Differentiation of bud meristems and cataphylls during adventitious bud formation on embryos of Picea abies

Abstract

Embryos of Picea abies were pulse-treated with benzyladenine for 24 h and then cultured on medium lacking growth regulators. Meristemoids developed on all embryos during the 2nd week after the cytokinin treatment. Cells within the meristemoids divided randomly. As the meristemoids developed, further cell divisions became more organized so that separate regions of meristematic activity could be distinguished within each meristemoid. These meristematic regions developed into individual nodules and each nodule developed further into either a bud meristem or a cataphyll. Cataphylls were composed of unorganized, vacuolated, thick-walled cells whereas bud meristems were composed of organized meristematic cells. Later, xylem elements developed at the base, and needle primordia at the top of bud meristems. The bud apex had cytohistological zonation typical of conifers. The appearance of the developing adventitious buds depended on the number of cataphylls formed per bud as well as on the marginal expansion of the cataphylls.