Formation and propagation of cell division-centers in the epidermal layer of internodal segments of Torenia fournieri grown in vitro. Simultaneous surface observations of all the epidermal cells

Abstract

A cytological study of bud neoformation was done using a technique of direct observation of whole epidermal strips excised and stained at different stages of development from one side of an internodal segment of Torenia fournieri grown in vitro. It was shown that cell divisions start at random points over the epidermis and spread out progressively and apparently by contagion, forming cell division-centers. These centers are each formed of a central, highly divided cell surrounded by several less divided cells. The number of divisions per original cell decreases with the distance from the highly divided central cell.The probable origin of bud meristems was shown to be either one part of an original cell, one cell, several parts of adjacent cells, or several entire adjacent cells.A competition phenomenon was shown to exist between cell division-centers; few centers form meristematic primordia and only a few of these last form buds (about 20). Thus, on an epidermal strip 10 × 2.5 mm containing about 5000–6000 cells, fewer than 100 cells are implicated in the formation of buds observed morphologically.