalis lacteal, the dominant grass of the alpine grasslands in the Eastern Qilian Mountains. They were screened using Pikovaskaia’s culture medium (PKO), and identified by physiological and biochemical tests and 16S rDNA analysis. How the endophytic phosphate-solubilizing bacteria affect the growth of corn was also studied. Four endophytic phosphate-solubilizing bacterial strains were isolated on media with phosphate (P₂O₅) contents between 65.24 and 315.36 mg/L. Isolate RA8 had the highest phosphate-solubilizing capacity and was identified as Paracoccus sp. on the basis of morphological, physiological, and biochemical characteristics, and on phylogenetic analysis of the 16S rDNA gene sequence. RA8 can produce acid, but the phosphate (P₂O₅) content had no correlation with the pH value of the culture media. It was the non-acid metabolic substances of RA8 that played a role in the mechanism of dissolving phosphate. RA8 can cooperate with indigenous microorganisms in the soil, and as a result, RA8 has a strong phosphate-solubilizing capacity in the soil. The plant biomass of the corn treated with RA8 was significantly (P<0.05) higher than that of the control at the 70th day and 100th day, and the plant height of the corn treated with RA8 was significantly (P<0.01) higher than that of the control at the 100th day showing that RA8 can significantly promote the growth of corn.

Canonical correlations between pests and natural enemies and their niches in alfalfa grasslands

ZHU Meng-meng, LIU Yan, ZHANG Rong, HUANG Wen-guang

2013, 22(6):  159-166.  DOI: 10.11686/cyxb20130620

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Alfalfa is an important forage in Northwest China but in recent years, several pests have seriously damaged alfalfa. To monitor the dynamics of pest populations, two typical regions in which alfalfa is the dominant crop were selected. The five-spot method was used to sample pests and natural enemies in alfalfa fields. The community structure of insects was stable with an increase in age of alfalfa crops. The relationships between pests and natural enemies in two monitoring sites were fitted with four equations: V₁=0.532X₁+0.326X₂+0.035X₃, W₁=0.108Y₁+0.482Y₂+0.035Y₃-0.113Y₄, V₁=0.356X₁-0.163X₂+0.008X₃, W₁=0.063Y₁+0.526Y₂+0.103Y₃-0.038Y₄. In addition, natural enemies played an important role in controlling pest population in these alfalfa fields. Sucking insects (aphids) had a high abundance but were attacked by a large number of natural enemies in alfalfa fields. Leaf eating pests, root pests, and flower eating pests had the potential to cause great damage to alfalfa grasslands, because of lack of natural enemies. Natural enemies had wider niches than pests, indicating that natural enemies needed to search for prey on a large spatial scale. Ladybirds were the dominant natural enemy, and had a similar niche to pest aphids. This work supplied an important basis and theory for integrating pest management and sustainable development of the alfalfa industry.

A study on the mode of action against Mythimna seperata of Hypecoum leptocarpum extracts obtained with different solvents

ZHANG Jun-xia, YANG Xiao-hua, YANG Shun-yi, ZHANG Xin-hu, SHEN Hui-min

2013, 22(6):  167-172.  DOI: 10.11686/cyxb20130621

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Hypecoum leptocarpum was used as a source of extracts to test insecticidal activity against Mythimna seperata. Two extraction methods (constant temperature oscillation method and Soxhlet extraction method) and four solvents (ethanol, methanol, hexane, dichloromethane) were used to study the mode of action of eight kinds of extracts on M. seperata. Ethanol and Soxhlet extraction method were the best insecticidal solvent and extraction method respectively. The eight kinds of extracts of H. leptocarpum showed strong antifeedant and growth inhibition effects on the 3 instar larvae of M. seperata and after 24 and 48 h feeding, the inhibition rates were above 70%, and with the ethanol extract were up to 90.78%. The four kinds of solvent extracts inhibited growth and development of M. seperata. The inhibition rates at 24 h after treatment were 74.1%-91.45%, and the ethanol extracts at 48 h after treatment was 87.00% with a final pupation rate of 23.33%. The growth rate was slow, and the progress of growth and development of M. seperata was delayed. The eight kinds of extracts had weak stomach and contact toxicity. The ethanol extract of 48 h contact and stomach poison was the highest, and the correction mortality was 33.33% and 23.30% respectively. The anti-feeding component of the H. leptocarpum extracts was mainly concentrated in the aboveground plant parts.

