Organospecific responses of lupin seedlings to lead I. localization of lead ions and stress proteins

A tissue-printing technique was used to follow distribution of lead ions in different organs of lupin seedling with the histological localization of pathogenesis-related proteins designated as PR-L1 to PR-L6, which were found to be induced in lupin roots by heavy metals (Przymusiński and Gwóźdź 1999). Lead nitrate solution was supplied to the root tips and the histological distribution of the metal in lupin organs was visualized by staining with 0.6 % (w/v) of sodium rhodizonate. As the distance from the site of lead application increased, the amount of free lead ions decreased and in the petioles the metal was not detected at all. Lead ions were localized mostly in vascular bundles, which suggests that it was transported into the upper parts of seedlings with the transpiration stream. Immunohistochemical analysis of the tissue prints showed that as compared to the control lead visibly increased the accumulation of the PR proteins in roots, hypocotyls, stems and leaf petioles of the lupin seedling. The histological distribution of the PR protein differs from that of lead, and was localized in parenchymatic cells of root cortex, hypocotyl and stem. It is worth noticing that the stress protein was also observed in the leaf petioles where lead was not detected. This fact as well as marked enhancement of PR (L1–L6) proteins accumulation in lead treated seedlings and our earlier studies (Przymusiński and Gwóźdź 1994, 1999, Przymusiński et al. 1995) suggests that these proteins could be elements of plant’s defence system against both biotic and abiotic stressing factors.