Cadmium uptake and translocation during reproductive development of peanut (Arachis hypogaea L)

The uptake and translocation of cadmium (Cd) by roots and below-ground developing reproductive structures of peanut (Arachis hypogaea L.) were examined under controlled growth conditions. Specially designed pots allowed separate Cd treatments of the root and fruit media to study uptake in both compartments. Results indicated uptake and translocation of Cd to various vegetative plant parts, reaching values close to 2.0 mu g . g(-1) DW in roots, leaves, and petioles. Values recorded for seed of Cd-treated plants remained on average slightly lower (1.7 mu g . g(-1) DW). Only 18 % and 32 % of the Cd found in seeds and pod walls, respectively, were directly taken up by the developing fruits. Uptake also occurred via below-ground portions of gynophores with some Cd even entering above-ground portions of this plant organ. However, seeds and pod walls received 82 % and 68 %, respectively, of their Cd from roots via gynophores. Since gynophores and peanut fruits have an extremely reduced xylem and a very large phloem, and since peanut fruits are hardly capable of transpiration, it is suggested that the majority of Cd translocated to the fruits was transported in the phloem.