Mônica Ferreira de Abreu

Cadmium Accumulation in Sunflower Plants Influenced by Arbuscular Mycorrhiza

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 μmol L−1) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg−1. Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 μg g−1 dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.

ROUTINE SOIL TESTING TO MONITOR HEAVY METALS AND BORON

Microelementos tem um papel importante na agricultura, devido a sua essencialidade para plantas e tambem a possibilidade de serem toxicos as plantas e aos animais. Os cinco micronutrientes (B, Cu, Fe, Mn, e Zn) sao comumente determinados nas analises rotineiras de solos com finalidade de recomendacao de adubacao. Os outros quatro elementos (Cd, Cr, Pb, e Ni) sao metais pesados importantes para os solos agricolas e nao sao normalmente determinados em amostras de solos enviadas pelos agricultores. Portanto, altos teores desses metais pesados em terras agricultaveis poderao passar despercebidos. O objetivo deste trabalho foi usar a analise de rotina de solo para monitorar o teor dos nove elementos em amostras de solo. Um total de 13.416 amostras de solo de 21 estados brasileiros, sendo 58% delas originarias do estado de Sao Paulo, foram analisadas. O boro foi determinado usando a agua quente e os outros metais foram extraidos pelo DTPA (pH 7,3). Considerando todas as amostras, as faixas dos teores, em de mg dm-3 foram: B, 0,01-10,6; Cu, 0,1-56,2; Fe, 0,5-476; Mn, 1-325; Zn, 1-453; Cd 0,00-3,43, Cr, 0,0-42,9; Ni, 0,00-65,1; Pb, 0,00-63,9. Os valores medios para amostras originadas do Estado de Sao Paulo foram de: 0,32-B, 2,5-Cu, 36-Fe, 16,1-Mn, 4,8-Zn, 0,02-Cd, 0,03-Cr, 0,18-Ni e 0,85-Pb. Resultados semelhantes foram obtidos para amostras de outros Estados. Os valores mais altos sao indicativos de acao antropogenica, devido a aplicacao de fertilizantes ou de atividades industriais de mineracao. Analises de rotina feitas na amostras de solos do Brasil, especialmente originarias do estado de Sao Paulo, podem servir com base de dados para indicar o potencial de deficiencia de micronutrientes ou fitotoxicidade de metal pesado em solos agricultaveis, permitindo a tomada de acoes preventivas.

DISTRIBUIÇÃO DE CHUMBO NO PERFIL DE SOLO AVALIADA PELAS SOLUÇÕES DE DTPA E MEHLICH-3

Significant increase in the Pb content in cultivated soils has been observed near industrial areas. The objective of this work was to evaluate the soil Pb distribution profile near and distant of the lead emiting point, located between the Presidente Dutra highroad and the Cacapava Velha City, State of Sao Paulo, Brazil and to compare the Pb contents found by using DTPA and Mehlich-3 extracting solutions. Soil samples were collected at 500 and 1.000 m distant from the lead emiting point, in the N, S, E, and W directions, at depths of 0-5, 5-10, 10-20, 20-40 and 0-20 cm. Samples were treated separately with DTPA and Mehlich-3 solutions for the Pb extraction. The highest Pb concentrations were found in the soil samples collected close to the source of contamination. The results obtained using DTPA and Mehlich-3 solutions showed clearly that the lead tends to accumulate in the surface ground layer, decreasing with the soil depth. This indicated that the procedures using either DTPA or Mehlich-3 solutions as Pb extractor from soils should be also considered as appropriate for environmental monitoring.

Lead uptake and tolerance of Ricinus communis L.

Phytoextraction is an important technique used for the decontamination of areas polluted by lead. Consequently, an understanding of the physiological responses to tolerance of tropical species subjected to increasing levels of contamination is fundamental before considering their use as phytoextractors in contaminated areas. The objective of this study was to assess the lead (Pb) uptake and the tolerance of Ricinus communis L. The plants were cultivated in nutrient solution in a greenhouse under controlled conditions. Lead was tested at concentrations of 0, 100, 200 and 400 µmol L-1. The experimental set-up was a block design, using a 4 x 1 factorial scheme, with three replicates. Biometric analyses, photosynthesis rates, and Pb content in the nutritive solution as well as in roots and shoots were performed. In conclusion, R. communis L is a hyperaccumulator species for Pb and presents tolerance properties in lead light concentration.

