bluuebunny/crossref_metadata_2025_split huggingface dataset:
Putative role of γ ‐aminobutyric acid (GABA) as a long‐distance signal in up‐regulation of nitrate uptake in Brassica napus L.
Authors: BEUVE N. , RISPAIL N. , LAINE P. , CLIQUET J.‐B. , OURRY A. , LE DEUNFF E. 
Published: July 2004

ABSTRACTThe relationship between nitrate influx, BnNrt2 nitrate transporter gene expression and amino acid composition of phloem exudate was investigated during N‐deprivation (short‐term experiment) and over a growth cycle (long‐term experiment) in Brassica napus L. The data showed a positive correlation between γ‐aminobutyric acid (GABA) in phloem exudate and nitrate uptake in the short‐ and the long‐term experiments. The hypothesis that this non‐protein amino acid could up‐regulate nitrate uptake via a long‐distance signalling pathway was tested by providing an exogenous GABA supply to the roots. The effect of GABA was compared with the effects of Gln, Glu and Asn, each known to be inhibitors of nitrate uptake. The results showed that GABA treatment induced a significant increase of BnNrt2 mRNA expression, but had less effect on nitrate influx. By contrast, Gln, Glu and Asn significantly reduced nitrate influx and BnNrt2 mRNA expression compared with the control plants. This study provides the first evidence that GABA may act as a putative long‐distance inter‐organ signal molecule in plants in conjunction with negative control exerted by Gln. The up‐regulation effect of GABA on nitrate uptake is discussed in the context of its role in N metabolism, nutritional stress and the recent discovery of a putative role of GABA as a signal molecule in plant development.
Photosynthesis or persistence: nitrogen allocation in leaves of evergreen and deciduous Quercus species
Authors: TAKASHIMA T. , HIKOSAKA K. , HIROSE T. 
Published: July 2004

ABSTRACTPhotosynthetic nitrogen use efficiency (PNUE, photosynthetic capacity per unit leaf nitrogen) is one of the most important factors for the interspecific variation in photosynthetic capacity. PNUE was analysed in two evergreen and two deciduous species of the genus Quercus. PNUE was lower in evergreen than in deciduous species, which was primarily ascribed to a smaller fraction of nitrogen allocated to the photosynthetic apparatus in evergreen species. Leaf nitrogen was further analysed into proteins in the water‐soluble, the detergent‐soluble, and the detergent‐insoluble fractions. It was assumed that the detergent‐insoluble protein represented the cell wall proteins. The fraction of nitrogen allocated to the detergent‐insoluble protein was greater in evergreen than in deciduous leaves. Thus the smaller allocation of nitrogen to the photosynthetic apparatus in evergreen species was associated with the greater allocation to cell walls. Across species, the fraction of nitrogen in detergent‐insoluble proteins was positively correlated with leaf mass per area, whereas that in the photosynthetic proteins was negatively correlated. There may be a trade‐off in nitrogen partitioning between components pertaining to productivity (photosynthetic proteins) and those pertaining to persistence (structural proteins). This trade‐off may result in the convergence of leaf traits, where species with a longer leaf life‐span have a greater leaf mass per area, lower photosynthetic capacity, and lower PNUE regardless of life form, phyllogeny, and biome.
Nest Crypsis, Reproductive Value of a Clutch and Escape Decisions in Incubating Female Mallards Anas platyrhynchos
Authors: Albrecht Tomáš , Klvaňa Petr 
Published: July 2004

