Structure and cytochemistry of the walls of urediospores, germ tubes, and appressoria of Puccinia graminis tritici

Abstract

Several cytochemical methods demonstrated that urediospore walls of Puccinia graminis f. sp. tritici were probably composed of five layers, including the pellicle as the outermost layer. Two previously undescribed layers were located around the inner periphery of the spore walls. Staining for periodate-sensitive glycosubstances occurred uniformly and heavily throughout the wall except that the pellicle was unstained, and the innermost layer (3c) was more lightly stained by periodic acid – thiocarbohydrazide – silver proteinate. There was little wheat germ lectin or concanavalin A binding to the urediospore wall except in the hilar region, where wheat germ lectin bound heavily, and in the germ pore region, where binding of concanavalin A occurred. The walls of about one-half of the urediospores that were examined contained silicon deposits. Germ tube walls were composed of two layers: a broad outer layer and a narrower inner layer. The inner layer stained more heavily for periodate-sensitive glycosubstances than did the outer layer. Germ tube walls bound wheat germ lectin, but not concanavalin A. Appressorial walls were also composed of two layers, but the inner layer was much broader than that of germ tube walls, and the outer layer stained more heavily for periodate-sensitive glycosubstances. There was strong wheat germ lectin binding to the appressorial walls, but concanavalin A binding was sparse. Both germ tubes and appressoria were coated with a mucilagenouslike substance.