Effect of Hydroxyurea on Mitotic and Meiotic Divisions in Explanted Lily Microsporocytes

The cytological effects of hydroxyurea (HU), an inhibitor of DNA synthesis, were examined on mitotic and meiotic divisions in lily micro-sporocytes. Microsporocytes in premeiotic stages and meiotic prophase were cultured in vitro for discrete periods in the presence of the inhibitor at various concentrations. Hydroxyurea interfered with mitotic development if admini-stered to cells during the late S or early G2 phase of premeiosis, when cells undergo mitotic division by explantation. When applied during leptonema, the main effects were the suppression of meiotic development and the produc-tion of sticky chromosomes. The affected cells progressed through early pro-phase without showing any gross cytological abnormalities ; the inhibition of DNA synthesis by hydroxyurea during zygonema did not interfere with synapsis. On further culture, cells did not progress beyond prophase; but remained suspended in some stage of lateprophase. Chromosome stickiness was the response of cells cultured with hydroxyurea during pachynema for a prolonged period. The relevance of these observations to microsporocyte development is discussed.