Brightness Contrast and White Illusion

Abstract

Silicon (Si) has been exploited for its prophylactic properties against plant disease for hundreds of years. Its role as a disease-preventing product has been well documented, but the mechanisms by which it exerts its beneficial properties in planta remain poorly understood. For a long time, the observation of a systematic accumulation of silica in cell walls and appositions occurring at pathogen penetration sites led to the conclusion that this parietal strengthening was responsible for the increased resistance of plants to diseases. However, recent evidence suggests that Si. would rather play an active role in reinforcing plant disease resistance by stimulating the expression of its natural defense reactions. Incidentally, in the cucumber (Cucumis sativus)-powdery mildew (Sphaerotheca fuliginea) system, this latter mechanism appears to be predominant, if not exclusive. A better understanding of this rather unique property of Si. could be exploited to optimize its use in agriculture and to help decipher how plants can be naturally stimulated to protect themselves against pathogens.