Effect of nitrogen nutrition on endosperm protein synthesis in wild and cultivated barley grown in spike culture.

In normal growth conditions, total protein percent (salt soluble plus hordein fractions) in the endosperm at maturity in barley cultivar Hordeum vulgare L. cv ;Ruth' was about 14%, whereas in an accession of wild barley, Hordeum spontaneum Koch line 297, it was about 28%. Spike culture experiments were conducted to ascertain whether there were basic differences between the two genotypes under conditions of widely different nitrogen supply. Spikes of each genotype were grown from 8 to 25 days after flowering in in vitro culture in a growth medium containing 0 to 4 grams per liter nitrogen supplied as NH(4)NO(3). Spikes were pulse-labeled at intervals from 12 to 24 days after flowering with 3.7 megabecquerel of [(3)H]leucine to determine relative rates of synthesis of hordein-1 and hordein-2 polypeptides. At low nitrogen levels ;Ruth' had a lower protein content than 297, but at increasing nitrogen levels its protein content increased rapidly and reached a maximum (35%) higher than 297 (30%). The relative contribution of the hordein fraction to total protein increased mainly with time, and hordein-1 to total hordein increased mainly with nitrogen level, in both genotypes. There appeared to be no fundamental limitations in the capacity of ;Ruth' to accumulate protein; 297 appears to have a greater basal level of nitrogen availability under normal conditions.