Effects of a Hydroxamate Siderophore on Iron Absorption by Sunflower and Sorghum

Characterization of Iron Uptake from Ferrioxamine B by Chlorella vulgaris

“…This does not necessarily imply that cells are unable to obtain sufficient iron from synthetic chelates, simply that the rate of iron acquisition is different. Under these conditions EDDHA should chelate 100% of the iron, while EDTA would only chelate 15% (5). The slow rate of iron uptake from Fe3+-EDDHA may reflect the inability ofthe cell to remove iron from the chelate due to its strong ferric affinity.…”

The Role of Ligand Exchange in the Uptake of Iron from Microbial Siderophores by Gramineous Plants

“…A variety of plant species have the ability to acquire Fe from MS, such as PSB, coprogen, ferrichrome A, and FeFOB (Jurkevitch et al, 1986(Jurkevitch et al, , 1988Crowley et al, 1991). Among plant species reported were peanut and cotton (Bar-Ness et al, 1991), oat (Powell et al, 1982;Reid et al, 1984;Crowley et al, 1988), sorghum and sunflower (Cline et al, 1984), and cucumber (Wang et al, 1993). However, the concentrations of siderophores required for a complete remedy of chlorotic plants were higher than those of the synthetic chelators.…”

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

“…Microbial siderophores in soils may be an important factor involved in iron solubility (17). However, a particular importance ofthese siderophores for the iron nutrition of grasses as it has been recently been suggested (8,17) must be questioned. The microbial Fe"'siderophores are poor sources of iron, also for plant species with strategy I since the ferric iron in these compounds is not easily reducible by the plasma membrane-bound reductase (2,20).…”

“…Thus, the principal step of regulation of iron uptake (Fig. 1) seems to be the rate of synthesis (S) from the possible precursor nicotionamine (9) and/or extrusion of phytosiderophores (8) but not the rate of uptake (® . In such a regulatory system the involvement of a shuttle transport mechanism, as it exists for siderophores in microorganisms (recycling of siderophores; 10) is not very likely.…”