Lead disturbs microtubule organization in the root meristem of Zea mays

Lead is an environmental pollutant that interferes with plant growth, Unfortunately, the mechanisms of lead toxicity in plants are still poorly understood. In this study, we have investigated both the deposition sites and sources of cellular toxicity of lead in maize seedlings (Zea mays L, cv, Golden Cross Bantam). Using atomic absorption spectroscopy and X-ray fluorescence microprobing, we show that lead accumulation is highest in the root meristem, and that the accumulation occurs both in the apoplast and symplast. Since cells are dividing vigorously in this region and because microtubules play an important role in cell division, we have further examined the effects of lead on microtubules in the root meristem. Lead treatment perturbed the alignment of microtubules in a concentration-dependent manner beginning at 10 pM. Microtubules of different regions of the root meristem and in different stages of the cell cycle showed differential susceptibility to lead, These effects do not appear to be general phenomena common to toxic metals, since aluminum and copper, at concentrations that decreased root growth to a comparable level, did not have the same detrimental effects on microtubules. Based on these results, we suggest that the damage to microtubules is partly responsible for lead-associated toxicity in plants.