The effects of iodine doses applied to growing media on iodine uptake and development of lettuce and spinach plants

Consumption of green leafy vegetables enriched with iodine may be an alternative method to salt in meeting the iodine needs of people exposed to iodine (I) deficiency. During iodine enrichment, it is very important for plant and human health that the uptake of other nutrients are also in balance. The amount of these elements in plants should be in a balance. For this reason, a study was conducted in the greenhouse of the Department of Soil Science and Plant Nutrition located in Agricultural Research and Application Center at Faculty of Agriculture, Bursa Uludağ University. Appropriate lettuce and spinach seeds determined for the study were germinated in perlite medium and grown in a hydroponic system with a flowing water culture where increasing amounts of I (0-2-4-8-16 μM) doses were applied. It was observed that increasing amounts of I application did not have a statistically significant effect on dry matter yield of spinach and lettuce plants, but it positively affected iodine and nutrient uptake of spinach and lettuce plants up to 4 µM I dose (p <0.01). The effect of high iodine doses (8-16 µM) applied was negative. It was observed that the amount of dry matter was higher in the leaves than the root, and with increasing iodine doses, root development was negativelly affected more than the leaves, Fe, Cu, Zn and Mn accumulation occurred especially in the roots of the plants. As a result of the study, it was determined that the amount of iodine contained in spinach and lettuce plants has the potential to meet the amount of iodine required for human health. The iodine content obtained from the first iodine dose, I1 (2 µM) application, was 2.57 mg kg-1 in spinach leaves and 1.98 mg kg-1 in lettuce leaves, and if approximately 60 g of dry plant is consumed from these plants, it has been seen that it can meet the iodine needs. Because of excessive amounts cause a decrease in the uptake of other nutrients as well as iodine, it was concluded that a limit dose should be found for the enrichment of plants with iodine. The maximum iodine dose that can be used in the nutrient solution for spinach and lettuce plants was determined as I2 (4 µM) according to the researche results.