Effects of Pb2+ on root growth, cell division and nucleolus of Brassica juncea L.

The effects of different concentrations (10(-5)-10(-2) M) of lead nitrate o n root growth and nucleoli in root tip cells of Brassica juncea L. were inv estigated. The results showed that lead nitrate has a stimulatory effect on root growth at lower concentrations, and an inhibitory effect at higher co ncentrations. Pb has toxic effects on chromosomal morphology, including c-m itosis and anaphase bridges, and on nucleoli, causing some particulate silv er-stained material scattered in the nuclei and inducing irregularly shaped nucleoli. Once the nucleolus was affected, the root growth almost or compl etely stopped.