Effect of supplied phytosiderophore on ^<59>Fe absorption and translocation in Fe-deficient barley grown hydroponically in low phosphorus media(Plant Nutrition)

Hydroponically grown barley plants (Hordeum vulgare L. cv. Minorimugi) under iron-deficient (-Fe) and high phosphorus (P) conditions (500μmolL^<-1>) showed Fe chlorosis and lower growth compared with plants grown in -Fe and low P conditions (50, 5 and 0.5μmolL-1). To understand the physiological role of P in regulating the growth of plants in -Fe medium, we carried out an Fe feeding experiment using four P levels (500, 50, 5 and 0.5μmolL^<-1>) and phytosiderophores (PS), mugineic acid. Our results suggest that plants grown in a high P medium had higher absorption activity of ^<59>Fe compared with plants grown in low P media, irrespective of the presence or absence of added PS. Translocation of ^<59>Fe from roots to shoots was not affected by the P level. The relative translocation rate of ^<59>Fe increased with decreasing levels of P in the medium. In general, the addition of PS enhanced the absorption of ^<59>Fe and its translocation. Taken together these results suggest that the lower relative translocation rate of Fe in high P plants may be induced by the physiological inactivation of Fe in the roots, and the higher absorption activity of Fe in high P conditions possibly results from the response of barley plants to Fe deficiency.