Meiotic Abnormalities Induced by Gamma Rays in <i>Vinca rosea</i> Linn

Abstract

Various meiotic abnormalities were studied in PMC's of plants raised from seeds irradiated with various doses of gamma rays. The timing of onset of meiosis is highly disturbed in these plants. In Prophase chromosomes exhibit stickness and clumping and towards the end of prophase irrespective of the dosage, the cells contain fragments of chromosomes, univalents and disturbed bivalent association resulting in different configurations of chromosomes. The number of fragments and chromosome chain appearing as multivalents become more apparent towards the end of diakinesis. Chromosomes of different configurations including fragments are delayed ins Metaphase orientation and they are seen laying scattered or in groups in cytoplasm. The disturbed formation of spindle and the orientation of chromosomes in groups in metaphase are remarkably high in PMC's. In anaphase formation of micronuclei of different numbers and sizes, lagging chromeomes, fragrpents of chromosomes and chromatids, bridges with or without fragments are also very common. These abnormalities are carried forward and are also very commonly observed during second meiotic division. The frequency of occurrence of fragments is proportional to the dosage of gamma rays and also the presence of multivalents increases with the dose. These abnormalities seem to induce pollen sterility which is proportional to dose of gamma rays. This pollen sterility seems to be the cumulative result of various aberrant meiotic stages as well as physiological and genetic damages induced probably by the breakage of chromosomes through the formation of antimetabolic agents in these cells.