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921.
Eileen K. Schofield 《Biological conservation》1973,5(1):48-51
A wide variety of cultivated plants has been introduced to the Galápagos Islands since settlements were first established there in the 1830s. Through poor management, many of these plants have escaped to the wild and are taking over extensive areas of native forest. Two endemic species, Scalesia pedunculata Hook.f. and Miconia robinsoniana Cogn., are especially endangered by farming practices. Some measures for the control and use of cultivated plants must be enforced to save the Galápagos flora from further damage. 相似文献
922.
N. K. Nielsen 《Potato Research》1973,16(3):180-182
Summary A method for a quick inspection of wound periderm formation is described. Sections are freehand cut into a stain solution,
and microscopic examination is accomplished with an epiplanatic lens. 相似文献
923.
The effects of 28 and 56 days' storage at 25°, 4° and ?20°C on the microbial biomass content of four soils from tussock grasslands were studied by three biochemical procedures. Two of the procedures involved measurement of CO2 and mineral-N (Min-N) production by chloroform-fumigated and unfumigated soil, and consequent estimation of biomass C and Min-N flush respectively. In the third, adenosine 5'-triphosphate (ATP) content was determined.Patterns of CO2 production were often influenced by storage treatment. The use of fixed incubation periods for estimating the CO2 flush of fumigated soil and the steady rate of CO2 production by unfumigated soil did, however, give biomass C estimates that were generally similar to those calculated from individually determined incubation periods for each treatment and soil.Biomass C values could change significantly at all storage temperatures, but generally least at ?20°C. Storage at ?20°C was also the most suitable for retaining ATP contents, whereas 4°C was best for values of Min-N flush. Values of Min-N flush after storage of soil at ?20°C decreased significantly in two of the soils but increased in another. No storage temperature was thus satisfactory for all three indices of microbial biomass. Generally, however, 4°C was adequate for short periods, and 25°C the least suitable. 相似文献
924.
The activity of the ovary-inhibiting hormone in the eyestalks of female prawns, Parapenaeopsis hardwickii, was determined during its ovarian developmental cycle. In the inactive (stage I) and post-spawned phases of ovarian development, the ovary-inhibiting hormone activity was found to be very high. During the phase of full vitellogenesis (stage IV), the inhibiting activity is almost negligible. After spawning (stage V) it is present, but at a lower level than during inactive and post-spawned phases. Hence it is inferred that ovary-inhibiting hormone appears to be responsible for the phase of ovarian quiescence and to control the rate of vitellogenesis. 相似文献
925.
Abstract. The circulating haemocytes of the tanner crab, Chionocetes bairdi , were studied and classified as hyalinocytes, intermediate granulocytes and eosinophilic granulocytes. Differential haemocyte counts of normal crabs and crabs infected with an apparently pathogenic unnamed ascomycete fungus revealed a shift in the hyalinocyte-granulocyte ratio in infected crabs. There was a highly significant increase in the percentage of granulocytes and a corresponding decrease in hyalinocytes in infected crabs. This shift was thought to be caused by a marked increase in the relative number of eosinophilic gianulocytes. There was also a highly significant statistical relationship between the severity of the internal fungus infection, established by histopathological analysis of the major organ systems, and the increased number of circulating eosinophilic granulocytes. The results of the study indicate that differential haemocyte counts may be a valuable tool in monitoring the health of C. bairdi populations. 相似文献
926.
Abstract. Starry flounder Platichthys stellatus (Pallas) from the Duwamish River estuary, which has received large volumes of pollutants in the past, and starry flounder from two relatively unpolluted reference areas were examined for pathological conditions. Gross and microscopic examination of starry flounders from the Duwamish River estuary revealed one or more of the following unusual liver characteristics in 92% (monthly range 85–100%) of the fish: liver discolouration, liver enlargement, severe fatty vacuolation of the hepatocytes, centrolobular cellular degeneration and necrosis of hepatocytes, megalocytic hepatocytes, proliferating perivascular fibroblasts displacing adjacent liver parenchyma, hepatic structural disarray and increased basophilia of hepatocytes in localized areas. Livers of starry flounders, usually spent spawners, from one of the reference areas also had one or more of these characteristics, although at a much lower frequency (<13%), and these included liver discolouration, increased fatty vacuolation of the hepatocytes and hepatic structural disarray. 相似文献
927.
The amounts of organic materials released into soil from roots during the first 4 weeks of growth were determined for 11 cultivars of wheat (Triticum aestivum L.). Carbon loss from roots was measured by supplying 14CO2 continuously to the shoots and measuring the 14C content of the roots, root-free soil, water-soluble material and CO2 flushed from the root chamber. Six cultivars were compared in each of two experiments, with the cultivar Condor common to both experiments. There were no significant differences between cultivars, relative to Condor, for 14C activity present in soil, roots, water-soluble material or rhizosphere CO2. There was a significant difference between cultivars in experiment 1, but not in experiment 2, for the variate log10 (14C lost from roots: 14C translocated to roots).There was evidence that a reduction in growth temperature, within the range 10–15°C, increased carbon loss from wheat roots into the rhizosphere. 相似文献
928.
929.
A 20 s exposure to 2450 MHz microwave radiation had a marked differential effect on the viable count of soil micro-organisms, had little influence on numbers of heterotrophic bacteria, but reduced fungal colonies on dilution plates to zero. The growth of fungi from soil particles was also reduced following treatment. Prolonging the exposure to microwave radiation progressively inhibited nitrification and S-oxidation, but stimulated ammonification. Brief exposures (20s) also stimulated S-oxidation and increased the numbers of thiobacilli in soil. Most of these effects are explained by reference to the marked increase in soil temperature resulting from microwave treatment. 相似文献
930.
W E Dunbar K E Stevenson 《Journal of the Association of Official Analytical Chemists》1979,62(3):642-647
Commercial infant formulas were analyzed simultaneously for thiamine and riboflavin by an automated fluorometric method and by the AOAC manual fluorometric methods. For 10 products, the mean thiamine and riboflavin results determined using the automated method ranged from 104 to 113% and 90 to 112%, respectively, of those by the AOAC manual methods. The coefficients of variation for thiamine and riboflavin ranged from 1.05 to 3.90% and 0.60 to 2.48%, respectively, for the automated methods, and 1.48 to 3.86% and 0.69 to 10.9%, respectively, for the manual methods. Using the automated method, mean recoveries of thiamine and riboflavin added to samples were 103 and 104%, respectively. The automated method used a common sample preparation to determine both thiamine and riboflavin, and gave results equivalent to, or better than, those obtained by the manual methods. 相似文献