Is arsenite more toxic than arsenate in plants?

In order to evaluate the differential absorption and toxicity of arsenate (AsV) and arsenite (AsIII), Lemna valdiviana plants were grown in a nutrient solution and subjected to 0.0 (control); 0.5; 1.0; 1.5; 2.0; 3.0; 4.0; 5.0 and 7.5 mg L-1 of AsIII or AsV for three days. Exposure to both chemical forms resulted in As bioaccumulation, although AsIII-grown plants showed higher As content in tissues. In AsV-grown plants, the relative growth rate (RGR) decreased to 50%, at a concentration of 4.0 mg L-1, while for treatments with AsIII, the same decrease was observed at 1.0 mg L-1. The tolerance index decreased with increasing concentrations, with lower values for AsIII. Plants treated with AsIII showed increased superoxide anion levels, whilst higher levels of hydrogen peroxide were present in AsV-treated plants. Moreover, malondialdehyde (MDA) levels were higher for plants subjected to AsIII when compared to AsV at lower concentrations. Concentrations of 1 mg L-1 of AsIII and 4 mg L-1 of AsV showed equivalent MDA levels. Superoxide dismutase and catalase activities were increased at low concentrations and were inhibited at higher concentrations of AsIII and AsV, whereas peroxidase activity was positively modulated by increased AsIII or AsV concentrations. In conclusion, L. valdiviana plants took up and accumulated arsenic as AsIII or AsV, demonstrating the potential for phytoremediation of this metalloid. Furthermore, AsIII-exposed plants showed enhanced toxicity when compared to AsV, at the same applied concentration, although toxicity was more related to internal As concentrations, regardless of the chemical form applied.

Evaluation of Metals in Soil and Tissues of Economic-Interest Plants Grown in Sites Affected by the Fundão Dam Failure in Mariana, Brazil.

The objective of this study was to evaluate the concentration of potentially toxic elements in Brachiaria decumbens, Stylosanthes guianensis, and Saccharum officinarum plants and soil samples in affected and unaffected areas by rupture of the Fundão dam, Brazil. Samples were collected in areas affected by residues from the Fundão dam (RAA1, RAA2, RAA3) and in an unaffected area (control). The material was analyzed for the composition of micronutrients and trace elements in soil and plants, as well as contamination factor (CF), accumulation factor, and translocation factor (TF). Overall, the results showed that soil and plant tissues had increased Fe, Mn, Cu, and Cr content and decreased Zn content in the affected areas, compared to the control. Leaves and roots of B. decumbens showed an increase in Fe content in affected areas, compared to the control, reaching a mean maximum value of 42 958 µg/g of roots of RAA2-collected plants. As a result, CF for Fe of B. decumbens was classified as very high and they presented low TF values. Furthermore, B. decumbens collected in affected areas showed an increase of Fe, Mn, Cu, and Cr in leaves, stems, and roots, whereas in Stylosanthes guianensis, there was an increase of Fe concentration in all tissues and Cr in leaves. Also, Saccharum officinarum showed the accumulation of Mn in the stem and Cu in leaves and stem. On the other hand, there was no contamination of plants by hazardous elements such as Pb, Cd, and As in the samples analyzed. In conclusion, increases in the content of Fe, Mn, Cu, and Cr were found in soil and several plant tissues of residue-affected areas, which could compromise plant growth and represent potential hazards arising from the biomagnification process in the food chain. Integr Environ Assess Manag 2020;16:596-607. © 2020 SETAC.

