Marlene Aparecida Schiavinato

Zn uptake, physiological response and stress attenuation in mycorrhizal jack bean growing in soil with increasing Zn concentrations

The influence of arbuscular mycorrhizal fungi (AMF) inoculation on Canavalia ensiformis growth, nutrient and Zn uptake, and on some physiological parameters in response to increasing soil Zn concentrations was studied. Treatments were applied in seven replicates in a 2 x 4 factorial design, consisting of the inoculation or not with the AMF Glomus etunicatum, and the addition of Zn to soil at the concentrations of 0, 100, 300 and 900 mg kg(-1). AMF inoculation enhanced the accumulation of Zn in tissues and promoted biomass yields and root nodulation. Mycorrhizal plants exhibited relative tolerance to Zn up to 300 mg kg(-1) without exhibiting visual symptoms of toxicity, in contrast to non-mycorrhizal plants which exhibited a significant growth reduction at the same soil Zn concentration. The highest concentration of Zn added to soil was highly toxic to the plants. Leaves of plants grown in high Zn concentration exhibited a Zn-induced proline accumulation and also an increase in soluble amino acid contents; however proline contents were lower in mycorrhizal jack beans. Plants in association or not with the AMF exhibited marked differences in the foliar soluble amino acid profile and composition in response to Zn addition to soil. In general, Zn induced oxidative stress which could be verified by increased lipid peroxidation rates and changes in catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase activities. In summary, G. etunicatum was able to maintain an efficient symbiosis with jack bean plants in moderately contaminated Zn-soils, improving plant performance under those conditions, which is likely to be due to a combination of physiological and nutritional changes caused by the intimate relation between fungus and plant. The enhanced Zn uptake by AMF inoculated jack bean plants might be of interest for phytoremediation purposes.

Lead tolerance and phytoremediation potential of Brazilian leguminous tree species at the seedling stage.

A greenhouse pot experiment was conducted to evaluate the potential of three Brazilian leguminous woody species, Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, for the revegetation of lead- (Pb-) contaminated areas. The response of seedlings to increasing Pb concentrations (0, 250, 500 and 1000 mg kg(-1)) in the soil was studied. In addition to Pb accumulation and translocation, the following parameters were assessed: chlorophyll, nitrate, ammonia, lipid peroxidation (MDA) and free amino acid content; seedling growth; and nitrogenase activity. No differences were observed in the germination of woody species seeds sown in soils with or without Pb addition. M. caesalpiniaefolia did not show visual symptoms of Pb toxicity, while the other two species demonstrated stress symptoms, including reduced shoot biomass yield, leaf area and height. Biochemical analyses of plant tissues revealed markedly different responses to increasing Pb concentrations, such as changes in foliar soluble amino acid composition in S. parahyba; changes in ammonia and nitrate content in E. speciosa, M. caesalpiniaefolia and S. parahyba; and changes in MDA content in S. parahyba. The levels of chlorophyll a and b and carotenoid were affected in the species studied. For the Nitrogen-fixing (N(2)-fixing) species E. speciosa, an increase of Pb in the soil affected nodule formation and growth, which led to reduced nitrogenase activity in seedlings. The concentration of Pb in shoots and roots increased with the Pb concentration in soil. However, most of the Pb absorbed accumulated in the roots, and only a small fraction was translocated to aboveground parts. These findings were confirmed by the low bioconcentration factor (BCF) and translocation factor (TF) values for the three species. The tolerance index (TI) values suggested that M. caesalpiniaefolia, a N(2)-fixing tree, was the species that was most tolerant to high Pb concentrations in soil, while E. speciosa and S. parahyba showed moderate tolerance. Of the three Brazilian native woody species studied, M. caesalpiniaefolia was found to have the highest Pb tolerance and phytostabilisation potential in Pb-contaminated soils.

Arbuscular mycorrhizal association in coffee

Despite previous research on mycorrhizal association with plants, the data on associations with coffee ( Coffea species) are very sparse despite the great economic importance of this crop for many tropical developing countries. The present paper reviews the main aspects of the association between arbuscular mycorrhizal fungi (AMF) and coffee plants. This review includes topics on mycorrhizal effects on coffee nutritional status, pathogen–AMF interactions and responses to several environmental stresses. It also summarizes findings about the natural occurrence of AMF in different soils in which coffee is cultivated, some ecological aspects of this specific association and outlines trends for future investigations, which must elucidate the real benefits of mycorrhizae to coffee plants.

