Defense Responses Induced by Soluble Silicon in Cucumber Roots Infected by<i>Pythium</i>spp.

Abstract

The role of silicon (Si) in plant growth was investigated on the basis of induction of defense mechanisms in response to fungal attacks. Amendment of cucumber plants with soluble Si (Si+) resulted in a marked stimulation of chitinase activity and in a more intense and rapid activation of peroxidases and polyphenoloxidases after infection with Pythium spp. Additionally, glycosidically bound phenolics extracted from Si+ plants and subjected to acid or β-glucosidase hydrolysis (Gly extracts) displayed a strong fungistatic activity against P. ultimum, P. aphanidermatum, and Cladosporium cucumerinum. Extracts obtained in the same way from control plants were not inhibitory to fungal growth, regardless of Si treatment [...]