Leaf chlorophyll parameters and photosynthetic characteristic variations with stand age in a typical desert species (Haloxylon ammodendron).

As a desert shrub, Haloxylon ammodendron combines ecological, economic, and social benefits and plays an important role in the ecological conservation of arid desert areas. Understanding its physiological characteristics and its mechanism of light energy utilization is important for the conservation and utilization of H. ammodendron. Therefore, we selected five stands (5-, 11-, 22-, 34-, and 46-year-old) of H. ammodendron as research objects in the study and measured their photosynthetic light response curves by a portable open photosynthesis system (Li-6400) with a red-blue light source (6400-02B). Then, we measured the leaf chlorophyll parameters in the laboratory, calculated the photosynthetic characteristics by using Ye Zipiao's photosynthetic model, analyzed their variation patterns across stand ages, and explored the relationships between leaf chlorophyll parameters and photosynthetic characteristics. The results showed that leaf chlorophyll parameters and photosynthetic characteristics of H. ammodendron at different stand ages were significantly different. Chl content, P nmax, and LUEmax of H. ammodendron were V-shaped with the increase of stand age. The 5-year-old H. ammodendron was in the rapid growth period, synthesized more Chl a+b content (8.47 mg g-1) only by using a narrower range of light, and the Pnmax and LUEmax were the highest with values of 36.21 µmol m-2 s-1 and 0.0344, respectively. For the 22-year-old H. ammodendron, due to environmental stress, the values of Chl a+b content, P nmax, and LUEmax were the smallest and were 2.64 mg g-1, 25.73 µmol m-2 s-1, and 0.0264, respectively. For the older H. ammodendron, its Chl content, P nmax, and LUEmax were not significantly different and tended to stabilize but were slightly higher than those of the middle-aged H. ammodendron. On the other hand, the other photosynthetic parameters did not show significant variation patterns with stand age, such as R d, AQE, LSP, LCP, and I L-sat. In addition, we found that the relationships between Chl a+b content and P nmax and between Chl a+b content and LUEmax were highly correlated, except for the older H. ammodendron. Thus, using leaf chlorophyll content as a proxy for photosynthetic capacity and light use efficiency should be considered with caution. This work will provide a scientific reference for the sustainable management of desert ecosystems and vegetation restoration in sandy areas.

Physiological response to salinity stress and tolerance mechanics of Populus euphratica.

The salinity stress inhibits the growth of Populus euphratica (P. euphratica), and the extent of inhibition tends to increase with a rise of salt concentration while the net photosynthesis rate, stomatal conductance, transpiration rate, and internal CO2 concentration are seen to decline with increasing salt concentration. Compared with the control group, the percentage decline is found to be about 48.50, 15.72, 42.09, and 48.33%, respectively. Although all chlorophyll fluorescence of P. euphratica exhibits a typical O-J-I-P curve in differently concentrated salt solutions, salinity stress shows a significant influence on the value of J and I step (P < 0.05). However, salinity stress was seen to induce a decrease in variable fluorescence (Fv)/maximal fluorescence value by 2.32, 8.78, 12.80, 12.93, 16.46, and 19.63% treated by 50-, 100-, 150-, 200-, 250-, and 300-mM salt solution compared with the control group, respectively. Salinity stress appeared also to induce a decrease in Fv/minimal fluorescence values by a magnitude of 5.22, 16.02, 18.06, 22.95, 26.34, and 32.19% in P. euphratica treated by 50-, 100-, 150-, 200-, 250-, and 300-mM salt solution relative to the control group, respectively. An increase in the content of malondialdehyde amounted to 4.12, 25.59, 34.60, 68.11, 70.72, and 67.68% in P. euphratica treated by 50-, 100-, 150-, 200-, 250-, and 300-mM salt solution compared to the control group, respectively. In terms of the content of proline, the salinity stress induced an increase by 4.94, 29.49, 53.20, 77.65, 82.46, and 90.68% in P. euphratica treated by 50-, 100-, 150-, 200-, 250-, and 300-mM salt solution, respectively.

Spatial Variations of Soil Microbial Activities in Saline Groundwater-Irrigated Soil Ecosystem.