Aspectos fisiológicos e microbiológicos de beterrabas minimamente processadas

The aim of this work was to evaluate physiological and microbiological aspects of fresh cut beet roots. Respiratory activity and ethylene evolution were evaluated during four hours after processing and during the storage period of ten days at 5 o C. Microbiological analysis was carried out right after processing and after ten days of storage. Intact roots showed the lower respiratory activity (5 mL CO 2 kg -1 h -1 ), whereas shredded and peeled beet roots presented a respiration rate of 30 mL CO 2 kg -1 h -1 four hours after processing. Fresh cut beet roots showed a peak during the second storage day (80 mL CO 2 kg -1 h -1 ), reducing to 30 mL CO2 kg -1 h -1 at the fourth day. No ethylene evolution was detected in intact and peeled beet roots whereas in the fresh cut material it was observed in the first hours after processing, reaching 0.90 µL kg -1 h -1 . Few variations were observed during the four-hour period after processing and during the refrigerated storage. Psychotrophic bacteria and total coliforms counts were within acceptable limits, and no Salmonella or fecal coliforms were detected.

Narrow band spectral indexes for chlorophyll determination in soybean canopies [Glycine max (L.) Merril]

Photosynthetic pigments are essential for plant development. Quantifying these pigments in great extensions of agricultural crops is an important objective in remote sensing for agricultural purposes. This information can be used to produce a more accurate estimation of the physiological state of the vegetation, for species discrimination and productivity estimation. The aim of the present study was to (a) evaluate the potential for estimating chlorophyll content of crop canopies, using narrow band spectral indexes, and (b) in this respect compare the performances of NDVI (a multispectral wide band index) and two narrow band vegetation indexes (R750/700 and R750/550). Experiments were carried out under greenhouse conditions whereby soybean [Glycine max (L.), Merril] was monitored with a high-resolution spectroradiometer (10 nm at 365-1,126 nm range) during the phenological cycle of the crop. Chlorophyll (a, b and total) contents were determined weekly in the laboratory. A statistical correlation analysis was performed between narrow band spectral indexes against chlorophyll content and r2 coefficients near 0.84 were obtained. For NDVI r2 was around 0.51. These analyses showed that R750/700 and R750/550 ratios are very useful indexes for chlorophyll determination and very effective compared with NDVI (one of the wide band indexes widely used). Thus, it can be stated that hyperspectral remote sensing has great potential for providing a reliable estimate of photosynthetic pigment content at the canopy level through evaluated indexes and other such indexes that might arise. Thus, further studies should be carried out for evaluating other indexes at the canopy level, both in the laboratory and under field conditions, using spectroradiometers and hyperspectral images, aimed at providing information for agricultural purposes.

Evaluation of Mycorrhizal Influence on the Development and Phytoremediation Potential of Canavalia Gladiata in Pb-Contaminated Soils

Soil contamination by heavy metals is a serious problem to humans due to its high level of toxicity. The heavy metal lead (Pb) is commonly used in industries and if the disposal of residues that contain this element is not done properly may result in tragic consequences to the organisms. In this experiment we assessed the potential of a forrage leguminous, Canavalia gladiata, to phytoremediate lead-contaminated soil under mycorrhizal influence. The experimental design was composed of 4 Pb doses (0, 250, 500, and 1000 mg kg−1 of soil) and the plants were inoculated or uninoculated with arbuscular mycorrhizal fungi (AMF). We observed that the nodulation was severely affected by the presence of Pb independently of the mycorrhizal status; most of the elements analyzed were affected independently of the mycorrhizal status with exception of P. The mycorrhizal colonization was able to restrict the entrance of Pb in plants under high concentrations of Pb but promoted its accumulation in both organs under intermediate concentrations of this element. Besides the mycorrhization did not promote plant growth under Pb stress, the use of this plant may be considered to be used for phytostabilization purposes.

Mycorrhization alters foliar soluble amino acid composition and influences tolerance to Pb in Calopogonium mucunoides

