Plant Hormones Influencing Iron Uptake in Plants

Abstract

The influence of hormones on Fe (iron) uptake has been studying since the beginning of the eighties, with the pioneering works of Landsberg suggesting a role for auxin in the regulation of Fe deficiency stress responses by Strategy I plants (Landsberg 1981a, b, and c). Before that, there were a few works relating hormone application to Fe chlorosis correction but with often contradictory results (reviewed in Landsberg, 1984). After first Landsberg’s works, and until now, several authors have studied the role of hormones (mainly auxin and ethylene) in the regulation of some of the Fe deficiency stress responses by Strategy I plants (Landsberg, 1986 and 1996; Romera and Alcántara, 1994; Schmidt et al., 2000b). There are almost no works relating hormones to the regulation of Fe deficiency stress responses by Strategy II plants. In Strategy I plants, it is widely accepted the probable roles of auxin and/or ethylene in the regulation of some of their Fe deficiency morphological responses, such as development of subapical root hairs and transfer cells (Landsberg, 1996; Romera and Alcántara, 2004; Schmidt and Bartels, 1996). However, it is more controversial the acceptance of the involvement of hormones in the regulation of their Fe deficiency physiological responses, such as enhanced ferric reductase activity and acidification (Curie and Briat, 2003; Schikora and Schmidt, 2001; Schmidt et al., 2003). In this chapter, the evidence suggesting a role for hormones in the regulation of Fe deficiency stress responses, and other aspects of Fe nutrition, will be reviewed. This evidence is related mainly to Strategy I plants, although the possible relationship between both Strategies will be discussed.