| Abstract: | Cadmium has been found to accumulate in peanut (Arachis hypogaea) kernels to levels exceeding the current maximum permitted concentration in Australia of 0.1 mg kg-1. Little is known of the mechanisms of Cd uptake into kernels by cultivars of peanut, so the aims of the experiments reported
here were to determine if Cd is absorbed directly through the pod wall or via the main root system, and if differences exist between cultivars in this respect. Split-pot soil and sand/nutrient solution
experiments were performed with two cultivars of peanut (cv. NC7 and Streeton) known to accumulate Cd to different levels
in the kernel. The growth medium was separated into pod and root zones with Cd concentrations in each zone varied. In confirmation
of previous field trial results, cv. NC7 had higher concentrations of Cd in kernels, given the same Cd levels in the external
medium (solution or soil). Despite total Cd uptake by cv. NC7 being similar to cv. Streeton, cv. NC7 appeared to retain more
Cd in the roots and translocate less Cd to shoots. Results from both soil and sand/solution culture indicated that the dominant
path of Cd uptake by peanut was via the main root system, with direct pod uptake contributing less than 5% of the total Cd in the kernel. There was little difference
between cultivars in this characteristic. This indicates that unlike Ca nutrition of peanuts, agronomic techniques to manage
Cd uptake will require modification of soil to the full depth of root exploration, rather than just the surface strata where
pods develop. Cadmium concentrations in testa were up to an order of magnitude higher than in the kernel, indicating that
blanching of kernels would be effective in reducing Cd in the marketed product.
This revised version was published online in June 2006 with corrections to the Cover Date. |
