Cadmium (Cd) is a highly toxic metal for plants, even at low concentrations in the soil. The annual production of world cocoa beans is approximately 4 million tons. Most of these fermented and dried beans are used in the manufacture of chocolate. Recent work has shown that the concentration of Cd in these beans has exceeded the critical level (0.6mgkg DM). The objective of this study was to evaluate the toxicity of Cd in young plants of CCN 51 cacao genotype grown in soil with different concentrations of Cd (0, 0.05 and 0.1gkg soil) through photosynthetic, antioxidative, molecular and ultrastructural changes. The increase of Cd concentration in the soil altered mineral nutrient absorption by competition or synergism, changed photosynthetic activity caused by reduction in chloroplastidic pigment content and damage to the photosynthetic machinery evidenced by the Fv/Fm ratio and expression of the psbA gene and increased GPX activity in the root and SOD in leaves. Additionally, ultrastructural alterations in roots and leaves were also evidenced with the increase of the concentration of Cd in the soil, whose toxicity caused rupture of biomembranes in root and leaf cells, reduction of the number of starch grains in foliar cells, increase of plastoglobules in chloroplasts and presence of multivesiculated bodies in root cells. It was concluded, therefore, that soil Cd toxicity caused damage to the photosynthetic machinery, antioxidative metabolism, gene expression and irreversible damage to root cells ultrastructure of CCN 51 cocoa plants, whose damage intensity depended on the exposure time to the metal.

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The use of micropropagation technique has been an alternative to conservation of endangered species, Comanthera mucugensis subsp. mucugensis (popular namely sempre viva de Mucuge); however, there is no information on the effect of arbuscular mycorrhizal fungi (AMF) on the acclimation process of micropropagated plants. This study evaluated the survival, growth and nutritional aspects of the species, C. mucugensis subsp. mucugensis inoculated with native AMFs in greenhouse condition. The design of the experiment consisted initially of 80 sampling units divided into four treatments: plants inoculated with native AMF, with microbiota filtrate from soil, with AMF plus filtrate and control (noninoculated plants). At three and eleven-month-old, the plants were collected for evaluation of growth, nutrition and mycorrhizal colonization. After eleven months of experiment, survival rate of AMF and AMF plus filtrate plants were 62.5 and 87.5%, respectively, and only one microbiota filtrate and one control plants survived. AMF inoculation also provided increase in n dry matter of rosettes and permitted obtaining flowering ten-month-growth plants. Rates of mycorrhizal colonization were high at three (aproximately 64.9%) and eleven (aproximately 94.5%) months for AMF and AMF plus filtrate plants. Number of spores in rhizosphere soil of mycorrhizal plants was also high (1599 per 100 dm 3 of soil) and seven diferent species of AMF were identified at the end of experiment. Data set evidenced mycortrophic character of C. mucugensis subsp. mucugensis and the importance of AMF inoculation for acclimation and survival of microprogagated plants which is essential for conservation of this endangered plant.

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