Pattern of Cell Division and Wound Vessel Member Differentiation in Coleus Pith Explants

When pith parenchyma explants are taken from Coleus blumei plants and cultured on an agar medium containing sucrose and indoleacetic acid wound vessel members differentiate in 10 days. The time course of wound xylem appearance and an auxin requirement suggest that this uncomplicated system is responding in a manner comparable to wounded Coleus plants and cultured stem segments.Histological examination and cell size comparisons confirm that parenchyma cells divide before differentiating. When colchicine is used to prevent mitosis no tracheary elements differentiate. Following the time course of this cytodifferentiation histologically shows that xylem differentiates from cells that are the products of several cell divisions.