Different effects of inorganic and triethyl lead on growth and ultrastructure of lily pollen tubes

Abstract

Pollen tubes ofLilium longiflorum growingin vitro were treated for 1 h with inorganic lead (Pb) and with triethyl lead (TriEL) and studied by light and electron microscopy. Pb was considerably more toxic in relation to inhibition of pollen tube growth (EC50=6 μM Pb) than was TriEL (EC50=60 μM TriEL). On the other hand, at almost the entire concentration range tested (25-500 μM) TriEL caused aberrant tubes and tube swellings. Pb did not cause tube swellings, even at highly growth-impairing concentrations. Pb (60 μM) predominantly affected the ultrastructure of the growing cell walls without impairing the distribution of the cell organelles in the tube tips. In contrast, 50 and 100 μM TriEL did not visibly influence cell wall ultrastructure but it severely damaged dictyosomes; 100 μM TriEL also disturbed the original order of cell organelles in the tube tips. Cortical microtubules were selectively and completely destructed by TriEL at concentrations (50 μM) where no effect on polar organization of the tube tips occurred but they remained unimpaired by 60 μM Pb, indicating selective and effective interaction of TriEL with these cell organelles.