Influence of bicarbonate and metal ions on the development of root Fe(III) reducing capacity by Fe-deficient cucumber (Cucumis sativus) plants

The effect of bicarbonate and selected metal ions on the development of enhanced root Fe(III) reducing capacity (a response to Fe deficiency of dicotyledons) was studied in young plants of cucumber ( Cucumis sativus L. cv. Ashley) grown in nutrient solution. Pretreatment of 11-day-old Fe-deficient cucumber plants with 20 m M NaHCO₃, for at least 23 h prior to determination of root Fe(III) reducing capacity, markedly inhibited this response. The inhibitory effect of bicarbonate could be partly reversed by a 4- to 8-h treatment with either 10 μ M MnSO₄, 10 μ M FeEDDHA, 2 μ M ZnSO₄, 0.5 μ M NiCl₂, or 0.25 μ M , or CoSO₄ (final concentrations), added to the nutrient solution. By contrast, the addition of other salts of metal ions, like CuSO₄ and Cd(NO₃)₂, at 0.25, 0.5 or 1 μ M , or MgSO₄, at 0.5, 1 or 2 m M (final concentrations), had no beneficial effect. The results suggest that bicarbonate may inhibit the development of root Fe(III) reducing capacity by diminishing the availability of certain metal ions required for this response.     

Restriction enzyme banding and in situ nick-translation on different types of hetero- and euchromatin.

We studied the role of chromatin accessibility and methylation in the banding patterns produced by means of in situ nick-translation (NT) and restriction enzyme (RE) banding techniques. For these studies we used the X chromosomes of Microtus cabrerae because of their large segment with four different types of constitutive heterochromatin and because in these chromosomes we can also compare active and inactive euchromatin. The results demonstrate that constitutive heterochromatin in the X chromosomes of M. cabrerae is methylated at specific sequences in both active and inactive Xs. They also show that NT-based techniques are suitable for detecting weak differences in chromatin accessibility, such as differences between active and inactive euchromatin, and are able to distinguish methylation only at the accessible sites. Thus, when methylation has to be mapped in situ, additional experiments have to be performed in order to distinguish findings due to differential accessibility. RE banding seems less sensitive to slight differences in chromatin accessibility, and might thus be more suitable than in situ NT-based techniques for methylation mapping. In harmony with these results, HpaII-based RE banding is able to distinguish between active and inactive euchromatin, possibly depending on its methylation status.     

Sotbean genetic differences in response to Fe and Mn: Activity of metalloenzymes

Summary Metalloenzymes as biochemical markers of nutritional status have been studied for 30 years since Brown and Hendricks proposed the use of enzyme activities as indicators for the diagnosis of micronutrient deficiencies. Enzyme activities can be used in other lines of research, such as the characterization of particular reactions of genotypes to nutritive imbalances. Catalase, peroxidase and superoxide dismutase activities were assayed in soybean cultivars growing in nutrient solutions with different Fe/Mn ratios. Considerable differences were observed between cultivars. Relationships between growth and enzyme activity were also studied. Although more information is required, our results provide an introduction to the knowledge of the mechanisms developed by genotypes in response to Fe−Mn imbalances.     

Does lack of diapause result in less insect seasonality?

Summary Unlike their temperate zone and tropical African relatives, flesh flies from the Neotropics lack the capacity for diapause. Yet, our trapping data reveal marked seasonality in flies from Panama, demonstrating that diapause is not essential for generating their seasonal patterns of abundance.     

Relationships between body size,reproductive traits,and food resource in three species of tropical flesh flies

Intra- and inter-specific comparisons in progeny size and clutch size were used to identify possible selection pressures acting on three sympatric species of ovoviviporous flesh flies. Both progeny and clutch sizes increased with body weight of the female parent in all species. There was no evidence for a simple trade-off between the two traits. In one species, the larger the female adult the smaller the relative biomass of larvae per clutch (total weight of larvae/body weight of female parent). Female flies produced similar progeny and clutch sizes over successive batches. Variation in progeny size did not influence either larval survival or duration of larval and pupal development. However, larger first instar larvae tended to form larger pupae in two of the species. The experiments testing the effect of progeny size on pupal weight under limited food conditions suggest a selective advantage for larger progeny size.