Spatial variations of soil microbial activities and its relationship with environmental factors are very important for estimating regional soil ecosystem function. Based on field samplings in a typical saline groundwater-irrigated region, spatial variations of soil microbial metabolic activities were investigated. Combined with groundwater quality analysis, the relationship between microbial activities and water salinity was also studied. The results demonstrated that moderate spatial heterogeneity of soil microbial activities presented under the total dissolved solids (TDS) of groundwater ranging from 0.23 to 12.24 g L(-1). Groundwater salinity and microbial activities had almost opposite distribution characteristics: slight saline water was mainly distributed in west Baqu and south Quanshan, while severe saline and briny water were dominant in east Baqu and west Huqu; however, total AWCD was higher in the east-center and southwest of Baqu and east Huqu, while it was lower in east Baqu and northwest Huqu. The results of correlation analyses demonstrated that high-salinity groundwater irrigation had significantly adverse effects on soil microbial activities. Major ions Ca(2+), Mg(2+), Cl(-), and SO4(2-) in groundwater decisively influenced the results. Three carbon sources, carbohydrates, amines, and phenols, which had minor utilization rates in all irrigation districts, were extremely significantly affected by high-salinity groundwater irrigation. The results presented here offer an approach for diagnosing regional soil ecosystem function changes under saline water irrigation.

[Spatial heterogeneity of plant community species diversity in Ejina Oasis at the lower reaches of Heihe River].

By the method of geostatistics, this paper studied the spatial heterogeneity of plant community species diversity in Ejina Oasis at the lower reaches of Heihe River. In the study area, the Margalef richness index (Ma), Simpson diversity index (Ds), Shannon diversity index (H') and Pielou evenness index (J') were in normal distribution, and the coefficient of variation (CV) ranged from 55.8% to 67.8%, suggesting a moderate variability. The Ma and H' were accorded with exponential models, and the Ds and J' were accorded with spherical models. The H' had the highest extent of spatial variation, followed by Ma, J' and Ds. Within the variable range, the structural factors in the spatial variation of Ma, Ds, H', and J' were dominant, ranging from 81.1% to 93.0%. The indices changed obviously parallel to the river, with significantly high values near Dalaihubu Town (42 degrees N, 101 degrees E), and obviously low values within the strips 100 degrees-101 degrees E and 102 degrees-102 degrees 30' E, mainly including east and west Gobi and the hinterland of Badain Jaran Desert.

[Analysis of the spatial and temporal changes in soil CO2 efflux and its related factors from alpine meadow in Qilian Mountains].

Continuous field experiment was carried out on alpine meadow along different elevation gradient in Qilian Mountains during the growing season of 2004 using a soil respiration chamber (Li-6400-09) connected to a portable photosynthesis system (Li-6400). The possible effect of water-heat factors and root parameter on characteristics of alpine meadow soil respiration was statistically analyzed. The results indicate that soil CO2 efflux has apparent spatial variation laws. Spatial variation patterns of soil respiration from different alpine meadow along elevation gradient are gradually decreased and its coefficient of variation increases gently. The curves of day change of soil CO2 efflux have a simple peak value, and it is low at night, with lowest at 02:00-06:00, and starts to rise rapidly during 07:00-08:30, and then descends during 16:00 -18:30. The peak CO2 efflux appears during 11:00-16:00. The diurnal average of soil CO2 efflux is between (0.56 +/- 0.32) - (2.53 +/- 0.76) micromol x (m2 x s)(-1). As for seasonal variation, soil CO2 fluxes of various are relatively high in summer and autumn but relatively low in spring and winter. The maximum of average soil CO2 efflux occurrs in July and August [4.736 micromol (m2 x s)(-1), and the second is in June and September, and the third is in May and October. Soil CO2 efflux of alpine meadow during growth season is positively correlated with soil temperature, root biomass and soil water content at depths of 10 cm to different degrees. These results indicate that the temperature, soil moisture and root biomass have great effects on the spatial variation of soil CO2 efflux in the area.

[Some medical staff positive for serum SARS coronavirus antibody IgG have only mild symptoms].

OBJECTIVE: To identify patients with SARS coronavirus infection who have only mild symptoms. METHOD: Enzyme-linked immunosorbent assay was employed to detect serum antibody against SARS coronavirus in the lysate of whole SARS coronavirus from 19 SARS patients and 200 medical staff members without obvious SARS symptoms after possible exposure to the virus during routine medical practice. RESULTS: Serum IgG antibody against SARS coronavirus was detected in all the 19 SARS patients, and among the 200 staff members, 20 (10%) were found positive for the antibody but with no obvious or only mild symptoms. CONCLUSION: Serum IgG antibody against SARS coronavirus is positive in a small proportion (around 10%) of the medical staff members exposed to the virus in our hospital, but may not cause obvious symptoms, suggesting SARS coronavirus infection might in some cases have mild or even no clinical manifestations.

