Study On The Iodine Enrichment Approaches And Mechanisms Of Vegetables From Environment

The absorption and enrichment of iodine from environment by plants are divided into two components—iodine absorption from soils by the roots and from air by the leaves. The enrichment of environmental iodine by plants which is controlled by the speciation of iodine and the nature of plants significantly influences the iodine contents of plants. Typical vegetables including leafy vegetables (Chinese cabbage), root vegetables (radish, carrot) and stem vegetables (celery, lettuce) were cultivated in sand accompanied by the addition of various exogenous iodine species including I-, IO3-, I2 and CH3I to investigate the absorption and enrichment mechanisms of various iodine species by vegetables. After sampling, the iodine contents in various parts of different vegetables and under different exogenous iodine contents were determined by hydrothermal pyrolysis-arsenic cerium catalysis spectroscopy method.By comparing the iodine enrichment factors of various parts in different vegetables and analyzing the iodine enrichment factors of various iodine species in each part of vegetables and under different iodine contents, the following conclusions are drawn:1. The iodine contents in the roots appeared to be significantly linearly correlated with the iodine contents in the leaves, which indicates that the absorbed iodine by the roots are transported to the leaves along with other nutrition. The iodine enrichment ratios of roots and leaves were higher than those of stems. Stems mainly function as a passageway for transportation and migration.2. Within certain range of iodine contents, I- was more highly enriched compared with IO3- by various plants since IO3- were not easily utilized by plants. The enrichment abilities of different exogenous iodine species by various plants deviated from each other. For I-, lettuce had the highest iodine enrichment abilities, followed by carrot, celery, Chinese cabbage and radish. For IO3-, the diminishing order of iodine enrichment abilities by various plants was carrot> Chinese cabbage> radish> celery> lettuce.3. The iodine contents of various parts in vegetables increased with the increasing of exogenous iodine contents and were significantly positively correlated with exogenous iodine contents. Thus the supply of exogenous iodine fertilizer for plants could significantly increase the iodine contents in plant, and consequently, increase the dietary iodine intake from plants.4. The iodine enrichment factors of various plants were linearly correlated with the iodine contents in nutrient solution when the iodine contents were below 0.5 ppm, showing the iodine enrichment by plants is completely dependent on exogenous iodine contents. While for higher exogenous iodine contents (>0.5 ppm), the iodine enrichment by plants is also dominated by iodine absorbing and enrichment abilities of plants themselves.