Polar Patierns of Periderm Onfogeny, Their Relationship to Leaves and Buds, and the Control of Cork Formation

Patterns of periderm ontogeny were studied in vigorously growing branches and leaders of Calotropis procera (Ait.) Ait. f., Carissa grandiflora A. DC., Ficus elastica Roxb., Ficus religiosa L. and Melia azedarach L. In all of these five woody species the periderm develops in clear polar patterns, with inhibitory zones, in which periderm formation is delayed, just beneath leaf bases and around dormant buds. A high rate of periderm production is induced by high sun irradiation in Calotropis procera . The polar patterns of periderm formation with retardation regions around leaves and buds probably indicate auxin involvement in the control mechanism of periderm differentiation. The role of both auxin and ethylene in periderm formation is discussed, as weIl as a proposed mechanism for rhytidome initiation.