Characteristics of iron uptake in Ni-tolerant mutant and wildtype of ryegrass

The uptake of Fe-59(II)SO4, Fe-59(III) phytosiderophores and the release of phytosiderophores (PS) in a Ni-tolerant mutant and its wild type of ryegra ss (Lolium perenne L.) were examined. The results showed that the uptake ra tes of Fe-59(2+) in the mutant were about 2-fold lower than those in the wi ld-type independently of the Fe nutritional status (+/- Fe preculture) and Ni supply levels. In contrast, the uptake rates for Fe-59(III)PS were highe r in the mutant than in the wild-type, particularly under Fe deficiency. Th e high Ni supply decreased Fe-59(III)PS uptake rate by 40% for the wild-typ e and by 20% for the mutant under Fe deficiency. However, the rate of PS re lease was significantly lower in the mutant than in the wild-type. These re sults indicated that the relatively high sensitivity of Ni-tolerant mutant to Fe deficiency is obviously due to a lower rate of Fe2+ uptake and PS rel ease. Further studies are needed to understand the relationship between upt ake and translocation of Ni and acquisition and translocation of Fe within the mutant.