Anatomical and biochemical changes during root formation in oak and apple shoots cultured in vitro

Abstract

The events leading to adventitious root formation in in vitro shoot cultures of Quercus robur L clone NL3 and Malus M9 Jork are described. Significant cellular changes were observed as early as 1-2 d after auxin treatment: in both species, some cambial and vascular parenchyma cells exhibited prominent nuclei and dense cytoplasm, and the first cell divisions were occasionally observed. Meristematic activity had increased by d 4, and meristemoids became individualized 1 or 2 d later. Roots emerged from the shoots by d 8 in oak and d 10 in apple. The vascular systems of the primordium and shoot joined just before root emergence. In oak shoots, peroxidase activity was similar in auxin-treated and untreated shoots during the first 4 d after treatment, but subsequently increased in treated shoots and decreased in untreated shoots. In auxin-treateo shoots, peroxidase activity stabilized after d 6. © 1992.