bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of temperature on the photoperiodic ‘counters’ for female morph and sex determination in two clones of the black bean aphid, Aphis fabae
Authors: Nunes Marlies VaZ. , Hardie JiM. 
Published: March 2003

AbstractExperiments were performed on two clones of the black bean aphid, Aphis fabae Scopoli – one from Aberdeen, Scotland (57°N), the other from Cambridge, England (52°N) − to determine the number of long‐ or short‐night cycles required for 50% induction of winged versus wingless females on the one hand and males versus females on the other (i.e. required day number, RDN), at three temperatures, 12.5, 15 and 17.5°C. In the case of female morph determination, the RDN for long‐night cycles was temperature compensated, whereas that for short‐night cycles was highly temperature dependent. For sex determination, the RDN for long‐night cycles was again temperature compensated, whereas, due to the mechanism of sex determination, male production was close to 100% in our protocol, even with a maximal number of short‐night cycles, and the RDN could therefore not be assessed. Model‐generated response curves, using the recently developed ‘double circadian oscillator model’ for photoperiodic time measurement in insects and mites, closely resembled the observations. It could also be shown that differences observed between response curves of female morph and sex determination in the Scottish clone were due, according to the model, to differences in their photoperiodic ‘counters’, rather than to differences in their clocks.
Reproductive development and ontogeny of queen pheromone production in the fire ant Solenopsis invicta
Authors: Vargo Edward L. 
Published: March 2003

AbstractQueens of the fire ant, Solenopsis invicta Buren, produce several releaser and primer pheromones. Using bioassays, the ontogeny of three of these pheromones related to reproductive development was investigated. Virgin queens, in which the process of wing‐shedding (dealation) serves as an indicator of the initiation of reproductive development, were studied. First, the production of two queen pheromones produced in the poison gland was examined. The pheromone responsible for initiation and maintenance of retinue formation, a releaser effect, was found to be produced in detectable quantities 2 days after dealation, at which time queens showed significant ovary development and many (30%) had started laying eggs. A primer pheromone that inhibits alate virgin queens from dealating was detected in queens 3 days following wing‐shedding, when 80% of the queens were ovipositing. Second, I examined the onset of a pheromone of unknown glandular origin produced by reproductively active virgin queens which leads to their destruction in queenright colonies by stimulating workers to attack and kill them. This pheromone is secreted in quantities detectable by bioassay 2 days after dealation. Thus, in S. invicta, the ontogeny of three distinct queen pheromones is tightly linked with ovary development and initiation of egg laying. These results demonstrate reproductive and communicative functions are closely associated during the transition from potential to functional queen.
The dark‐colour‐inducing neurohormone of locusts in relation to an albino mutant of Schistocerca gregaria
Authors: Yerushalmi Yoram , Livshits Leonid , Pener Meir Paul 
Published: March 2003

SummaryIn the albino mutant of an Okinawa strain of Locusta migratoria (L.) (Orthoptera: Acrididae), albinism is caused by the absence of the dark‐colour‐inducing neurohormone (DCIN), which is present in the corpora cardiaca (CC) of normally coloured phenotypes. This study tests whether the absence of DCIN is responsible for albinism in an albino mutant of another locust, Schistocerca gregaria (Forsk.) (Orthoptera: Acrididae). This seemed feasible because a single Mendelian unit controls albinism in both species. However, implantation of CC, or injection of an extract of CC, from albino donors of S. gregaria, induce dark coloration in crowded nymph recipients of the Okinawa albino mutant of L. migratoria, as effectively as do implanted CC, or injections of extract of CC, from normal phenotype donors of S. gregaria. Therefore, DCIN is present in the albino mutant of S. gregaria, and consequently, the albinism in this mutant is not caused by its absence.Implantation of CC, or injection of extracts of CC, from albino donors of S. gregaria to conspecific albino nymphs does not induce darkening. Only extremely high doses of synthetic DCIN injected into albino nymphs of S. gregaria are effective, inducing some darkening. The dose to induce such darkening in albino nymphs of S. gregaria is 50 nmol, ≈ 5 × 106 times higher than that (10 femtomol) needed to induce equivalent darkening in nymphs of the Okinawa albinos of L. migratoria. The results are discussed and some possible explanations of the observed effects outlined.
Measuring the heart rate of the spider, Aphonopelma hentzi: a non‐invasive technique
Authors: Coelho FlÁvio C. , Amaya Carlos C. 
Published: March 2003

