Histology of Shoot Bud Ontogeny from Seedling Root Segments of Brassica napus L.

Root explants of Brassica napus cultured in vitro form adventitious shoots. The root buds originated at the base of the newly initiated lateral root. Cells in association with the differentiating phloem of the developing lateral roots were the sites for root bud formation. A nodular mass of cytoplasmic cells developed by day 7 at the base of the lateral root. This group of cells continued to divide an enlarge. The cells in the peripheral region of the nodular cell mass differentiated further into a meristematic zone. The meristematic cells grew towards the periphery of the cortex by crushing the outer layer of cortical cells. Further development of the meristematic layer resulted in the formation of shoot primordia with organized shoot apical meristems and leaf primordia.