SE induction within primordial shoots of adult white spruce trees. (A) Longitudinally sectioned preflush bud representative of those collected for SE induction. (B) A shoot primordium explant following one week of induction treatment, the time point at which tissues were collected for microarray analysis. (C) Formation of embryonal masses (EM) that occurs within some of the G6 explants after about three weeks of induction. (D) Subsequent proliferation generates EM that can then be subcultured and used to generate unlimited numbers of seedlings that are clones of the parental tree from which the buds were collected. d: days of induction treatment, bars = 0.8 mm.