Other mechanisms by which Si
confers resistance to certain diseases are associated with the
physical barrier formed by the deposition of this element under the
cuticle and on the epidermal cell wall (Kim et al., 2002) or with the
enhancement of defense mechanisms (Datnoff et al., 2007). However,
Carre-Missio et al. (2009) reported that the activities of glucanases,
chitinases, and peroxidases increased in the presence of
Hemileia vastatrix regardless of the presence of Si in the nutrient
solution. Datnoff et al. (2007) also reported that Si is not translocated
from older to newer leaves or even from one application
site to another. Thus, to ensure reduced disease intensities, possibly
via osmotic effects, potassium silicate should be continually applied
to all organs of the plant to be protected