SummaryIn this work we describe a non‐invasive and precise technique to record the heartbeats of a spider. A linear output Hall effect transducer in conjunction with a small magnet was used to monitor the micromovements on the dorsal surface of the abdomen of the tarantula Aphonopelma hentzi (Girard) (Theraphosidae). The exoskeleton in this region is in direct contact with suspensory ligaments connected to the heart, and the dorsal cuticle of the opisthosoma moves with each heartbeat. The technique allowed the discrimination of the different stages of the spider's cardiac cycle. The method can be also adapted for a smaller spider or other arthropods. We believe that the method proposed in this paper allows investigators to gain insights into a spider's natural heart rate by gathering unbiased data with a non‐invasive and very precise technique. We have found the resting heart rate of A. hentzi to be 5.6 ± 1.47 beats/min, which is lower than previously reported values.
Allatotropic and allatostatic activities in extracts of brain and the effects of Manduca sexta allatotropin and Manduca sexta allatostatin on juvenile hormone synthesis in vitro by corpora allata from the Eri silkworm, Samia cynthia ricini
Authors: Li Sheng , Jiang Rong‐Jing , Cao Mei‐Xun 
Published: March 2003

Abstract.Both allatotropic and allatostatic activities were found in crude extracts of brain from adult and larval Eri silkworm, Samia cynthia ricini, but it seems that allatotropic activity dominates in each stage. There was a high level of allatotropic activity in the crude extract of brain from newly emerged female adults, but allatostatic activity appeared in the bioassay when excessive amounts of crude extracts of brain were added. Crude extracts of brain from premoulting fourth‐instar larvae and from newly ecdysed fifth‐instar larvae exhibited allatotropic activities, whereas extracts of brain from the second and third day of the fifth‐instar larvae inhibited juvenile hormone (JH) release slightly. Allatotropic activity from the brains of adults and larvae stimulated both adult and larval corpora allata (CA) to synthesize JH. Manduca sexta allatotropin (AT) (Mas‐AT) and M. sexta allatostatin (AST) (Mas‐AST) also stimulated and inhibited both adult and larval S. cynthia ricini CA to synthesize JH, respectively. Higher concentrations of Mas‐AT (10−4 or 10−3 M) showed an inhibitory effect on adult CA. CA from newly emerged female adults were the most sensitive to inhibition by Mas‐AST, whereas CA from female pharate adults at about 6 h before adult emergence were the most sensitive to stimulation by Mas‐AT and S. cynthia ricini brain allatotropic activity. An extract of brain and Mas‐AT induced some of the non‐active female pharate adult CA at 12 h before emergence to synthesize a small amount of JH.
Significance of antioxidants and electron sinks for the cold‐hardening‐induced resistance of winter rye leaves to photo‐oxidative stress
Authors: Streb P , Feierabend J. 
Published: March 2003

ABSTRACTThe contents of ascorbate and glutathione and the activities of superoxide dismutase and glutathione reductase were increased to levels as high as those in cold‐hardened leaves (CHL) by incubating non‐hardened leaves (NHL) of winter rye (Secale cereale L.) with the precursor substrates
L‐galactonic acid‐γ‐lactone and 2‐oxothiazolidine‐4‐carboxylate. Reduced glutathione was rapidly depleted from NHL after application of
D,
L‐buthionine sulfoximine, an inhibitor of its biosynthesis. In spite of greatly divergent antioxidant contents the rates of photo‐inactivation of photosystem II (PSII) and catalase observed in the presence of translation inhibitors did not differ greatly. The paraquat‐induced catalase inactivation and chlorophyll degradation in light were reduced in NHL with increased antioxidant levels. Paraquat‐induced photo‐inactivation of PSII was, however, not mitigated. The CHL had a higher capacity to prevent paraquat‐induced oxidation of ascorbate and glutathione than NHL with increased antioxidant contents. Increased antioxidant contents did not establish resistance to low temperature‐induced photo‐inactivation of PSII and catalase in NHL. The resistance of CHL to low temperature‐induced photo‐inactivation of PSII and catalase required repair at low temperature and active carbon assimilation but was only little affected when photorespiration was suppressed by phosphinothricin. Protection of PSII depended also on non‐photochemical quenching of excitation energy.
The isolation of wall‐bound proteins regulating yield threshold tension in glycerinated hollow cylinders of cowpea hypocotyl
Authors: Okamoto‐Nakazato A. , Nakamura T. , Okamoto H. 
Published: March 2003

