Characteristics of Cd uptake and translocation in two cultivars of Amaranth (Amaranthus mangostanus L.)

ObjectivesCharacteristics of absorption and translocation of Cd in amaranth (Amaranthus mangostanus L.) with different Cd accumulation abilities were compared under cadmium (Cd) stress.

MethodsHydroponic experiments basing Hoagland nutrient solution were conducted with two amaranth cultivars, Zibeixian (ZBX, a low Cd accumulator) and Tianxingmi (TXM, a high Cd accumulator) as testing materials. Plant samples were collected after the exposure to Cd stress solution (30 μmol/L CdCl₂) of 4 h, 8 h, 16 h, 1 d and 2 d. The Cd contents were determined using ICP-OES method, and the dynamic accumulation in roots was monitored using none-invasive micro-test technique (NMT). The responses of the two cultivars to metabolic inhibitor were also compared.

ResultsAfter 1 d exposure, the total dry biomass of TXM is twice of ZBX, and reached to the maximum value of 5.90 g/plant. The cadmium contents in the roots, stems and leaves of TXM reached 609, 254 and 62.3 mg/kg, which were 1.4, 1.9 and 1.6 times of those of ZBX. The Cd accumulation amounts in the shoots and whole plants of TXM reached 602.0 and 1308 μg/plant. The bioaccumulation factor and translocation factor of TXM were 2.1 and 1.5 times of those of ZBX. All these results were significant difference between the two cultivars of amaranth (P < 0.05). The biggest net Cd²⁺influx difference in the screening test of roots was within 0-300 μm from the tips. The net Cd²⁺influx in roots of TXM was 3.75 times of that of ZBX, and the enrichment characteristic was consistent with the result of NMT. Metabolic inhibitor significantly reduced the Cd indexes of TXM (P < 0.05), but had little effect on Zibeixian.

ConclusionsCompared with the cultivar ZBX, the cultivar TXM has stronger ability of Cd uptake and root-to-shoot translocation capacity, which is an active process, and has the symplastic pathway rather than the apoplastic bypass.