Soil contamination by lead (Pb) is a problem due to the persistence of this element on soil. High amounts of Pb in soil impair plant establishment, however some plants may increase tolerance to heavy metals when colonized by arbuscular mycorrhizal fungi (AMF). The leguminous plant, Calopogonium mucunoides, is Pb-sensitive that is tolerant to Pb when associated to AMF. We performed a chromatographic analysis of foliar free-amino acid in non-mycorrhizal and mycorrhizal plants to determine its relation with Pb tolerance. Mycorrhization caused drastic increase in aspartate, glutamine, glycine, threonine, alanine, isoleucine and gamma-aminobutiric acid (GABA), while depletion of asparagine, histidine and arginine was observed in AMF-associated plants. When grouped according to common metabolic precursor, it was found that amino acids derived from 3-phosphoglicerate and pyruvate was higher in mycorrhizal plants while amino acids derived from glucose-6-phosphate and 2-oxoglutarate were higher in non-mycorrhizal plants; phosphoenolpyruvate and oxaloacetate pathways were not influenced by mycorrhization. Summarizing, mycorrhization changed soluble amino acids profile in C. mucunoides leaves, especially aspartate, alanine and GABA, which may be involved in tolerance to abiotic stress. Additionally the depletion of asparagine, histidine and arginine may be related to a deviation for metabolic pathways not related to protein biosynthesis but to the synthesis of polyamines, especially in the case of arginine. Therefore, we suggest that mycorrhization influence on soluble free amino acid profile in leaves can be one of the factors involved with the attenuation of Pb toxicity in AMF-associated C. mucunoides plants.

Tolerância e potencial fitorremediador de Stizolobium aterrimum associada ao fungo micorrízico arbuscular Glomus etunicatum em solo contaminado por chumbo

Heavy metal pollution of soils has increased significantly in the last years owing to anthropic action. Several techniques can be used to revert or to minimize soil contamination, although many of these techniques are harmful to the soil. An alternative is to use a new technique, called phytoremediation, based on the ability of plants to take up elements from soils with excessive high levels of metals or of other potentially toxic elements and thus contribute to soil decontamination. The inoculation of plants with arbuscular mycorrhizal fungi (AMF) can influence the absorption of these elements. The phytoremediation potential of Stizolobium aterrimum plants with or without AMF in soils with increasing lead concentrations was evaluated in a greenhouse experiment, in a 4 x 2 factorial design. The treatments consisted of the addition of four Pb rates (0, 250, 500 and 1000 mg dm-3) to the soil where black velvet bean plants associated or not with Glomus etunicatum AMF where grown. The results showed that black velvet bean was Pb tolerant at the tested rates. The association with AMF did not influence the Pb plant uptake. However, the mycorrhiza influenced biological nitrogen fixation by increasing the activity of the enzyme nitrogenase in mycorrhizal plants. Despite the good results obtained in relation to Pb tolerance of black velvet bean, further studies on the uptake of this element are needed, above all in the case of multicontaminated soils, as actually observed in polluted systems.

Biochemical, histochemical and ultrastructural characterization of Centrolobium robustum (Fabaceae) seeds

Centrolobium robustum seed coat is made up of an external layer of macrosclereids and an internal layer of osteosclereids, followed by a layer of dead cells. The endosperm is closely united to the seed coat and is made up of up to three layers of living cells rich in lipid and protein bodies. All the embryonic cells that form the different tissues of the cotyledons and embryonic axis, including the apical meristematic tissues, are storage tissues since they accumulate mainly lipids and proteins, in the form of lipid and protein bodies, water-soluble polysaccharides, and starch. In the seed coat, lignin, simple phenols and hydrolysable tannins were chemically detected.

Photosynthetic performance in jack bean [Canavalia ensiformis (L.) D.C.] under drought and after rehydration

Os efeitos do deficit hidrico e posterior reidratacao foram avaliados em Canavalia ensiformis (L.) D.C., mediante parâmetros de trocas gasosas: fotossintese (A), condutância estomatica (gs), razao Ci/Ca e transpiracao (E); fluorescencia da clorofila a: razao Fv/Fm e Fv/F0. As plantas cresceram em casa de vegetacao e apos apos 30 dias da emergencia, suspendeu-se a irrigacao naquelas submetidas ao deficit hidrico, obtendo-se os seguintes potenciais hidricos na antemanha (Yam): -0,40 MPa (controle), -1,00 MPa (deficit hidrico moderado) e -2,30 MPa (deficit hidrico severo). Apos, foram realizadas as analises de trocas gasosas e de fluorescencia. As plantas foram reidradatas e, apos um periodo de 24 h, as mesmas analises foram repetidas. Os regimes de deficit hidrico provocaram decrescimos significativos em A, E, gs e na razao Ci/Ca; contudo, nao alteraram as razoes Fv/Fm e Fv/F0. Apos a reidratacao houve o restabelecimento das trocas gasosas. Conclui-se que o deficit hidrico afetou negativamente a fotossintese, mediante uma limitacao estomatica, o que se confirma pelos decrescimos em gs, na razao Ci/Ca e na manutencao da eficiencia fotoquimica do FS II. Provavelmente, mecanismos de protecao tenham sido responsaveis pelo restabelecimento das trocas gasosas apos a reidratacao.