Resumo em Inglês:
Zinc deficiency is a global problem of considerable importance for agriculture and human health. Under zinc deficiency conditions, many essential zinc-dependent physiological functions are unable to operate normally, and the cellular homeostasis is adversely affected. This paper described the potential damages that low-zinc bioavailability in soil can have for plants, humans, and animals. In addition, current knowledge on physiological and molecular aspects of zinc homeostasis in plants and strategies used to increase zinc deficiency tolerance were discussed.Resumo em Inglês:
The growth and nutrient assimilation was evaluated in CaCl2- and CaSO4-supplemented cowpea plants subjected to salt stress (75 mM NaCl). The salinity significantly reduced the cowpea vegetative growth. The addition of CaCl2 in the growth medium did not significantly affect plant growth, while for the CaSO4, the beneficial effects of Ca2+ were moderate. Salinity increased the Na+, K+, Cl-, N and P content in the plants, however it decreased the content of Ca2+ and Mg2+. Increases in Ca2+ concentration in the nutrient solution caused decreases in the Na+ and Mg2+ contents and increases in Ca2+, K+, P, and Cl- contents. The supplemental Ca2+ may alleviate the Na+ toxicity and may improve nutritional and ionic balance in cowpea, but it cannot overcome the osmotic effects associated with the increased total salt concentration.Resumo em Inglês:
Glutamate metabolism and amino acid translocation were investigated in the control and cadmium stressed shoots of tomato (Solanum lycopersicum - 63/5 F1), using (15N) ammonium and (15N) glutamate tracers. Regardless of organ type, [15N] ammonium assimilation occurred via glutamine synthetase (EC 6.3.1.2), in the control and stressed plants, and it did not depend on glutamate dehydrogenase (EC 1.4.1.2). The [15N] ammonium and ammonium accumulation patterns support the role of glutamate dehydrogenase in the deamination of [15N] glutamate to provide 2-oxoglutarate and [15N] ammonium. In the presence of cadmium, excess [15N] ammonium was incorporated into asparagine, which served as an additional detoxification molecule. In the presence both of methionine sulfoximine and cadmium, glutamate, alanine, and γ-amino butyrate of leaf tissue continued to become labelled with 15N. The labelling kinetics of amino acids in leaves of tomato plants in the presence of cadmium show that continued assimilation of [15N] ammonium can occur when the glutamine synthetase-glutamate synthase cycle is inhibited. The data provided evidence that the glutamine synthetase pathway and glutamate dehydrogenase play distinct roles in the source-sink nitrogen cycle of tomato leaves under cadmium stress conditions.Resumo em Inglês:
Studies involving amplified fragment length polymorphism (cDNA-AFLP) have often used polyacrylamide gels with radiolabeled primers in order to establish best primer combinations, to analyze, and to recover transcript-derived fragments. Use of automatic sequencer to establish best primer combinations is convenient, because it saves time, reduces costs and risks of contamination with radioactive material and acrylamide, and allows objective band-matching and more precise evaluation of transcript-derived fragments intensities. This study aimed at examining the gene expression of commercial cultivars of P. guajava subjected to water and mechanical injury stresses, combining analyses by automatic sequencer and fluorescent kits for polyacrylamide gel electrophoresis. Firstly, 64 combinations of EcoRI and MseI primers were tested. Ten combinations with higher number of polymorphic fragments were then selected for transcript-derived fragments recovering and cluster analysis, involving 45 saplings of P. guajava. Two groups were obtained, one composed by the control samplings, and another formed by samplings undergoing stress, with no clear distinction between stress treatments. The results revealed the convenience of using a combination of automatic sequencer and fluorescent kits for polyacrylamide gel electrophoreses to examine gene expression profiles. The Unweighted Pair Group Method with Arithmetic Mean analysis using Euclidean distances points out a similar induced response mechanism of P. guajava undergoing water stress and mechanical injury.Resumo em Inglês:
