Characterization of Cadmium Uptake by Plant Tissue

Abstract

Since it is now well demonstrated that Ca is required to maintain the structural and functional integrity of plant cell membranes (1,2,12,14,18), Ca was included at 0.2 mm in all experimental solutions. The pH of absorption solutions, initially 5.5, did not vary by more than 0.2 units during the experiments. The absorption period, which varied from 2 to 120 min, was terminated by one of two methods, depending on whether or not that fraction of labeled Cd associated with the tissue in readily exchangeable form was to be removed. When it was desirable to desorb the labile fraction the absorption period was followed by a desorption period in a solution containing 0.2 mm Ca(NO3)2 and unlabeled Cd, or other ions. When it was not desirable to remove this labile fraction, the samples were rinsed in water after the absorption period. All experimental solutions were of sufficient volume that depletion did not exceed 10% of the initial Cd content.Analyses of roots, as described by Epstein et al. (3), were carried out on a Beckman Low Beta II Counter. All points plotted in the figures represent the mean of duplicate analyses on two or more root samples.

Cadmium accumulation in crops

“…In studies with radiolabelled Cd, Cutler and Rains (1974) found that 79% of tracer accumulated by excised barley roots during a 30-min exposure to 9 × 10 -5 M 115 Cd could be desorbed by 4.5 × 10 -4 M unlabelled Cd. After exposure to 0.05-5.0 × 10 -6 M 109 Cd for 5 h, 41-48% of tracer was desorbed from spruce seedling roots by a 20-fold concentration of unlabelled Cd (Godbold 1991).…”

“…Cutler and Rains (1974), working with 8.9 × 10 -6 M Cd in nutrient solution and excised barley roots, concluded that accumulation of Cd in barley tissue was a non-metabolic (passive) process, involving diffusion coupled with sequestration. However, 8.9 × 10 -6 M Cd is a high, probably phytotoxic, level of Cd exposure, and the conclusion that Cd uptake was a passive process (Cutler and Rains 1974) should not be applied to lower, more environmentally relevant concentrations.…”

“…Cutler and Rains (1974), working with 8.9 × 10 -6 M Cd in nutrient solution and excised barley roots, concluded that accumulation of Cd in barley tissue was a non-metabolic (passive) process, involving diffusion coupled with sequestration. However, 8.9 × 10 -6 M Cd is a high, probably phytotoxic, level of Cd exposure, and the conclusion that Cd uptake was a passive process (Cutler and Rains 1974) should not be applied to lower, more environmentally relevant concentrations. Other authors of studies with wheat (Smeyers-Verbeke et al 1978), soybean (Cataldo et al 1983), and spruce seedlings (Godbold 1991) have concluded that there was a metabolically active component in total cadmium accumulation by intact plants.…”

Cadmium induced changes in cell wall peroxidase isozyme pattern in barley root tips

“…The uptake of cadmium by roots and its transport to the upper part of plants is a very fast process. Cd content in barley tissues can excess Cd concentration in soil after longer exposure (Cutler and Rians 1974). The rapid Cd accumulation in plants became crucial agricultural problem all over the world causing a reduction in crop growth and productivity, but it has also several consequences to human health.…”

Alternating current electrical field effects on lettuce (Lactuca sativa) growing in hydroponic culture with and without cadmium contamination

“…8). The mechanism of Cd uptake to the plant root is exchange absorption, diffusion and irreversible binding [22]. This is due to the large negative electric potential existing at the exterior surface of the root plasma membrane, provides enough energy to drive the uptake of Cd 2+ [6].…”