Tolerance and prospection of phytoremediator woody species of Cd, Pb, Cu and Cr

Abstract

High concentrations of Cd, Pb, Cu and Cr can cause harmful effects to the environment. These highly toxic pollutants constitute a risk for aquatic and terrestrial life. They are associated with diverse bioavailable geochemical fractions, like the water-soluble fraction and the exchangeable fraction, and non-available fractions like those associated with the crystalline net of clays and silica minerals. Depending upon their chemical and physical properties we can distinguish different mechanisms of metal toxicity in plants, such as production of reactive oxygen species from auto-oxidation, blocking and/or displacement of essential functional groups or metallic ions of biomolecules, changes in the permeability of cellular membranes, reactions of sulphydryl groups with cations, affinity for reactions with phosphate groups and active groups of ADP or ATP, substitution of essential ions, induction of chromosomal anomalies and decrease of the cellular division rate. However, some plant species have developed tolerance or resistance to these metals naturally. Such evolution of ecotypes is a classic example of local adaptation and microevolution, restricted to species with appropriate genetic variability. Phytoremediator woody species, with (i) high biomass production, (ii) a deep root system, (iii) high growth rate, (iv) high capacity to grow in impoverished soils, and (v) high capacity to allocate metals in the trunk, can be an alternative for the recovery of degraded soils due to excess of metallic elements. Phytoremediation using woody species presents advantageous characteristics as an economic and ecologically viable system, making it an appropriate, practical and successful technology. Key-words: decontamination, heavy metals, hyperaccumulation, phytodegradation, phytostabilization, phytotoxicity Tolerância e prospecção de espécies lenhosas fitorremediadoras de Cd, Pb, Cu e Cr: Altas concentrações de Cd, Pb, Cu e Cr podem provocar efeitos danosos ao ambiente. Esses poluentes altamente tóxicos constituem um risco para a vida aquática e terrestre. Encontram-se associados às diversas frações geoquímicas biodisponíveis, a exemplo da fração solúvel em água e da fração trocável, e as não disponíveis como a fração associada à rede cristalina de argilas e de minerais silicatados. Conforme as suas propriedades químicas e físicas podem-se distinguir mecanismos diferentes de toxicidade de metais em plantas, tais como produção de espécies reativas de oxigênio pela auto-oxidação, bloqueio e, ou, deslocamento de grupos funcionais ou de íons metálicos essenciais de biomoléculas, mudanças na permeabilidade de membranas celulares, reações de grupos sulfidrílicos com cátions, afinidade para reações com grupos fosfatos e grupos ativos de ADP ou ATP, substituição de íons essenciais, indução de anomalias cromossomais e decréscimo da taxa de divisão celular. Várias espécies vegetais desenvolveram, naturalmente, tolerância ou resistência a esses metais. Essa evolução de ecótipos é exemplo clássico de adaptação local e de microevolução,...

Changes in protein profile detected in seedlings of Caesalpinia peltophoroides (Fabaceae) after exposure to high concentration of cadmium

“…Negative effects on protein activity, such as the photosystem I assembly protein ycf3 (spots 50 and 55), photosystem Q(B) protein (spot 16), NAD(P)H-quinone oxidoreductase subunit 3, chloroplastic (spots 22, 56, 57, 75, and 163), and cytochrome b6-f complex subunit 4 (spot 54), compromised the performance of photosynthetic activity. Reduction in net photosynthetic rate is one of the factors that cause a decrease in growth and productivity in plants ( MacFarlane and Burchett, 2001;Almeida et al, 2007;Zhang et al, 2010). There may be changes in the growth of shoots and roots and in chlorophyll biosynthesis, lower rates of transpiration, photosynthesis and stomatal conductance, induction of premature senescence of leaves, and leaf chlorosis (Clemens, 2006).…”

Induction of phytochelatins and flavonoids in cadmium polluted Berberis thunbergii

“…Salix, Populus, etc. (Almeida et al, 2007;Unterbrunner et al, 2007;Capuana, 2011;Hayakawa et al, 2011) Apart from phytochelatins, other metabolites may be involved in tolerance mechanisms to heavy metals. Flavonoids exhibit a broad range of biological activity, connected to their antioxidant activity, free radicals scavenging and metal ion chelation (Korkina, 2007;Landi et al, 2015;Michalak, 2006).…”

Anatomical variability of the trunk wood and root tissues of <i>Rhizophora racemosa</i> (G. Mey) and <i>Avicennia nitida</i> (Jacq.) and bio-accumulation of heavy metals in mangrove trees

“…Furthermore, Avicennia marina roots concentrated more heavy metals compared to its air parts (MacFarlane and Burchett, 2002). On the other hand, the high capacity of trunk woody tissues to allocate metals was described to be an alternative for the recovery excess metallic elements from degraded soils (Almeida et al, 2007).…”