Insecticidal activity of ethyl acetate extract from dry buds on dark condition and flowers of Solanum tuberosum

GUO Zhi-jie, HU Guan-fang, LIU Min-yan, NIU Shu-jun, YU Hai-tao, ZHANG Xin-hu

2013, 22(6):  173-181.  DOI: 10.11686/cyxb20130622

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Insecticidal activities on buds and flowers of Solanum tuberosum were not reported at home and abroad. Study on insecticidal activities and action ways of extracts from dry buds on dark condition and flowers of S. tuberosum against Mythimna separate can provide clue and theoretical basis for formulating new type of botanical insecticide. The thesis conducted insecticidal activity of ethyl acetate extracts from dry buds on dark condition and flowers of S. tuberosum (Zhuangshu 3) by immersion and sandwich methods. The results showed that ethyl acetate extracts from dry buds and flowers had very strong contact toxicity against 5th instar larva of M. separate, the corrected mortality were 52.0% and 61.36%, respectively when the extracts were diluted 5 times. The extracts had very strong developmental inhibition action against the 3rd instar larva, developmental inhibition rates of 1, 2, 3, 4, 5 and 6 d after treatment were 100% and 100%, 76.92% and 61.54%, 66.67% and 59.26%, 70.27% and 45.95%, 72.55% and 49.02%, 67.12% and 35.62%, respectively. The extracts had very strong anaesthesia action against the larva, anaesthesia rate were 68.0% and 66.0% in one hour, regression equation were Y=2.0542+3.1331X and Y=3.0114+2.3334X, RT₅₀ were 8.71 and 7.12 h. The extracts had very strong contact toxicity against larvae of Plutella xylostella, Pieris rapae, Artogeia brassicae and Pontia daplidice, corrected mortality were 75.0% and 58.33%, 87.50% and 95.0%, 100% and 93.33%, 100% and 100% (diluted 5 times, 4 times to P. xylostella ), respectively. The extracts also had very strong contact toxicity against Lipaphis erysimi with corrected mortality of 98.52% and 97.79% (diluted 30 times).

Effect of a high-concentrate diet on the distribution and redistribution of amino acids in liver and on milk protein of lactating goats

YE Ping-sheng, JIANG Xue-yuan, ZHANG Shu-kun, NI Ying-dong, ZHUANG Su, ZHANG Yuan-shu, SHEN Xiang-zhen

2013, 22(6):  182-189.  DOI: 10.11686/cyxb20130623

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This study explored the effects and probable mechanisms of distribution and redistribution of amino acids in liver of lactating goats fed with different concentrates of forage diet. Six lactating goats fitted with hepatic vascular fistulas were used and they were randomly divided into two groups, in a 2×2 Latin square experiment design with different concentrates to forage ratios of 40∶60 (the control group) and 60∶40 (the high-concentrate group). The experimental interval was 16 weeks. Milk samples were collected and assayed by measuring milk protein content, and plasma samples, including hepatic portal vein, hepatic vein and femoral artery. They were collected via the hepatic vascular fistulas and the contents of free amino acids in plasma were analysed by RP-HPLC. The milk protein content in the high-concentrate group was significantly (P<0.05) lower than that in the low-concentrate group. However, the hepatic portal vein plasma free amino acids content was higher but the contents of hepatic vein and femoral artery plasma free amino acids were lower in the high-concentrate group compared with the low-concentrate group. Thus in the high-concentrate group, the consumption of free amino acids in the liver was more than that in the low-concentrate group, and the content of available free amino acid which transferred into mammary tissue via the femoral artery was less than that in the low-concentrate group. This indicated that long-time feeding with a high-concentrate diet could reduce the milk protein content. Furthermore, it explained that the mechanism of influencing milk protein synthesis was an alteration in concentrations of available free amino acids associated with distribution and redistribution of amino acids in the liver. The amino acids expended in the liver reduced the contents of the mammary gland available amino acids, which are used to synthesize milk protein.