Variability of Soil Analysis in Commercial Laboratories: Implications for Lime and Fertilizer Recommendations

Abstract Data of soil analysis of 20 samples of 84 commercial laboratories were used to estimate discrepancies among results and analyze the implications for fertilizer recommendations. More than 90% of the laboratories had all results of basic routine analysis of individual samples within the confidence interval (CI). Laboratories with the best performance in the proficiency test (grade A) had only 2.9 and 4.0% of the results outside the CI for the basic and the micronutrient set, respectively. However, the corresponding figures for grade C and D laboratories were 26.2% (basic) and 20.7% (micronutrients). Lime recommendation for a soil with 32% of soil base saturation reached the target value of 70±8% in 74% of the cases. In about 90% of the cases, fertilizer recommendations were on or close to the target rates Sizeable deviations of the fertilizer recommendations for P and K that could affect profit occurred in less than 5% of the results reported.

Efficiency of multinutrient extractants for the determining of available zinc in soils

The increasing use of the ICP-AES (inductively coupled plasma atomic emission spectrophotometry) as a multielement analytical technique has stressed the preference for the use of multinutrient extractants in routine soil analysis. However, few studies relating the extraction of zinc (Zn) from soil with such extractants and the absorption of the element by plants have been published. Two experiments under greenhouse conditions were carried out in order to determine the efficiency of some multinutrient extractants for the determination of available Zn in 44 soils from the State of São Paulo, Brazil, for corn and soybean. All soil samples were limed to increase the CECs base saturation at pH 7 to 70%. Twenty-two soil samples with DTPA (diethylenetriaminepentaacetic acid) extractable Zn concentration lower than 0.6 mg dm−3 received either the application of B, Cu, Mn, Zn or of these micronutrients excluding Zn. The remaining 22 soil samples, with Zn concentration above 0.6 mg dm−3, received application of three micronutrients (B, Cu and Mn). Macronutrients were applied to all pots as needed for crop development. Zinc was extracted from the soils before each planting using the extracting solutions, DTPA, Mehlich 1 (M-1), Mehlich 3 (M-3) and AB-DTPA (ammonium bicarbonate-DTPA) and determined by ICP-AES. The results showed significant correlations between plant Zn concentration and soil Zn concentration. The correlation values between soil-Zn and plant-Zn were of 0.74 (M-3), 0.73 (DTPA), 0.62 (AB-DTPA) and 0.61 (M-1) for corn, and of 0.71 (DTPA), 0.63 (M-1), 0.58 (M-3) and 0.46 (AB-DTPA) for soybean. Thus, the DTPA solution was the most efficient extractant for the determination of bioavailable Zn when both crops are considered together.

Restrictions in the use of correlation coefficients in comparing methods for the determination of the micronutrients in soils

Abstract Fifty nine soil samples from the State of Sao Paulo were collected from the plow layer, with about half of these samples presenting low or medium concentrations of micronutrients. Micronutrients were extracted by one of the following solutions: DTPA at pH 7.3, DTPA at pH 5.3, Mehlich‐1 BR, Mehlich‐1 USA, Mehlich‐3, and 0.01 mol L‐1 calcium chloride (CaCl2), and then determined by inductively coupled plasma emission spectrometry (ICP‐AES). Simple linear correlations were calculated for the results of all methods against the DTPA method at pH 7.3. Two sets of calculations were always considered: one including all 59 soil samples and another set including only those samples containing low and medium amounts for each element. Higher correlation coefficients were observed when samples with high contents were included. For example, the range of correlations (R2) obtained for zinc (Zn) varied from 0.41 to 0.98, if all samples were considered in the calculations, but the range decreased to 0.41 ‐ 0.55 if...

