A Preliminary Note on the Histochemical Localization of Dna and Rna in Rust-Infected Wheat Leaves

I<urnick (1955) has demonstrated that the methyl green-pyronin Y stain mixture can be used to identifv DNA and RNA in tissue sections. This method has since been used, wliill a slight modification, by Craigie (1959) in his studies on diploidization in sunflower rust. In the work reported here the method Mias used to localize DNA and RNA in rusted and healthy wheat leaves. The localization of DNA by this method was re-tested, using the feulgen stain, and that of the RNA was confirmed, using ribonuclease. For the ribonuclease treatment a slide bearing several serial sections was brought to water and, after a thorough washing, a wall of high melting-point (60 C.) wax was laid around the edge of the slide and across the centre to divide it into two compartn~ents, each containing a few sections. The sections in one compartment received 0.5 ml. of 0.1% ribonuclease, those in the other 0.j rnl. of water, before incubation at 37 C. for 30 minutes. Aftcr incubation the slide was washed, the wax removed, and the sections stained with methyl green-pyronin Y in the usual way. Structures whose staining capacities were removed by pre-treatment with ribonuclease were presumed to contain RNA. Fully susceptible reactions, induced by both leaf and stem rusts on the variety Little Club, were studied. Typical staining reactions for the various treatments are given in the accompanying table; no differences between infections induced by leaf and stem rusts were recorded.