AbstractIn cryptically coloured birds, remaining on the nest despite predator approach (risk‐taking) may decrease the likelihood that the nest will be detected and current reproductive attempt lost. By contrast, flushing may immediately reveal the nest location to the predator. Escape decisions of incubating parents should therefore be optimized based on the risk‐to‐parent/cost of escape equilibrium. Animal prey may assess predation risk depending on a variety of cues, including the camouflage that vegetation provides against the predator. We examined interactive effects of nest crypsis and the current reproductive value of a clutch on flushing distances in incubating mallards (Anas platyrhynchos) approached by a human. Our results were consistent with predictions of parental investment theory: flushing distances were inversely correlated with measures of the reproductive value of the current clutch, namely with clutch size, stage of incubation and mean egg volume. Independently of a reproductive value of a clutch, nest concealment explained a significant portion of the variation in flushing distance among females; individual females tended to increase/decrease flushing distances according to change in nest cover. The results further suggest that vegetation concealment greatly influenced the risk of nest detection by local predators, suggesting that vegetation may act as a protective cover for incubating female. A female's ability to delay flushes according to the actual vegetation cover might thus be viewed as an antipredator strategy that reduces premature nest advertising to visually oriented predators. We argue, however, that shorter flying distances from densely covered sites might be maladaptive in areas where a predator's ability to detect incubating female does not rely on visual cues of nests.
Sun Compass Orientation of Tylos europaeus (Crustacea, Isopoda) Under Artificial Light
Authors: Ugolini A. , Castellini C. 
Published: July 2004

AbstractTo provide a first assessment of the parameters used by adult individuals of the supralittoral isopod Tylos europaeus to recognize the sun as a compass orienting reference, we used the apparatus designed and tested with the amphipod T. saltator. The apparatus reproduces a scenario similar to the natural one (with a false sun and sky illuminated artificially). The scenario produced inside the apparatus is sufficient to induce the isopods to exhibit solar orientation similar to that of conspecifics tested under the natural sun and sky. Nevertheless, this ability depends on some threshold values of illumination of the artificial sun and sky: to obtain a good orientation the irradiance of the artificial sun and sky should be more than 0.4 and 1.3 μW/cm2 respectively. When the artificial sky is not illuminated, the individuals show only a photopositive tendency.
Breeding Tubercles, Papillomatosis and Dominance Behaviour of Male Roach (Rutilus rutilus) During the Spawning Period
Authors: Kortet Raine , Taskinen Jouni , Vainikka Anssi , Ylönen Hannu 
Published: July 2004

AbstractWe studied the relationship between the breeding tubercle ornamentation (i.e. skin roughness) and male pre‐spawning dominance and courtship behaviour in roach (Rutilus rutilus) within an experimental laboratory system. Sexually mature fish were caught during their migration to their spawning pond and their behaviours were studied in an artificial spawning arena. Males behaved naturally both in terms of male–male interactions and attempts to achieve spawnings. Males having many, large breeding tubercles (i.e. rough skin) were significantly more often dominant in our dyadic trials than those with smooth skin. The dominant male in the trial exhibited a more active courtship behaviour than its subordinate rival. Papilloma skin disease did not affect the dominance rank. As a result of the relationship between skin roughness and male dominance, breeding tubercles may be used by the females as a cue for choosing a high‐quality mate in a roach lek. Thus, breeding tubercles might offer a workable tool for examination of sexual selection among cyprinids.
Variability in the Assessment of Snake Predation Risk by Liolaemus Lizards
Authors: Labra Antonieta , Niemeyer Hermann M. 
Published: July 2004

AbstractThe ability to assess and respond to predation risk is a strong selective force. Detection of predators is carried out by one or more sensory modalities, but the use of chemoreception has significant advantages. This study examines the chemosensorial assessment of snake predation risk and corresponding behaviours in different species and populations of Liolaemus lizards naturally exposed to different levels of snake predation pressure. The species studied were sympatric (Liolaemus lemniscatus), parapatric (L. nigroviridis) and allopatric (L. fitzgeraldi) to the saurophagous snake, Philodryas chamissonis. Additionally, two populations of L. lemniscatus from areas differing in snake densities were compared. Chemo‐assessment of predation risk was determined by comparing the number of tongue‐flicks (TF) and the behavioural responses of lizards submitted to three treatments (with semiochemicals of snake, conspecifics, and without semiochemicals – control). The results suggest that Liolaemus lizards can chemo‐assess snake predation risk, but this was modulated by the predation pressure experienced by lizards in their natural habitats. When exposed to snake semiochemicals, the sympatric prey showed less chemical exploratory behaviour (i.e. lower number of TF), a higher frequency of antipredator behaviours that would reduce its detection by a predator, and did not show the behaviour triggered by conspecific semiochemicals. The parapatric prey showed similar number of TF across different treatments, suggesting an absence of recognition of snake semiochemicals; however, it did show antipredatory behaviours when confronted with snake semiochemicals. The allopatric prey showed similar behaviour in all treatments. Both populations of the sympatric species, L. lemniscatus, showed a similar ability to detect predation risk when confronted with snake semiochemicals (i.e. similar number of TF), but antipredatory behaviours were diminished, and marking behaviours were present in the population subject to lower predation pressure. Relaxed predation pressure from a predator that releases and detects semiochemicals had similar consequences at species and population levels.
Pathogenic Variability and Genetic Diversity of Phaeoisariopsis griseola Isolates from Two Counties in the State of Goias, Brazil
Authors: Sartorato A. 
Published: July 2004

