Concentration and Translocation of Nitrogen Compounds in the Corn Plant (Zea Mays) During Grain Development

Abstract

The N compounds of 2 corn hybrids, U.S. 13 and Funk''s G-80 were studied. The corn plant was divided into stalk, above and below the point of attachment of the shank, upper and lower leaves, grain, shank, and husks. The total, water-insoluble, water soluble, protein, non-protein, nitrate, ammonia, glutamine amide, asparagine amide, free [alpha] -amino, and residual N were measured in the various plant parts. It was found that: (1) The percentage of total N decreased in all vegetative parts from pollination to maturity. (2) Approx. 67% of N found in the plant at maturity was in the grain. (3) Just after pollination there was enough N in the corn plant to completely supply the maturing grain if it could have been translocated. (4) The above ground parts supplied approx. 60% of the grain N while approx. 40% was contributed by the roots and/or soil after pollination. (5) Of the total N contributed by the plant parts to the grain, 60% came from the leaves, 26% from the stalk, 12% from the husk, and 2% from the shank. (6) Plant proteins and N compounds more complex than amino acids contributed the major portion of N to the corn grain. Smaller, but nevertheless important, donations of N to the developing grain were made by the simpler compounds, including nitrate, ammonia, amide, and a amino N. (7) The evidence favors the view that nitrates were converted to protein or protein-like substance in the plant and then translocated to the grain.