Anatomical aspects of IBA-treated microcuttings of Gomphrena macrocephala St.-Hil.

Gomphrena macrocephala St.-Hil. (Amaranthaceae) is a perennial herb from th e cerrado with medicinal properties and ornamental interest. Plants can be micropropagated through nodal segments, but acclimatization is difficult. T he aim of this study was to establish a relationship between anatomical asp ects of the roots and the acclimatization process. When cultures were suppl emented with IBA, callus and thick and frangible roots appeared at the base of the microcuttings. A fragile vascular connection between roots and shoo ts was observed. Abnormal adventitious roots showing alteration in the vasc ular cylinder and hypertrophy of the cortical cells were also noted. These roots interfere in the transfer to extra vitrum conditions. When no growth regulator was used, no callus was formed the adventitious roots were simila r to those found in seedlings, and acclimatization could proceed. The resul ts show that the origin and the structure of roots formed in the microcutti ngs play an important role in the acclimatization process and thus in the e stablishment of the micropropagated plants.