Effects of Cd,Zn and Their interactions on Accumulation,Subcellular distribution and Chemical Forms of Heavy Metals in Spartina alterniflora

A pot culture experiment was carried out to study the effects of cadmium(Cd) and zinc(Zn) singly and in combination on the accumulation,subcellular distribution of Cd and Zn in Spartina alterniflora,and the chemical forms of Cd and Zn in leaves of S.alterniflora were also determined.The results showed that the content of Cd in shoots and roots of S.alterniflora under Cd-Zn treatment was significantly higher than Cd treatment.Cd content in roots was significantly lower under Cd-Zn treatment than Zn treatment,while there was no significant difference for shoots.These results showed that Zn accelerated the uptake of Cd,while Cd restained the uptake of Zn.Cd accumulation was significantly higher in shoots under Cd-Zn treatment than Cd treatment,while the trend was opposite in roots.Zn accumulation was greatly higher in shoots and roots under Zn treatment than control and Cd-Zn treatment.Cd was mainly accumulated in cell wall under Cd treatment,while it was mainly accumulated in cytoplasmic supernatant under Cd-Zn treatment.Zn was mainly accumulated in cytoplasmic supernatant under Zn and Cd-Zn treatments,and the subcellular distribution of Zn presented the following order: cytoplasmic supernatantcell wallcell organelle.These results indicated an interaction between Cd and Zn at subcellular level.Most of the Cd and Zn in leaves of S.alterniflora was extracted by 1 mol·L-1 NaCl,indicating most Cd and Zn was integrated with pectates and protein.