Differential Effects of the Parental Photothermal Environment on Development of Dormancy in Caryopses of Aegilops Kotschyi

Aegilops Kotschyi Boiss. plants produce three florets per spikelet(of which the terminal floret is commonly sterile) and exhibitphysiological heterocarpy in the two caryopses which developin each spikelet. Germinability of the basal caryopsis, butnot of the upper one, was subject to environmental influencesto which the parent plant was exposed during its development.Basal caryopses produced by plants grown at low temperature,or in 16-h photoperiods, were more dormant than when producedby plants grown at higher temperature, or in 8-h photo-periods.Germinability of the upper caryopses was equally high in allcases and independent of the parental environment. The photoperiodeffects on germinability were exerted after anthesis. Matureweight of both basal and upper caryopses was higher when producedon plants grown at low temperature, or transferred from 16-hto 8-h photopenods at emergence of the flag leaf     

Differential requirement for NO during ABA-induced stomatal closure in turgid and wilted leaves

Abscisic acid (ABA)-induced stomatal closure is mediated by a complex, guard cell signalling network involving nitric oxide (NO) as a key intermediate. However, there is a lack of information concerning the role of NO in the ABA-enhanced stomatal closure seen in dehydrated plants. The data herein demonstrate that, while nitrate reductase (NR)1-mediated NO generation is required for the ABA-induced closure of stomata in turgid leaves, it is not required for ABA-enhanced stomatal closure under conditions leading to rapid dehydration. The results also show that NO signalling in the guard cells of turgid leaves requires the ABA-signalling pathway to be both capable of function and active. The alignment of this NO signalling with guard cell Ca²⁺-dependent/independent ABA signalling is discussed. The data also highlight a physiological role for NO signalling in turgid leaves and show that stomatal closure during the light-to-dark transition requires NR1-mediated NO generation and signalling.     

Evolution of alternative sex-determining mechanisms in teleost fishes

We compiled information from the literature on the taxonomic distributions in extant teleost fishes of alternative sex-determination systems: male-heterogametic (XY) gonochorism, female-heterogametic (ZW) gonochorism, hermaphroditism, unisexuality, and environmental dependency. Then, using recently published molecular phylogenies based on whole-genomic or partial mitochondrial DNA sequences, we inferred the histories and evolutionary transitions between these reproductive modes by employing maximum parsimony and maximum likelihood methods of phylogenetic character mapping. Across a broad teleost phylogeny involving 25 taxonomic orders, a highly patchy distribution of different sex-determination mechanisms was uncovered, implying numerous transitions between alternative modes, but this heterogeneity also precluded definitive statements about ancestral states for most clades. Closer inspection of family-level and genus-level phylogenies within each of four orders further bolstered the conclusion that shifts in sex-determining modes are evolutionarily frequent and involve a variety of distinct ancestral-descendant pathways. For possible reasons discussed herein, the evolutionary lability of sex-determining modes in fishes contrasts strikingly with the evolutionary conservatism of sex determination within both mammals and birds. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 83–93.     

Hitchhikers at the dinner table: a revisionary study of a group of ant parasitoids (Hymenoptera: Eucharitidae) specializing in the use of extrafloral nectaries for host access

Extrafloral nectaries (EFNs) are nectar‐secreting glands found on plants independent of their flowers. EFNs are diverse in form, present on a wide variety of plants, and their secretions are known to recruit ants. However, much less information has been published on insects with known EFN associations other than ants. Two distinct species groups of Orasema Cameron (Hymenoptera: Eucharitidae) deposit their eggs close to the EFNs of their plant hosts. The simulatrix group comprises six species found in deserts and xeric shrublands of the southwestern United States and Mexico. This species group is revised, retaining O. aureoviridis, O. beameri and O. simulatrix as valid species, and describing O. cancellata sp.n. , O. difrancoae sp.n. and O. zahni sp.n. The wayqecha group is from Peru and Colombia and includes the newly described O. wayqecha sp.n. and O. quadrimaculata sp.n. Members of the simulatrix group oviposit near EFNs of Chilopsis linearis Cav. (Bignoniaceae), Prosopis glandulosa Torr. (Fabaceae), Prosopis velutina Wooton (Fabaceae) and Populus angustifolia James (Salicaceae), whereas Orasema wayqecha oviposit on leaves of two species in the family Primulaceae. Monophyly of the two species groups is proposed based on a molecular analysis of ribosomal (28S and 18S) and mitochondrial (cytochrome c oxidase subunit I) DNA, morphological features of the adults and planidia larvae, and their shared behavioural association with EFNs. Adults of both species groups have an expanded postgena that encloses the mouthparts, but are otherwise morphologically divergent. The planidia of both groups also share several features, including long cerci that may facilitate their movements within EFNs. Oviposition near EFNs is proposed as a means of increasing encounter rates of the first‐instar larvae with their myrmicine ant host; however, it remains unclear whether the planidia are transported directly by the foraging workers of their host Pheidole (Formicidae: Myrmicinae) or indirectly with the help of an intermediate host. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:EA112E3D-52BE-45D1-B03B-8764E8C94BE0 .     

Cloning and Molecular Analysis of the Plasma Membrane Ca2+ -ATPase Gene in Paramecium tetraurelia

ABSTRACT. We have determined the DNA sequence of the gene encoding the protein of the plasma membrane Ca²⁺-ATPase in Paramecium tetraurelia . The predicted amino acid sequence of the plasma membrane Ca²⁺-ATPase shows homology to conserved regions of known plasma membrane Ca²⁺-ATPases and contains the known binding sites for ATP (FITC), acylphosphate formation, and calmodulin, as well as the "hinge" region: all characteristics common to plasma membrane Ca²⁺-ATPases. The deduced molecular weight for this sequence is 131 kDa. The elucidation of this gene will assist in the studies of the mechanisms by which this excitable cell removes calcium entering through voltage gated calcium channels and the pump functions in chemosensory signal transduction.     

Identification of 'Haemophilus somnus' by rapid tests for pre-formed enzymes

In rapid tests for pre-formed enzymes, all strains of ' Haemophilus somnus ' examined gave positive reactions for alkaline phosphatase, cytochrome oxidase, β-glucosidase, β-glucuronidase and hippurate hydrolase but were negative for α-mannosidase, β-galactosidase and β-xylosidase, tributyrin esterase, cystine aminopeptidase and γ-glutamyl aminopeptidase. The pattern of results differed from those given by Actinobacillus, Haemophilus, 'Histophilus', Pasteurella and Taylorella species.