Histological and Biochemical Characterization of Adventitious Root Formation in Walnut Cotyledon Fragments

Abstract

Studies conducted on the plant model Arabidopsis thaliana demonstrate that primary and lateral root meristem formation are controlled by different factors including the number, nature and environment of the original cells as well as hormonal and genetic controls (Aeschbacher et al., 1994, Celenza et al., 1995). The primary root meristem derives from one cell of the embryo and the hypophysis whereas the lateral root meristem rises from pericycle cells of primary root system. Adventitious root formation (ARF) is a mul- tistep developmental process in which competent cells are induced to form a root meristem (Mohnen, 1994). Thus, it can be hypothesized that adventitious root meristem (ARM) formation has its own characteristics. This specificity could reside in 1) the induction process since ARM can be formed from differenciated cells of variable origins (Chriqui, 1985) and 2) the ARM organization process which depends on the cellular neighbouring of the pre-meristematic cells.