ABSTRACT. Agricultural species are subjected to a variety of biotic and abiotic stresses, which are the main limitations to crop production. In this context, contamination by trace elements is characterized as an abiotic stress that represents an environmental problem. Due to the physical and chemical similarities between cadmium and zinc, these elements may interact in the environment and may cause antagonistic or synergistic effects. In this way, physiological mechanisms to exclude, detoxify or compartmentalize trace elements that are in excess are crucial for plant survival when exposed to high concentrations of these elements. In this way, the aim of this study was to understand the physiological responses of Phaseolus vulgaris plants subjected to increasing doses of Cd and Zn for 21 days in different soil, Cambisol and Latosol. The activity of antioxidant enzymes, such as SOD, CAT, and APX; hydrogen peroxide content; lipid peroxidation; chlorophyll index; photosynthetic rate; stomatal conductance; and transpiration were analysed. The data obtained showed a specific behaviour of Phaseolus vulgaris plants in each soil analysed. Moreover, it was observed that interactions between both elements resulted in a synergistic effect, negatively affecting all of the parameters analysed.

RESUMO. O objetivo desse trabalho foi avaliar a relação entre a toxicidade de manganês e a tolerância ao alagamento em plantas de Zea mays L. cv. Saracura do 18º ciclo de seleção. Plantas de milho foram transferidas para recipientes plástico contendo soluções com diferentes concentrações de manganês. Folhas e raízes foram coletadas antes dos tratamentos, 7, 14 e 21 após a imposição dos tratamentos para as análises de conteúdo de clorofilas e carotenoides, produção de biomassa e metabolismo antioxidante. O Mn foi fortemente translocado das raízes para as folhas desencadeando uma considerável redução no conteúdo foliar de clorofila. O excesso de Mn desencadeou uma aumento na produção de espécies reativas de oxigênio, o que foi acompanhado por uma elevação na atividade das enzimas do metabolismo antioxidante e da peroxidação lipídica. Zea mays L. cv. Saracura demonstrou ser eficiente no sequestro de uma grande quantidade de Mn nas folhas, com um significativo impacto no metabolismo, no entanto sem o aparecimento de sintomas visuais e sem uma grande redução no seu crescimento.

ABSTRACT. The objective of this study was to evaluate the relationship between excess manganese and waterlogging tolerance in 18th selection cycle Zea mays L. cv. Saracura plants. Maize plants were transferred to plastic receptacles containing solutions with different concentrations of manganese. Leaves and roots were evaluated at the beginning of treatment and after 7, 14, and 21 days for chlorophyll content, biomass production and antioxidant metabolism. Mn was strongly translocated from the roots to the leaves, triggering a decrease in chlorophyll content. Excess Mn promoted an increase in reactive oxygen species that was accompanied by higher levels of antioxidative enzyme activity and lipid peroxidation. Zea mays L. cv. Saracura efficiently sequestered relatively large amounts of Mn in the leaves, with a significant impact on metabolism; however, we did not observe visual symptoms or a large decrease in biomass production.

ABSTRACT In order to investigate the existence of a possible abscission zone in the binding region between the peduncle and the coffee fruit, as well as the biochemical events involved in fruit ripening, we studied peduncles and fruits of Coffea arabica L. cv. “Icatu amarelo”. Coffee fruits were harvested at different maturation stages by using specific intervals of detachment force. It was observed a breakdown in the cells of the connecting region between peduncles and fruits throughout the maturation process. This disruption is probably caused by increased activity of the cell wall-loosening enzymes (polygalacturonase and cellulase) as well as by higher levels of lipid peroxidation in the final maturation stages. In general, physiological differences between maturation stages were observed and can largely explain the different detachment forces required at different stages. In conclusion, there is no clear abscission zone between the peduncle and the coffee fruit cv. “Icatu amarelo”. Nevertheless, the decrease in the detachment force throughout the maturation process can occur due to the activity of cell wall-degrading enzymes together with increased oxidative stress during the fruit ripening.