林可-大观可溶性粉治疗雏鸡大肠杆菌和支原体人工混合感染试验

目的:观察国产盐酸林可霉素-硫酸大观霉素(Lincomycin Hydrochloride and Spectinomycin Sulfate)可溶性粉对鸡支原体和大肠杆菌混合感染所致雏鸡气囊病的治疗效果.方法:雏鸡气囊人工混合感染鸡毒支原体和大肠杆菌.结果:林可-大观可溶性粉按0.75～1.88g/l饮水治疗5 d,能有效地控制雏鸡大肠杆菌及支原体感染,降低感染鸡发病率、气囊病变指数、支原体抗体阳性率和死亡率;其效果与对照药物利高霉素100相近.     

Improvement of Rice Seedling Establishment in Sulfate-Applied Submerged Soil by Application of Molybdate

Abstract

Sulfide ion generation in strictly reduced soil might be a factor impairing rice seedling establishment. The molybdate ion is known to suppress the microbial transformation of sulfide ions from sulfate ions. I investigated the effect of molybdate on rice establishment in sulfate-applied submerged soil. The establishment of rice seeds sown in sulfate-applied submerged soil was markedly improved by application of potassium molybdate at a rate of 1.5?15 mmol kg-¹ dried soil. The application of potassium molybdate delayed the decline of the sulfur concentration in the soil solution near the seeds and the appearance of circular black stains, or insoluble iron sulfide indicating the generation of sulfide ion, around seeds in the soil. Irrespective of the application of molybdate, the redox potential near the seeds was low enough to allow generation of sulfide ions, implying that molybdate suppresses the generation of sulfide ions with no effect on redox potential. These results suggest that the application of molybdate could improve rice seedling establishment in sulfur-rich submerged soil by suppressing the generation of sulfide ions, that is a possible factor suppressing the establishment of rice seeds sown in sulfur-rich submerged soil.     

Ectomycorrhizal impacts on nutrient uptake pathways in woody roots

Ectomycorrhizae are a common symbiosis between the roots of woody plants and fungi common to the soil. That ectomycorrhizae can assist the plant partner in absorbing mineral nutrients has long been established. However, the impact of mycorrhizae on pathways available for soil nutrients to enter the root system is not clear. In particular, the impact of the fungal mantle, which surrounds the root tips, is most critical. In the present study, we assessed the permeability of the Pinus banksiana/Hebeloma cylindrosporum fungal mantle to both berberine and radioactive sulfate ions. It was found that the fungal mantle was completely impermeable to tracer dye. To test the permeability to sulfate ions, a novel technique called the internal perfusion technique was employed. By this method, permeability can be assessed. The fungal mantle proved to be impermeable to sulfate over a 24-hour exposure period. Based on recent findings pertaining to root anatomy, this result suggests that the plant may be highly dependent on the fungus to supply mineral nutrients as there is little plant tissue capable of nutrient absorption outside the fungal mantle.     

Factors affecting sulfate adsorption,organic sulfur formation,and mobilization in forest and grassland spodosols

Forest and grassland soils that contained varying amounts of Fe and Al were collected from England and Wales. Fractionation of free Fe and Al was accomplished to determine which components affected sulfate adsorption. Organic Fe and Al were the dominant fractions in most soil horizons and high amounts of these organically bound metals and, to some extent, crystalline Fe oxide were associated with high sulfate adsorption potentials. These adsorption potentials reflected naturally occurring amounts of absorbed sulfate and ester sulfate. Overall, the C content exhibited a positive relationship with sulfate adsorption potentials. Soils with a high C content also exhibited high rates of organic S formation. The rate of organic S mobilization was greater in soils with higher amounts of soluble sulfate. Organic S was the largest pool and, typically, sulfonate S was the most abundant constituent of the organic pool.     

镉硫交互处理对水稻吸收累积镉及其蛋白巯基含量的影响

研究了不同硫镉浓度组合短期处理 (6d)对水稻幼苗吸收累积镉的影响及其植株体内蛋白质和非巯基硫蛋白含量的变化。结果表明 ,短期单镉胁迫处理下 ,水稻幼苗的生物量没有明显变化 ,但是镉硫交互作用明显地影响镉在水稻苗中的累积。供硫处理能有效地增加镉在水稻叶片中的累积。不同镉、硫处理下植株体内缓冲液可提态蛋白质含量变化不明显。镉胁迫明显增加植株体内NPT含量 ,尤其是根中NPT的含量。供硫也能显著地提高NPT的含量。硫镉交互作用对植株体内NPT含量的影响更为明显。上述结果证实 ,介质中硫的充分供应在有效地提高植物对镉胁迫耐性的同时 ,也显著地促进镉在水稻地上部的积累。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

秃杉制浆造纸的研究

本文测定了秃杉的纤维形态和化学组成;研究了硫酸盐法蒸煮特性和强度性能;并采用模糊数学理论中的欧几里德贴近度法全面评价秃杉的制浆造纸适应性能。结果表明,秃杉可作为造纸用材。     

Abundance and community structure of sulfate reducing prokaryotes in a paddy soil of southern China under different fertilization regimes

Flooded rice paddy soils represent a typical anaerobic freshwater habitat of microorganisms. The abundance and community structure of sulfate reducing prokaryotes (SRP) were investigated in order to understand their response to different fertilization practices in rice paddy, including control without fertilizers (CT) and arrangements of different chemical fertilizers of nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK and NPK. The abundance of total bacteria and sulfate reducing prokaryotes of the rice paddy in summer and in winter were quantified by real-time PCR assays based on the 16S rRNA gene and the dissimilatory (bi)sulfite reductase gene (dsrAB) β-subunit. No significant differences in the bacterial and SRP abundance were observed among different fertilization treatments in both winter and summer. The mean copy numbers of bacteria was 7.26 × 10⁹ copies g⁻¹ dry soil in winter and 1.27 × 10¹⁰ copies g⁻¹ dry soil in summer. The average dsrAB gene copy numbers of the SRP was 5.08 × 10⁸ copies g⁻¹ dry soil in winter and 5.92 × 10⁸ copies g⁻¹ dry soil in summer. The dsrAB gene clone libraries of the five fertilization treatments were constructed and their RFLP analysis yielded 22-25 restriction patterns, suggesting a high degree of dsrAB sequence diversity in different fertilization treatments. There was no significant change in the soil SRP community structure among the different fertilization regimes. More than half of the sequences were affiliated with novel branching clusters which were uncultured SRP. Clostridia and Deltaproteobacteria were also found with a high proportion in the clone libraries, while Desulfovibrionaceae was absent. High proportion of novel uncultured SRP implies that they may play important roles in paddy soils and deserve further studies.     

采油废水中硫酸盐还原菌Fe(VI)杀灭试验

采油所产生的废水中产生的硫酸盐还原菌(SRB)可造成注水系统的腐蚀、结垢和阻塞,严重影响原油的开发与生产。以Fe(VI)作为氧化型杀菌剂杀灭SRB,试验结果表明:Fe(VI)对SRB具有很强的灭菌能力;Fe(VI)投加量C>10 mg/L时就能满足回注水的要求;适宜的接触反应时间为t>10 min;相应地有Ct>100 mg·min·L-1。