Various 4-substituted amino derivatives of 2-methylpyrido [3, 4-dlpyrimidine were prepared to investigate their structure-cytokinin activity relationships. Both an Amaranthus betacyanin and a lettuce seed germination bioassay revealed that most anilino and some alkylamino derivatives were active, whereas benzylamino derivatives were inactive, indicating that the new cytokinin analogs differ from NG-adenines in their substituent effects on the activity. ...