Utilization of Nitrogen Sources by Immature Soybean Cotyledons in Culture

Immature Glycine max (L.) Merrill cotyledons were cultured ina defined medium containing different nitrogen sources. Glutaminewas the most efficient source in terms of protein accumulationin the cotyledons. Asparagine was less efficient (about 70 percent that of glutamine) while allantoin was a poor source ofnitrogen. This was also true for older cotyledons where asparaginaseand allantoinase activities were maximal. The utilization ofboth asparagine and allantoin (but not glutamine) was totallyinhibited by methionine sulfoximine suggesting that their metabolisminvolves ammonia assimilation via glutamine synthetase. Apparently,neither exogenous or endogenously-generated ammonia had mucheffect on glutamine utilization, but ammonia did have a smallinhibitory effect on asparagine, which may in part account forthe lower efficiency observed with this amide. Glycine max, soybean, cotyledon culture, nitrogen metabolism