E. Falistocco et al., Enhancement of micronuclei frequency in the Tradescantia /micronuclei testusing a long recovery time, HEREDITAS, 133(2), 2000, pp. 171-174
The Tradescantia/micronuclei test (TRAD/MCN) is a well-validated test for m
onitoring environmental genotoxicants. These pollutants induce at the early
meiotic stage of pollen mother cells chromosome fragments which become mic
ronuclei at the tetrad stage. The standard test protocol requires some hour
s of exposure of the inflorescences and a recovery time of about 24 hours t
o reach the early tetrad stage. Since the recovery period represents a crit
ical step of the TRAD/MCN, experiments were performed to establish its leng
th in plants of clone #4430 of the hybrid T. hirsutiflora x T. subacaulis w
hich is widely used in environmental monitoring. The aim of the present res
earch was to ascertain the exact duration of recovery time in order to impr
ove the sensitivity of the TRAD/MCN test. First, studies were performed to
select the flowers at the beginning of the meiosis, and then anthers were s
ampled and studied for a period of 48-86 hours. The complete meiosis in the
plants examined required about 80 hours. Second, exposure to genotoxic sub
stances followed by different recovery times was carried out to demonstrate
that effectiveness of the TRAD/MCN test is closely related to the duration
of the recovery time. The test was carried out by exposing inflorescences
to known mutagens (sodium azide and maleic hydrazide) for six hours followe
d by different recovery times (24-72 hours). The results showed that the fr
equency of micronuclei in the pollen mother cells increased with the length
of the recovery time.