Plants, iodine content

Occurrence. Iodine [7553-56-2] is widely distributed in the Hthosphere at low concentrations (about 0.3 ppm) (32). It is present in seawater at a concentration of 0.05 ppm (33). Certain marine plants concentrate iodine to higher levels than occur in the sea brine these plants have been used for their iodine content. A significant source of iodine is caUche deposits of the Atacama Desert, Chile. About 40% of the free world s iodine was produced in Japan from natural gas wells (34), but production from Atacama Desert caUche deposits is relatively inexpensive and on the increase. By 1992, Chile was the primary world producer. In the United States, underground brine is the sole commercial source of iodine (35). Such brine can be found in the northern Oklahoma oil fields originating in the Mississippian geological system (see Iodine and iodine compounds). 

Tab. 9.4-1 Iodine content (pg I kg DM) of indicator plants growing on boulder clay and diluvial sand as a function of distance from the seaside (n = 34, 49 and 72)...

Tab. 9.4-5 Influence of plant age on iodine content (pg kg DM) in several species ...

The iodine content from food of plant origin is low in comparison to food of animal origin (Table 9-4.11). In Gentral Europe, foodstuffs rich in sugar and starch, such as cereals, pudding, honey, bread, rolls, rolled... 

In general, soluble forms of iodine seem to be easily available to plants therefore, terrestrial plants contain much less iodine than do marine plants, which are known to concentrate iodine from 50 to 8800 mg kg DM (Shaklette and Cuthbert 1967). Organically bound iodine is scarcely available to plants soil iodine becomes available after the decomposition of organic matter by bacteria (Selezniev and Tiuriuka-nov 1971). Atmospheric iodine also contributes to the iodine content of plants (Kabata-Pendias and Pendias 1992), as plants can... 

Iodine has not been shown to be essential to plants, and stimulatory effects on plant growth at low levels have not been reported. Mengel and Kirkby (1978) reported that a stimulatory effect of iodine was observed at 100 pg I L in nutrient solutions, whereas toxic effects in plants occurred at an iodine concentration of 500-1000 pg L b As the toxic concentration is higher than the soluble iodine content of soils, iodine toxicity is rare in plants under natural field conditions. However, a physiological disease of rice plants named Akagare has been reported (Yuita 1979), induced by excessive absorption of iodine from soil enriched with easily soluble iodine when land was converted for submerged paddy fields (Kabata-Pendias and Pendias 1992). 

Geoppel B and Anke M (1986) Iodine content of foodstuffs, plants and drinking water in the GDR. In Anke M ed. 5. Spurenelement-Symposium, University Leipzig and Jena, pp. 19-29. Kon-gress- und Werbedruck Oberlungwitz, Germany. 

Shacklette HT and Cuthbert ME (1967) Iodine content of plant groups as influenced by variation in rock and soil type. Geol Soc Am Spec Pap 90 31 —... 

Despite the low iodine content of plants, the development or severity of iodine deficiency is amefiorated by the trace amounts of iodine in some feeds, drinking water and even air. As a result of the iodine content of seawater and its vaporization and precipitation air, water, soil and plants in coastal regions contain more iodine (McDowell, 2003). Livestock kept on coastal farms are therefore less at risk of iodine deficiency than those reared on mountains. In addition, the types and amounts of iodine antagonists, the iodine reserves and salvaging mechanisms vary between farm animal species, categories, herds and individuals. 

The iodine content of plants reflects passive uptake from contamination or diffusion of iodine in the air, water and soil. The iodine concentration in German and Austrian soils is around 1—3mg/kg (Anke et al, 1993 Jopke et al., 1997 Gerzabek et al, 1999). Whitehead (1979) reported higher concentrations in soil samples from the UK. There is a correlation between the clay and organic carbon content of a given soil and the iodine content. 

The iodine content of plant and animal foods depends on the environment in which they grow hence, the low iodine content of New Zealand soils results in low concentrations in locally produced foods (Hercus et al., 1925). Prior to iodization of salt in the 1930s, Hercus analyzed a selection of foods (Table 129.1) and estimated daily intake from these values the intake in areas where goiter was endemic was around 26 pg/day while in non-goitrous areas it was around 40 pg/day (20 and 35 pg/day respectively, if fish was not included) (Hercus and Roberts, 1927) (Table 129.2). 

Seaweed is a primary source of iodine, and in some seaweed, iodine content exceeds its dietary minimum requirement (150 pg/day). The highest iodine content is found in brown algae (1500-8000 ppm), and in most instances, red and green algae have lower contents. Iodine amount in the seaweed remains comparatively high than that in the land plants. Since animal- and plant-derived foods are very low in iodine, seaweeds can be considered as the best inexpensive food to fulfill the iodine requirement of human. 

He qualified in Montpellier with a thesis on cyanogen, but had previously been investigating the iodine content of sea-water and marine plants and animals, and noticed that when chlorine water was added to a solution of seaweed ash, or the residual mother-liquor from the manufacture of solar salt, to which... 

Iodine occurs in traces in most foods and is present mainly as inorganic iodide, in which form it is absorbed from the digestive tract.The richest sources of this element are foods of marine origin, and values as high as 6 g/kg DM have been reported for some seaweeds fishmeal is also a rich source of iodine. The iodine content of land plants is related to the amount of iodine present in the soil, and consequently wide variations occur in similar crops grown in different areas. 

In principle, the iodine content increases with a higher proportion of leaves and reaches almost 200 ug/kg dry matter in beet leaves. However, it must be taken into consideration that the high iodine proportion in beet leaves as well as in cereal straw results from their contamination by soil. Since the different soils have a mean iodine content of 3 mg/kg, even small contaminations by soil increase the iodine content of plants and of straw significantly (Table 4). 

In recent control of salt from all manufactures in former state of Yugoslavia out of 55 samples, 70% showed iodine contents lower than the prescribed amount (7.6 mg I/kg of salt or 10 mgKI). In Pag salt plant 55% of samples, in Ston and Nin 100% of samples had less than the prescribed amount of iodine. It was observed that about 30% of I was lost from salt during one year in laboratory conditions (19). 

The use of iodine in determining total alkaloid content has been developed by plant breeders in field conditions up to the present. The basic iodine solution contains 100 gJ and 140 gKJ as well as 1000 ml water. Before application, the basic iodine solution is diluted by 1 3 or 1 5. The colour of leaves without alkaloids is not changed after application of the iodine solution. Following this method, the leaf colour changes to red-brown . 

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