Effect of the Nitrogen Supply on the Activities of Isoenzymes of NADH-dependent Glutamate Synthase and Glutamine Synthetase in Root Nodules of Phaseolus vulgaris L.

This paper has investigated the regulation of the activitiesof glutamine synthetase (GS) and NADH-dependent glutamate synthase(NADH-GOGAT) of Phaseolus vulgaris in relation to the nitrogensupply. The activity of NADH-GOGAT II, which is the most abundantisoenzyme of glutamate synthase in root nodules of P. vulgaris,was either absent or barely detectable in other organs of thisspecies. Moreover, its activity in roots could not be inducedby ammonium. In nodules NADH-GOGAT II activity was detectedin nodules grown under an atmosphere of 80% argon: 20% oxygenand in nodules formed with a Fix- Rhizobium mutant. However,in these non-fixing nodules the activity of this isoenzyme attainedless than 15% of the activity in fixing nodules and switchingargon/oxygen grown nodules to nitrogen/oxygen led to an increasein this isoenzyme within 24 h. This effect could not be mimickedby the addition of exogenous ammonium. Ammonium addition, however,promoted nodule senescence and also led to a decrease in theactivities of nitrogenase and plant GS. In particular, the nodule-enhancedGS isoenzyme but not the GSß isoenzyme was affectedby these changes and in a manner similar to the changes in NADH-GOGATII. The activity of the NADH-GOGAT I isoenzyme was detectablein other organs of P. vulgaris and in nodules its activity alsoshowed some changes in response to the rate of dinitrogen fixation. Key words: Glutamate synthase, glutamine synthetase, nitrogen fixation, nodule metabolism, Phaseolus vulgaris     

Consequences of infanticide for a gregarious ectoparasitoid of leafroller larvae

1. In this laboratory study, the clutch size and handling time of Goniozus jacintae were investigated, a comparison of its life‐history performance between primary and secondary (laid after infanticide events) broods was carried out, and the lipid and protein concentrations in the haemolymph of non‐parasitised and parasitised hosts were estimated. 2. It was found that G. jacintae temporarily paralysed its host larvae for 66 min and briefly guarded its brood for 66 min. The clutch size of G. jacintae increased from two to seven with increasing larval fresh weight of its host, and both ovicide and larvicide of primary clutches occurred in 81% of encounters. 3. Secondary clutches of G. jacintae were significantly larger than primary clutches in two of three ovicide treatments for the same host individuals. Secondary clutches also experienced greater brood survivorship than primary clutches. 4. Lipid concentrations were consistently higher in the haemolymph of parasitised hosts, and protein concentrations were initially higher (until egg hatch), but increased at a lower rate in parasitised hosts than in non‐parasitised hosts. 5. This study is the first to provide evidence that improved nutritional quality could be an important benefit of infanticide for an insect parasitoid, allowing for larger clutch size and improved brood survivorship among secondary broods.     

Pollen Development in Actinidia deliciosa var. deliciosa: Histochemistry of the Microspore Mother Cell Walls

The development of the microspore mother cell walls in Actinidiadeliciosa (kiwifruit) has been studied using light and electronmicroscopy. The microspore mother cell wall is similar, histochemically,and structurally in anthers from both functionally staminateand functionally pistillate flowers. Deposition, which beginsduring early prophase I, produces an electron-dense multilaminatedwall layer (layer a) and by the end of meiosis I a thick electron-lucentlayer (layer b) to the inside of this multilayered wall. Thereasons for histochemical differences and similarities betweenthese layers are discussed. The original primary wall persistsuntil the late uninucleate microspore stage. Layer (b), whichis probably mainly callose, dissolves at the late tetrad/earlymicrospore stage while layer (a), which probably also containsother polysaccharides, persists and dissolves concurrently withthe primary wall. Actinidia deliciosa, kiwifruit, microspore mother cell wall, callose, histochemistry, light microscopy, electron microscopy, male sterility     

Ultrastructural Changes of the Two Types of Differentiated Cells during the Migration and Early Culmination Stages of Dictyostelium discoideum

Changes of fine structure during prolonged migration of Dictyostelium discoideum slugs were studied by electronmicroscopy. Prespore specific vacuoles of cells located near the substratum gradually degenerated and the prespore antigen contained in them was lost. During the process, mitochondria in the prespore cells were transformed dramatically: as the mitochondrion elongates, its central part becomes thinner and the cristae become localized at its two ends. Then it bends and its two ends fuse to segregate part of the cytoplasm. The cristae then accumulate in the original ends. Similar mitochondrial transformation was observed in prespore cells of cell masses induced to culminate after a long period of migration.     

Changes in Elk Resource Selection and Distributions Associated With a Late-Season Elk Hunt

ABSTRACT Changes in resource selection associated with human predation risk may alter elk distributions and availability for harvest. We used Global Positioning System data collected from telemetered female elk (Cervus elaphus) to evaluate effects of refuges (areas where hunting was prohibited), spatial variation in hunting risk, and landscape attributes on resource selection within an established Greater Yellowstone Area, USA, winter range. We also evaluated elk distributions during and outside of a late-season hunting period. Refuge areas and landscape attributes such as habitat type and snow water equivalents (SWE) affected resource selection. Elk selection for flat grasslands increased as SWE increased, likely because these areas were windswept, leaving grasses exposed for foraging. Elk distributions differed during hunting and no-hunting periods. During the hunting period, elk shifted to privately owned refuge areas and the estimated odds of elk occupying refuge areas more than doubled. Risk-driven changes in resource selection resulted in reduced availability of elk for harvest. Elk selection for areas where hunting is prohibited presents a challenge for resource managers that use hunting as a tool for managing populations and influences grazing patterns on private ranchlands.     

Placing Animals in the Neolithic: Social Zooarchaeology of Prehistoric Farming Communities

Placing Animals in the Neolithic: Social Zooarchaeology of Prehistoric Farming Communities. Arkadiusz Marciniak. Portland: Cavendish Publishing, 2005. 279 pp.     

Role of hydrology in development of a vernal clear water phase in an urban impoundment

1. Grazer control of phytoplankton and water transparency was responsive to interannual variations in river discharge and corresponding water retention time in Ford Lake, Michigan, U.S.A. 2. A simple mathematical model was developed to separate the effects of washout from in situ zooplankton population dynamics. The threshold reservoir flushing time for development of a large Daphnia population and corresponding clear water phase during May was about 20 days. Predation by Leptodora was insufficient to cause the subsequent decline of the Daphnia population. 3. Recruitment success by the zebra mussel Dreissena polymorpha appeared responsive to flushing time indirectly, through hydrological effects on the magnitude of the spring diatom crop.     

Marketing Heritage: Archaeology and the Consumption of the Past

Marketing Heritage: Archaeology and the Consumption of the Past. Yorke Rowan and Uzi Baram, eds. Walnut Creek: AltaMira Press, 2004. 315 pp.     

Distance from a Promoter Mutation to an RNA Synthesis Startpoint on Bacteriophage λ DNA

Sites of promoter and operator mutations are separated from the RNA synthesis startpoint by approximately 200 nucleotide pairs. Several models could explain how RNA polymerase can interact with such widely separated sites without transcribing the intervening region into RNA.