The effects of rind damage and regeneration on permeability of the apoplast in sclerotia of Sclerotinia minor

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Sclerotia of Sclerotinia minor Jaggar have the ability to regenerate a new rind when the old rind is damaged before or after maturity. Regeneration involves growth of a completely new rind to cut off the exposed damaged surface. New, more or less spherical rind and cortical cells form by outgrowth of existing medullary hyphae. The new rind cells become pigmented over several days and new cortical cells contain reserves when the new rind has become fully pigmented. This process is most rapid in immature sclerotia but even in mature sclerotia, a new rind is fully regenerated within 8 d. Intact mature sclerotia exclude the apoplastic tracer sulforhodamine C but when the rind is damaged they become leaky to the fluorochrome. Regeneration of a new rind reduces permeability to sulforhodamine but the initial impermeable state is not fully regained, even when regeneration is complete. Sclerotia that have been damaged in the field, despite regeneration, might be more susceptible to external influences than those in which the rind has remained intact.

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