TRADESCANTIA BIOASSAYS AS MONITORING SYSTEMS FOR ENVIRONMENTAL MUTAGENESIS - A REVIEW

Since the early studies on the genetic effects of chemical and physica l agents, species and clones of Tradescantia have been used as experim ental subjects, by virtue of a series of favorable genetic characteris tics. Bearing just six pairs (2n = 12) of large, easily observable chr omosomes, cells from almost every part of the plant, from the root tip s to the developing pollen tube, yield excellent material for cytogene tic studies. As a consequence of the intensive use of Tradescantia in genetic studies, a series of genetic characteristics have been found t hat offer opportunities for the detection of agents affecting the stab ility of the genome. At least five such characteristics have been sele cted as endpoints for the establishment of assays to evaluate mutagene sis. Three of these, root-tip mitosis, pollen-tube, and microspore mit osis are essentially chromosome aberration assays, wherein one observe s and evaluates the visible damage in the chromosomes. A fourth, the s tamen-hair mutation assay (Trad-SHM), is a point mutation mitotic assa y based on the expression of a recessive gene for flower color in hete rozygous plants. The fifth assay is a cytogenetic test based on the fo rmation of micronuclei (Trad-MCN) that result from chromosome breakage in the meiotic pollen mother cells. This article examines the charact eristics and fundamentals of the Trad-MCN and the Trad-SHM assays and reviews the results obtained to date with these systems in the assessm ent of environmental mutagenesis.