the herbicide , paraquat ( 1,1'-dimethyl-4,4'-bipyridylium ion ) , was found to be toxic and lytic to nostoc muscorum in n2 ( at the expense of elemental nitrogen , i.e . unsupplemented with any combined nitrogen source ) and no-3 media , without any apparent inhibitory or stimulatory effect on its nitrogen-fixing apparatus , i.e . heterocyst formation .
C0013879
elemental
C0028158
nitrogen