Response of the Yellow-Stripe Maize Mutant (ys1) to Ferrous and Ferric Iron

1. This investigation was designed to determine whether the appearance and growth of the ys1mutant in maize were related to its iron or magnesium metabolism. 2. No differences were observed in iron or magnesium concentrations of yellow interveinal areas in the leaves as contrasted with green tissue confluent with the main vascular bundles. 3. Plants of genotypes ys1and ± ys1responded alike when grown in nutrient solutions with a ferrous source of iron. Such plants produced completely green leaves at ferrous iron levels of 2.0 p.p.m. or higher. The yellow-stripe condition occurred in plants grown in nutrient solutions containing ferrous iron at levels of 0.25-1.0 p.p.m. 4. Plants of genotypes ys1and ± ys1responded differently to ferric iron in nutrient culture. The ± ys1responses to a given level of ferrous or ferric iron supplied to the roots were identical, whereas ys1plants appeared to be unable to utilize ferric iron efficiently under these conditions. 5. Non-green leaf segments from minus-iron ys1and ± ys1plants, however, responded by greening and similarly to ferrous and ferric iron when floated on plus-iron nutrient solutions containing sucrose. 6. The metabolic lesion in the ys1mutant appears to involve iron metabolism at a site other than the leaves.