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The silicon (Si) reduced tan spot ( Pyrenophora tritici-repentis ) severity up to 40%, through both biochemical defense mechanisms and histo-cytological defense responses. The activities of enzymes involved in plant defense system such as superoxide dismutase, peroxidase and chitinase showed greater activity in inoculated plants supplied with Si. Histo-cytological analysis indicated that Si potentiated the accumulation of hydrogen peroxide in the beginning of infection process. Together, these defense mechanisms resulted in the reduction of cell death at the infection sites in plants supplied with Si, which in turn showed lower disease severity. Si appears to be a promising alternative control measure for use in integrated management of tan spot. [ABSTRACT FROM AUTHOR]

Rice plants cultivated under 700 ppm atmospheric CO 2 concentration presented a reduction in the progress and severity of the brown spot disease (Bipolaris oryzae), through the enhancement of biochemical defense mechanisms. Plants exposed to 700 ppm of CO 2 had higher activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, polyphenoloxidase and chitinase, and increased phenolic compounds and lignin concentration, independent of the rice cultivar. Therefore, the lower severity values of the disease were related to changes in the development of the lesions as a result of the defense responses, which were stimulated in the rice plants by the increase of CO 2 concentration. • This study demonstrated that increase of atmospheric CO 2 improves rice resistance to brown spot. • Rice under enhanced atmospheric CO 2 concentration have a better attenuation of the oxidative damages. • Rice under enhanced atmospheric CO 2 concentration have the reduction on the severity of the brown spot. • Rice exposed to 700 ppm of CO 2 had higher activity of antioxidant enzymes. • Rice exposed to 700 ppm of CO 2 had higher concentration of phenolic compounds and lignin content. [ABSTRACT FROM AUTHOR]