Citrus plants were grown under two thermal conditions for evaluating carbon metabolism acclimation to moderate warm temperature (30/20ºC, day/night), and its likely impact on plant growth. As reference, plants were grown at 25/20ºC, in which they were subjected to optimum temperature for photosynthesis during the diurnal period (25ºC). Higher photosynthetic rates were found at 30/20ºC as compared to 25/20ºC in both mature and young leaves, being this response associated with higher stomatal conductance. After 30 days of thermal treatment, plants grown at 30/20ºC presented higher shoot growth as compared to those at 25/20ºC. The carbohydrate concentration decreased in stem and root tissues, while it increased in leaf tissues under moderate warm conditions. Both mature and young leaves showed higher photoassimilate consumption/exportation at 30/20ºC than at 25/20ºC. In this paper, we have proven that citrus plants present a positive balance in carbon metabolism as an acclimation mechanism to temperature changes, with plants presenting increased photosynthesis. Such photosynthetic acclimation was associated with improved vegetative growth, being both mature and young tissues sensitive to changes in thermal regimen.Resumo em Inglês:
We explore physiological and biochemical response under increasing aluminium stress at different time interval in chickpea seedlings (Cicer arietinum L.). Germination percentage and root length were found to be highly reduced under increasing metal stress. Aluminium induced oxidative stress and led to fluctuations in antioxidative activity responses. Roots showed higher antioxidative activity compared to shoots. Low concentration of aluminium after a brief treatment induced higher superoxide dismutase (SOD; EC 1.15.1.1), ascorbate peroxidase (APX; EC 1.11.1.11) and guaiacol peroxidase (GPX; EC 1.11.1.7) activity whereas longer duration of treatment led to decrease in these activities. Malondialdehyde concentration indicated higher oxidative damage in roots compared to shoots. Taken together the data obtained indicated that high concentration and long exposition of aluminium increases oxidative stress and impairs antioxidative defense system, overall leading to poor growth and survival of seedlings.Resumo em Inglês:
Biodiesel is an alternative to petroleum diesel fuel. It is a renewable, biodegradable, and nontoxic biofuel. Interest in the production of biodiesel from Jatropha curcas L. seeds has increased in recent years, but the ability of J. curcas to grow in salt-prone areas, such as the Caatinga semiarid region, has received considerably meager attention. The aim of this study was to identify the main physiological processes that can elucidate the pattern of responses of J. curcas irrigated with saline water, which commonly occurs in the semiarid Caatinga region. This study measured the activity of the antioxidant enzymes involved in the scavenging of reactive oxygen species, which include catalase (CAT) and ascorbate peroxidase (APX), as well as malondialdehyde (MDA) levels. The levels of chlorophyll (Chl), carotenoids, amino acids, proline, and soluble proteins were also analyzed. The net carbon assimilation rate (P N), stomata conductance (g s), and transpiration rate (E) decreased with salt stress. The activities of CAT and APX were decreased, while H2O2 and MDA levels as well as electrolyte leakage were significantly increased in salt-stressed plants compared to the untreated ones. These observations suggest that the ability of J. curcas plants resist to salt stress is associated with the activities of protective enzymes and their defensive functions. However, our results indicate that the reactive oxygen species scavenging system is not sufficient to protect J. curcas leaves against oxidative damage caused by salt stress, and, therefore, it cannot be treated as a salt tolerant plant species.Resumo em Inglês:
A full-length cDNA clone encoding cyclophilin gene of 848 bp, including a 519 bp open reading frame, has been isolated from the cDNA library constructed from etiolated seedlings of Vigna mungo (GenBank FN668732). The cDNA sequence showed 97% identity with Vigna radiata cyclophilin mRNA. The sequence was GC rich and lacked introns. The open reading frame encoded 172 amino acid polypeptide with molecular weight 18.3 kDa and theoretical pI 8.61. BlastP analysis indicated that its putative amino acid sequence shared 100% identity with several plant cyclophilins particularly legumes. The conserved seven amino acid residues region in V. mungo cyclophilin was RSGKPLH (present in legumes) instead of KSGKPLH, indicating its similarity to the cyclophilins of other legumes. This novel V. mungo cyclophilin gene will broaden the pool of plant cyclophilin genes for further studies.