APOPLASTIC PERMEABILITY OF SCLEROTIA OF SCLEROTIUM-ROLFSII, SCLEROTIUM-CEPIVORUM AND RHIZOCTONIA-SOLANI

Intact mature sclerotia of Sclerotium rolfsii Sacc. and Sclerotium cepivorum Berk. produced in culture are impermeable to the apoplastic tracer sulphorhodamine G. Both of these species produce sclerotia with rinds. Some movement of sulphorhodamine into sclerotia of Rhizoctonia solani Kuhn: which have no rind, occurred but the fluorochrome was arrested after permeation of at most the outer five layers of cells. In all cases, low permeability depended on an intact outer layer, and when sclerotia of each species were bisected to provide direct access of sulphorhodamine to all tissue layers, the fluorochrome permeated the cell walls and extracellular matrix (where present) of many cells within the sclerotium. A marked reduction in permeability of intact sclerotia occurs at maturity in a number of species and might be important in long-term survival.