ABSTRACTTo isolate and purify the factor regulating the yield threshold tension (y) through acidification of the cell wall, proteins were extracted from hypocotyls of Vigna unguiculata L. Their effects on the pH‐dependencies of the wall extensibility (φ) and y were examined with reconstitution experiments by incorporating them into the heat‐denatured glycerinated hollow cylinders (GHCs). The wall mechanical properties of the reconstituted GHCs were determined using stress–strain experiments. Only the proteins extracted with 1 kmol m–3 of NaCl from the wall of elongation region restored the pH‐dependencies of φ and y once extinguished with heat‐denaturation, but proteins extracted from the other cell constituents or from the mature region of hypocotyl affect neither properties. Fractionation of the wall‐bound proteins by a hydrophobic column chromatography showed that the two different fractions affected φ or y independently. The sodium dodecyl sulphate‐polyacrylamide gel electrophoresis showed that the active fraction which restored the pH‐dependency of y still consists of two proteins of 30 and 32 kDa after purification by the sequential fractionation with cation‐exchange and gel filtration. These two proteins were named as ‘yieldin 30’ and ‘32’. Western blotting analysis using the rabbit‐antiserum against the cucumber expansin indicated that the yieldins are independent of cucumber expansin.
Molecular cloning of yieldins regulating the yield threshold of cowpea cell walls: cDNA cloning and characterization of recombinant yieldin
Authors: Okamoto‐Nakazato A. , Takahashi K. , Kido N. , Owaribe K. , Katou K. 
Published: March 2003

ABSTRACTcDNA for yieldin of Vigna unguiculata L. was cloned with reverse transcriptase‐polymerase chain reaction using synthetic oligonucleotides as primers. The primers were designed on the basis of the N‐terminal amino acid sequence of the yieldins isolated from the wall preparation of cowpea hypocotyls. The 1·2 kbp cDNA for yieldin contained an open reading frame of 981 base pairs, encoding 327 amino acids including 23 amino acids as a putative signal sequence. An homology search of the deduced amino acid sequence revealed that the yieldin was homologous to acidic class III endochitinases (EC 3·2.1·14) and concanavalin B. A cDNA fragment containing the yieldin‐coding region was introduced to Escherichia coli cells using an expression vector to express the recombinant protein. The recombinant yieldin was obtained from the recombinant E. coli and its effect on the wall mechanical properties was examined by reconstitution experiments. The recombinant yieldin fully restored the acid‐induced change of the yield threshold tension (y) of heat denatured glycerinated hollow cylinders (GHCs) of cowpea hypocotyls. Northern hybridization analysis revealed that the yieldin mRNA was expressed mainly in the rapid and moderate elongation region of the etiolated hypocotyl of Vigna unguiculata L.
Induction of 1‐aminocyclopropane‐1‐carboxylate oxidase mRNA by ethylene in mung bean roots: possible involvement of Ca2+ and phosphoinositides in ethylene signalling
Authors: Jung T. , Lee J. H. , Cho M. H. , Kim W. T. 
Published: March 2003

