Phytosiderophores are a relatively small group of siderophores and their chemical properties are similar with plant nicotine amines. In fact, phytosiderophores are non-protein-amino acids released by plant roots. It is suggested that the release of phytosiderophores is a mechanism of gramineae species to combat micronutrients deficiency. Although the role of phytosiderophores in plant uptake of zinc (Zn) and iron (Fe) under their deficiency has been approved, there is no evidence on the role of these exudates on uptake of other micronutrients i.e., nickel (Ni) under deficiency conditions. A better understanding of how root exudates affect plant Ni uptake may aid in the opti mization of plant Ni nutrition. The aim of this study was to investigate in a hydroponic system how Ni deficiency affects release of phytosiderophores from plant roots. This experiment was conducted at research greenhouse of Soilless Culture Research Centre, Isfahan University of Technology. The experiment was set up in a completely randomized design with three plants i.e., two cultivars of wheat ( Triticum aestivum L. cvs. Kavir and Rushan) and a triticale cultivar ( x Triticosecale cv. Elinor), two levels of Ni treatments (addition of Ni versus no Ni addition to the nutrient solution), and two levels of Fe treatments (25 and 100 µM). The significance of the effects of the treatments and their interactions was evaluated by analysis of variance (ANOVA) using SAS software. According to the results, the effect of Ni deficiency on the release of phytosiderophores varied upon the plant type and sampling period. At week 1, root exudates were not detected using the method used in the present study. At weeks 2 and 3, the amount of root exudates differed by the plant type and Ni nutrition status. At week 4, no significant difference was found among various Ni and Fe treatments in the concentration of phytosiderophores released by the plant roots. Among the plants studied, the highest concentration of phytosiderophore was released by the roots of Rushan wheat cultivar. Nickel deficiency resulted in higher release of phytosiderophores from roots of Rushan wheat cultivar and triticale (as micronutrient-efficient plants) while in the micronutrient-inefficient Kavir wheat cultivar, addition of Ni increased the release of phytosiderophores. The suggested reason for higher release of phytosiderophores under Ni deficiency is reduction of plant Fe uptake in the presence of Ni. In Rushan wheat cultivar, Ni deficiency resulted in higher release of phytosiderophores. This result is similar to the previously reported response of this cultivar under Zn deficiency conditions. Based to the results, it is suggested that due to similarity of Ni and Fe, deficiency of Ni caused in higher release of phytosiderophores from roots of Rushan wheat cultivar and triticale. Results obtained from the present study showed differential response of plants species to Ni deficiency in release of phytosiderophores. Further studies are needed to investigate physiological mechanisms of phytosiderophore release from plant roots under Ni deficiency. Keywords: Nickel, Iron, Root exudates, Triticum aestivum, x Triticosecale