Heavy metal contamination of soils and crops from auto traffic,sewage sludge,pig manure and chemical fertilizer

The present paper describes heavy metal contamination of soils and crops resulting from auto traffic, sewage sludge, pig manure and chemical fertilizers, in three separate experiments.The first experiment revealed that although the ADDT (average annual daily traffic) value of the Agricultural Area was lower, higher concentrations of Cu, Cd, Zn, Pb and Mn were obtained in soil when compared with the Commercial-Residential Area. Contaminations of trace metals from various source, e.g., chemical fertilizer, animal manure, night soil and pesticides of the nearby agricultural land were suspected.The second experiment compared the effects of adding a commercial fertilizer and digested sludge which contain substantial amounts of various trace metals to a sandy loam for growing Chinese radish. The results indicated that repeated applications of the fertilizer elevated the contents of various trace metals in the roots of Chinese radish. The phenomenon was further aggravated when digested sludge was also incorporated.The third experiment compared the contents of trace metals in the root and leaf tissues of tree seedlings (Acacia confusa) added with a single dose of the trace metalenriched fertilizer, and different portions of pig manure compost. It was revealed that the fertilizer-treated tree seedlings had a higher content of trace metals in the tissues than those amended with manure compost. Although the metal contents of soil increased as more manure compost was added, the contents in plant tissues did not increase correspondingly.     

Regulation of hepatocyte proliferation

After partial hepatectomy the low proliferation rate of hepatocytes increases dramatically. This is based on a feed-back system whose central link is a liver cell proliferation hormon, the so-called hepatopoietin. The hormon originates from the Peyer's patches: after their resection, the liver cell proliferation after partial hepatectomy decreases by about 80%. Hepatopoietin effects organ specific but species nonspecific.     

Relationship between abundance of rodents and damage to agricultural crops

Developing a relationship between pest abundance and damage to crops is essential for the calculation of economic injury levels (EIL) leading to informed management decisions. The crop modelling framework, APSIM, was used to simulate the impact of mouse damage on yield loss on wheat where a long-term dataset on the density of mice was available (1983–2003). The model was calibrated using results from field trials where wheat plants were hand clipped to imitate mouse damage. The grazing effect of mice was estimated using the population density, daily intake per mouse and the proportion of wheat grain and plant tissue in the diet to determine yield loss. The mean yield loss caused by mice was 12.4% (±5.4S.E.; range −0.5 to 96%). There were 7/21 years when yield loss was >5%. A damage/abundance relationship was constructed and a sigmoidal curve explained 97% of variation when accounting for different trajectories of mouse densities from sowing to harvest. The majority of damage occurred around emergence of the crop when mouse densities were >100 mice ha⁻¹. This is the first time that field data on mouse density and a crop simulation model have been combined to estimate yield loss. The model examines the efficacy of baiting and how to estimate EILs. Because the broadscale application of zinc phosphide is cheap and effective, the EIL is very low (<1% yield loss). The APSIM model is highly flexible and could be used for other vertebrate pests in a range of crops or pastures to develop density/damage relationships and to assist with management.     

Cells of the connective tissue differentiate and migrate into pollen sacs

In angiosperms, archesporial cells in the anther primordium undergo meiosis to form haploid pollen, the sole occupants of anther sacs. Anther sacs are held together by a matrix of parenchyma cells, the connective tissue. Cells of the connective tissue are not known to differentiate. We report the differentiation of parenchyma cells in the connective tissue of two Gordonia species into pollen-like structures (described as pseudopollen), which migrate into the anther sacs before dehiscence. Pollen and pseudopollen were distinguishable by morphology and staining. Pollen were tricolpate to spherical while pseudopollen were less rigid and transparent with a ribbed surface. Both types were different in size, shape, staining and surface architecture. The ratio of the number of pseudopollen to pollen was 1:3. During ontogeny in the connective tissue, neither cell division nor tetrad formation was observed and hence pseudopollen were presumed to be diploid. Only normal pollen germinated on a germination medium. Fixed preparations in time seemed to indicate that pseudopollen migrate from the connective tissue into the anther sac.     

Modifying traditional and high-input agroecosystems for optimization of microbial symbioses: a case study of dry beans in Costa Rica

Optimization of symbioses between plants and microbes has been suggested as method for enhancing nutrient uptake in low-input agroecosystems. In generall symbioses may be maximized through: (1) the selection of plant cultivars responsive to symbiontss; (2) ionoculation with highly efficient strains of symbionts; (3) habitat modification to encourage symbioses. These methods were tested under a traditional, slash mulch, ‘frijol tapado’ en agroecosystem and/or a high-input (‘espequeado’) system to increase nodulation and vesicular-arbuscular mycorrbizae (VAM) of beans with the following results: (1) Under the espequeado system (modified by the exclusion of fertilizer application), four cultivars of indeterminate, vining dry beans (Phaseolus vulgaris) nodulated more than two determinate, bush varieties, especially under low available soil phosphorus (P). VAM levels were not statistically different under these conditions. (2) Under the tapado system, pelletization with rock phosphate and Rhizobium inoculum did not significantly change nodule biomass, dinitrogen (N₂)-fixation or yield. (3) Without P application, neither nodulation nor % VAM were significantly different between the two systems of bean production. However, as applied P increased, differences in %VAM of the two systems became significant, decreasing more sharply with increasing P in the tapado system.The tripartite symbiosis of beans can be influenced by various factors such as cultivar, nutrient application and production system. Although traditional varieties and systems may optimize certain microbial symbioses, the quantity of the symbiosis appears to depend on a number of complex factors. An intermediate agricultural technology, the mixing of traditional and modern, is exemplified here by the application of moderate levels of fertilizer to the tradional, tapado systems. This intermediate approach promises to decrease inputs in comparison to the espequedo system, as well as the need for shift cultivation, but long-term testing is needed.