Effect of alfalfa hay substituting for part of the concentrate, on the production of cows and economic profit

LIU Yan-na,SHI Ying-hua, YAN Xue-bing, WANG Cheng-zhang, LIANG Ming-gen, ZHOU Lu

2013, 22(6):  190-197.  DOI: 10.11686/cyxb20130624

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The effect of alfalfa (Medicago sativa) hay substituting for part of the concentrate on production performance, milk quality of dairy cows and economic profit was studied. Twenty-four multiparous Holstein lactation cows in mid lactation with similar body weights and milk production were selected and randomly divided into four groups. The diet for the control group included corn silage, peanut vine and concentrate, and in the test groups A, B and C, 3 kg alfalfa hay were used to substitute for 1.5, 2.0 and 3.0 kg concentrate, respectively, in 70 days of a feeding trial. The milk yield of the test groups was significantly (P<0.01) higher than that of the control group and milk yield of group A was significantly (P<0.05) higher than those of groups B and C, while there was no significant difference in milk yield between groups B and C. There were significant (P<0.05) differences between test groups and the control group in milk protein with groups B and C significantly (P<0.05) higher than group A. Compared with those of the control group, fat percentage (P<0.01), lactose and dry matter (P<0.05) of the test groups were significantly increased, but the differences were not significant between the three test groups. Dry matter intake of group A was the highest, and that of groups A and B were significantly (P<0.01) higher than group C and the control group, although, the difference was not significant between group C and the control group. Compared with that of the control group, somatic cell count of the test groups was reduced, but the differences between the four groups were not significant. The apparent digestibility of crude protein (P<0.05) and neutral detergent fiber (P<0.01) of groups B and C were significantly higher than those of the control group, but the difference was not significant between group A and the control group. At 7.92 yuan/days, the profit of group A was the greatest. This research has shown that substituting 3 kg alfalfa hay in concentrate can improve the milk yield, the quality of milk and the profit. Three kg alfalfa hay substituting for 1.5 kg concentrate is recommended.

A study on the burrow features and functions of plateau pika

WEI Wan-rong, ZHANG Ling-fei, YANG Guo-rong, XU Ji-wei, FAN Xu-dong, ZHANG Wei-guo

2013, 22(6):  198-204.  DOI: 10.11686/cyxb20130625

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A field investigation used 900 holes of pika burrows in alpine meadow grassland in Gannan Maqu county to study the burrow features of plateau pika, including hole number, location, orientation, pattern, burrow structure. The dark side, semidark side, sunny side of hole orientation of plateau pika showed extremely significant differences. There was no correlation between diameter and orientation of the holes. Holes with less than a 55° angle were mainly concentrated in the SW, SE and S directions and accounted for 48.6% of the total number of holes. Holes with a greater angle than 55° were mainly focused in NW, NE and N directions and accounted for 52.1% of the holes. The hole temperature in the south and partial south was higher than that in north and partial north with a 13.2℃ difference. The hole temperature in the west and partial west was higher than that in the east and partial east with about a 6.0℃ difference. The tunnel structure features of plateau pika were consequences of adaptive selection to the plateau circumstances. Considering the advantages and disadvantages of the temperatures inside holes, air convection and cold wave resistance, habitat exclusion and risk avoidance are fundamental functions of burrow orientation.

Acquirement of self-compatible somatic mutants induced by colchicine in Paspalum vaginatum

ZHONG Xiao-xian, LIU Zhi-wei, CHANG Pan-pan, WU Juan-zhi, ZHANG Jian-li

2013, 22(6):  205-212.  DOI: 10.11686/cyxb20130626

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Seashore paspalum plays an important role in grassland systems in saline soil because of its strong salinity tolerance and other multiple stress resistance and high quality performance. P. vaginatum is a self-incompatible, sexual diploid. Cross-fertilization is difficult because its genome (D) is different from that of most other Paspalum species. P. vaginatum cv. adalayd was induced with colchicine in callus subculture medium, and embryogenic calli were obtained from immature inflorescences in order to explore the possibility of creating self-compatible somatic mutants. One thousand nine hundred and sixty plantlets from treatments with 250, 500, 1000, 1500, and 2000 mg/L colchicine for 24, 48, and 72 h on callus, and six hundred and eighty eight plantlets from the control were obtained. Characteristics of seed set from regenerated plants indicated that four seeds and three seeds were harvested from two different plants from treatments with 1000 mg/L colchicine for 24 h, and one seed from the treatment with 500 mg/L colchicine for 24 h. One seed per plot from three different plants of M₁ generation were sown, and every seed germinated. The three plants from seeds were named as SP2008-1, SP2008-2, and SP2008-3. Two hundred fifty three, thirty eight, and forty five self-compatible seeds from SP2008-1, SP2008-2, and SP2008-3 respectively were harvested, and weights per one thousand seeds were 0.471, 0.440, and 0.496 g respectively. The somatic chromosome number was 2n=20 in SP2008-1 and SP2008-2 and both were diploid. Somatic chromosome number 2n=20 was 86.7%, and somatic chromosome number 2n=40 was 13.3% in SP2008-3. SP2008-3 was a chimera mixed with diploid and tetraploid. RAPD analysis confirmed that SP2008-1, SP2008-2 and SP2008-3 plants were different from control adalayd plants at the molecular leve1. Two self-compatible diploids and one chimera with diploid and tetraploid somatic mutants were created using P. vaginatum cv. Adalayd callus induced with colchicine.

