A Histological Evaluation of Adventitious Bud Formation in Cotyledons in Crotalaria juncea L

In Crotalaria juncea L., adventitious buds were formed in cotyledonary explants cultured on 0.8% agar-solidified 1/2 MS basal medium containing B5 vitamins, 1.0 or 0.5 mg L -1 NAA, 5.0 or 10.0 mg L -1 BA and 3% sucrose. The frequency of adventitious bud formation was 30-45% in all combinations of NAA and BA. In histological observations, prominent mitotic figures were observed in several cells of the subepidermal palisade layers on the adaxial side of the explants in contact with medium after 3 days of culture. Calli were formed within 6 days of culture. After 10 days of culture, numerous mature tracheary elements were produced at random in the proliferated regions, and cell divisions at the superficial region led to the formation of the meristematic structure. The shoot apex of the seedling produced numerous trichomes from superficial cells, but the adventitious bud formed on the cotyledon produced no trichomes. Initiation of the meristematic region in the explant could be used as a target site for gene transfer experiments.