A histologic study of the retroperitoneal lymph vessels was carried out in the tufted capuchin (Cebus apella). The organization of the intima, media and surrounding adventitia is compared with that of other animals and man. 相似文献
Different management practices are commonly applied to increase pasture yield of Mediterranean open woodlands, but the consequences of increasing competition for soil resources with these practices on tree recruitment are still unknown. In a greenhouse study, belowground competition of Quercus suber L. seedlings growing together with natural (OakNP) or improved pasture (OakIP) was evaluated, and their root systems compared with those of seedlings growing in bare soil (OakBS). Two watering levels and two regimes of P2O5 fertilisation were also tested. Because of competition, the OakIP seedlings had their fine root mass density, coarse root length, and shoot mass reduced by up to 40, 36, and 39%, respectively, when compared to OakNP seedlings. OakNP and OakBS seedlings showed similar average root density parameters and shoot mass values, indicating that Q. suber seedlings growing with natural pasture is a low competitive system. High availability of water and phosphorus did not mitigate the strength of competition between herbaceous plants and oak seedlings, and favoured the pasture to the detriment of the trees. Our findings suggest that P2O5 fertilisation and irrigation practices performed to improve herbaceous productivity will negatively influence recruitment of Q. suber seedlings. 相似文献
To evaluate the influence of irrigation and fertilization on the productivity of E. globulus a field experiment was started in 1986 in Central Portugal. The nutrients accumulated in the biomass and their allocation to the various biomass components as well as the changes in soil chemical characteristics were also followed. Irrigation and fertilization resulted in a significant increase of biomass production during the first 2 yr. A similar trend occurred with the net primary production and leaf litterfall. The differences between treatments in the amounts of accumulated nutrients in the aboveground biomass were similar to those of biomass accumulation. However, there was a small but consistent effect related to the average concentration of nutrients in the plant tissues. This effect occurred essentially in the leaves and branches. The concentration of N and P in the leaf litterfall was higher in the fertilized treatments than in the others. Fertilization alone induced a slight increase in the soil pH values, C content, exchangeable Ca and available P levels. Such increase was more pronounced in the fertilized with dripping irrigation treatment. This was due to the accumulation of nutrients in the wetted soil volume. 相似文献
Chestnut plantations for fruit production in Northern Portugal have been subjected to intensive management system, including
soil tillage, mineral fertilization and pruning. Some of these practices have no positive effect on productivity and soil–plant–water
relations. Other systems (e.g., no tillage with maintenance of grass cover) have been adopted, aiming a multifunctional land
use, exploiting nuts, pasture and edible mushrooms. Thus, an experimental trial was installed to assess the effects of such
systems on productivity, sustainability and annual net income, as compared with the conventional system, over a six-year period.
The treatments were: conventional soil tillage (CT); no tillage with permanent spontaneous herbaceous vegetation cover (NV);
no tillage with permanent rainfed seeded pasture cover (NP); and as NP but with irrigation (NIP). Production of nuts, forage
and edible mushrooms were measured and sustainability was assessed by production and diversity of fungal sporocarps. Annual
net income was estimated by the difference between the annual gross outputs (market values for nuts, forage and edible commercial
mushrooms) and the annual input costs. The greatest nut and edible mushroom production and sporocarp biodiversity were achieved
in the NIP and NV and the smallest in the CT treatment. The highest annual gross output was estimated for the NV and NIP treatments,
whereas the highest annual net income was obtained for the NV. No tillage with maintenance of spontaneous grass cover showed
to be the most favourable management system, as it has increased productivity and biodiversity. 相似文献
We assess the effects of changing land use and crop management on alfalfa insect abundance by comparing it in 50 alfalfa fields when they were inserted in landscapes with different proportions of arable crops and orchards. Land use in a buffer of 500 m was assessed, and alfalfa insect abundance was estimated with sticky yellow traps. The number of catches of several herbivores and predators was related to the proportion of landscape components and several field variables. Results indicated that the proportion of orchards in the buffer negatively affected the abundance of predators on alfalfa, likely because orchards treated with pesticides are a sink for predators moving in the landscape, among other possible causes. Other landscape variables such as noncrop habitats, winter cereals, and landscape diversity analysed by the Shannon index had a minor influence. Among field variables, field size influenced positively the abundance of insects on alfalfa, whereas alfalfa growth stage and age affected positively or negatively the different herbivores and predators. Of course, abundance of predators and prey was affected by the abundance of prey and predators, respectively. These findings suggest that a high proportion of intensively managed crops (orchards) in the landscape interferes with the role of alfalfa as a reservoir of predatory insects for adjacent crops and that the responses to local and landscape structures are temporal and species-specific as previously concluded for maize. Consequently, landscape and field management strategies to improve pest control must consider both types of variables as well as their changing influence when we modify them.
The main goal in this research was to determine the beneficial effect of incorporating biological procedures in parasite control programs for equids in zoological parks. Two trials were developed for Equus quagga, E asinus , and E africanus asinus. The first trial (September 2010 to August 2011) consisted of chemotherapy only (ivermectin plus praziquantel), and the second trial (September 2011 to September 2012) consisted of administration of chemotherapy and chlamydospores of the nematophagous fungus Arthrobotrys (Duddingtonia) flagrans. The effect of these measures was evaluated by the estimation of the reduction in the fecal egg counts (FECR). In the first trial, 100% FECR values were achieved 15 days after treatment in all the animals. The egg reappearance period (ERP) was 2-3 months for the equids, and all of them were passing strongyle eggs in the feces at 2-4 months after their deworming. In the second experiment, the FECR values were 100% in the three species. ERPs of 3 months in the European donkeys, 4 months in the Africans, and 6 months in the zebras were recorded. All the equids had positive results for the coprological flotation test 4-8 months after anthelmintic administration. This preliminary study demonstrates the incorporation of chlamydospores of nematophagous fungus, as A flagrans appears highly promising for reduction of the infective stages of the strongyles affecting captive animals, but the experimental design precludes true determination of whether the treatment is fully efficacious. 相似文献
Insecticides exert antilytic effects on pig erythrocytes by preventing osmotic disruption of membranes in critical hypotonic saline media. The order of effectiveness is the following: lindane > aldrin ≈ azinphos > parathion ≈ DDT > malathion; empirical protective indexes estimated for K+ leakage, at 0.09 M NaCl, were 5.6, 3.9, 2.9, 2.8, and 2.0, respectively. Erythrocytes swell and hemolyze in solutions containing glycerol below 0.6 M. At higher concentrations and temperatures below 20°C, the extent of cell lysis is very limited and virtually nil in 1 M glycerol. In hypertonic glycerol solutions, cells swell until the initial equilibrium volume is reached and, then, the swelling process ceases. Swelling in 1 M glycerol is related to its permeation through hydrophobic membrane domains. The activation energies of permeation are similar to the dehydration energies of glycerol molecules. As the temperature is increased above 20°C, erythrocytes undergo lysis. The organophosphorus insecticides, parathion and azinphos (10?4M), significantly increase the swelling rates and the extent of cell lysis. Malathion and chlorinated insecticides do not exert apparent effects. However, these compounds are effective in liposomes reconstituted with lipids extracted from erythrocyte membranes. 相似文献