Meiosis in the Oömycetes: II. A Microspectrophotometric Analysis of Dna in Apodachlya Brachynema

SUMMARY

A cytological and microspectrophotometric study of Apodachlya brachynema (Hildebrand) Pringsheim was made to determine the site of meiosis in a member of the Leptomitales. Cytological observations revealed two successive nuclear divisions in the developing gametangia. Oögonial nuclei begin division prior to the nuclei in the attendant antheridium. The nuclei in any one gametangium enter into prophase of the first division synchronously and this synchrony is maintained into the following metaphase at which time the divisional figures become asynchronous. The synchronous prophase nuclei in the developing gametangia are 1.8-2.0 μ in diameter whereas the gamete nuclei resulting from the two divisions are 0.5-0.7 μ in diameter. Microspectrophotometric analysis reveals that the synchronous prophase and metaphase nuclei in the developing gametangia are 4C and a subsequent reduction division results in the formation of 1C gamete nuclei. Likewise, analysis of the hyphal nuclei clearly indicates a 2C DNA content. The evidence is completely consistent with, and indicative of, gametic meiosis in Apodachlya brachynema.