Search

Growth redundancy, the overgrowth of resource-foraging organs in crop stands, is often detrimental to yield and is thus called a 'tragedy of the commons'. A tragedy can also arise owing to the plastic overproduction of competitive structures when intra-variety individuals forage in close proximity to each other. However, little is known about the sensitivity of crop varieties and resource availability to this 'plastic' tragedy. Pot experiments were designed to investigate this issue. The root competition environment was imposed by growing two plants of the same variety in mesh and plastic partitions. Two wheat varieties (old Monkhead and modern 92-46) were used, and two resource levels were established. Compared with 92-46, Monkhead allocated more biomass to stems and leaves and concurrently less to seeds. We identified intra-variety neighbour effects only in 4 out of 24 allometric comparisons with a small magnitude. Allometric data also revealed a lowered response to fertilizer addition in 92-46 than in Monkhead. Based on a limited sample size, our results revealed a trade-off between above-ground vegetative growth and crop yield. This trade-off resulted in a tragedy of the commons in old Monkhead and enhanced yields in modern 92-46. The tragedy of the commons in wheat may generally arise from genetically fixed traits in terms of growth redundancy in old varieties, rather than from the plastic behaviour of individuals. Modern 92-46 may adopt a conservative strategy of resource use, whereas old Monkhead employs an exploitative strategy. Our findings highlight breeders should select genotypes with low individual competitiveness. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) has been proven to effectively immobilize Cd2+ and Pb2+ using a single bacterium. However, there is an urgent need for studies of Cd2+ and Pb2+ immobilized by a bacterial consortium. In this study, a stable consortium designated JZ1 was isolated from soil that was contaminated with cadmium and lead, and the dominant genus Sporosarcina (99.1%) was found to have carbonate mineralization function. The results showed that 91.52% and 99.38% of Cd2+ and Pb2+ were mineralized by the consortium JZ1 with 5 g/L CaCl2 at an initial concentration of 5 mg/L Cd2+ and 150 mg/L Pb2+, respectively. The bioprecipitates were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Moreover, the kinetic studies indicated that the urea hydrolysis reaction fit well with the Michaelis–Menten equation, and the kinetic parameters Km and Vmax were estimated to be 38.69 mM and 58.98 mM/h, respectively. When the concentration of urea increased from 0.1 to 0.3 M, the mineralization rate increased by 1.58-fold. This study can provide a novel microbial resource for the biomineralization of Cd and Pb in soil and water environments. [ABSTRACT FROM AUTHOR]

This paper presents the development of the wideband power amplifier (PA) for application to intelligent cognitive radios. The load-tracking based on the frequency-varied load-pull technique is proposed for the PA design. The load impedance tracking is realized by filter network synthesis. A 3-7.5-GHz broadband PA is demonstrated in 0.15-[micro]m InGaAs pseudomorphic HEMT technology. Operated at 3.5 V, the [P.sub.1 dB] and power-added efficiency of the PA are better than 21.4 dBm and 20%, respectively. Index Terms--Cognitive radio (CR), frequency agile, load-tracking, power amplifier (PA), pseudomorphic HEMT (pHEMT), software-defined radio (SDR), wideband.

Surface soil samples collected from Nansi Lake catchment were analyzed for mercury (Hg) to determine its spatial trends and environmental impacts. Results showed that the average soil Hg contents were 0.043 mg kg. A positive correlation was shown between TOC and soil Hg contents. The main type of soil with higher TOC contents and lower pH values showed higher soil Hg contents. Soil TOC contents and CV values were both higher in the eastern catchment. The eastern part of the catchment, where the industry is developed, had relatively high soil Hg contents and a banding distribution of high Hg contents was corresponded with the southwest-northeast economic belt. Urban soils had higher Hg contents than rural soils. The urbanization pattern that soil Hg contents presented a decreasing trend from city center to suburb was shown clearly especially in the three cities. Soil Hg contents in Jining City showed a good consistency with the urban land expansion. The spatial trends of soil Hg contents in the catchment indicated that the type and the intensity of human activities have a strong influence on the distribution of Hg in soils. Calculated risk indices showed that the western part of the catchment presented moderately polluted condition and the eastern part of the catchment showed moderate to strong pollution level. The area with high ecological risk appeared mainly along the economic belt. [ABSTRACT FROM AUTHOR]