Nutrient allocation might affect the cadmium accumulation of Bermuda grass (Cynodon dactylon).

Hydroponic experiments with different cadmium (Cd) concentrations were conducted to explore the impacts of nutrient allocation on the Cd enrichment of Bermuda grass. The results demonstrated with the Cd concentration increase, the accumulation of nitrogen (N), phosphorus (P) and potassium (K) in roots, stems and leaves increased first and then decreased, while the accumulation of Cd had no significant difference. The biomass and N, P and K accumulation of CD1 and CD2 were significantly different from those of CD3 and CD4, but there was no significant difference in Cd accumulation. The root N, P and K distribution ratio of CD4 increased by 47.9%, 114.3% and 64.3% compared with those of CD2 treatment, the values of stem decreased by 29.4%, 22.4% and 17.2%, and the values of leaves increased by 15.8%, 19.8% and 23.6% respectively. The K ratio of root and leaf increased and that of stem decreased. Cd reduced N and K distribution ratio of stem and increased N and K distribution ratio of root and leaf. Pearson correlation analysis showed that the accumulation of N, P and K in stems was positively correlated with the accumulation of Cd in stems, and the accumulation of N, P and K in roots, stems and leaves were positively correlated with the Cd accumulation in leaves. Bermuda grass can schedule the nutrient allocation to adapt to the Cd absorption and enrichment in different organs under different Cd concentrations. In conclusion, nutrient allocation might affect the Cd accumulation of Bermuda grass.

Soil nutrient heterogeneity affects the accumulation and transfer of cadmium in Bermuda grass (Cynodon dactylon (L.) pers.).

There have been no studies demonstrating the correlation between soil nutrient heterogeneity and cadmium (Cd) absorption of Bermudagrass. In this study, a pot experiment was carried out to study the correlation between them. The purpose is to find soil nutrient factors which are conducive to improving the Cd absorption and translocation. The eighth group had the largest total number of surviving plants, the highest Fv/Fo value (3.24) and the best growth characteristics. The fifth group had the lowest total number of surviving plants, Fv/Fo (2.47) and the worst growth. The Cd content of the fifth group (36.11 mg kg-1) was close to the eighth group (35.72 mg kg-1), but the two groups had significant differences in plant height, stem node length and stem node number (P < 0.05). The eighth group showed the highest contents of nitrate nitrogen (NO3--N), available potassium and urease activity. The fifth group showed the lowest NO3--N content, but the highest ammonium nitrogen (NH4+-N) and available phosphorus content. There was significant difference of the Cd bioconcentration factors (BCF) and translocation factor (TCF) between the fifth and the eighth group although they had the similar total soil Cd content (P < 0.05). The fifth group had the highest BCF and TCF. RDA analysis indicated the BCF and TCF were positively correlated with soil NH4+-N and available phosphorus and negatively correlated with soil NO3--N. The results demonstrated that soil NH4+-N and available phosphorus were important soil ecological factors to enhance Cd absorption and translocation of bermudagrass.

Spatial and temporal characteristics of soil conservation service in the area of the upper and middle of the Yellow River, China.

Soil erosion is an important environmental problem in the area of the upper and middle of the Yellow River (AUMYR), China, one of the most severe soil erosion areas in the world. It is significantly influences on the ecological security and sustainable development of the region. Soil conservation (SC) service, as one of the most important regulating services provided by ecosystems, can alter soil and water processes and improve ecosystem services that ensure human welfare. Investigations of spatial and temporal characteristics of SC service play important roles in soil erosion control and ecosystem protection in AUMYR. In the past several years, restoration projects (e.g. the Grain-for-Green project) were implemented to improve SC in most of AUMYR. It is needed to evaluate the change of SC service brought about by the projects. This study carries out quantitative spatial analysis of SC services through Universal Soil Loss Equation (USLE) model and geographic information system (GIS) manipulation based on various datasets, such as remote sensing image, digital elevation model (DEM), climate, and land use/cover maps. Soil retention calculated as potential soil erosion (erosion without vegetation cover) minus actual soil erosion was applied as indicator for SC service. The results are like these. (1) The total amount and mean capacity of SC service in AUMYR were 7.22 billion t/a and 142.2 t/hm2·a in 2000 and 10.19 billion t/a and 200.8 t/hm2·a in 2010, respectively. South-east AUMYR exhibited a much higher capacity of soil retaining than the north-west. (2) Forest ecosystems displayed higher SC capacity than other types of ecosystems. Moreover, the SC capacity of ecosystems increased with the increasing of slope gradient. (3) Variations of SC rate (the ratio of SC to potential soil erosion in percentage) in different units (ecosystem, slope zone and city) were relatively small and ca. 90% of potentially eroded soil was retained in AUMYR. (4) The spatial characteristics of SC service in AUMYR were primarily controlled by topography at the regional scale. Vegetation cover restoration significantly improved the capacity of SC service in AUMYR in the midst year of 2000 and 2010. The results revealed that ecological restoration efforts significantly enhanced SC service of ecosystem in the study area.

