Evidence for a Specific Uptake System for Iron Phytosiderophores in Roots of Grasses

Abstract

Roots of grasses in response to iron deficiency markedly increase the release of chelating substances ('phytosiderophores') Studies on root responses to iron deficiency during the last three decades were mainly focused on dicotyledonous species. Root responses of most dicotyledonous and in some monocotyledonous species to iron deficiency are characterized by an increase in the activity of a NADPH dependent reductase (2, 20,

Nutritionally Enhanced Staple Food Crops

“…The environmental variables such as pH, temperature, solar radiation, precipitation, organic matter, and soil texture have the potential to influence nutrient concentration (Tisdale and Nelson 1975;R€ omheld and Marschner 1986;Cabuslay et al 2003;Abilgos-Ramos et al 2004;Joshi et al 2010) and must be taken into consideration while explaining the variation for seed micronutrients in germplasm or when assessing the nutritional quality of staple food crops grown in diverse agroecological conditions.…”

Revisiting the Metal-Binding Chemistry of Nicotianamine and 2′-Deoxymugineic Acid. Implications for Iron Nutrition in Strategy II Plants

“…Norvell et al, 1993), the redox activity of a given Fe III complex can be computationally assessed by considering the sum of following three reactions: When combined with the appropriate log K for the second reaction (12.5 at I ϭ 0.1 m; Morel and Hering, 1993), followed by conversion to E H notation, the corresponding constants for the net reaction are 0.278, 0.089, and 0.053 V for NA, EDTA, and DMA, respectively. As with any so-ordered ranking of standardized redox potentials, the higher E H value for NA implies that its Fe III complex is a comparatively good oxidant, and thus more readily reduced by strong reductants such as NAD(P)H (Morel and Hering, 1993 (Romheld and Marschner, 1986;Grusak et al, 1999), NA and DMA might compete for Fe III in the cytoplasm, and von Wirén et al (1999) suggested the transfer of Fe III from DMA to NA upon entry into the cytoplasm. However, inclusion of the Fe III -DMA(H Ϫ1 ) Ϫ complex in the chemical modeling implies that Fe III would remain approximately 100% complexed to DMA in the cytoplasm.…”

“…Deoxymugineic acid is representative of the family of phytosiderophores that are excreted by Strategy II species into the rhizosphere in response to Fe deficiency (Ma and Nomoto, 1996). Phytosiderophores increase the solubility of Fe III by chelation, and are absorbed as the intact Fe III ligand by Strategy II plants (Romheld and Marschner, 1986;Grusak et al, 1999).…”

Siderophores, the iron nutrition of plants, and nitrate reductase

“…Barley assimilates iron from ferriphytosiderophores lOO-lOOO-times faster than from other ferrichelators, including ferrisiderophores. In addition, reduction of the ferriphytosiderophores by barley does not occur during iron assimilation, as occurs with non-graminaceous monocotyledonous and dicotyledonous plants [34].…”