Analysis on genetic diversity of germplasm resources of switchgrass (Panicum virgatum) as shown by ISSR

ZHANG Yu, HUANG Lin-kai, ZHANG Xin-quan, JIANG Xiao-mei, YANG Sheng-ting, NIE Gang, YAN Hai-dong

2013, 22(6):  213-221.  DOI: 10.11686/cyxb20130627

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The inter-simple sequence repeat (ISSR) method was used to study the genetic diversity and genetic structure of 138 switchgrass accessions to provide information on how to improve the utilization of switchgrass germplasms. 1) Sixteen primers were selected from 100 ISSR primers, and a total of 220 bands were amplified. Of these bands, 196 were polymorphic (89.09%) and the average number was 13.75 per primer. 2) POPGENE analysis showed that the average information index of Shannon (I) was 0.3880 and gene diversity of Nei (H) was 0.2498, indicating a rich genetic diversity of switchgrass germplasm resources. 3) Analysis of AMOVA showed genetic variance within an ecotype was larger than that between ecotypes, while the genetic variance within an ecotype and between ecotypes was 56.60% and 43.40%, respectively. 4) Using NTsys-pc V2.1 software, the 138 accessions were clustered into two groups (lowland and upland ecotypes) by UPGMA clustering and principal component analysis (PCA) with the similarity coefficient ranging from 0.4000 to 0.8818 (average of 0.7237). In the upland ecotype, six subgroups were distinguished. Some cultivars and populations could not be grouped according to their pedigrees or collection area.

Over-expression vector construction and genetic transformation of a protein kinase NtCIPK2 from Nitraria tangutorum

ZHENG Lin-lin, WANG Jia, HE Long-mei, WANG Xue-feng, WANG Ying-chun

2013, 22(6):  223-229.  DOI: 10.11686/cyxb20130628

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Adverse environmental factors such as salinity, drought and cold limit the growth and productivity of Medicago sativa, the most economically important forage legume worldwide. In this study, the complete coding sequence of NtCIPK2 was cloned from a halophyte Nitraria tangutorum, ligated into a pMD-19T simple vector and bi-directionally sequenced. The CDS of NtCIPK2 was 1362 bp and was identical with a NtCIPK2 gene in GenBank (accession number KC823044). This fragment was inserted into the plant transformation vector pPZP221 under the control of the cauliflower mosaic virus (CaMV) 35S promoter, and then the recombinant vector pPZP221-NtCIPK2 was transferred to Agrobacterium tumefaciens strain GV3101 by the CaCl₂ freeze-thaw method. Hypocotyls of M. sativa were transformed with GV3101 cells harboring pPZP221-NtCIPK2 by co-cultivation. Seven seedlings were obtained after callus induction and gentamycin selection. Then the seedlings were sampled to detect the gentamycin-resistant gene aacC1 by PCR and target gene NtCIPK2 by reverse transcription-PCR analysis. PCR detection indicated that NtCIPK2 was integrated into the Medicago genome in all seedlings. However, RT-PCR detection suggested that NtCIPK2 was overly expressed at the transcriptional level in three seedlings, and gene silencing might be occurring in some seedlings due to the difference in insertion sites of the exogenous gene. A solid foundation for further study of the performance and genetic stability of transformed plants and advanced breeding of Medicago varieties with strong resistance to abiotic stresses is offered.

