Objetivou-se avaliar a eficácia da aplicação foliar de silício nos aspectos fisiológicos e bioquímicos em um genótipo de Theobroma cacao inoculado com Moniliophthora perniciosa, fungo causador da vassoura-de-bruxa, importante doença da cacauicultura. Mudas do genótipo Catongo foram submetidas a um experimento com dois fatores (inoculação e não inoculação das plantas com M. perniciosa) cada um com dois níveis de Si (0.0 mg e 1.0 mg mL-1 de AgriSil contendo 98% de SiO2 aplicado por pulverização). Verificou-se que plantas inoculadas e submetidas à aplicação foliar com Si apresentaram aumento na fotossíntese, das atividades de peroxidases, quitinases e polifenoloxidases e da densidade estomática. Os resultados indicam que a aplicação de silício é benéfica aumentando as defesas contra Moniliphthora perniciosa em mudas de cacaueiros.

This study aimed to verify the efficiency of silicon leaf application in the physiological and biochemical characteristics in a Theobroma cacao genotype inoculated with Moniliophthora perniciosa fungus, which causes the witches’ broom disease, important cocoa disease in Brazil and worldwide. Seedlings of Catongo genotype were used. The experimental design used was a randomized block design with four replicates, including two inoculation factors (inoculated and non-inoculated plants), each one with two levels of silicon application (0.0 mg and 1.0 mg mL-1 with AgriSil containing 98% of SiO2). We observed that plants that were inoculated with M. perniciosa and subjected to leaf application with silicon presented enhanced photosynthesis, peroxidases, chitinase, polyphenoloxidases activities and stomatal density. Results have shown that silicon application is beneficial and increases the defenses against Moniliophthora perniciosa in cocoa seedlings.

Most studies of chromium have been realized in the sediments and in mangrove trees. However, little is known about its effect on growth and metabolism in this vegetation. L. racemosa plants were grown in solution with 20% of ionic strength of Hoagland and Arnon containing 100 mM NaCl and supplemented with 0.00, 0.05 and 0.50 mg L-1 of Cr+3. The growth, the pigments and gas exchange measurements showed no changes in response to doses of chromium. After 30 days the initiation of treatments, plants of L. racemosa had average 0.559 g of total dry weight, 1.34 mg L-1 of total chlorophyll and 7.9 µmol m-2 s-1 of A (CO2 photosynthetic assimilation). The photochemical potential efficiency was affected by the intermediate dose of 0.05 mg L-1 of Cr+3 (Fv/Fm=0.73) and it was associated with improved translocation of chromium from root to leaves. L. racemosa accumulated Cr+3 in the root, especially in the highest dose (560 mg g-1 DW) representing twenty-eight times the value obtained in control. The concentration of chromium in stem and leaves was not influenced by the tested doses. There was a reduction of fructose and sucrose in the largest dose of chromium, suggesting the drain of these carbohydrates to meet the energy demand of root absorption. The results suggest that L. racemosa owns characteristics of a chromium-tolerant species.

As concentrações de nutrientes das folhas e do sedimento e a capacidade de acumulação de elementos químicos dos tecidos foliares das espécies Avicennia germinans (L.) Stearn., Avicennia schaueriana Staft & Leechm., Laguncularia racemosa (L.) Gaertn. f. e Rhizophora mangle L. foram analisadas em quatro estações de estudo no manguezal do estuário do Rio São Mateus, no Estado do Espírito Santo. De modo geral, os elementos determinados no sedimento seguiram a ordem: Mg > Ca > Fe > K > Mn > P > Zn > Cu, apresentando variações inter e intraespecíficas. No tecido foliar, as espécies de Avicennia apresentaram maiores teores de N, K e Mg e menores concentrações de Ca. Rhizophora mangle exibiu maior concentração de Mn e Laguncularia racemosa, maior teor de Fe em relação às demais espécies. Os resultados demonstraram que a concentração de nutrientes do sedimento refletiu a influência da granulometria neste compartimento. O acúmulo de nutrientes nas folhas variou de acordo com a espécie e estação de estudo, mas não refletiu as concentrações do sedimento. Os dados confirmaram o papel do manguezal como barreira biogeoquímica ao trânsito de metais pesados. Entretanto, torna-se desejável uma amostragem periódica para um melhor entendimento da dinâmica de nutrientes.

We analyzed nutrient concentrations in leaves and sediments, and element accumulation capacity in foliar tissues of Avicennia germinans (L.) Stearn., Avicennia schaueriana Staft & Leechm., Laguncularia racemosa (L.) Gaertn. f. and Rhizophora mangle L. in four sites along the São Mateus River estuary mangrove, Espírito Santo State, SE-Brazil. In sediment, elements decrease following the sequence: Mg > Ca > Fe > K > Mn > P > Zn > Cu and showed inter and intraespecific variation. Avicennia leaves showed the greatest N, K and Mg concentrations and lowest Ca concentrations. Rhizophora mangle presented the greatest Mn concentration, and Laguncularia racemosa the greatest Fe level. Sediment nutrient concentrations reflected the influence of granulometry in this compartment. Nutrient accumulation in leaves varied according to species and study site but it was not correlated with sediment concentrations. Results confirmed the mangrove role as a biogeochemistry barrier blocking heavy metal up to tropical coastal areas. However, it is necessary periodic sampling so that it can be possible a better understanding of the nutrient dynamic.