Changes in Cell Dimensions in Developing Roots of In vitro Cultured Immature Maize Embryos (Zea mays L.)

Abstract

The pattern of tissue organization in roots of cultured immature maize embryos was studied using morphometric methods. After five periods of in vitro culture, ranging from 0 h up to 48 h, cell dimensions were measured in various regions of the root using an image analyzer. Cell elongation was scored directly; because mitotic figures were rarely observed, cell division activity was derived indirectly from planes of new cell walls and the decrease in cell lengths. The tissues, distinguished as protoderm, outer ground meristem, pro-endodermis, pericycle, procambium, and pith, displayed different patterns of development. Proceeding from the root tip to the base, various regions were defined. After 24 h of culture new transverse cell walls were observed in most tissues. In the stele they occurred just behind the root tip. In the ground meristem-protoderm complex they were found at some distance from the tip. After 42 h of in vitro culture new cells were observed from the region bordering the quiescent center u...