AbstractAngular leaf spot disease of common bean (Phaseolus vulgaris), caused by Phaeoisariopsis griseola, is one of the most important disease of this crop in Brazil. Control strategies for the disease include cultural practices, chemical control and genetic resistance. This pathogen is known to vary greatly in pathogenicity. For durable use of genetic resistance to control this disease, it is necessary to manage resistant cultivars by taking into account the population structure of P. griseola. Isolates of the pathogen from Goias, Brazil exhibited an important virulence polymorphism when inoculated on 12 differential cultivars. A total of 13 pathotypes was identified within a series of 96 isolates collected in Inhumas and Damolandia counties. Only pathotypes 63‐15, 63‐23, 63‐31 and 63‐63 were identified in both counties. Since all the isolates were capable of inducing disease in both Andean and Mesoamerican differential cultivars, they were considered to be of Mesoamerican origin. Random amplified polymorphic DNA (RAPD) analysis performed on the same 96 isolates revealed a great genetic diversity clustering the series into five groups at an Euclidean distance of 62.5%. Although the results did not show any clustering according to the isolate origin, it was possible to observe a tendency of the isolates to cluster in different groups according to their origin. No pathotype‐specific band was observed in the present study.
Occurrence of Bremia lactucae in Natural Populations of Lactuca serriola
Authors: Petrželová I. , Lebeda A. 
Published: July 2004

AbstractIn the period 1996–2001 the natural occurrence of Bremia lactucae (lettuce downy mildew) on Asteraceae plants was studied in the Czech Republic. Lactuca serriola (prickly lettuce) is the most common naturally growing host species of B. lactucae. Infection of plants was recorded during the whole vegetation season with the first occurrence in April and last in November. Bremia lactucae was found on host plants in all developmental stages. High percentages of naturally infected populations of L. serriola were recorded. Host plants exhibited broad variation in phenotypic expression of disease symptoms and degree of infection, however, the intensity of infection was rather low in the majority of populations. Geographic distribution of B. lactucae was studied in the two main parts of Czech Republic, central and southern Moravia, and eastern, northern and central Bohemia. Bremia lactucae was recorded in all these areas. Nevertheless, in the warmest parts of the Czech Republic (southern Moravia) only sporadic occurrence of the pathogen was recorded. Bremia lactucae infection on L. serriola and disease severity was judged also in relation to the type of habitat, and the size and density of host plant populations. However, no substantial differences among various habitats were found; only host plants growing in urban areas were frequently free of infection and the degree of infection was very low. Nevertheless, these plants were commonly infected with powdery mildew (Golovinomyces cichoracearum), which is most aggressive pathogen of this type of habitat.
Pathogenesis of Potato Gangrene Caused by Phoma exigua var. foveata: II. Activities of some Hydrolases and Dehydrogenases
Authors: Giebel J. , DopieraŁa U. 
Published: July 2004

AbstractThe location of enzyme activity in gangrene‐diseased tubers was determined using the nitrocellulose blotting method. The activity of aminopeptidase and esterase was located in tissues adjacent to dry rot caused by Phoma exigua var. foveata and in other apparently healthy tissues. The activity of glucuronidase, succinic and glucose‐6‐phosphate dehydrogenases (G‐6‐PDH), however, was confined to tissues adjacent to the rotted tissue. The pathogen produces very active α‐ and β‐glycosidases, so their highest activity occurred in rotten tissue that was filled with fungal mycelium. Results suggest that all these enzymes are involved in alteration of cell metabolism and the destruction of diseased tuber tissue.
Detection and Differentiation of Comoviridae Species using a Semi‐nested RT‐PCR and a Phylogenetic Analysis based on the Polymerase Protein
Authors: Maliogka V. , Dovas C. I. , Efthimiou K. , Katis N. I. 
Published: July 2004

