The Common Ice Plant (Mesembryanthemum crystallinum L.)–Phytoremediation Potential for Cadmium and Chromate-Contaminated Soils

Abstract

The common ice plant (Mesembryanthemum crystallinum L.) is a widely studied model due to its tolerance to numerous biotic and abiotic stresses. In this study, carried out in model pots, the plants were treated with variant doses of Cd(II) and Cr(VI) and proved resistant to extreme levels of these heavy metals. Initial toxicity symptoms were observed upon final concentrations of 818 mg Cd kg−1 soil d.w., and 1699 mg Cr kg−1 applied as potassium chromate. Biometric analyses revealed that none of the Cr(VI) doses affected dry weight of the plant organs thus maintaining the shoot-to-root ratio. The Cd and Cr hypertolerance strategies were divergent and resulted in different accumulation patterns. For the case of Cd(II), an excluder-like mechanism was developed to prevent the plant from toxicity. For chromate, high accumulation potential together with Cr(VI) root-to-shoot translocation at sublethal concentrations was revealed (up to 6152 mg Cr kg−1 shoot at 4248 mg Cr kg−1 soil). It is concluded that M. crystallinum reveals considerable phytoremediation capabilities due to unique growth potential in contaminated substrates and is suitable for bioreclamation of degraded soils. The plant is especially applicable for efficient phytoextraction of chromate-contamination, whereas for Cd-affected areas it may have a phytostabilizing effect.

Chromium Stress in Plants: Toxicity, Tolerance and Phytoremediation

“…A widely studied model plant Mesembryanthemum crystallinum L. has high tolerance capacity against various biotic and abiotic stresses and it is suitable for bio-reclamation of contaminated soils due to considerable phytoremediation capabilities and unique growth potential. This plant is also especially capable of efficient phytoextraction from chromate-contamination due to its vigorous growth without exhibiting any physiological or anatomical disorders [141]. Thus, it was confirmed that this plant could perform as excellent decontamination for the Cr heavy metal under controlled (pH, redox potential, water disturbances) conditions.…”

Cadmium-Tolerant Rhizospheric Bacteria of the C3/CAM Intermediate Semi-Halophytic Common Ice Plant (Mesembryanthemum crystallinum L.) Grown in Contaminated Soils

“…Next, the 8-week old plants were treated with CdCl 2 (Sigma-Aldrich, United States) solutions applied at the following concentrations: 0 (control), 0.01, 0.1, 1.0, and 10 mM administered daily as 10 cm 3 doses per pot for consecutive 8 days. This experimental approach was analogous to the model elaborated by us earlier and previously described ( Nosek et al, 2019 , 2020 ; Śliwa-Cebula et al, 2020 ). Such treatment led to the final Cd doses of 0 (control), 0.8, 8.0, 80, and 800 μmol per pot, respectively, which were calculated as 0.82, 8.2, 82, and 818 mg Cd per kg of soil d.w. During the Cd-treatment microbial community frequency and diversity was monitored.…”

“…Based on the described extraordinary properties of the common ice plant and considering our recent data on its extreme resistance to cadmium and chromium ( Nosek et al, 2019 ; Śliwa-Cebula et al, 2020 ), we have postulated M. crystallinum as a particularly favorable candidate for environmental biotechnology applications. For the case of heavy metal-contaminated saline areas, halophytes including the common ice plant can serve as potentially efficient phytoremediators ( Wang et al, 2014 ; Lutts and Lefèvre, 2015 ), since plants tend to respond to both heavy metals and salinity by triggering similar physiological and biochemical mechanisms ( Zhu, 2001 ).…”

“…The common ice plant ( Mesembryanthemum crystallinum L.) can serve as an interesting example of plants proposed for successful use in phytoremediation ( Śliwa-Cebula et al, 2020 ). It is a semi-halophyte revealing high tolerance to many stresses including excess light, elevated salt concentrations, nutrients or water deficiency, low temperature, poor soil structure, and heavy metal presence ( Adams et al, 1998 ; Kuznetsov et al, 2000 ; Libik-Konieczny et al, 2019 ).…”

“…It is known as C 3 -CAM photosynthetic intermediate plant with a possibility to switch between the two ways of CO 2 metabolism as an effect of exposure to stress factors ( Winter et al, 2015 ; Libik-Konieczny et al, 2019 ). It reveals fast growth and strong root system development even at salt concentrations in soil reaching 1 M ( Bohnert and Cushman, 2000 ; Kuznetsov et al, 2000 ; Śliwa-Cebula et al, 2020 ). NaCl is transported through roots to the specialized structures called epidermal bladder cells, which are developed on leaf and stem surfaces and are responsible for saline sequestration and osmotic pressure adjustment ( Bohnert and Cushman, 2000 ; Kim et al, 2021 ).…”