Evaluation of the potential effect of transgenic rice expressing Cry1Ab on the hematology and enzyme activity in organs of female Swiss rats.

To assess the safety of transgenic rice expressing Cry1Ab protein to vertebrates, the effect of Cry1Ab rice on broad health indicators in blood and various organs of Swiss rats were analyzed. The 30 and 90 day safety studies of Cry1Ab rice on female Swiss rats revealed that Cry1Ab rice had no significant effect on the several elements of blood lymph including hemogram, calcium ion concentration and apoptosis rate of lymphocytes, indicating that Cry1Ab protein could not affect the blood lymph of Swiss rat. Similarly, Cry1Ab rice had no effect on enzyme activities in a variety of organs of Swiss rat. However, Cry1Ab rice did have significant effects on the blood biochemistry indexes including urea, triglyceride (TG), glutamic oxalacetic transaminase (AST) and alkaline phosphatase (ALP) after the rats were fed with Cry1Ab rice for 30 days, but not after 90 days, indicating that Cry1Ab protein may influence blood metabolism for a short duration. Quantitative real-time PCR (qPCR) analysis of the 6 genes encoding enzymes responsible for the major detoxification functions of liver revealed that Cry1Ab rice exerted no influences on the levels of these transcripts in liver of Swiss rat, indicating that significant differences registered in part of the blood biochemical parameters in the 30 day study might result from other untested organs or tissues in response to the stress of exogenous Cry1Ab protein. The results suggest that Cry1Ab protein has no significant long-term (90 day) effects on female Swiss rat.

The negative effects of cadmium on Bermuda grass growth might be offset by submergence.

Revegetation in the water-level-fluctuation zone (WLFZ) could stabilize riverbanks, maintain local biodiversity, and improve reservoir water quality in the Three Gorges Reservoir Region (TGRR). However, submergence and cadmium (Cd) may seriously affect the survival of transplantations. Bermuda grass (Cynodon dactylon) is a stoloniferous and rhizomatous prostrate weed displaying high growth rate. A previous study has demonstrated that Bermuda grass can tolerate deep submergence and Cd stress, respectively. In the present study, we further analyzed physiological responses of Bermuda grass induced by Cd-and-submergence stress. The ultimate goal was to explore the possibility of using Bermuda grass for revegetation in the WLFZ of China's TGRR and other riparian areas. The Cd-and-submergence-treated plants had higher malondialdehyde contents and peroxidase than control, and both increased with the Cd concentration increase. All treated plants catalase activity increased with the experimental duration increases, and their superoxide dismutase also gradually increased with the Cd concentration from 1 day to 15 days. Total biomass of the same Cd-and-submergence plants increased along the experimental duration as well. Plants exposed to Cd-and-submergence stress showed shoot elongation. The heights of all treated plants were taller than those of the control. Leaf chlorophyll contents, maximum leaf length, and soluble sugars contents of all the Cd-and-submergence-treated plants were more than those of the untreated control. Although Cd inhibits plants growth, decreases chlorophyll and biomass content, and with the submergence induced the leaf and shoot elongation, more part of the Cd-and-submergence stress plants appeared in the air, exhibited fast growth with maintenance of leaf color, which guaranteed the plants' photosynthesis, and ensured the total biomass and carbohydrate sustainability, further promoting Cd-and-submergence tolerance. The results imply that the negative effects of cadmium on Bermuda grass growth might be offset by submergence.

Rare earth elements tracing the soil erosion processes on slope surface under natural rainfall.

A field experiment using rare earth elements (REEs) as tracers was conducted to investigate soil erosion processes on slope surfaces during rainfall events. A plot of 10m×2m×0.16m with a gradient of 20° (36.4%) was established and the plot was divided into two layers and four segments. Various REE tracers were applied to the different layers and segments to determine sediment dynamics under natural rainfall. Results indicated that sheet erosion accounted for more than 90% of total erosion when the rainfall amount and density was not large enough to generate concentrated flows. Sediment source changed in different sections on the slope surface, and the primary sediment source area tended to move upslope as erosion progressed. In rill erosion, sediment discharge mainly originated from the toe-slope and moved upwards as erosion intensified. The results obtained from this study suggest that multi-REE tracer technique is valuable in understanding the erosion processes and determining sediment sources.