Microscopie de la mycoflore des aiguilles de Sapin blanc (Abies alba). IV. Décomposition de la cuticule, de l'hypoderme et de l'épiderme

Abstract

Degradation of protective tissues of coniferous needles (Abies alba Mill.) was examined by light and electron microscopy. Cuticle and hypodermis were destroyed at the beginning of the F1 stage, 1 year after needle fall. Hyphae from the superficial mycelium penetrated and colonized the cuticle, giving rise to numerous cavities throughout the cuticular layers. At the same time the cell wall of the hypodermis was invaded by soft rot fungi (type I) and hyphae grew within cavities within the secondary wall. During the F2 stage the epidermis was also destroyed by formation of cavities in the cell wall. At this time the remaining cuticle gave a typical wrinkled appearance to the needle surface. Hypotheses about the fungal species implicated in these activities are discussed. These processes do not affect residual cytoplasm of parenchyma cells and appear to be strongly different from white rot degradation of litter.