Haploid meiosis as a regular phenomenon in the life cycle of Ulva mutabilis

Abstract

Cytological and chemical studies of the parthenosporophytes (PS) of Ulva mutabilis Føyn, mutant Slender, indicate that while the PS‐plants of mating‐type plus mostly diploidize during development and form zoospores through a normal meiosis, the PS‐plants of mating‐type minus mostly remain haploid. The data presented suggest that these haploid cells, nevertheless, produce zoospores by a type of division that biochemically must be characterized as meiotic. The chromosomes (n = 8) apparently segregate randomly to the daughter cells. As expected, the resulting zoospores show low viability (0.0022 viable spore per sporangium, compared with 1.1 for the normal diploid). The possible role of the haploid meiosis and its apparent uniqueness as a regular event in the life cycle of Ulva is discussed. © 1974 Mendelian Society of Lund