Cloning and analysis of sequence characteristics of cDNA encoding the AtHKT1 gene from Arabidopsis thaliana leaves

WANG Li^1,2,3, ZHANG Jun-lian, ZHANG Jin-wen, LIU Yu-hui, Bai Jiang-ping, YU Bin, YANG Hong-yu, WANG Di

2013, 22(6):  230-238.  DOI: 10.11686/cyxb20130629

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The full length coding sequence of AtHKT1 was cloned via RT-PCR (reverse transcription-polymerase chain reaction) from the leaves of Arabidopsis thaliana seedling under NaCl stress. The full-length cDNA contained 1521 bp and encoded a polypeptide of 506 amino acids and a termination codon. The sequence shared 99.34% homology with the reported sequence (accession number AF237672), but the homologies were very low compared with similar genes from other plants. The gene was submitted to GenBank and was given the registration number AY685182. Bioinformatics softwares were used to predict and analyze the protein function and structure of the AtHKT1 gene cDNA sequence. The molecular weight of the deduced polypeptide of AtHKT1 was 57.45 kD. The theoretical pI was 9.33. The N-terminal amino acids from 1 to 40 formed a classic signal peptide sequence. The peptide from 152 to 500 was a Trk H cation transporter conserved domain. It might also carry protein kinase C, tyrosine kinase, cAMP-and cGMP-dependent protein kinase phosphorylation, glycosylation, N-myristoylation sites and other function sites. The deduced peptide contained 10 transmembrane domains. The transmembrane domains near the N-terminus, the C-terminus and the middle part of the peptide displayed high hydrophobicity. Therefore, it is suggested that the gene product of AtHKT1 might play roles in facilitating cation transportation.

Changes in the dominant pathogens causing Fusarium dry rot of potato in rhizospheric soil under continuous potato cropping systems based on real-time quantitative PCR

LI Rui-qin, LIU Xing, QIU Hui-zhen, ZHANG Wen-ming, ZHANG Chun-hong, WANG Di, ZHANG Jun-lian, SHEN Qi-rong

2013, 22(6):  239-248.  DOI: 10.11686/cyxb20130630

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The relationship between continuous cropping obstacles and accumulation of pathogens in rhizospheric soil was evaluated, and the mechanisms of continuous potato cropping obstacles explored, using an optimized SYBR Green I dye real time fluorescent quantitative PCR approach. The methods were used to perform quick checks and quantification of Fusarium sambucim and F. solani in soils infested with potato Fusarium dry rot disease and to investigate the dynamic changing trends of F. sambucim and F. solani in rhizospheric soil of continuously cropped potato. The concentration of primers was 0.4 μL (10 mmol/L), of DNA template was 3 μL, and the annealing temperature was 60℃. With an increase in years of continuous cropping potato, the numbers of F. solani and F. sambucim in rhizospheric soil showed an upward trend. The largest amount (1.45×10⁴ copies/g) of F. solani accumulated during the squaring period of five years and it increased 27.8 times compared with the control group (CK). F. solani cumulants CP4, CP3, CP2, CP1 were more than those of RP and increased by 11.4, 35.5, 6.9 and 2.8 times respectively. The largest amount of F. sambucim cumulants (2.21×10⁴ copies/g) was also during the squaring period of five years and compared to the CK they increased 25.0 times. The F. sambucim cumulants CP4, CP3, CP2, CP1 were more than those of the CK and increased by 10.5, 16.31, 8.32 and 3.51 times respectively. Accumulation of rhizospheric Fusarium may be one of the main reasons for the occurrence of obstacles to continuous potato cropping.

Effect of alfalfa flavonoids on reproductive performance of female rats in pregnancy and on gene expression in the hypothalamus-pituitary-ovarian gonadal axis

WANG Wei, TIAN Miao-miao, LIANG Xin-ping, ZHAN Hong-rui, WANG Cheng-zhang, YAN Xue-bing

2013, 22(6):  249-256.  DOI: 10.11686/cyxb20130631

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This study aimed to elucidate the effects of alfalfa flavonoids on reproductive performance, reproductive organs, hormone level, and gene expression in the hypothalamus-pituitary-ovarian gonadal axis in pregnant animals. Three doses of alfalfa flavonoids (120, 400 and 1200 mg/kg) and two control groups (diethylstilbestrol 0.5 mg/kg, blank control group) were used. The middle and high doses of alfalfa flavonoids significantly (P<0.05) increased the level of estradiol (E2) (P<0.05), while the low dose of alfalfa flavonoids highly significantly (P<0.01) increased the level of E2. There was no evident difference of progesterone level between the groups. The number of live fetus significantly (P<0.05) increased in three doses of alfalfa flavonoids, the weight of live fetus was highly significantly (P<0.01) increased with the high dose of alfalfa flavonoids. There was no evident difference in the number of luteum although there was a declining trend. Moreover, compared with control group, diethylstilbestrol, reduced the number of luteum. Compared with the control group, the three doses of alfalfa flavonoids significantly (P<0.05) increased the litter size, and the newborn litter weight increase was highly significant (P<0.01). Expressions of GnRH in the hypothalamus and FSH in the pituitary were highly significantly (P<0.01) reduced by alfalfa flavonoids and diethylstilbestrol. The expression of FSHR in the ovaries was reduced by the high dose of alfalfa flavonoids, but the expression of LHR was increased. The expressions of other genes showed no significant difference compared with the control group. In conclusion, the reproductive performance of rats was improved, because the alfalfa flavonoids influenced the hypothalamus-pituitary-ovarian gonadal axis.