AbstractA nested reverse transcription polymerase chain reaction (RT‐PCR) method is described that allows detection and identification of Comoviridae species and possibly other bipartite plant picorna‐like viruses. It involves an RT‐PCR, in which a combination of degenerate deoxyinosine (dI)‐substituted primers amplified part of the RNA‐dependent RNA polymerase (RdRp) domain, followed by a semi‐nested PCR amplification that increased detection sensitivity. The PCR amplicons can be easily cloned and sequenced to obtain initial sequence information of Comoviridae genomes for virus species differentiation and characterization. The method can be used on total RNA extracts from infected plants, when viral genomic double‐stranded RNA (dsRNA) or the viral RNA is unavailable. Previously uncharacterized RdRp domains of Potato black ringspot virus (PBRSV), Cherry leafroll virus (CLRV) and Arracacha virus B (AVB) were amplified and sequenced. Neighbour‐joining trees calculated from the homologous partial RdRp amino acid sequences were used to establish the taxonomic relationships between members of plant picorna‐like viruses, revealing lineages that classified all species within their respective genera and clearly distinguished each genus from the other genera. Phylogenetic analysis confirmed the classification of PBRSV and CLRV within the genus, Nepovirus whereas AVB was placed into a cluster different from the Nepovirus, Comovirus and Fabavirus lineages.
Effect of Leaf Infection by Kabatiella zeae on Stalk Rot Prevalence and Grain Yield of Maize Hybrids
Authors: Prończuk M. , Bojanowski J. , Warzecha R. 
Published: July 2004

AbstractEight maize hybrids were tested for resistance to eyespot (Kabatiella zeae) and stalk rot (Fusarium spp.) under field conditions in 1993–1995. The relationship between eyespot and stalk rot and their effect on grain yield of hybrids were studied. Effectiveness of the prochloraz fungicide in controlling both diseases was evaluated. The experiments were performed in three subtrials where plants were naturally infected, inoculated with K. zeae or treated with the fungicide, Sportak 450 EC. The relationship between intensity of leaf damage by eyespot and incidence of stalk rot has been evidently confirmed. High infection of leaf by K. zeae reduced grain yield of hybrids. However, considerable differences in prevalence of disease and yield losses were noted in successive years. The intensity of eyespot depended upon environmental conditions highly variable over the years: it was enhanced by low temperature and high air humidity in July and August. Hybrids showed significant differences in susceptibility to both diseases. Mona – hybrid from the USA and two experimental hybrids from Poland were less affected by diseases than Smolimag and Hidosil (commercial hybrids from Poland). The fungicide Sportak was effective in controlling eyespot and had an indirect influence on decreasing fusarium stalk rot.
Diversity among Grapevine Leafroll‐associated Virus 2 Isolates Detected by Heteroduplex Mobility Assay
Authors: Angelini E. , Bertazzon N. , Borgo M. 
Published: July 2004

AbstractGrapevine leafroll‐associated virus 2 (GLRaV‐2) was detected by serological and molecular analyses in several grapevine accessions of different varieties from Italian, Greek, French and Brazilian vineyards in a 2001–2002 survey. In order to study the genetic variability among GLRaV‐2 isolates in the open reading frame (ORF) coding the coat protein (CP), heteroduplex mobility assays were performed on 17 isolates and six strains used as reference. Eight diverse GLRaV‐2 variants were identified among the infected grapevines tested. The most common variant was found in the majority of the samples characterized; it was indistinguishable from the reference strains from the Semillon and Pinot noir 95 accessions. GLRaV‐2 variants found in Italian cvs Negro amaro and Vermentino were identical to the reference strain from cv. Muscat de Samos (Greece). Three other GLRaV‐2 variants from Southern and Central Italy were different from all the reference strains. A grapevine accession from Tuscany was found to contain two diverse GLRaV‐2 variants. None of the variants tested sample identical to the American strain H4 or the reference strains from cvs Chasselas 8386 (Switzerland) or Alphonse Lavallée 224 (France); the latter three accessions were different from one another. The estimated nucleotide homology in CP gene among 23 GLRaV‐2 isolates was in some cases <88%.
Presidential Address, Committing to Commit: Short‐term Debt When Enforcement Is Costly
Authors: Diamond Douglas W. 
Published: July 2004

