A comparison of spike and spikelet survival in mainstem and tillers of barley

Initiation and abortion of spikelet primordia on primary tillers and mainstem were compared for plants of spring barley, Maris Mink, sown on two sowing dates during 1983, in plots at the Scottish Crop Research Institute (SCRI) and at Long Ashton Research Station (LARS). Sowing date had no effect on the number of spikelets initiated on either mainstem or surviving tillers and many more spikelets were initiated on equivalent stems at LARS than at SCRI but more spikelets aborted at the former site. The final number of spikelets produced was eventually similar. Spikelet abortion was complete by anthesis and coincided with the period of rapid stem and rachis elongation and with the time over which tiller death occurred. Despite the fact that plants at SCRI produced fewer fertile tillers they outyielded those at LARS because much heavier grains were produced on the mainstem and tiller 1 of plants at the Scottish site. An interval of 2 wk between sowing had only small effects on the components of yield.     

Polarity of Acetabularia mediterranea: Stability in the Anucleate State

Concomitant with the outgrowth of the cap in cells of Acetabulariamediterranea Lamouroux, the stalk acquires a pale green appearance(‘Aufhellung’) and the chlorophyll and protein contentdecreases due to the translocation of part of the cytoplasmfrom the stalk into the cap. This process also occurs in anucleatecells or apical fragments during cap formation and in inversegrafts constructed either from two anucleate cells or apicalfragments or from two basal fragments containing the rhizoids.The cytoplasm's translocation does not depend on the presenceof the nucleus. It is suggested that the unidirectional flowof the cytoplasm during cap formation is generated by the electricalcharge across the cell and that this electrical charge is maintainedafter removal of the nucleus. Acetabularia, polarity, anucleate cells, grafts     

Gene transfer between canola (Brassica napus L. and B. campestris L.) and related weed species

Brassica species are particularly receptive to gene transformation techniques. There now exists canola genotypes with transgenic herbicide resistance for glyphosate, imidazolinone, sulfonylurea and glufosinate herbicides. The main concern of introducing such herbicide resistance into commercial agriculture is the introgression of the engineered gene to related weed species. The potential of gene transfer between canola (Brassica napus and B. campestris) and related weed species was determined by hand pollination under controlled greenhouse conditions. Canola was used as both male and female parent in crosses to the related weed species collected in the Inland Northwest region of the United States. Weed species used included: field mustard (B. rapa), wild mustard (S. arvensis) and black mustard (B. nigra). Biological and cytological aspects necessary for successful hybrid seed production were investigated including: pollen germination on the stigma; pollen tube growth down the style; attraction of pollen tubes to the ovule; ovule fertilisation; embryo and endosperm developmental stages. Pollen germination was observed in all 25 hybrid combinations. Pollen tubes were found in the ovary of over 80% of combinations. About 30% of the hybrid combinations developed to the heart stage of embryo development or further. In an additional study involving transgenic glufosinate herbicide resistant B. napus and field mustard it was found that hybrids occurred with relatively high frequency, hybrids exhibited glufosinate herbicide resistance and a small proportion of hybrids produced self fertile seeds. These fertile plants were found to backcross to either canola or weed parent.     

Differential susceptibility of tree species to oviposition by periodical cicadas

Abstract 1. Periodical cicadas occur widely in deciduous forests of eastern North America and represent the largest insect emergences in the world. Their effects on forest community dynamics, via oviposition damage and root feeding, are potentially great but not well understood. If tree species vary in their susceptibility to cicada oviposition and root colonization, then periodical cicadas may affect ecological interactions among tree species and forest composition. 2. We measured oviposition damage on 63 tree species at 52 sites in southern Indiana, U.S.A. for two broods of periodical cicadas. We compared oviposition damage among different sites, habitats, and tree species. We also measured cicada emergence rates in mature and successional forest habitats and from beneath different tree species. 3. Certain tree species received significantly more oviposition damage than others, and the most and least damaged species were consistent between the two broods. For some species, oviposition damage varied between mature and successional sites. Despite the differences in oviposition rates among species, there was no difference in emergence rates from beneath different tree species, suggesting that initial differences in cicada density among tree species are not maintained through the nymphal life cycle. 4. Cicadas oviposited more at successional sites, but emerged more in mature forest stands, suggesting that successive generations of cicadas represent a shifting mosaic between forests of different ages. As tree species consistently vary in their susceptibility to oviposition damage, periodical cicadas could alter local competitive interactions and therefore affect forest dynamics.     

