Modyfikacja procesu transpiracji a efektywność indukowanej fitoekstrakcji ołowiu i kadmu w wybranych gatunkach roślin

Abstract

The aim of this paper was to determine the relationship between transpiration and the effectiveness of induced phytoextraction of Pb and Cd in Indian mustard (Brassica juncea) and sunflower (Helianthus annuus) plants. Fusicoccin (FC) at the concentration of 10–6 M and KCl (25—100 mM), which were sprayed on the shoots of Indian mustard, increased considerably transpiration in plants grown in hydroponic culture, both in basal medium and basal medium supplemented with EDTA, Pb and Cd. Although the total amount of transpired water was significantly greater in the treated plants when compared with control, the dynamics of transpiration varied during the experiment and depended on the composition of hydroponic solution. In Indian mustard plants grown in the basal medium supplemented with EDTA, Pb and Cd and sprayed with FC and KCl on the above ground parts of plants a positive correlation between transpiration and the content of lead and cadmium in the shoots was observed. A significant positive relationship between the translocation of Pb and Cd and their accumulation in shoots was found 20—35 hours after spraying. In the processes of translocation and accumulation the synergistic effect of FC and KCl was observed. The investigation also showed a high positive correlation between the concentration of the KCl sprayed on the above ground parts and the content of Pb and Cd in the shoots of Indian mustard, which does not depend on transpiration. In Indian mustard and sunflower plants grown in metal contaminated soil supplemented with EDTA no correlation between transpiration and the content of Pb and Cd in the shoots was found. The synergistic effect of FC and KCl on accumulation of Pb and Cd in the above ground parts was also not observed. Pot experiments showed that in induced phytoextraction the content of Pb and Cd is regulated by the level of induction of hyperaccumulation in plants and not by transpiration. Investigations on induced phytoextraction of Pb and Cd showed that when the transpiration is modified discrepancies between the results obtained in experiments in hy-droponic cultures and pot experiments can be found. For this reason pot experiments should be the main point of reference in planning field experiments. The spraying of Indian mustard and sunflower plants with glyphopsate and the application of EDTA to the Pb, Cd and Zn contaminated soil resulted in a marked increase in the Pb and Cd content in the shoots and the level of metal accumulation was similar in both investigated plant species. Moreover, it was found that glyphosate significantly increased the membrane permeability and the inductive effect of EDTA. Simultaneous application of EDTA and glyphosate resulted in apoplastic and symplastic transport of PbEDTA and CdEDTA through the endodermis. Transpiration plays a negligible role in this transport. The low membrane permeability caused by the low level of induction of metal hyperaccumulation is mainly connected with apoplastic transport of PbEDTA and CdEDTA. This transport depends on transpiration and can be modified by factors that have an effect on transpiration rate.