O objetivo deste estudo foi avaliar a concentração de elementos potencialmente tóxicos em plantas de Brachiaria decumbens, Stylosanthes guianensis e Saccharum officinarum e amostras de solos em áreas afetadas e não afetadas pelo rompimento da barragem de Fundão. As amostras foram coletadas em áreas afetadas por resíduos da barragem de Fundão (RAA1, RAA2, RAA3) e em uma área não afetada (controle). O material foi analisado quanto à composição de micronutrientes e elementos-traço no solo e plantas, além de fatores de contaminação (CF), bioacumulação e translocação (TF). No geral, os resultados mostraram que o solo e as plantas apresentaram maiores teores de Fe, Mn, Cu e Cr e menores teores de Zn nas áreas afetadas em comparação ao controle. Folhas e raízes de B. decumbens apresentaram aumento no teor de Fe nas áreas afetadas em relação ao controle, atingindo o valor máximo médio de 42.958 µg/g nas raízes de plantas coletadas em RAA2. Como resultado, CF para Fe de B. decumbens foi classificado como muito alto, mas com baixos valores de TF. Além disso, B. decumbens coletadas nas áreas afetadas apresentaram aumento de Fe, Mn, Cu e Cr nas folhas, caules e raízes, enquanto que em Stylosanthes guianensis houve aumento da concentração de Fe em todos as partes das plantas e Cr nas folhas. Saccharum officinarum também apresentou acúmulo de Mn no caule e Cu nas folhas e caule. Por outro lado, não há contaminação das plantas por elementos perigosos como Pb, Cd e As nas amostras analisadas. Concluindo, foram encontrados aumentos nos teores de Fe, Mn, Cu e Cr no solo e em vários tecidos vegetais, o que pode comprometer o crescimento das plantas e representar riscos potenciais decorrentes do processo de biomagnificação na cadeia alimentar. Integr Environ Assess Manag 2020;16:596-607.

Análise comparativa de métodos de determinação de área foliar em genótipos de cacau / Comparative analysis of methods of determining leaf area in cocoa genotypes

O conhecimento da área foliar é uma ferramenta importante na análise do crescimento e desenvolvimento vegetal. Desse modo, objetivou-se comparar os métodos, integrador de área foliar, software DDA, software ImageJ e de medição das dimensões foliares, visando definir o fator de correção mais adequado para estimar a área foliar de genótipos cacau. O experimento foi desenvolvido na Estação Experimental Filogônio Peixoto no delineamento de blocos casualizados com quatro repetições em arranjo fatorial 4 x 8, sendo 4 métodos de avaliação de área foliar e oito genótipos de cacau (Variedade Comum; TSH 1188; Catongo; CCN 51; ICS 1; ESFIP 02; SJ 02 e PH 16). Os resultados foram submetidos a análises de variância e correlação e as médias comparadas pelo teste Tukey 5%. Não houve diferença entre os métodos de determinação de área foliar, sendo constatada correlação positiva entre os métodos DDA, ImageJ e Dimensões foliares com o método do integrador de área foliar (padrão), com valores dos coeficientes de correlação (r) superiores a 0,98. Os genótipos TSH 1188, Catongo e CCN 51 apresentaram maior área foliar média. Os métodos testados mostraram-se viáveis para estimar área foliar do cacaueiro com precisão, contudo, foram encontrados três grupos de fatores de correção, sendo K = 0,682 para os genótipos SJ 02 e Variedade Comum, K = 0,670 para os genótipos CCN 51, Catongo, TSH 1188 e ICS 01 e K = 0, 655 para os genótipos ESFIP 02 e PH 16.

The knowledge of the leaf area is an important tool in the analysis of plant growth and development. Thus, the objective was to compare the methods, integrating leaf area, software DDA, software ImageJ and measurement of leaf dimensions, aiming to define the most appropriate correction factor to estimate the leaf area of cacao genotypes. The experiment was conducted at the Experimental Station Filogônio Peixoto in a randomized block design with four replications in a factorial arrangement of 4 x 8, being 4 assessment methods of leaf area and eight cacao genotypes (Common Variety; TSH 1188; Catongo; CCN 51; ICS 1; ESFIP 02; SJ 02 e PH 16). The results were submitted to analysis of variance and correlation and means were compared by Tukey test 5%. There was no difference between the methods of determining leaf area, being found positive correlation between the methods DDA, ImageJ and leaf dimensions with the integrative method of leaf area (default), with values of correlation coefficients (r) greater than 0,98. The genotypes TSH 1188, Catongo and CCN 51 have higher average leaf area. The methods tested were shown to be viable to estimate leaf area of cacao accurately, however, we found three groups of correction factors, being K = 0,682 for genotypes SJ 02 and Common Variety, K = 0,670 for genotypes CCN 51, Catongo, TSH 1188 and ICS 01 and K = 0, 655 for genotypes ESFIP 02 and PH 16.