Multiple statistical analysis of the phenotypic characters of Cichorium intybus

LIANG Xiao-yu, ZHANG Xin-quan, BAI Shi-qie, JI Yang, HUANG Lin-kai, ZHOU Kai

2013, 22(6):  257-267.  DOI: 10.11686/cyxb20130632

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Based on the variation coefficient, correlation analysis, cluster analysis and principal component analysis of 80 chicory (Cichorium intybus) materials from different origins, the phenotypic characteristics variations were analysed for an explaination of their geographical origins. There was wide variance of phenotypic characters among the different chicory germplasm resources. The third grade fertile tillers had the most significant variance coefficient of 31.11%. There were significant correlations among morphological characteristics. Chicory with a wide leaf was from tall plants with many strong reproductive branches but fewer single flowers. Clustering analysis showed that the materials could be divided into three groups with similar phenotypes: narrow leaved creeping type, mid-wide leaved erect type, and wide leaved erect type. The principal coordinate analysis indicated that the differences between chicory materials were derived from leaf size, plant height, flower number, and reproductive flower diameter.

Assessing cold resistance of mutagenic strains of perennial ryegrass under artificial low-temperature stress

ZHAI Fei-fei, HAN Lei, LIU Jun-xiang, QIAN Yong-qiang, JU Guan-sheng, LI Wei, ZHANG Shao-wei, SUN Zhen-yuan

2013, 22(6):  268-279.  DOI: 10.11686/cyxb20130633

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In order to evaluate the cold resistance of mutagenic lines of perennial ryegrass and obtain more cold resistance perennial ryegrasses, we studied the physiological and biochemical responses of perennial ryegrasses under low temperature (above zero) treatment, and the materials of this experiment are five mutagenic lines-G3-2, G10-5, G16-1, CK9-3, CK14-3 and one variety with good cold resistance-‘Pinnacle’. The results of this study show that, in the process of cold acclimation, the leaf water content decrease: G16-1’s leaf water content decreases by up to 3.12%. Relative membrane permeability increases and malondialdehyde accumulates: CK14-3 has the lowest relative membrane permeability, which is 25.40%; while CK9-3 accumulates the lowest malondialdehyde content, which is 38.06 μmol/g. The osmotic regulation substances increase: CK14-3 and ‘Pinnacle’ have lower proline content with 0.18% and 0.15% respectively; G16-1’s solute protein content increases by 83.08%, which is the largest; ‘Pinnacle’s solute sugar content is the lowest increaseing by 34.18%, and CK9-3 takes the second place with 53.41%; the reducing sugar content of G10-5 and G16-1 weigh against ‘Pinnacle’ with 9.01% and 9.79% separately. The antioxidant enzymes are enhanced, the superoxide dismutase activity and catalase activity of CK14-3 are lower, with5171.21 U/(g·h) and 171.04 U/(g·min) respectively, but the changing rate are quicker with 169.07% and 47.06% respectively. As to potential photochemical efficiency, G3-2 and G16-1 decreases by 3.46% and 3.44% separately, which are small. By principal component analysis and membership function calculating, the cold-resistance ranking of the experiment materials is ‘Pinnacle’, G16-1, CK9-3, G10-5, CK14-3, G3-2 from strong to weak. The experiment materials are classified into three types: ‘Pinnacle’’s cold-tolerance is strong, G16-1, CK9-3, G10-5 and CK14-3’s are medium and G3-2’s is poor. Considering the results, we find that the more cold-resistance the perennial ryegrass is, the less relative membrane permeability it has; the less leaf water content, malondialdehyde content, proline content and reducing sugar content it have, the quicker the soluble protein content, superoxide dismutase and catalase activities change, the slower solute sugar content and potential photochemical efficiency change.

