AUXIN-INDUCED GROWTH OP TUBER TISSUE OP JERUSALEM ARTICHOKE: III. EFFECT OF ACTINOMYCIN D ON AUXIN-INDUCED EXPANSION GROWTH AND RNA SYNTHESIS

1. The following results were obtained using tissue slices excisedfrom cold-stored Jerusalem artichoke tubers.
2. Actinomycin Dat the concentration of 20 µg/ml given duringthe agingperiod did not affect the subsequent expansion growthcausedby auxin or auxin plus kinetin.
3. Actinomycin D given in thegrowth period, on the other hand,strongly inhibited the expansiongrowth of tissue slices agedin the absence of the antibiotic.
4. In the growth period, auxin or auxin plus kinetin promotedtheincorporation of uracil-2-¹⁴C into RNA fraction.
5. ActinomycinD inhibited the incorporation of ³²P orthophosphateinto ribosomalRNA during the aging period.
6. In the growth period, the incorporationof ³²P into RNA wasenhanced by auxin and was inhibited by actinomycinD, more remarkablyin ribosomal RNA than in lighter RNA.

¹A part of this paper was presented at the Conference on PlantGrowth Regulators held by the New York Academy of Sciences onMay 16, 1966.