EFFECT OF IODINE FERTILIZATION AND SOIL APPLICATION OF SUCROSE ON THE CONTENT OF SELECTED HEAVY METALS AND TRACE ELEMENTS IN SPINACH

Iodine is not an essential nutrient for plants. Side-effects of its application on mineral nutrition of plants have not yet been thoroughly documented. The aim of the study was to evaluate the influence of soil application of iodine and sucrose on accumulation of heavy metals and trace elements in spinach. In 2009–2010, a pot experiment was carried out with spinach Spinacia oleracea L. ‘Olbrzym zimowy’ cv. cultivated on mineral soil. The research included diverse combinations with pre-sowing iodine fertilization (in the form of KI) and soil application of sucrose: 1) – control (without iodine fertilization and sucrose application), 2) – 1 mg I dm-3 of soil, 3) – 2 mg I dm-3 of soil, 4) – 1 mg I + 1 g sucrose dm-3 of soil and 5) – 2 mg I + 1 g sucrose dm-3 of soil. In spinach as well as soil after its cultivation the content of 29 elements was determined by ICP-OES technique, including: Ag, As, Be, Bi, Cs, Dy, Er, Eu, Hg, Ho, In, Li, Lu, Ni, Pb, Pr, Sb, Sc, Sm, Sn Sr, Tb, Th, Ti, Tl, Tm, V, Y and Yb. A significant influence of iodine fertilization as well as its interaction with sucrose was found in respect of: Li, Ni, Pb, Sr, Ti, Y, V, Ag, Lu, Sc, Tb, Th, Yb, Dy and Sn level in spinach leaves. Fertilization with iodine only (in both tested doses) contributed to a significant increase in V, Sc and Th as well as reduced Ag content in spinach when compared to the control plants. Application of the higher iodine dose (2 mg I dm-3 of soil) resulted in greater accumulation of Pb and Sn in spinach as well as lowered Sr concentration in comparison to plants treated with 1 mg I dm-3. Simultaneous application of iodine (in both doses) and sucrose decreased spinach content of: Li, Ni, Pb, Sr, Y, V, Sc, Tb and Yb when compared to the control object as well as plants fertilized only with iodine. In the case of Li, Y, V, Sc and Tb, a stronger influence was found for sucrose applied together with the higher dose of I. Obtained decrease in Sr, Y, Sc and Tb accumulation in spinach (after iodine and sucrose application) correlated with lower soil content of these elements.