Ultraviolet radiation and consumer effects on a field-grown intertidal macroalgal assemblage in Antarctica

Ultraviolet radiation (UVR) research on marine macroalgae has hithero focussed on physiological effects at the organism level, while little is known on the impact of UV radiation on macroalgal assemblages and even less on interactive effects with other community drivers, e.g. consumers. Field experiments on macrobenthos are scarce, particularly in the Antarctic region. Therefore, the effects of UVR and consumers (mainly limpets were excluded) on early successional stages of a hard bottom macroalgal community on King George Island, Antarctica, were studied. In a two‐factorial design experimental units [(1) ambient radiation, 280–700 nm; (2) ambient minus UVB, 320–700 nm and (3) ambient minus UVR, 400–700 nm vs. consumer–no consumer] were installed between November 2004 and March 2005 (n= 4 plus controls). Dry mass, species richness, diversity and composition of macroalgal assemblages developing on ceramic tiles were followed. Consumers significantly suppressed green algal recruits and total algal biomass but increased macroalgal richness and diversity. Both UVA and UVB radiation negatively affected macroalgal succession. UVR decreased the density of Monostroma hariotii germlings in the first 10 weeks of the experiment, whereas the density of red algal recruits was significantly depressed by UVR at the end of the study. After 106 days macroalgal diversity was significantly higher in UV depleted than in UV‐exposed assemblages. Furthermore, species richness was significantly lower in the UV treatments and species composition differed significantly between the UV‐depleted and the UV‐exposed treatment. Marine macroalgae are very important primary producers in coastal ecosystems, serving as food for herbivores and as habitat for many organisms. Both, UVR and consumers significantly shape macroalgal succession in the Antarctic intertidal. Consumers, particularly limpets can mediate negative effects of ambient UVR on richness and diversity till a certain level. UVB radiation in general and an increase of this short wavelength due to stratospheric ozone depletion in particular may have the potential to affect the zonation, composition and diversity of Antarctic intertidal seaweeds altering trophic interactions in this system.     

Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi (Woodward, 1910) from the Middle Jurassic of England

The cranial osteology of the small theropod dinosaur Proceratosaurus from the Bathonian of Minchinhampton, England, is described in detail, based on new preparation and computed tomography (CT) scan images of the type, and only known, specimen. Proceratosaurus is an unusual theropod with markedly enlarged external nares and a cranial crest starting at the premaxillary–nasal junction. The skull is highly pneumatic, with pneumatized nasals, jugals, and maxillae, as well as a highly pneumatic braincase, featuring basisphenoid, anterior tympanic, basipterygoid, and carotid recesses. The dentition is unusual, with small premaxillary teeth and much larger lateral teeth, with a pronounced size difference of the serrations between the mesial and distal carina. The first dentary tooth is somewhat procumbent and flexed anteriorly. Phylogenetic analysis places Proceratosaurus in the Tyrannosauroidea, in a monophyletic clade Proceratosauridae, together with the Oxfordian Chinese taxon Guanlong. The Bathonian age of Proceratosaurus extends the origin of all clades of basal coelurosaurs back into the Middle Jurassic, and provides evidence for an early, Laurasia‐wide, dispersal of the Tyrannosauroidea during the late Middle to Late Jurassic. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009.     

Molecular and morphological characterization of Crataegus L. species (Rosaceae) in southern Syria

The systematics of the genus Crataegus (Rosaceae) have been considered problematic owing to the fact that hybridization, introgression, polyploidy and apomixis may occur in this genus. A study of the Crataegus species from the Arab mountains, Sweida Province, Syria, has been undertaken based on both plastid DNA sequences ( trn L- trn F, psb A- trn H) and morphological data. In the investigated region, three morphologically distinguishable Crataegus species: C. azarolus var. aronia L., C.  ×  sinaica Boiss. ssp. sinaica and C. monogyna var. monogyna Jacq. were investigated. Crataegus azarolus can be clearly distinguished morphologically from C. monogyna by the colour, size and structure of fruits, the number of pyrenes, the flowering and ripening time, the density of thorns, the tree shape and also the leaf shape. According to our morphological data, in Syria, C.  ×  sinaica is variable and could represent a hybrid of C. azarolus  ×  C. monogyna ; the cpDNA sequence analysis showed sequences corresponding to C. monogyna as the plausible mother of the hybrid.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 255–263.