LAUSR

Abstract In the greenhouse, rice (Oryza sativa L. cv. Akitakomachi) were grown at pH 5.5, treated with 26.8 μM As (arsenite; NaAsO2) for 14 days. We found that As-induced whitish chlorosis in the fully developed young leaves. Control and As-treated seedlings were fed with 10 μM 59Fe in the absence or in the presence of 10 μM PS (phytosiderophores, mugineic acid) for 4 h in the phytotron to observe the efficiency of PS on 59Fe absorption and translocation in plants. Absorption and translocation of 59Fe increased in control plants fed with PS as compared with those without being fed with PS, indicating that PS effectively elevated 59Fe absorption and translocation. In As-treated plants, PS enhanced 59Fe absorption by roots but did not enhance 59Fe translocation from roots to shoots. In addition, 59Fe absorption was lower in As-treated plants as compared to control plants in the absence or presence of PS. In the phytotron, a similar experiment with barley (Hordeum vulgare L. cv. Minorimugi) was conducted. Barley were grown at pH 6.5 treated with 33.5 μM As for 14 days, showing chlorosis, were fed with 59Fe in the absence or presence of PS. In control plants, PS enhanced 59Fe absorption and translocation similarly to rice. In As-treated barley, PS enhanced 59Fe absorption in roots and PS activity enhanced 59Fe translocation from roots to shoots. Our results suggested that As repressed or inhibited the system for PS-Fe3+ absorption in gramineae under severe As-stress condition, resulting in appearance of Fe chlorosis.