I. Chemotherapy of high temperature inhibition of plant growth. II. Studies on the relationship between tobacco mosaic virus infection and the DNA metabolism of tobacco leaves. III. The conservation of microsomal RNA in Escherichia coli

摘要

Part I. Chemotherapy of High Temperature Inhibition of Plant Growth:The effects of biochemical supplements on the growth of five subterranean clover varieties grown under supra-optimal temperature conditions were studied. Some evidence of a chemotherapeutic effect of the high temperature growth inhibition was obtained.Part II. Studies on the Relationship between Tobacco Mosaic Virus Infection and the DNA Metabolism of Tobacco Leaves:A comparison of the DNA metabolisms of uninfected and TMV infected excised tobacco leaves, using p(32)-orthophosphate incorporation into the DNA as a measure of its metabolism, indicated that the DNA metabolism is not affected by TMV infection. This result was corroborated by the results of studies on the effect of 5-fluorouracil, a specific inhibitor of DNA synthesis, on the multiplication of TMV in tobacco-leaf discs. Although partial inhibition of TMV multiplication was observed, the absence of inhibition reversal thymidine, indicated that the mechanism of TMV inhibition probably did not involve a specific block of DNA synthesis. Finally unsuccessful attempts were made to see if intact host DNA was necessary for TMV infection by treating tobacco-leaf discs with DNAase.Part III. The Conservation of Microsomal RNA in Escherichia coli:A uniformly C13 N15 labeled exponentially growing culture of E. coli was transformed to light isotope substrates, and the metabolic fate of the pre-transfer synthesized heavy isotope microsomal RNA molecules followed by means of equilibrium sedimentation analysis of the RNA molecules in a density gradient. The results demonstrated complete conservation of the heavy isotopes by the pre-transfer RNA molecules remaining intact after transfer.