Iron stress response and composition of xylem sap of strategy II Plants

Abstract

A method for the detection of the regions releasing phytosiderophores (PS) in the roots of barley was developed using filter paper and a Fe3+ solubilizing assay. The characteristics of the PS release by young roots and root tips are discussed. Feeding experiments with 14C-PS or 14C-PS-Fe3+ indicate that both free PS and chelated PS could be absorbed at similar rates by barley roots. It is tentatively suggested that free PS might be absorbed and then subsequently released by roots. The concentrations of PS, organic acids, amino acids, and metal micronutrients were measured in the xylem sap of barley and rice. Phytosiderophore concentrations in the xylem sap of Fe deficient barley were approximately 10-and more than 100-fold higher than those of organic acids and metal micronutrients, respectively. When PS were supplied with Fe3+ to barley roots for 4 hours and under hydroponical conditions, the Fe concentrations in xylem sap were enhanced more than 10 times as compared to plants fed with Fe3+ only. © 2006 Springer.