Enhanced cadmium accumulation in maize roots—the impact of organic acids

Abstract

Low molecular weight organic acids are important components of root exudates and therefore, knowledge regarding the mechanisms of cadmium (Cd) uptake and distribution within plants under the influence of organic acids, is necessary for a better understanding of Cd behavior in the plant-soil system. In this study, acetic and malic acids increased the uptake of Cd by maize (Zea mays L. cv. TY2) roots and enhanced Cd accumulation in shoots under hydroponic conditions. Concentration-dependent net Cd influx in the presence and absence of organic acids could be resolved into linear and saturable components. The saturable component followed Michaelis-Menten kinetics, which indicated that Cd uptake across the plasma membrane was transporter-mediated. While the K m values were similar, the V max values in the presence of acetic and malic acids were respectively 6.0 and 3.0 times that of the control. Zinc transporters were the most probable pathways for Cd accumulation. It was hypothesized that Cd(II)-organic acid complexes associated with the root zone, could decompose and liberate Cd 2+ for subsequent absorption by maize roots; and that in the layer of the roots or within the root free space, depletion of Cd 2+ was buffered by the presence of Cd(II)-organic acid complexes. Plant response to elevated Cd levels involved overproduction of organic acids in maize roots as a resistance mechanism to alleviate Cd toxicity.

Influência genotípica na absorção e na toxidez de manganês em soja

“…Essa capacidade depende, em parte, da formação de complexos no sistema radicular (Yang et al, 1997;Han et al, 2006). Por sua vez, esses complexos podem apresentar diferenças quanto à sua mobilidade das raízes para a parte aérea.…”

Interaction of organic acids and pH on multi-heavy metal extraction from alkaline and acid mine soils

“…Low molecular weight organic acids, mainly originating from the decomposition of soil organic matter, plant root exudates and microbial metabolites (Jones 1998;Strobel 2001), play important roles in controlling the solubility of heavy metals and their subsequent uptake by plants due to the chelation or complexation between organic acids and heavy metals (Krishnamurti et al 1997;Han et al 2006). Naidu and Harter (1998) reported that organic ligands increased the extractability of Cd from soils.…”

Root exudates from sunflower (Helianthus annuusL.) show a strong adsorption ability toward Cd(II)

“…In contrast, some studies showed that root exudates could increase the solubility of metal ions in soils and consequently increase their accumulation in plant (Cies´lin´ski et a1. 1998;Fan et al 2001;Han et al 2006;Luo et al 2008;Kim et al 2010). As characterized by Fan et al (2001), all the major components of root exudates by high-resolution Nuclear Magnetic Resonance and mass spectrometry.…”