Dynamics of Architectural Development of Isolated Plants of Maize (Zea mays L.), in a Non-limiting Environment: The Branching Potential of Modern Maize

The maximal architectural development of a modern maize cultivar(Zea mays L. ‘Dea’) was studied in fully isolatedand carefully irrigated plants. Under these favourable conditions,this (usually) non-tillering and non-prolific cultivar displayeda large amount of branching (down to the third order), includinglarge basal tillers and prolific ear shoots. This developmentwas analysed by combining: (1) architectural analysis, initiallydeveloped for trees; and (2) quantitative analysis of tilleringkinetics, designed for other grass species. The architecturalunit of maize included a main long axis (A1) and lateral shortshoots bearing a terminal spike (A2). The basal tillers (notedA1') resulted from a complete and sylleptic reiteration. Itskinetics were consistent with tillering models, but with a particularlylong delay in branch emergence (seven phyllochrons), comparedto other grass species. This delay is likely to enhance regulationby leaf (or root) density in stands and explains the inhibitionof branch development, as usually observed in field conditions,even at low density. Similarly, the suppression of the basalreiteration in secondary branches observed in isolated plantsprobably results from increased intra-tussock density. In isolatedplants, androgenous axes combining A1' and A2 morphologies werealso produced in intermediate positions. It is shown that theycan result from a basipetal sequence of A2 differentiation reachingbuds in the course of their A1' development. The consequencesof these unexpected results are discussed in terms of maizedevelopment and architectural analysis of grasses. Copyright1999 Annals of Botany Company Plant architecture, development, maize (Zea mays L.), tillering, branching, shoot, prolificacy, phyllochron.     

A revision of the genus Halectinosoma (Harpacticoida: Ectinosomatidae): a reappraisal of H. sarsi (Boeck) and related species

Ectinosomatid material was examined from extensive collections around the British Isles and from several additional world localities and museum collections, permitting a revision of the genus Halectinosoma. This paper describes 12 morphologically similar species and erects five new species. H. sarsi (Boeck) is regarded as species incertae sedis, while H. sarsi sensu Sars (1904) is redescribed as H. pseudosarsi sp. nov.; H. sarsi sensu T. & A. Scott (1894) is synonymized with H. canaliculatum (Por). H. propinquum is regarded as a junior subjective synonym of H. chrystalli (T. Scott). H. clavatum (Sars) is resurrected, having previously been regarded as a synonym of H. brunneum (Brady). A key for the identification of females belonging to this group of species is provided.     

Molecular phylogeny and morphological analysis resolve a long‐standing controversy over generic concepts in Ecdyonurinae mayflies (Ephemeroptera: Heptageniidae)

Heptageniidae is a species‐rich mayfly family (Ephemeroptera), whose taxonomy and phylogeny have been based almost exclusively on traditional morphological studies. Inconsistent use of diagnostic characters and the general lack of molecular studies have led to vague generic concepts, and the phylogenetic relationships among taxa in the family remain unclear. Afronurus Lestage is an Old World heptageniid genus of 66 species. The generic assignment of two species within this genus, A. kugleri Demoulin and A. zebratus (Hagen), has been the subject of much debate, because they share many apomorphic features that distinguish them from other congeners. We combined a thorough morphological study of all life stages of 28 representative heptageniid species with a molecular phylogenetic analysis of four mitochondrial and nuclear markers to resolve the generic position of A. kugleri and A. zebratus as well as the integrity of Afronurus and related genera. Our results confirm the monophyly of Afronurus and Electrogena and support the assignment of A. kugleri and A. zebratus to a newly described genus, Anapos Yanai & Sartori gen.n . We provide clear, diagnostic morphological characters for the genus and discuss the need for a thorough revision of generic concepts in the subfamily Ecdyonurinae. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:075E40C6-BAFE-4184-A2C2-E3BCFBC0BC15 .