ABSTRACTIn legal systems with expensive or ineffective contract enforcement, it is difficult to induce lenders to enforce debt contracts. If lenders do not enforce, borrowers will have incentives to misbehave. Lenders have incentives to enforce given bad news when debt is short‐term and subject to runs caused by externalities across lenders. Lenders will not undo these externalities by negotiation. The required number of lenders increases with enforcement costs. A very high enforcement cost can exceed the ex ante incentive benefit of enforcement. Removing lenders' right to immediately enforce their debt with a “bail‐in” can improve the ex ante incentives of borrowers.
Why Do Firms Use Incentives That Have No Incentive Effects?
Authors: Oyer Paul 
Published: July 2004

ABSTRACTThis paper illustrates why firms might choose to implement stock option plans or other pay instruments that reward “luck.” I consider a model where adjusting compensation contracts is costly and where employees' outside opportunities are correlated with their firms' performance. The model may help to explain the use and recent rise of broad‐based stock option plans, as well as other financial instruments, even when these pay plans have no effect on employees' on‐the‐job behavior. The model suggests that agency theory's often‐overlooked participation constraint may be an important determinant of some common compensation schemes, particularly for employees below the highest executive ranks.
The Timing of Option Repricing
Authors: Callaghan Sandra Renfro , Saly P. Jane , Subramaniam Chandra 
Published: July 2004

ABSTRACTWe investigate whether executive stock option repricings are systematically timed to coincide with favorable movements in the company's stock price. For a sample of 236 repricing events, we observe sharp increases in stock price in the 20‐day period following the repricing date. In addition, repricing dates tend to either precede the release of good news or follow the release of bad news in the quarterly earnings announcements. Since information about stock option repricing is not generally released to the public around the repricing date, these findings suggest that CEOs opportunistically manage the timing of the option repricing date.
Estimation and Test of a Simple Model of Intertemporal Capital Asset Pricing
Authors: Brennan Michael J. , Wang Ashley W. , Xia Yihong 
Published: July 2004

ABSTRACTA simple valuation model with time‐varying investment opportunities is developed and estimated. The model assumes that the investment opportunity set is completely described by the real interest rate and the maximum Sharpe ratio, which follow correlated Ornstein–Uhlenbeck processes. The model parameters and time series of the state variables are estimated using U.S. Treasury bond yields and expected inflation from January 1952 to December 2000, and as predicted, the estimated maximum Sharpe ratio is related to the equity premium. In cross‐sectional asset‐pricing tests, both state variables have significant risk premia, which is consistent with Merton's ICAPM.
The Cash Flow Sensitivity of Cash
Authors: Almeida Heitor , Campello Murillo , Weisbach Michael S. 
Published: July 2004

ABSTRACTWe model a firm's demand for liquidity to develop a new test of the effect of financial constraints on corporate policies. The effect of financial constraints is captured by the firm's propensity to save cash out of cash flows (the cash flow sensitivity of cash). We hypothesize that constrained firms should have a positive cash flow sensitivity of cash, while unconstrained firms' cash savings should not be systematically related to cash flows. We empirically estimate the cash flow sensitivity of cash using a large sample of manufacturing firms over the 1971 to 2000 period and find robust support for our theory.
The Price Response to S&P 500 Index Additions and Deletions: Evidence of Asymmetry and a New Explanation
Authors: Chen Honghui , Noronha Gregory , Singal Vijay 
Published: July 2004

ABSTRACTWe study the price effects of changes to the S&P 500 index and document an asymmetric price response: There is a permanent increase in the price of added firms but no permanent decline for deleted firms. These results are at odds with extant explanations of the effects of index changes that imply a symmetric price response to additions and deletions. A possible explanation for asymmetric price effects arises from the changes in investor awareness. Results from our empirical tests support the thesis that changes in investor awareness contribute to the asymmetric price effects of S&P 500 index additions and deletions.