Role of potassium in the iron-stress response mechanism of iron-efficient oat
1992
Hughes, D.F. | Jolley, V.D. | Brown, J.C.
Adequate soil K enhances the ability of certain Fe-deficiency-stressed monocotyledonous and dicotyledonous plants to obtain Fe. In dicotyledonous plants, this increased capacity to obtain Fe where adequate K is present is associated with specific Fe-stress response mechanisms including H+ ion efflux, reductant release, and reduction of Fe3+ to Fe2+ at the root (Strategy I). A different Fe-stress response mechanism recently identified in Fe-efficient grasses is the release of phytosiderophore (a plant-produced Fe3+ chelator, Strategy II). Our objective was to determine if varied K additions affect either the production and release of phygosiderophores or the uptake of Fe in oat (Avena sativa L.; a Strategy II plant). A series of hydroponic experiments was conducted imposing varying solution K concentrations on Fe-deficiency-stressed 'Coker 227' oat, an Fe-efficient cultivar. Significantly more phytosiderophere was released by roots of oat plants grown with adequate K (84 mg K L-1) than by roots of plants grown at low concentrations of solution K (0 and 7 mg K L-1). The diminished phytosiderophore production in the absence of K corresponded significantly with greater Fe-deficiency chlorosis and lower leaf Fe contents. Oat plants grown in adequate K successfully competed with equimolar concentrations of Fe and EDDHA [ethylene-diamine di (O-hydroxyphenylacetic acid)], but did not compete for Fe where excess EDDHA was added, further substantiation of a role for K in the production and release of phytosiderophore.
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