1968 Volume 14 Issue 2 Pages 171-182
The duration of nuclear cycle and activities of RNA and protein syntheses along the length of growing hyphae of Aspergillus oryzae were estimated by the techniques of autoradiography. The labeling of DNA was effected by incubating the hyphae in the presence of adenine-3H followed by the removal of the labeled RNA with ribonucleases I and T1. For the estimation of the duration of the nuclear cycle, two methods were presented. Estimations of activities of RNA and protein syntheses were carried out by the short term labeling with adenine-3H and L-leucine-3H, respectively. The statistic analysis of the data on the labeling of nuclear regions showed that, in short hyphae of several hundreds microns in length, the generation time of the end nuclei was 1.5-2 times longer than that of the head nuclei. Activities of RNA and protein synthesis, so far observed by autoradiography, were apparently less active in the apical region than in regions behind the apex. It is discussed that the latter observation may not necessarily gives the real picture, since the presence of the nucleotide and amino acid pool highly concentrated in the apical region possibly causes the dilution of radioactive precursors taken up by hyphae.