THE NORMALIZING FACTOR FOR THE TOMATO MUTANT CHLORONERVA .41. NICOTIANAMINE AND THE DISTRIBUTION OF IRON INTO APOPLAST AND SYMPLAST OF TOMATO (LYCOPERSICON-ESCULENTUM MILL)

The influence of nicotianamine (NA) on the distribution of iron into apoplast and symplast of a NA-containing tomato wild-type and its NA-less mutant was investigated. Isolated protoplasts from wild-type and mutant leaves are able to reduce exogenous iron(III)citrate at equal rates. In spite of this, protoplasts from mutant leaves take up more iron from iron(III)citrate than wild-type protoplasts. The mutant leaves accumulate higher amounts of iron in apoplast and symplast than wild-type leaves with an iron supply of 10-mu-M FeEDTA in nutrient solution. NA treatment of the mutant leaves decreases both apoplasmic and symplasmic iron in the direction of wild-type values. It is concluded that NA is not essential for iron transport through the plasmalemma of protoplasts, but that endogenous NA decreases the high amount of iron in protoplasts by affecting the feed-back regulation of iron uptake by leaf cells.