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
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.