Study on the simulation methods of grassland soil organic carbon: a review

REN Ji-zhou, LIN Hui-long

2013, 22(6):  280-294.  DOI: 10.11686/cyxb20130634

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Grassland soils are considered to have great potential for carbon sequestration. It is an essential part and also one of the biggest challenges to detect the soil organic carbon storages of global grassland ecosystem for regulating the global carbon cycle. This paper reviewed the research progress on soil organic carbon stocks of grassland ecosystem, and analyzed the main technical features of the existing models for simulating soil organic carbon. The existing technical weakness of the models, especially involving data accuracy, model structure and function formulization, are inquired in detail with relevant suggestions for improvement provided. The integrated use of sample inventory, remote sensing analysis, and simulating models would be the fundamental way to solve this problem. Finally, a framework of the Classification Indices-based Model on grassland soil organic carbon was presented based on the comprehensive sequential classification system of grassland (CSCS). Coupling the sample inventory and the Classification Indices-based Model with the high spatial and temporal resolution characteristic of remote sensing, the accuracy of the estimating grassland soil organic carbon will be improved greatly among the different grassland classes, ecological or climatic zones. There is no absolute conflict between the capacity of grassland soil carbon sink and grazing utilization, and precise estimation of grassland soil organic carbon is a premise of the grazing modern transformation.

Research progress on molecular regulation mechanisms in bulbous plants at dormancy

LIU Fang, WANG Jia-yan, ZHOU Yun-wei

2013, 22(6):  295-304.  DOI: 10.11686/cyxb20130635

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The main factor of dormancy induction in bulbs is the repression of DNA activation. A series of cell genes and proteins are activated during dormancy breaking, Using Arabidopsis, poplar, and potato as model plants it has been found that the systems of endogenous hormone balance and their levels regulate the processes of dormancy, and that carbohydrates are continually transformed in the bulbs. The degradation of starch provides materials and energy. Dormancy characteristics can be delayed or brought forward using genetic engineering. Recent research progress on inducing dormancy and on dormancy breaking in bulbous plants are summarized in this review and the prospects for further research on bulb dormancy are discussed.

Pollen release mechanisms of papilionaceous plants (Faboideae)

HUANG Li-chun, JIN Liang, ZHANG Shu-zhen, LI Jing, YANG Yang, ZHANG Xiao-qiang, WANG Xiao-juan

2013, 22(6):  305-314.  DOI: 10.11686/cyxb20130636

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Pollen is the foundation of plant reproduction, and successful release of pollen is essential for plant reproduction. Due to the complexity and the diversity of the process of pollen release in papilionaceous plants, the picture of the physiological and the mechanical mechanisms in pollen release is still incomplete. In this paper, the mechanism of pollen release in papilionceous plants is reviewed. The pollen release in papilionceous plants is a complex process, which includes a physiological process (internal release) and a mechanical (or physical) process (extrinsic release). The physiological process of pollen release includes anther formation and anther dehiscence. The formation of viable pollen depends on accurate execution of developmental programmes, and the tapetum cells are essential for the development of the pollen grain. In the case of anther dehiscence, four types of anther wall have been observed in papilionaceous plants including basic type, monocotyledonous type, dicotyledonous type and reduced type. The mechanical process of pollen release shows that there are four patterns in papilionaceous plants: the explosive model, piston model, brush model, and valvular model. Comparisons of pollination efficiency made between these models, showed that the piston and valvular models may be the two basic evolutionary branches of pollen release in papilionaceous plants. The spatial and temporal patterns of pollen release are still a hotspot of evolution in papilionaceous plants and are related to flower morphology, pollination biology and mating system.

A comparison of salt resistance of three kinds of Zoysia at different salt concentrations

XUE Xiu-dong, DONG Xiao-ying, DUAN Yan-xin, LI Pei-huan, WANG Bin

2013, 22(6):  315-311.  DOI: 10.11686/cyxb20130637

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To determine the difference in salinity resistance of Zoysia species, Z. macrostachya, Z. metrella and Z. japonica were used to study the effects on leaf protective enzymes (POD, SOD, CAT), MDA, proline, chlorophyll, and soluble protein content under different salinity treatments (0, 0.20%, 0.40%, 0.60% and 0.80%) after a 40 days incubation. As the salt concentration increased, the changes in activities of leaf protective enzymes and the proline content increased. At 0.80% salt concentration, leaf protective enzymes of Z. macrostachya had higher activity and lower MDA and proline contents. At lower salt concentrations (<0.40%), as the salt concentration increased, the total chlorophyll content and the soluble protein content of all Zoysia species increased, while they decreased at higher concentrations (>0.60%). At 0.80% salt concentration, the total chlorophyll and soluble protein contents of Z. macrostachya were higher, and the decline was smaller than in the other Zoysia species. This showed that Z. macrostachya had the highest salt resistance of the three Zoysia species.