Crescimento de orquídeas epífitas in vitro: adição de polpa de frutos

THE PULPS OF FRUITS IN THE GROWTH OF EPIPHYTIC ORCHIDS This work was carried out with the aim of studying the effect of pulp of fruits on the growth of orchids seedlings in vitro . Three species of epiphytic brazilian orchids were used: Laelia longipes Rchb.f., Laelia tenebrosa Rolfe e Miltonia spectabilis (Lindley). The following nutritive media were tested: 10:10:10 (N:P:K), at 1 gL -1 , 10:30:20 at 1 gL -1 , apple pulp, at 10 gL -1 , tomato pulp at 10 gL -1 , banana pulp at 50 gL -1 , and also the KNUDSON, VACIN and WENT, MURASHIGE and SKOOG (MS) media. In seedlings of L. Longipes cultivated in 10:10:10 and banana pulp was observed higher accumulation, and the lowest one in MS. Analysis of dry mass results for Miltonia spectabilis showed that the media 10:30:20 and banana pulp propiciated the highest dry mass accumulation and the MS medium, the lowest. In decreasing order of total dry mass accumulation are the media 10:30:20 and banana pulp, followed by 10:10:10, tomato pulp, KNUDSON (58,3%), VACIN e WENT (18,7%), apple pulp (13,2%) and MS (4,1%). For Laelia tenebrosa, seedlings cultivated in banana pulp incorporated higher dry mass content, followed by those cultivated in 10:10:10, whereas the remaining media propitiated reduced accumulation.

Direct voltammetric determination of Mo(VI) in plants: the need for a multivariate study of interferences

A multivariate modelling procedure using a second order composite design showed that the adsorptive stripping voltammetry (AdSV) technique used for molybdenum determination in a N,N-dimethylformamide (DMF)–ethanol–water homogeneous ternary solvent system (HTSS) using-benzoinoxime (BO) as the complexing agent and a sodium acetate–acetic acid buffer as the supporting electrolyte is much more tolerant to the presence of phosphorous (as phosphate) and iron than it could be presumed. Instead of the concentration ratios of P/Mo = 100 and Fe/Mo = 500, determined by univariate experiments, these values were respectively raised to 97,500 and 4200 when the phosphate and Fe(III) levels are varied simultaneously from 0.625 to 2.500 and from 0.006 to 0.150 mg l −1 , respectively, in the voltammetric cell, keeping the molybdenum concentration constant at 3.00 gl −1 . This allowed us to propose a straightforward AdSV–HTSS procedure for the determination of Mo(VI) in plants. The AdSV results compared favourably with those obtained by using graphite furnace atomic absorption spectrometry (GFAAS) and with the results of samples from the International Plant-Analytical Exchange (IPE) programme of Wageningen University (The Netherlands).

Comparison of Methods to Quantify Organic Carbon in Soil Samples from São Paulo State, Brazil

Soil carbon (C) determinations are important for soil quality assessment. The standard method that is used in São Paulo state to determine soil organic C is a modified Walkely–Black method. This method has some disadvantages because of the time needed for implementation and the use of potassium dichromate. Therefore, the aims of this work were to test the efficiency and compare the following methods: (a) wet oxidation of organic C (OC-HO) followed by spectrophotometer determination, (b) dry incineration at 550 °C with a muffle furnace plus gravimetric determination (TC-I), and (c) dry combustion with a C–nitrogen (N)–sulfur (S) elemental analyzer (TC-EA). Sixty-one soil samples were collected at the 0- to 20-cm depth on agricultural soils of São Paulo state. Samples were dried at 65 °C, ground, and sieved through a 0.09-mm sieve. Carbon content was determined in triplicate. These sets of samples exhibited a wide range of C content: TC-EA was from 0.43 to 9.14 g 100 g−1. Mean C contents were 6.76 g 100 g−1, 2.31 g 100 g−1, and 2.52 g 100 g−1 for TC-I, OC-HO, and TC-EA, respectively. Moreover, in all the studied soil samples, the TC-I method overestimated the C content when compared with OC-HO and TC-EA methods. Losses of structural water and inorganic colloidal compounds, such as gibbsite, induced by high temperature during incineration probably were responsible for the greater C contents obtained by the TC-I method. Correlation coefficients between the three methods were rather similar: TC-I and TC-EA (r = 0.87), TC and OC-HO (r = 0.83), and TC-EA and OC-HO (r = 0.84). It was concluded that C extraction by the standard, routinely employed OC-HO method can be replaced by the TC-EA method, which has environmental advantages.