Is callose a barrier for lead ions entering Lemna minor L. root cells?

Plants have developed a range of strategies for resisting environmental stresses. One of the most common is the synthesis and deposition of callose, which functions as a barrier against stress factor penetration. The aim of our study was to examine whether callose forms an efficient barrier against Pb penetration in the roots of Lemna minor L. exposed to this metal. The obtained results showed that Pb induced callose synthesis in L. minor roots, but it was not deposited regularly in all tissues and cells. Callose occurred mainly in the protoderm and in the centre of the root tip (procambial central cylinder). Moreover, continuous callose bands, which could form an efficient barrier for Pb penetration, were formed only in the newly formed and anticlinal cell walls (CWs); while in other CWs, callose formed only small clusters or incomplete bands. Such an arrangement of callose within root CWs inefficiently protected the protoplast from Pb penetration. As a result, Pb was commonly present inside the root cells. In the light of the results, the barrier role of callose against metal ion penetration appears to be less obvious than previously believed. It was indicated that induction of callose synthesis is not enough for a successful blockade of the stress factor penetration. Furthermore, it would appear that the pattern of callose distribution has an important role in this defence strategy

Sadržaj toksičnih i esencijalnih metala u ljekovitom bilju koje raste u onečišćenim i neonečišćenim područjima u Makedoniji

The aim of this study was to determine and compare Ba, Cr, Cd, Fe, Sr, Pb, and Zn content in medicinal herbs Urtica dioica L., Taraxacum officinale, and Matricaria recutita growing in polluted and unpolluted areas of the Republic of Macedonia. The metal content was determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the unpolluted area of Mt. Plačkovica the metal content in Taraxacum officinale was in the descending order: Fe>Sr>Zn>Ba>Cr, while Pb and Cd were below the limit of detection. In the polluted area of Veles, the order was as follows: Fe>Zn>Sr>Pb>Ba>Cd>Cr. Our results suggest that quality assurance and monitoring of toxic metals is needed for plants intended for human use and consumption. Medicinal plants should be picked in areas free of any contamination sources.Cilj je ovoga istraživanja bio utvrditi i usporediti sadržaj Ba, Cr, Cd, Fe, Sr, Pb i Zn u ljekovitom bilju Urtica dioica L., Taraxacum offi cinale i Matricaria recutita koje raste u onečišćenome odnosno neonečišćenome području u Republici Makedoniji. Sadržaj metala utvrdili smo s pomoću atomske emisijske spektroskopije induktivno spregnutom plazmom (engl. inductively coupled plasma atomic emission spectroscopy, krat. ICP-AES). U neonečišćenome području planine Plačkovice, sadržaj metala u Taraxacum offi cinale kretao se kako slijedi: Fe>Sr>Zn>Ba>Cr, dok su Pb i Cd bili ispod granice detekcije. U onečišćenome području blizu talionice olova i cinka u Velesu redoslijed je bio ovakav: Fe>Zn>Sr>Pb>Ba>Cd>Cr. Naši rezultati upućuju na potrebu za osiguranjem kakvoće i praćenjem razina toksičnih metala u biljaka namijenjenih ljudskoj uporabi. Ljekovito bilje valja brati u područjima bez izvora onečišćenja