[Development and application of a new hepatitis C virus genotyping method with polymerase chain reaction-reverse blot dot technique].

OBJECTIVE: Using polymerase chain reaction-reverse blot dot (PCR-RDB) technique to establish a new method for hepatitis C virus (HCV) genotyping and to study the distribution of HCV genotypes in Foshan area. METHODS: HCV primers and probes were designed in 5'-untranslated region (nt-1-nt-299) of HCV. HCV RNA in serum was isolated and purified, and its cDNA was obtained by reversed transcription. Nested PCR using biotin-labelled primers, was done. PCR products were hybridized with immobilized specific probes (genotype 1a to 3b) on Biodyne C membrane to genotype HCV by color development while adding POD and TMB. A certain judgment could be made according to the position of color reaction. The reliability of this new method was verified by sequencing. HCV RNA levels in serum were determined by real time fluorescent quantitative (FQ)-PCR. 60 FQ-PCR-positive HCV sera from Foshan area were genotyped using this assay. RESULTS: All 60 sera could be successfully genotyped by PCR-RBD. 50 (83.3%) cases were found to be genotype 1b, 2 (3.3%) as genotype 1a and 2 (3.3%) as genotype 2a while 5 (8.0%) to be mixture of genotype 1a and 1b, and 1 (1.7%) to be mixture of genotypes 1b and 2a. No genotypes 2b, 3a and 3b were found. The results of PCR-RDB genotyping methods coincided with sequence analysis. CONCLUSION: Newly established HCV genotyping system was proved to be sensitive, specific, precise and economic, thus suitable for clinical and epidemiologic studies. The results of HCV genotyping showed that genotype 1b was the predominant genotype in Foshan area.

[Establishment of a new HBV genotyping method with PCR-RBD and its application].

OBJECTIVE: Using PCR-RDB to establish a new method for HBV genotyping, and to survey the distribution of HBV genotypes in the Foshan area. METHODS: Biotin-labeled primers for amplification of HBV region X (nt1550-1789) were used to amplify extracted HBV DNA. HBV was genotyped by hybridization of the PCR products with immobilized specific probes (genotype A to F) on C membrane. Color development was achieved by adding POD and TMB. A judgment was made according to color reactions. The reliability of this new method was verified by gene sequencing. 300 samples of HBV DNA-positive sera from the Foshan area were genotyped using this assay. RESULTS: Of the 300 sera genotyped by PCR-RBD, 147 (49.0%) cases were genotype B, 136 (45.3%) were genotype C, 1 (0.3%) genotype D, and 12 (4.0%) were mixtures of genotype B and C, and 4 (1.3%) were mixtures of genotype C and D. No genotype A, E or F were found. The results of PCR-RDB genotyping were consistent with the results obtained with sequence analysis. CONCLUSION: This newly established HBV genotyping system proved to be sensitive, specific, precise and economic, and should be suitable for clinical practice and epidemic study. The results of HBV genotyping show that genotype B and C are the predominant genotypes in the Foshan area.

[Farm compost polluted water may induce pharyngo-esophageal, gastric and liver carcinoma in the chicken].

OBJECTIVE: To study farm compost polluted water that may induce pharyngo-esophageal, gastric and liver carcinoma in chickens. METHODS: 280 chickens were randomized into 4 groups: experiment group 100 chickens fed with compost water + NaNO(2) by stomach tube. The other 180 were evenly randomized into 3 control groups (60 each), fed with compost water, NaNO(2) and tap water in the same way. The farm compost was prepared with corn stalks, rice straws, excreta of men and livestock. The compost water, after being nitrosified and acidified, was fed through stomach tube 5 - 7.5 ml/session, twice a week. Besides, a solution consisting of the respective formula of each group added with 3 - 4 L water with pH adjusted to 3 - 4 by 1N HCL was given ad lib to all chickens in each group for 26.5 months. RESULTS: In the experiment group, there were pharyngo-esophageal carcinoma 16 (16.3%), gastric adenocarcinoma 5 (10.4%) and liver carcinoma 3 (6.3%), in contrast to none in the 3 control groups, showing significant differences (P < 0.01, P < 0.01, P < 0.05). CONCLUSION: Successful simulation of the layout of esophageal carcinoma high morbidity area and the mimic of chicken gastric fluid strongly support our compost etiological hypothesis that the nitrosified and acidified compost water are carcinogenic, very well causing esophageal, gastric and liver carcinoma.