Root elongation method may be implemented using two internationally accepted protocols: exposing plants to either soil-water extract or whole soil. But which of the two protocols is more suitable for root elongation analysis undertaken for the quality assessment of metal-polluted soils? Soils were sampled at various distances from the site of the Middle Urals Copper Smelter located in Russia. White mustard was used as a bioindicator. We observed considerable differences in root elongation under the two protocols. In plants grown in whole soil, root length inversely correlated with pollution index, but in soil-water extract, metal concentrations had no effect on root length. Nutrient and metal concentrations in the soil-water extract were not buffered, due to the absence of the solid soil phase. It is for this reason that in highly polluted soils, root growth was greater in soil-water extracts rather than in whole soils, whereas in background soils (in the absence of toxicity), root growth was greater in whole soils compared with soil-water extracts. The quantity, intensity, and capacity factors are a plausible explanation for the differences in root length between the two protocols. The soil-water extract does not represent actual soil with respect to the desorptiondissolution reactions that take place between the soil solid phase and the soil solution. For this reason, whole soil protocol should be used for measuring root elongation given that only under this protocol, direct contact between metal-polluted soil and test organisms correctly replicates the risks inherent in the actual soil habitat.
Ecotoxicological studies of soil metal toxicity conventionally rely on the use of uncontaminated soils gradually enriched with metals in the form of soluble salts. Although this method is very useful in many ways, it is continually complicated by the difficulty of extrapolating laboratory results to actual field-collected soils exposed to decades of contamination. Although many studies emphasize the importance of using field-contaminated soils for toxicity bioassays, the number of studies actually conducted based on this premise is relatively small. This review provides an in-depth recompilation of data on metal toxicity thresholds in field-contaminated soils. We have summarized the EC10, EC25, and EC50 values for metals, i.e., values of metal concentrations that reduce the response of specific organisms by 10%, 25%, and 50% of the value in uncontaminated soils. In our summary, most studies show that total metal content can predict organismal responses as well as bioavailable fractions. These results are consistent with the intensity/capacity/quantity concept proposed for plant nutrient uptake. In addition, microorganisms are thought to be more sensitive to metals than plants and invertebrates. However, our analysis shows that there is no statistically significant difference between the sensitivity of microorganisms and other organisms (plants and invertebrates) to any metal or metal pool. We expect that this information will be useful for environmental assessment and soil quality decisions. Finally, we encourage future studies to analyze dose-effect relationships in native field-collected soils with varying degrees of metal contamination from long-term anthropogenic pollution.
Background: The size and weight of tomato seeds depend on genetics and can be modified by environment and management. In some species, a strong relation has been described between physical aspects of the seeds and the quality of the corresponding seedlings, but this cannot be considered a general rule. The objective of this research was to identify any association between the biometric characteristics of tomato seeds and the growth and development of their seedlings. Results: A total of 18 lots of hybrid tomato seeds were used (from indeterminate plants with round fruits), belonging to six varieties from two reproduction seasons. Each lot was evaluated for seed size and weight, and seed quality, in terms of the germination test (5 and 14 d after sowing). The number of normal roots emerged with a length above 2 mm was also evaluated at d 3, 4 and 5 after sowing. The length of the seedlings and their total and partial dry weight were measured 5 d after sowing. The results indicate that there was no association between seed size and weight and subsequent seedling emergence, and only weak correlations were found between the dry weight of the radicle and cotyledon and seed size. Conclusion: There is little association between the physical characteristics of the seeds and the subsequent seedlings, making it impossible to propose the use of seed weight or size as a compliment to quality evaluation tests.
crispa Lindl. Se pudo observar las cuatro etapas de germinación propuestas por Mitchell. La etapa cero corresponde a semillas sin germinar, éstas son alargadas, curvadas en uno de sus extremos, y alcanzan un largo promedio de 0,5 mm. En la etapa uno se aprecia un incremento sólo en ancho debido al crecimiento del embrión, en la etapa dos hay cambios tanto en la forma como en el aumento del diámetro. En la etapa tres, única visible a simple vista, se inicia la germinación fisiológica. El porcentaje de germinación determinado por esta técnica varió entre 33 y 40 %, resultado coincidente con otros autores.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.