ABSTRACTEthylene markedly induces an increase in the mRNA level of 1‐aminocyclopropane‐1‐carboxylate (ACC) oxidase, the final step of its biosynthetic pathway, in mung bean roots. To investigate the second messengers that possibly participate in ethylene signalling various pharmacological reagents known to affect the cytosolic calcium level and phosphoinositide (PI) metabolism were applied to mung bean roots, and then the induction pattern of ACC oxidase (VR‐ACO1) by ethylene was monitored as a molecular paradigm for ethylene‐dependent responses in this tissue. The ethylene‐induced VR‐ACO1 gene expression was effectively inhibited by ruthenium red, a putative inhibitor of intracellular Ca2+ fluxes, and to a lesser extent by ethyleneglycotetraacetic acid, a calcium chelator and GdCl3, the plasma membrane calcium‐channel inhibitor. However, LaCl3 and verapamil, another type of plasma membrane calcium‐channel blockers, did not prevent the ethylene action. The calmodulin antagonist W‐7 significantly reduced the hormone‐dependent expression of VR‐ACO1. Treatment with neomycin or Li+, the antagonists of PI metabolism, almost completely blocked the ethylene‐induced accumulation of VR‐ACO1 transcript in a dose‐dependent manner, whereas the addition of exogenous Ca2+ along with antagonists effectively restored the ethylene‐induced VR‐ACO1 gene activation. The results showed that the ACC oxidase enzyme activities and protein levels were in parallel with the abundance of transcript in response to various antagonists and exogenous Ca2+. These results are discussed in light of suggestion that the PI‐derived second messenger and cytosolic calcium are necessarily involved in the ethylene‐induced ACC oxidase gene activation in mung bean root tissue.
Expression and activity of isoenzymes of superoxide dismutase in wheat roots in response to hypoxia and anoxia
Authors: Biemelt S. , Keetman U. , Mock H.‐P. , Grimm B. 
Published: March 2003

ABSTRACTWe investigated the effects of hypoxia, anoxia and reaeration on enzymatic activity and expression of superoxide dismutase (SOD) isoforms in wheat roots (Triticum aestivum L.). Neither hypoxia nor subsequent re‐aeration caused significant changes in SOD isoenzyme pattern compared with aerated controls. However, anoxia led to the appearance of additional activity bands of SOD in native gels resulting in an increase in total activity. Additional isoformic bands remained also apparent in the following recovery period. Re‐aeration following both hypoxia and anoxia resulted in an increased content of hydrogen peroxide in roots. SOD transcript and protein levels were only slightly altered in response to hypoxia. Although SOD mRNA levels were diminished, protein content of different SOD isoforms increased with duration of anoxia. Incubation of roots with cycloheximide revealed that the additional activity bands and higher SOD protein content under anoxia were not due to de novo synthesis. Crude subcellular fractionation experiments implied that the anoxia‐responsive SOD isoforms might be plastid‐associated. We suggest that SOD is a very stable enzyme which, under anoxia, accumulates relative to total protein content and remains active even after protein modification under severe environmental stress conditions.
A comparative kinetic analysis of nitrate and ammonium influx in two early‐successional tree species of temperate and boreal forest ecosystems
Authors: Min Xiangjia , Siddiqi M. Yaeesh , Guy Robert D. , Glass Anthony D. M. , Kronzucker Herbert J. 
Published: March 2003

ABSTRACTRoot NO3− and NH4+ influx systems of two early‐successional species of temperate (trembling aspen: Populus tremuloides Michx.) and boreal (lodgepole pine: Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest ecosystems were characterized. NO3− and NH4+ influxes were biphasic, consisting of saturable high‐affinity (HATS) and constitutive non‐saturable low‐affinity transport systems (LATS) that were evident at low and relatively high N concentrations, respectively. NO3− influx via HATS was inducible (IHATS); nitrate pre‐treatment resulted in 8–10‐fold increases in the Vmax for influx in both species. By contrast, HATS for NH4+ were entirely constitutive. In both species, Vmax values for NH4+ influx were higher than those for NO3− uptake; the differences were larger in pine (6‐fold) than aspen (1·8‐fold). In aspen, the Km for NH4+ influx by HATS was approximately 3‐fold higher than for IHATS NO3− influx, while in pine the Km for IHATS NO3− influx was approximately 3‐fold higher than for NH4+ influx. The aspen IHATS for NO3− influx appeared to be more efficient than that of pine (Vmax values for aspen being approximately 10‐fold higher and Km values being approximately 13‐fold lower than for pine). By contrast, only small differences in values for the NH4+ HATS were evident between the two species. The kinetic parameters observed here probably result from adaptations to the N availabilities in their respective natural habitats; these may contribute to the distribution and niche separation of these species.
Photosynthesis, immediate export and carbon partitioning in source leaves of C3, C3‐C4 intermediate, and C4Panicum and Flaveria species at ambient and elevated CO2 levels
Authors: Leonardos E. D. , Grodzinski B. 
Published: March 2003

