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

Intact mature sclerotia of Sclerotium rolfsii Sacc. and Sclerotium cep ivorum Berk. produced in culture are impermeable to the apoplastic tra cer sulphorhodamine G. Both of these species produce sclerotia with ri nds. Some movement of sulphorhodamine into sclerotia of Rhizoctonia so lani Kuhn: which have no rind, occurred but the fluorochrome was arres ted after permeation of at most the outer five layers of cells. In all cases, low permeability depended on an intact outer layer, and when s clerotia of each species were bisected to provide direct access of sul phorhodamine to all tissue layers, the fluorochrome permeated the cell walls and extracellular matrix (where present) of many cells within t he sclerotium. A marked reduction in permeability of intact sclerotia occurs at maturity in a number of species and might be important in lo ng-term survival.