Accumulation patterns of Cr in Callitriche organs—qualitative and quantitative analysis

Abstract

The aims of this study were both the qualitative and quantitative analysis of chromium accumulation in the shoots of Callitriche cophocarpa. This globally distributed, submersed macrophyte exhibits outstanding Cr phytoremediation capacity in an aquatic environment. Cr was applied separately for 7 days at two stable forms as Cr(VI) and Cr(III), known from their diverse physicochemical properties and toxicities. The maps of Cr depositions in young leaves, mature leaves, and stems were obtained by micro X-ray fluorescence spectroscopy (μXRF). The detailed analysis of XRF maps was done based on Image-Pro PLUS (Media Cybernetics) software. Cr was accumulated either in trichomes or vascular bundles in respect to the element speciation and the plant organ. The concentration of Cr significantly increased in the following order: Cr(VI) mature leaves < Cr(VI) young leaves = Cr(VI) stems < Cr(III) young leaves ≤ Cr(III) mature leaves ≤ Cr(III) stems. The observed differences in distribution and accumulation of Cr were correlated with the different reduction potential of Cr(VI) by particular plant organs. The reduction of Cr(VI) is considered the main detoxification mechanism of the highly toxic Cr(VI) form. The unique L-band electron resonance spectrometer (L-band EPR) was applied to follow the reduction of Cr(VI) to Cr(III) in the studied material.

Callitriche cophocarpa (water starwort) proteome under chromate stress: evidence for induction of a quinone reductase

“…At first, a 3-h treatment was examined, which revealed direct reaction to Cr(VI) by strongly increasing CAT and peroxidase activities. This early-response stage (an alarm phase of plant response as indicated by Kosová et al 2011 ) is consistent with our previous observations which showed immediate reaction of C. cophocarpa shoots treated with chromate and manifested by a rapid (in a matter of hours) reduction of Cr(VI) to the Cr(V) intermediate which is generated upon Cr(VI) → Cr(III) bioconversion (Augustynowicz et al 2013a , 2016 ). During prolonged (3-day) incubation, only Px activities were kept elevated while CAT was back at the level determined for control plants.…”

“…Plants were grown in a phytotron chamber (model FD 500, Biosell, Poland) under the following conditions: 16 h of photon flux density of 40 μmol m −2 s −1 and 8 h of darkness, at 22-°C day/18-°C night. Light spectrum and intensity were similar to that applied in previous studies (Augustynowicz et al 2016 ) and were found sufficient for normal plant growth resembling the conditions typical of Callitriche natural environment.…”

“…Our earlier research work revealed that Cr(VI) presence negatively affected C. cophocarpa shoots leading to several physiological changes such as a decrease of photosynthetic pigment content and a decline of photosynthesis quantum efficiency, distortion of leaf structure, and electrolyte leakage (Augustynowicz et al 2010 , 2013a , b ). Moreover, chromate uptake was followed by its rapid reduction (Augustynowicz et al 2013a , 2016 ) similarly to the other tested macrophytes Eichhornia crassipes (Mart.) Solms, Salvinia auriculata Aubl., Pistia stratiotes L., and Spirodela polyrhiza (L.) Schleid.…”

“…Besides bacteria, Cr(VI)-reducing activities were also observed in yeast, microalgae, fungi (Joutey et al 2015 ; Viti et al 2014 ), as well as plants (Prado et al 2016 ; Shanker et al 2009 ) including macrophytes (Espinoza-Quiñones et al 2009 ; Kaszycki et al 2005 ) and C. cophocarpa in particular (Augustynowicz et al 2013a , 2016 ). Importantly, for the latter case, chromate bioreduction occurred exclusively within the plant shoots and was not observed outside the macrophyte tissue (that is in a surrounding growth medium).…”

“…In particular, Callitriche cophocarpa Sendtn. (water starwort), a widespread species growing both in stagnant and running waters, was shown to reveal unusual response to chromate proving to be a potent Cr phytoremediator and accumulator (Augustynowicz et al 2010 , 2013a , 2013b , 2016 ). It exhibited enhanced capability of both Cr(VI) and Cr(III) phytoextraction from contaminated waters and extremely high capacity to bind Cr (3900 mg kg −1 for 5-day treatment at 1 mM Cr(VI)).…”