Involvement of superoxide radical in extracellular ferric reduction by iron-deficient bean roots. [Phadeolus vulgaris L. var Prelude]
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), Vol. 85:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IRON COMPOUNDS
REDUCTION
PHASEOLUS
NUTRITIONAL DEFICIENCY
ROOTS
SUPEROXIDE DISMUTASE
BIOCHEMICAL REACTION KINETICS
INHIBITION
MEMBRANE TRANSPORT
OXYGEN
PH VALUE
RESPONSE MODIFYING FACTORS
SCAVENGING
SUPEROXIDE RADICALS
BACTERIA
CHEMICAL REACTIONS
ELEMENTS
ENZYMES
KINETICS
LEGUMINOSAE
MICROORGANISMS
NONMETALS
OXIDOREDUCTASES
PLANTS
RADICALS
REACTION KINETICS
RHIZOBIUM
TRANSITION ELEMENT COMPOUNDS
550200* - Biochemistry