Degradation of pruning wastes by Phanerochaete sordida growing in SSF: Ultrastructural, chemical, and enzymatic studies

A solid standard fermentation (SSF) with the fungus Phanerochaete sordida in a medium with Nephrolepis cordifolia (entire pinnae separated from the rachis) and Laurus nobilis (fragmented leaves) was performed over 92 days to study the degradation of leaves with histological, chemical, and enzymatic methods. The fungus entered the leaves early, through the stomata in N. cordifolia and L. nobilis, and also through mechanical cuts that had been made in the latter. The initial attack affected the mesophyll in both plant species, and the phloem in L. nobilis. The vascular bundle of N. cordifolia was protected by a sheath of cells with thick lignified walls. The collenchyma cell walls situated near the principal vein in L. nobilis swelled during the initial stages of enzymatic action, but reduced their thickness afterwards, mainly in regions of contact with the hyphae. At the end of the experiment, no species had leaves with mesophyll. In L. nobilis, phloem was also lacking, and a partial and heterogeneous attack on the xylem became evident. The histological changes are compared with the enzymatic activities and the chemical composition of the culture media, describing the stages of fungal colonization.