Short-term chromium(VI) stress induces different photosynthetic responses in two duckweed species, Lemna gibba L. and Lemna minor L.

Abstract

Physiological responses of two duckweed species, Lemna gibba and Lemna minor, to hexavalent chromium [Cr (VI)] were studied in axenic cultures using short-term (48 h) treatments by K 2 Cr 2 O 7 (0-200 μM). Chlorophyll (Chl) fluorescence parameters and photosynthetic pigment composition of plants were screened to determine the effects of Cr(VI) exposures. The two duckweed species exhibited different sensitivity in the applied Cr(VI) concentration range. Chl fluorescence parameters of dark-adapted and light-adapted plants and electron transport inducibility were more sensitive to Cr(VI) in L. minor than in L. gibba. We also found fundamental differences in quantum yield of regulated, Y(NPQ), and nonregulated, Y(NO), non-photochemical quenching between the two species. As Cr(VI) concentration increased in the growth medium, L. minor responded with considerable increase of Y(NPQ) with a parallel significant increase of Y(NO). By contrast, in L. gibba only 200 μM Cr(VI) in the growth medium resulted in elevation of Y(NPQ) while Y(NO) remained more or less constant within the regarding Cr(VI) concentration range during 48 h. Photosynthetic pigment content did not change considerably during the short-term Cr(VI) treatment but decrease of Chl a/b and increase of Car/Chl ratios were observed in good accordance with the changes in Chl fluorescence parameters. The data suggest that various duckweed species respond with different sensitivity to the same ambient concentrations of Cr(VI) in the growth medium, and presumably to other environmental stresses too, which may have an influence on their competitive relations when heavy metal pollution occurs in aquatic ecosystem.

Lead-induced toxicity and interference in chlorophyll fluorescence in Talinum triangulare grown hydroponically

“…However, decrease in the F m in Pb-treated T. triangulare resulted from decrease in the Chl fluorescence intensity when all PSII reaction centers were closed. Similar response reported in Pb-, Hg-, and Cu-treated spinach (Boucher and Carpentier 1999), Cr-treated duckweed (Oláh 2010), and Ni-treated maize (Drążkiewicz and Baszyński 2010).…”

Study on Chromium-Binding Capacity of Callitriche cophocarpa in an Aquatic Environment

“…Furthermore, 0.5 mM Cr(VI) caused an F V / F M decrease comparable with that of 2 mM and much greater that that of 1 and 1.5 mM. This observation is not consistent with our earlier observation concerning the action of a lower Cr(VI) concentration (Augustynowicz et al 2010) as well as the one reported by other investigators (Hörcsik et al 2007; Oláh et al 2010). In the previously mentioned works, direct dependence of Cr(VI) on F V / F M was measured.…”

Short term exposure of Lemna minor and Lemna gibba to mercury, cadmium and chromium

“…The induction of L. gibba, but not L. minor, antioxidative enzymes at lower Hg, Cd and Cr concentrations suggests a better antioxidative status of L. gibba. Additionally, Oláh et al [43] reported that L. gibba can maintain physiological stability under 48 h of Cr treatment more effectively then L. minor.…”