Responses of benthic macroinvertebrates in small intermittent streams to silvicultural practices

We examined macroinvertebrate communities in small(0.1-1.0 m²) pools of intermittent streams (alwayscontainingsome water but without perennial flow) with small watersheds(2-6 ha) subjected to five types of forest harvest to assesspotential impacts of the different harvest methods. Bufferstrips10 m wide were left on each side of the streams. Each harvesttreatment was coupled with a similar unharvested referencestand.An incomplete block design included three 0.05 m² vacuumsamples from each treatment paired with three from theadjacentreferences. There was a high degree of similarity amongreferencesfor parameters other than taxonomic composition (e.g.macroinvertebrate density, number of species, Shannondiversity,functional groups, etc.). Statistically significantdifferenceswere found between references and treatments and among harvestmethods but the responses varied among response variables(density,Shannon-Weiner diversity, species composition), differentspeciesassemblages (all invertebrates, chironomids,Ephemeroptera-Plecoptera-Trichoptera [EPT], isopods), andfunctional group categories (shredders, collector-gatherers).Wecollected 56 taxa, 7–16 per site, with low communitysimilarity(mean Jaccards=0.18, mean Bray-Curtis percentdissimilarity=81). The most severe harvest treatmentsresultedin the highest diversities of total invertebrates in thesesmallspring pool communities.     

Uncertain branch lengths, taxonomic sampling error, and the egg to body size allometry in temperate butterflies (Lepidoptera)

The allometry of egg to body size in temperate butterflies, and the relationships between egg size and larval host structure, taxonomy, voltinism, and duration of the egg stage, are investigated using cross-species analysis and the comparative analysis of independent contrasts. In addition, the effect of two sources of uncertainty that may affect continuous data when treated under a statistical, comparative, framework, is assessed: (1) unknown evolutionary distances, and (2) taxonomic representativity (proportion of species of a given taxon, from which data are available). It is suggested that the effects of taxonomic under-representation could be important in comparative, quantitative studies, but this problem may be tempered by means of weighted regression. Under the assumption that taxonomy represents butterfly phylogeny, egg and adult body size are related by negative allometry (i.e. the slope of the line fitted to the logarithmically transformed data is lower than 1.0). However, the precise slope (0.2-0.9) depends on the method used, branch lengths, and taxonomic sampling. There is evidence for a relationship between a species' voltinism and the number of days it spends in the egg stage, as well as between adult butterfly size and the gross structure of the plants used as larval hosts (woody plants or herbs). Egg size proves to be related to foodplant taxonomy, voltinism, and duration of the egg stage when the data are analysed using species means, but these relationships become non-significant when the comparative method is employed.     

Production of gliotoxin during the pathogenic state in turkey poults byAspergillus fumigatus Fresenius

Turkey poults were given either of two different dosages of two different gliotoxin-producing strains ofAspergillus fumigatus. Infected lung tissue was examined postmortem for the presence of gliotoxin. Gliotoxin was found in lung tissue of ten poults infected with one strain and in seven of ten poults infected with the other strain. Concentrations of gliotoxin in the tissue exceeded 6 ppm in some of the infected tissues. The concentration of gliotoxin found in infected tissue did not appear to be correlated with the dosage of organism given. Considering the pathologic changes observed in turkey poults with aspergillosis and the production of gliotoxin during the pathogenic state in turkey poults, gliotoxin is considered likely to be involved in avian aspergillosis. Disclaimer: Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Microscopic contributions to the pressure-volume diagram of the cell-water relations as demonstrated with tissue cells

Summary Continuing microscopic studies on cell-water relations with single cells (Gerdenitsch 1979) based on the relationship between the osmotic potential and the cell water volume, tissue cells were investigated. The experiments were done with inner epidermis of the bulb scale of onion (Allium cepa) which seemed to be most suitable for those investigations. Using a diagram described byRichter (1978) pressure volume curves of cells at the margin of the epidermis pieces neighboured by a various amount of dead cells and of cells in the center of tissue were worked out. They were contributed to one of three groups according to their amount of free surface (group 1: >1/3 free surface, group 2: <1/3 free surface, group 3: cells surrounded only by living-cells). Curves of the mean values of each of the three groups were compared as well as the mean -values, calculated as a measure for the elasticity of the cell wall.It was found that cells surrounded only by living cells had -values less than with both other groups. Assuming from observations during the experiments that all cells had very similar properties, this difference could be attributed to the expression of the effect of tissue counterpressure.     

