Glutamine Metabolism in Corn Kernels Cultured In Vitro

The fate of glutamine, the major source of nitrogen supplied to the developing maize endosperm, has been examined in endosperm tissues of corn caryopsis grown under sterile conditions. In the culture system, [U-(14)C]glutamine was included in the medium or was injected directly into the endosperm. Samples were harvested at intervals up to 168 hours. Protein and starch fractions were then separated and analyzed for their (14)C content. At 168 hours, 31% of the total label incorporated in the endosperm was in zein, 15% in glutelin, and 24% in starch. When individual amino acids and sugars in the endosperm powders were analyzed, the (14)C still remaining in the glutamine accounted for only 12 to 14% of the total radioactivity.