[Characteristics of iodine uptake and accumulation by vegetables]

With seaweed iodine and KI as exogenous iodine sources, a pot experiment was conducted to study the characteristics of iodine uptake and accumulation by pakchoi cabbage, celery, capsicum, and radish. The results showed that the iodine content in the edible parts of test vegetables increased with increasing amount of exogenous iodine, but the iodine accumulation rate differed with the kinds of vegetables, in the order of pakchoi > celery > radish > capsicum. The majority of iodine was accumulated in roots, with lesser amount transferred to shoots. The distribution of iodine in vegetables was commonly in the order of root > leaf > stem > fruit, but the iodine in radish is lower in its rhizome than in its shoot. Low concentrations (0-25 mg x kg(-1)) of exogenous iodine had little effects on the growth of vegetables, while high concentrations (> or = 50 mg x kg(-1)) of it had inhibitory effects, resulting in a decreased vegetable biomass. The sensitivity of test vegetables to the adverse effect of exogenous iodine was in the order of capsicum > pachoi > celery > radish. Compared with seaweed iodine, KI decreased the biomass of first cutting significantly (P < 0.05), but for the second cutting, little difference was observed between these two iodine sources. The uptake and accumulation of these two iodine sources by vegetables also differed with cuttings, i.e., the first cutting vegetables absorbed more KI, while the second cutting vegetables absorbed more seaweed iodine (P < 0.05), suggesting that seaweed iodine had a longer efficacy than KI.