Abstract: The bractlets in a inflorescence of Nicotiana tabacum, which were cultured in MS medium containing 2. Omg/1 6-BA, 0.2mg/l IBA directly formed vegetative buds, floral buds, or / and callus. The histological aspect of flower bud development in vitro were studied. It was found that the floral buds may originated from sub-epidemic layers. The physiological state of mother plant strongly effected the flowering of bractlets in inflorescence of N. tabacum in vitro. Only when the mother plants entered the stage of reproductive growth, the floral bud might form in vitro.

Key words: Nicotiana tabacum Ge Xing No1