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Environmental pollution is one of the most serious causes of degradation of Mediterranean wetlands. Mercury (Hg) and cadmium (Cd) are of particular concern due to biomagnification. Here, we used red swamp crayfish (Procambarus clarkii) to monitor the spatial and temporal patterns of these two metals in a Portuguese rice field system. We sampled the crayfish in three different sites and three different time periods in the Sado River Basin (Portugal). We measured temperature, pH, total dissolved solids and conductivity in the water. Hg and Cd were measured in the crayfish abdominal muscle tissue and exoskeleton. In muscle, a spatial pattern was found for the accumulation of Cd while for Hg, only a temporal pattern emerged. The spatial pattern for Cd seemed to reflect the mining history of the sites, whereas the temporal pattern for Hg seemed related to the flooding of rice fields. We suggest that this flooding process increases Hg bioavailability. 相似文献
174.
The Brazilian shrub Baccharis megapotamica contains significant amounts of antibiotic trichothecenes. When these plants are grown in the United States, they are devoid of the mycotoxins. Feeding experiments with fungus-produced trichothecenes show that Baccharis megapotamica absorbs, translocates, and chemically alters these compounds to ones with structures analogous to those found in the plant in its native habitat. The mycotoxins, which have no apparent ill effect in Baccharis megapotamica, kill tomatoes, peppers, and artichokes. 相似文献
175.
The recent development of beta gauges for the indirect determination of the water status of plants has had a widespread impact on plant ecological-physiological research. Calibration of these instruments has, however, been tedious and cumbersome, involving repeated simultaneous measurements of beta absorption and leaf water content. This procedure can be much simplified, as long as the beta absorption at a single known relative water content is measured, together with the turgid and dry weights of a sample of leaf discs. 相似文献