In this study, the effects of Cd on root growth, respiration, and transmembrane electric potential (Em) of the outer cortical cells in maize roots treated with various Cd concentrations (from 1 µM to 1 mM) for several hours to one week were studied. The Em values of root cells ranged between −120 and −140 mV and after addition of Cd they were depolarized immediately. The depolarization was concentration-dependent reaching the value of diffusion potential (ED) when the Cd concentration exceeded 100 µM. The values of ED ranged between −65 to −68 mV (−66 ± 1.42 mV). The maximum depolarization of Em was registered approx. 2.5 h after addition of Cd to the perfusion solution and in some cases, partial (Cd > 100 µM) or complete repolarization (Cd < 100 µM) was observed within 8-10 h of Cd treatment. In the time-dependent experiments (0 to 168 h) shortly after the maximum repolarization of Em a continuous concentrationdependent decrease of Em followed at all Cd concentrations. Depolarization of Em was accompanied by both increased electrolyte leakage and inhibition of respiration, especially in the range of 50 µM to 1 mM Cd, with the exception of root cells treated with 1 and 10 µM Cd for 24 and 48 h. Time course analysis of Cd impact on root respiration revealed that at higher Cd concentrations (> 50 µM) the respiration gradually declined (∼ 6 h) and then remained at this lowest level for up to 24 h. All the Cd concentrations used in this experiment induced significant inhibition of root elongation and concentrations higher than 100 µM stopped the root growth within the first day of Cd treatment. Our results suggest that Cd does not cause irreversible changes in the electrogenic plasma membrane H + ATPase because fusicoccin, an H + ATPase activator diminished the depolarizing effect of Cd on the Em. The depolarization of Em in the outer cortical cells of maize roots was the result of a cumulative effect of Cd on ATP supply, plasmalemma permeability, and activity of H + ATPase.

The Echinacea species are native to the Atlantic drainage area of the United States of America and Canada. They have been introduced as cultivated medicinal plants in Europe. Echinacea purpurea, E. angustifolia and E. pallida are the species most often used medicinally due to their immune-stimulating properties. This review is focused on morphological and anatomical characteristics of E. purpurea, E. angustifolia, E. pallida, because various species are often misidentified and specimens are often confused in the medicinal plant market.

Effect of beauvericin on root cell transmembrane electric potential (E M ), electrolyte leakage and respiration of roots were studied in two maize cultivars (Zea mays L.) with different susceptibility to this toxigenic metabolite produced by Fusarium. Beauvericin treatment induced rapid and significant depolarisation of membrane potentials of the outer cortical cells of maize roots of tolerant cv. Lucia. The range of depolarisation was dose dependent with maximum depolarisation of 55 mV (55 ± 7 mV, n = 7) at 200µM beauvericin. In contrast, membrane potentials of beauvericin susceptible cv. Pavla was only slightly depolarised by identical concentrations of beauvericin and the value of depolarisation represented only half of the value of tolerant cv. Lucia (27 ± 6 mV, n = 8). The values of membrane potentials of root cells of tolerant cv. Lucia were higher (137 ± 9 mV, n = 26) and more electrogenic (60 ± 2 mV, n = 3) than in susceptible cv. Pavla (125 ± 7 mV, n = 28), (47 ± 2 mV, n = 3), respectively. Our results confirmed that 2 h treatment with 50µM beauvericin does not cause irreversible changes in plasma membrane H + -ATPase, because fusicoccin, an H + -ATPase activator diminished the depolarizing effect of beauvericin on the E M . Further experiments revealed beauvericin-induced increase of membrane conductivity in root cells of Pavla but not in root cells of Lucia. Time-coarse experiments showed that 25µM beauvericin induced slight, but significant inhibition of root respiration in both cultivars during the first two hours of treatment, and the inhibition was higher in cv. Lucia than in cv. Pavla. The depolarisation of E M in the outer cortical cells of maize roots may be the result of a cumulative effect of beauvericin on ATP supply, activity of H + -ATPase and mainly on the permeability of plasmalemma. Increased beauvericin tolerance in maize might be associated with the increased ability of tolerant plant to maintain normal ion fluxes and membrane potentials across the plasmalemma of root cells in the presence of beauvericin.

In the present study the impact of beauvericin (BEA) on the cell membrane properties and respiration of young initial leaves of maize were studied using two maize cultivars differing in their susceptibility to Fusarium sp. BEA significantly depolarized E M of leaf parenchymal cells and this depolarization showed time and dose dependency regardless on the sensitivity of maize cultivars to Fusarium. However, the extent of BEA-induced depolarization was 2-5 times higher in sensitive cv. Pavla than in tolerant cv. Lucia. Membrane permeability and K + leakage from leaves cells treated with BEA was higher in sensitive cv. Pavla but the differences were not so considerable than the depolarization of E M . Treatment of maize young initial leaves with 40 μmol BEA significantly inhibited respiration. In accord with electrophysiological measurements inhibition of respiration was higher in sensitive cv. Pavla showing 70% inhibition already after 90 min of BEA treatment while in tolerant cv. Lucia inhibition represented only 27%. The biological activity of BEA seems to be mediated by the ability of BEA to affect membrane permeability and ion transport. This is probably the initial effect of BEA on plant cell leading to subsequent effect on other cell organelles (mitochondria) and cell metabolism.

The aim of this work was to study and verify the effect of the Hattrick DP-50 fungicide on quality and content of essential oil in Mentha × piperita (L.) HUDS. Cv. Perpeta (peppermint) during different developmental phases. The fungicide was applied approximately one month before the first collection. The results have shown that the phase of full bloom may be regarded as a period with the highest content of essential oil in herb and leaves of peppermint; its greatest amount was found in the youngest leaves. The content of menthol gradually increased to its maximum value in the full bloom phase, while that of menthone was decreasing. The treatment with Hattrick DP-50 did not influence the essential oil content and its changes during vegetation when compared to untreated plants. Similarly, the application of fungicide did not cause detectable changes in relative representation of main and secondary components of the essential oil.