Effects of temperature and moisture on urease activity in semi-arid tropical soils

Summary Studies of urease activity in an Indian Vertisol and Alfisol using both buffer (THAM pH 9.0) and non-buffer methods for assay of the urease activity showed that activity increased with increase in temperature from 10°C to a maximum at 60°C (Vertisol) and 70°C (Alfisol). Further increase in temperature decreased urease activity which was nearly totally inhibited at 100°C. Urease activity was not detected in soil samples collected in late summer when the soil moisture content was far below — 15 bar pressure. Urease activity increased with increase in moisture content up to field capacity and remained constant with further increase in moisture content. The relevance of these findings to the ICRISAT improved management practices for Vertisols, which involve seeding of crops into dry soil just before the onset of rains is discussed. Approved as Journal Article No. 288 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).     

A comparison of two methods for the microscopic determination of age at death.

The precision and accuracy of the Kerley and Ahlqvist-Damsten microscopic methods of age determination are compared. Both methods were applied to the same sample of 40 femoral thin sections of documented age at death. The results indicate that (1) both methods can be used with equal precision, as suggested by comparable observer errors; and (2) the Kerley method produces overall more accurate age estimates. The low previously published standard error of the Ahlqvist-Damsten method (6.71 years) apparently results from the uneven age distribution and small size (20) of their sample.     

Terminal distribution of retinal fibers in the tegu lizard (Tupinambis nigropunctatus)

Summary The retinal projections in the tegu lizard were traced using degeneration-silver methods. Bilateral projections were found to the dorsolateral geniculate and the posterodorsal nuclei. Unilateral, crossed projections were traced to the suprachiasmatic nucleus, the ventrolateral geniculate nucleus, the mesencephalic lentiform nucleus, nucleus geniculatus praetectalis, the ectomammillary nucleus, and the optic tectum. Some of these connections are distinctly different from those reported in other reptiles and suggest that important interspecific variations occur among reptiles.     

用固定化方法研究超氧化物歧化酶的活性与结构的关系

 采用吸附、包埋、共价交联等方法固定化超氧化物歧化酶(SOD)所得固定化酶活力回收都不高,表明酶的催化反应速率受超氧阴离子自由基(O_2~-)扩散速率的控制。用海藻酸钠包埋SOD,固定化酶不表现活力,破固定化后所得的糊状物却有很高的活力。用戊二醛交联所得的固定化酶活力回收率也很低,表明ε-NH_3~+的正电荷是酶活力所必需。     

Biological N2 Fixation in wetland rice fields: Estimation and contribution to nitrogen balance

