Mixed first and second division restitution in male meiosis of hierochloë odorata (l.) beauv (holy grass)

Abstract

Hierochloë odorata is a rhizomatous perennial grass of northern latitudes with a highly restricted distribution in Britain and Ireland. Six clones sampled from Scotland are tetraploid (2n = 4x = 28) and most show irregular male meiosis, characterized by the exclusion of laggards as micronuclei, and are probably pseudogamous. In both these respects they resemble H. odorata from Swedish Lapland which is octaploid (2n = 8x = 56). Material from one Scottish locality shows meiotic restitution in the majority of its pollen mother cells (77 per cent). One in two first divisions leads to restitution (52 per cent) and one in seven of these (14 per cent) remains undivided even at telophase-II. Of those dyads formed from normal first division, almost half (46 per cent) show failure of one of the second divisions but only one in 20 shows double second division failure. This remarkable mixture of first and second division restitution is reflected in an extensive range of ploidy (n = 2x, Ax, 8x) and pollen grain size (35-113 μm3). Seed-set in this material is low (2 per cent). Genetic variation in British material is revealed by isozyme electrophoresis while studies of total seed proteins in Swedish material indicate genetic uniformity. Implications for parthenogenesis are discussed. © The Genetical Society of Great Britain.