Meiosis in Hypericum punctatum
1931; University of Chicago Press; Volume: 92; Issue: 4 Linguagem: Inglês
10.1086/334214
ISSN1940-1205
Autores Tópico(s)Plant Pathogens and Fungal Diseases
Resumo1. Microsporogenesis of Hypericum punctatum is interesting for the following reasons: (a) The chromosomes fail to pair at "diakinesis," and instead become fastened end-to-end in a chain: (b) at the first metaphase the chromosomes tend to separate so that the alternating members pass to opposite poles; (c) often irregularities occur so that the chromosome complements, at the time of the second metaphase, instead of having the usual haploid number of eight have seven and nine; (d) during the first division, chromosomes may lag and be lost from the spindle; (e) extra nuclei may be formed; (f) at interkinesis the chromosomes split longitudinally in the usual manner, and separate at the second anaphase; (g) during second division the extra chromosomes may form their own spindle and divide; (h) sometimes small abortive pollen grains are present; (i) at maturity nearly one-half of the pollen grains are morphologically sterile. 2. Megasporogenesis shows the same tendency to chain formation and to alternation of chromosomes at the first metaphase as found in microsporogenesis. 3. Meiosis in general is very similar to that found by Cleland and others in certain Oenothera species. 4. The question of parasynapsis versus telosynapsis is discussed. 5. The general cytological situation closely resembles that found in many natural hybrids, but external characteristics are different from those of any other species of the New England region.
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