Involvement of superoxide radical in extracellular ferric reduction by iron-deficient bean roots. [Phadeolus vulgaris L. var Prelude]

Journal Article · Tue Sep 01 04:00:00 EDT 1987 · Plant Physiol.; (United States)

OSTI ID:6998485

Cakmak, I; van de Wetering, D A.M.; Marschner, H; Bienfait, H F

The recent proposal of Tipton and Thowsen that iron-deficient plants reduce ferric chelates in cell walls by a system dependent on the leakage of malate from root cells was tested. Results are presented showing that this mechanism could not be responsible for the high rates of ferric reduction shown by roots of iron-deficient bean (Phaseolus vulgaris L. var Prelude) plants. The role of O/sub 2/ in the reduction of ferric chelates by roots of iron-deficient bean plants was also tested. The rate of Fe(III) reduction was the same in the presence and in the absence of O/sub 2/. However, in the presence of O/sub 2/ the reaction was partially inhibited by superoxide dismutase (SOD), which indicates a role for the superoxide radical, O/sub 2//sup -/, as a facultative intermediate electron carrier. The inhibition by SOD increased with substrate pH and with decrease in concentration of the ferrous scavenger bathophenanthroline-disulfonate. The results are consistent with a mechanism for transmembrane electron in which a flavin or quinone is the final electron carrier in the plasma membrane. The results are discussed in relation to the ecological importance that O/sub 2//sup -/ may have in the acquisition of ferric iron by dicotyledonous plants.

• Research Organization: Universitaet Hohenheim, Stuttgart (West Germany)
• OSTI ID: 6998485
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 85:1; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BIOCHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
ELEMENTS
ENZYMES
INHIBITION
IRON COMPOUNDS
KINETICS
LEGUMINOSAE
MEMBRANE TRANSPORT
MICROORGANISMS
NONMETALS
NUTRITIONAL DEFICIENCY
OXIDOREDUCTASES
OXYGEN
PH VALUE
PHASEOLUS
PLANTS
RADICALS
REACTION KINETICS
REDUCTION
RESPONSE MODIFYING FACTORS
RHIZOBIUM
ROOTS
SCAVENGING
SUPEROXIDE DISMUTASE
SUPEROXIDE RADICALS
TRANSITION ELEMENT COMPOUNDS