ABSTRACTImmediate export in leaves of C3‐C4 intermediates were compared with their C3 and C4 relatives within the Panicum and Flaveria genera. At 35 Pa CO2, photosynthesis and export were highest in C4 species in each genera. Within the Panicum, photosynthesis and export in ‘type I’ C3‐C4 intermediates were greater than those in C3 species. However, ‘type I’ C3‐C4 intermediates exported a similar proportion of newly fixed 14C as did C4 species. Within the Flaveria, ‘type II’ C3‐C4 intermediate species had the lowest export rather than the C3 species. At ambient CO2, immediate export was strongly correlated with photosynthesis. However, at 90 Pa CO2, when photosynthesis and immediate export increased in all C3 and C3‐C4 intermediate species, proportionally less C was exported in all photosynthetic types than that at ambient CO2. All species accumulated starch and sugars at both CO2 levels. There was no correlation between immediate export and the pattern of 14C‐labelling into sugars and starch among the photosynthetic types within each genus. However, during CO2 enrichment, C4Panicum species accumulated sugars above the level of sugars and starch normally made at ambient CO2, whereas the C4Flaveria species accumulated only additional starch.
Ionic and osmotic components of salt stress specifically modulate net ion fluxes from bean leaf mesophyll
Authors: Shabala S. 
Published: March 2003

ABSTRACTIonic mechanisms of salt stress perception were investigated by non‐invasive measurements of net H+, K+, Ca2+, Na+, and Cl− fluxes from leaf mesophyll of broad bean (Vicia faba L.) plants using vibrating ion‐selective microelectrodes (the MIFE technique). Treatment with 90 m
M NaCl led to a significant increase in the net K+ efflux and enhanced activity of the plasma membrane H+‐pump. Both these events were effectively prevented by high (10 m
M) Ca2+ concentrations in the bath. At the same time, no significant difference in the net Na+ flux has been found between low‐ and high‐calcium treatments. It is likely that plasma membrane K+ and H+ transporters, but not the VIC channels, play the key role in the amelioration of negative salt effects by Ca2+ in the bean mesophyll. Experiments with isotonic mannitol application showed that cell ionic responses to hyperosmotic treatment are highly stress‐specific. The most striking difference in response was shown by K+ fluxes, which varied from an increased net K+ efflux (NaCl treatment) to a net K+ influx (mannitol treatment). It is concluded that different ionic mechanisms are involved in the perception of the ‘ionic’ and ‘osmotic’ components of salt stress.
Seasonal changes in hydraulic conductance, xylem embolism and leaf area in Eucalyptus tetrodonta and Eucalyptus miniata saplings in a north Australian savanna
Authors: Prior L. D. , Eamus D. 
Published: March 2003

ABSTRACTEucalypt saplings in north Australian savannas commonly die back, sometimes to ground level, during the 5 months of the long dry season. Water potentials are lower in saplings than large trees during the dry season, and we hypothesized that low water potentials may lead to high levels of xylem embolism and consequent death of branches and whole shoots. As the dry season progressed, hydraulic conductance of terminal branches decreased by 50% in Eucalyptus tetrodonta but not in Eucalyptus miniata saplings. Hydraulic conductance per leaf area decreased seasonally by 34% in E. tetrodonta branches. These decreases may be associated with the loss of leaves recorded from E. tetrodonta but not E. miniata branches. We modelled the effect of sequential loss of parallel resistors, representing petioles on a branch. This showed there is a non‐linear decrease in flow as basal resistors are lost, which can lead to a decrease in mean flow per resistor due to increased mean path‐length. Thus the observed loss of basal leaves, together with xylem embolism, probably contributed to the seasonal loss of hydraulic conductance in E. tetrodonta saplings. Loss of hydraulic conductance due to xylem embolism was generally low (< 15%) in both species, and the seasonal increase in embolism could not fully account for the decline in hydraulic conductance of E. tetrodonta branches. There was little evidence that branch and shoot death was caused by these levels of embolism. Developing an embolism vulnerability curve for species with long vessels is problematic and this issue is discussed.