Iodine [I, 53]

Iodine is broadly used in a number of chemicals and pharmaceutics, for both external and internal medical applications. Atmosphere is considered the main source of Iodine, which is emitted mainly from sea and ocean surface. Microorganism biomass may contain up to above 3% of Iodine present in surface soil layer. However, there are some reports on Iodine toxicity to rice plants grown in submerged paddy fields. Because Iodine in water is easily phytoavailable, marine plants may contain greater amounts of Iodine than terrestrial plants. Organically bound Iodine in soils is scarcely available to plants, but after the decomposition of soluble organic matter, it becomes phytoavailable. However, there are also some reports that its higher contents are in top plants. Iodine deficiency reduces the production of thyroid hormones in humans and animals, leading to morphological and functional changes of the thyroid gland, and reduction of the formation of thyroxin.