Cadmium Uptake, Growth and Phytochelatin Contents of <i>Triticum </i><i>A</i><i>estivum</i> in Response to Various Concentrations of Cadmium

Abstract

Cadmium (Cd) contamination of the environment is a major concern because of its impact on human health, food supply chain, and ecosystems. Phytoremediation has emerged as an alternative technology to expensive engineering techniques. The objectives of this research were to evaluate the growth and cadmium uptake of wheat (Triticum aestivum L. cv TAM 109) plants exposed to Cd at different periods; and assess whether phytochelatin (PC) synthesis can explain the wheat's tolerance mechanism to cadmium. Wheat seeds were grown in sand medium for 30 days (pre-metal treatment). After initial exposure to different Cd concentrations using hydroponic systems, plants were harvested at different day intervals, separated into roots and shoots, dried at 75℃ for 2 days, weighed for dry biomass, and acid-digested for cadmium uptake determinations. Cadmium uptake and PC contents of roots and shoots were quantified using established procedures. Results showed that shoot and root biomass increased with exposure time, and was more pronounced in the shoot than in the roots. Shoot Cd uptake increased with increasing Cd concentrations, except at days 8, 12, and 15 wherein Cd uptake was very minimal especially at 20 µM. Root Cd uptake increased with increasing exposure periods and Cd concentrations. The syntheses of PC in shoots were significantly enhanced only at 20 µM Cd. There were no significant differences in quantity of roots' PC regardless of Cd treatments.

Heavy Metal Stress and Some Mechanisms of Plant Defense Response

“…Zhang et al [ 170 ] suggested that principal Cd detoxification mechanism in hyperaccumulator Sedum alfredii mediated by PCs occurs in shoots, which is similar to nonresistant plants. However, this event for wheat plant, as an efficient Cd accumulator, happened in roots [ 171 ]. In hyperaccumulators, it appears that they adopt mechanisms that involve long-distance translocation of PCs from root to shoot [ 172 ].…”

Molecular Defense Mechanisms in Plants to Tolerate Toxic Action of Heavy Metal Environmental Pollution

“…The translocation of Cd from root to shoot is through the xylem appears to be the main process for shoot accumulation. At a relatively high Cd treatment (20 μM) phytochelatin biosynthesis was enhanced more evidently in shoots [50]. The phytochelatin independent mechanism of tolerance of higher plants to Cd toxicity also exists and can be attributed to the highly developed apoplastic transport systems [51].…”