Characterization of cadmium (108Cd) distribution and accumulation in Tagetes erecta L. seedlings: Effect of split-root and of remove-xylem/phloem

Tagetes erecta has a high potential for cadmium (Cd) phytoremediation. Through several hydroponic experiments, characteristics of 108Cd distribution and accumulation were investigated in T. erecta with split -roots or removed xylem/phloem. The results showed that 108Cd transport from roots to aboveground tissues showed the homolateral transport phenomenon in split-root seedlings. 108Cd content of leaves on the +108Cd side and the −108Cd side was not significantly different, which implied that there was horizontal transport of 108Cd from the +108Cd side to the −108Cd side in cut-root seedlings. Like 108Cd transport, the transport of 70Zn was homolateral. Reduction of water consumption in the removed xylem treatment significantly decreased 108Cd accumulation; whereas, the removed phloem treatment had no significant effect on water consumption, but did decrease 108Cd accumulation in leaves of the seedlings. The removal of phloem significantly reduced distal leaf 108Cd content, which was significantly lower than that in the basal leaves in both the split-root and unsplit-root seedlings. Overall, the results presented in this study revealed that the root to aboveground cadmium translocation via phloem is as an important and common physiological process as xylem determination of the cadmium accumulation in stems and leaves of marigold seedlings.