Formation mechanism and community characteristics of fenced grassland in desert steppe

XIAO Xu-pei, SONG Nai-ping, XIE Teng-teng, FANG Kai

2013, 22(6):  321-327.  DOI: 10.11686/cyxb20130638

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The community characteristics and soil moisture of 9-year fenced grassland in Yanchi county were studied. Vegetation community characteristics of the fenced grassland had high heterogeneity and presented a mosaic distribution of three plant communities (Stipa bungeana+Agropyron mongolicum, Pennisetum centrasiaticum, and Leymus secalinus). Soil moisture was the key impact factor for vegetation growth in fenced grassland, and soil moisture influenced the community characteristics to different degrees. The soil moisture had great influence on the biomass, vegetation height and coverage, but had little influence on the species richness. The community spatial distribution pattern of fenced grassland was the main factor influencing community characteristics and the spatial variability of soil moisture of the three plant communities caused different vegetation growth within each plant community.

Influence of different weed populations on cotton yield in saline and alkaline land in Shandong

LI Mei, GAO Xing-xiang, LIU Shi-guo, BAI Xing-yong, GAO Zong-jun, FANG Feng, SUN Zuo-wen, ZHANG Bo-song

2013, 22(6):  328-334.  DOI: 10.11686/cyxb20130639

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Experiments on the influence of different weed populations on cotton yield were conducted in saline and alkaline land in Gaotang, Shandong Province, China in 2011 and 2012. There were four replicates of four treatments: weed free, grass weeds, broadleaf weeds and mixed weeds. The cotton varieties were Lumianyan 28 in 2011 and Lumianyan 37 in 2012. Cotton yield losses were 24.3% and 20.3% in grass weed plots (mainly Eleusine indica, Setaria viridis and Phragmites communis) at weed densities of 202.0 and 291.6 stem/m², and were 27.1% and 60.2% in broadleaf weed plots (mainly Chenopodium album, Portulaca oleracea and Eclipta prostrate) at densities of 230.5 and 122.2 stem/m² in 2011 and 2012 respectively. The yield loss was 37.5% in mixed weed plots (mainly C. album, E. indica and Echinochloa crusgalli) at 277.0 stem/m² in 2011, and was 68.4% (mainly C. album, P. oleracea and E. indica) at 201.0 stem/m² in 2012. The damage rate per stem caused by broadleaf weeds was higher than that caused by grass weeds. Weeds reduced the height of cotton plants, number of cotton bolls, boll branches and weight of bolls. The number of bolls per plant in weed free plots was 11.5 on average in both 2011 and 2012. The number decreased by 34.0% in 2011 and 72.0% in 2012 in mixed weed plots, 11.5% and 53.6% in broadleaf weed plots, 10.8% and 12.1% in grass weed plots. The height decreased by 0.4%-18.7% in weed plots compared with that in weed free plots. The number of boll branches decreased by 11.9%-18.0%, and the weight of bolls decreased by 6.3%-18.2%. In addition, weeds also reduced the survival rate of cotton seedlings by 0-3.6%. No effect was observed on ginning outturn and seed index. The influence of weed populations on cotton yield was closely related to weed species, density and biomass as well as to cotton variety and climatic factors.

Antibiosis of five alfalfa cultivars to two colour morphs of Acyrthosiphon pisum

JIN Juan, LIANG Jin, HE Chun-gui

2013, 22(6):  335-340.  DOI: 10.11686/cyxb20130640

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Five cultivars of alfalfa (Medicago sativa) were used to identify their antibiosis to two colour morphs of the pea aphid Acyrthosiphon pisum. Life tables were constructed at a constant temperature of 21-23℃, relative humidity of 50%-70%, and illumination time of 14 h per day. The antibiosis of the same alfalfa and of different alfalfa cultivars to the two colour morphs differed. Using the intrinsic rate of increase (R_m) as the index of alfalfa resistance to the aphid, the resistance of Russian Medicago varia (RM) to green aphid was stronger than to the pink aphid but the resistance of Algonquin (AL) to the pink aphid was stronger than to the green aphid, while G₅ showed a certain resistance to both colour morphs. The order of antibiosis of the different alfalfa cultivars to pink aphid was RM<SW<AL=G₃<G₅, and to the green aphid was AL<RM<SW= G₃<G₅.