This paper 1) reviews improvements and new approaches in methodologies for estimating biological N₂ fixation (BNF) in wetland soils, 2) summarizes earlier quantitative estimates and recent data, and 3) discusses the contribution of BNF to N balance in wetland-rice culture.Measuring acetylene reducing activity (ARA) is still the most popular method for assessing BNF in rice fields. Recent studies confirm that ARA measurements present a number of problems that may render quantitative extrapolations questionable. On the other hand, few comparative measures show ARA's potential as a quantitative estimate. Methods for measuring photodependent and associative ARA in field studies have been standardized, and major progress has been made in sampling procedures. Standardized ARA measurements have shown significant differences in associative N₂ fixation among rice varieties.The ¹⁵N dilution method is suitable for measuring the percentage of N derived from the atmosphere (% Ndfa) in legumes and rice. In particular, the ¹⁵N dilution technique, using available soil N as control, appears to be a promising method for screening rice varieties for ability to utilize biologically fixed N. Attempts to adapt the ¹⁵N dilution method to aquatic N₂ fixers (Azolla and blue-green algae [BGA]) encountered difficulties due to the rapid change in ¹⁵N enrichment of the water.Differences in natural ¹⁵N abundance have been used to show differences among plant organs and species or varieties in rice and Azolla, and to estimate Ndfa by Azolla, but the method appears to be semi-quantitative.Recent pot experiments using stabilized ¹⁵N-labelled soil or balances in pots covered with black cloth indicate a contribution of 10–30 kg N ha^-1 crop^-1 by heterotrophic BNF in flooded planted soil with no or little N fertilizer used.Associative BNF extrapolated from ARA and ¹⁵N incorporation range from 1 to 7 kg N ha^-1 crop^-1. Straw application increases heterotrophic and photodependent BNF. Pot experiments show N gains of 2–4 mg N g^-1 straw added at 10 tons ha^-1.N₂ fixation by BGA has been almost exclusively estimated by ARA and biomass measurements. Estimates by ARA range from a few to 80 kg N ha^-1 crop^-1 (average 27 kg). Recent extensive measurements show extrapolated values of about 20 kg N ha^-1 crop^-1 in no-N plots, 8 kg in plots with broadcast urea, and 12 kg in plots with deep-placed urea.Most information on N₂ fixed by Azolla and legume green manure comes from N accumulation measurements and determination of % Ndfa. Recent trials in an international network show standing crops of Azolla averaging 30–40 kg N ha^-1 and the accumulation of 50–90 kg N ha^-1 for two crops of Azolla grown before and after transplanting rice. Estimates of % Ndfa in Azolla by ¹⁵N dilution and delta ¹⁵N methods range from 51 to 99%. Assuming 50–80% Ndfa in legume green manures, one crop can provide 50–100 kg N ha^-1 in 50 days. Few balance studies in microplots or pots report extrapolated N gains of 150–250 kg N ha^-1 crop^-1.N balances in long-term fertility experiments range from 19 to 98 kg N ha^-1 crop^-1 (average 50 kg N) in fields with no N fertilizer applied. The problems encountered with ARA and ¹⁵N methods have revived interest in N balance studies in pots. Balances are usually highest in flooded planted pots exposed to light and receiving no N fertilizer; extrapolated values range from 16 to 70 kg N ha^-1 crop^-1 (average 38 kg N). A compilation of balance experiments with rice soil shows an average balance of about 30 kg N ha^-1 crop^-1 in soils where no inorganic fertilizer N was applied.Biological N₂ fixation by individual systems can be estimated more or less accurately, but total BNF in a rice field has not yet been estimated by measuring simultaneously the activities of the various components in situ. As a result, it is not clear if the activities of the different N₂-fixing systems are independent or related. A method to estimate in situ the contribution of N₂ fixed to rice nutrition is still not available. Dynamics of BNF during the crop cycle is known for indigenous agents but the pattern of fixed N availability to rice is known only for a few green manure crops.     

Settlement of the diazotrophic,phytoeffective bacterial strain Pantoea agglomerans on and within winter wheat: An investigation using ELISA and transmission electron microscopy

The aim of this study was to investigate the ability of Pantoea agglomerans, a plant growth-promoting bacterium, to colonize various regions and tissues of the wheat plant (Triticum aestivum L.) by using different inoculation methods and inoculum concentrations. In addition, the enzyme-linked immunosorbent assay (ELISA) and transmission electron microscopy (TEM) were used to determine: (a) the ability of the bacterial cells to grow and survive both on the surface and within internal tissue of the plant and (b) the response of the plant to bacterial infection. After inoculation, cells of the diazotrophic bacterial strain P. agglomerans were found to be located in roots, stems and leaves. Colony development of bacterial cells was only detected within intercellular spaces of the root and on the root surface. However, single bacterial cells were observed in leaves and stems on the surface of the epidermis, in the vicinity to stomatal cells, within intercellular spaces of the mesophyll and within xylem vessels. Inoculated bacterial cells were found to be able to enter host tissues, to multiply in the plant and to maintain a delicate relationship between endophyte and host. The density of bacterial settlement in the plant in all experiments was about 10⁶ to 10⁷ cells per mL root or shoot sap. Establishment was confirmed by a low coefficient of variation of ELISA means at these concentrations.