FORMATION OF THE SHOOT APICAL MERISTEM IN ARABIDOPSIS-THALIANA - AN ANALYSIS OF DEVELOPMENT IN THE WILD-TYPE AND IN THE SHOOT MERISTEMLESS MUTANT

The primary shoot apical meristem of Arabidopsis is initiated late in embryogenesis, after the initiation of the cotyledons. We have identif ied a gene, called SHOOT MERISTEMLESS, which is critical for this proc ess. shoot meristemless mutant seedlings lack a shoot apical meristem but are otherwise healthy and viable. The anatomy of mutant embryos de monstrates that the shoot meristemless-1 mutation completely blocks th e initiation of the shoot apical meristem, but has no other obvious ef fects on embryo development. The failure of shoot meristemless tissue to regenerate shoots in tissue culture suggests that this gene regulat es adventitious shoot meristem formation, as well as embryonic shoot m eristem formation.