COMPARATIVE EFFECTS OF SOME ANTIMETABOLITES ON RIBONUCLEIC ACID SYNTHESIS AND INDUCTION OF NITRATE REDUCTASE IN CAULIFLOWER LEAF TISSUES

The effect of three antibiotics, actidione, patulin and polymyxinB, one synthetic antimetabolite, l-2-dichloro-4(p-nitrobenzenesulphonylamido)-5-nitrobenzene (DCDNS) and ribonuclease on the induction of nitratereductase, gross ribonucleic acid content and the incorporationof phosphorus into the ribonucleic acid of cauliflower leaveshas been studied. The effects of inhibitor concentration and duration of incubationon the inhibition of enzyme production were tested. The induction of the enzyme by molybdenum was inhibited by allcompounds tested. Induction by nitrate was inhibited by actidione,patulin and ribonuclease. Gross ribonucleic acid was decreasedby ribonuclease, patulin and DCDNS in nitrate-starved tissue. Phosphorus incorporation into ribonucleic acid was inhibitedby actidione, patulin, polymyxin B and DCDNS when infiltratedwith nitrate into nitrate starved tissue and by patulin, polymyxinB and DCDNS with molybdenum as the inducer in molybdenum deficienttissue. Ribonuclease in nitrate starved tissue increased theincorporation of phosphorus. Some possible explanations of theseresults are advanced. ¹Present address: Aligarh Muslim University, U. P., India.