bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the immunoglobulin E responses to Teladorsagia circumcincta in sheep: purification of a major high molecular weight allergen
Authors: Huntley J.F. , Redmond J. , Welfare W. , Brennan G. , Jackson F. , Kooyman F. , Vervelde L.
Published: March 2003

Studies on the immunoglobulin (Ig)E immune responses to the gastric nematode, Teladorsagia circumcincta, have demonstrated a major high molecular weight allergen (HMWTc). Cross reactive allergens of similar MW were demonstrated for Trichostrongylus colubriformis and Cooperia curticei, but not for Haemonchus contortus. Purification of HMWTc was achieved by gel‐filtration chromatography, and nonreducing SDS‐PAGE and Western blot analysis revealed two closely associated bands with a molecular weight of approximately 140–150 kDa. Reduction showed four IgE reactive bands of 120, 50, 45 and 30 kDa, and deglycosylation abrogated the immunoreactivity of the 120 and 30 kDa bands. Ultrastructural immunolocalization by electron microscopy revealed that the IgE reactivity was confined to the cuticular surface of the infective (L3) larvae. ELISA studies to determine the IgE anti‐HMWTc responses in lambs during their first grazing season, demonstrated significantly higher IgE antibody in lambs with low accumulative faecal egg count (FEC) compared to animals with high accumulative FEC. These studies provide evidence for a protective function of IgE antibody in Teladorsagia infections in lambs.
Murine schistosomiasis mansoni: coordinate cytokine regulation and differences in cellular immune responses of granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigens
Authors: King Christopher L. , Xianli Jia , Stavitsky Abram B.
Published: March 2003

To better understand the cellular immune mechanisms that regulate granulomatous inflammation to Schistosoma mansoni ova, we examined the dynamics of lymphocyte proliferation and cytokine expression by granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigen (SEA) 6–19 weeks postinfection. Compared to splenocytes, granuloma cells (partially CD4+ cells) which are at the site of antigen release were highly activated by endogenous SEA and terminally differentiated as indicated by the more than 10‐fold greater frequency of ex vivo interleukin (IL)‐4, IL‐5 and interferon (IFN)‐γ ‐secreting cells, greater levels of constitutive cytokine production and failure to proliferate to either endogenous or exogenous SEA. Endogenous cytokine production by granuloma cells was coordinately regulated, enhanced little by exogenous SEA, and temporally correlated with granulomatous inflammation. By contrast, CD4+ splenocytes produced comparatively little cytokine release by endogenous antigen, whereas exogenous SEA strongly induced IL‐4, IL‐5, IL‐10 and IFN‐γ production and lymphocyte proliferation that correlated poorly with the dynamics of granulomatous inflammation. These results show that cytokine responses to endogenous SEA correlated better with granulomatous inflammation than responses to exogenous SEA. Furthermore, granuloma cells and splenocytes demonstrated strikingly different proliferative responses and dynamics of cytokine expression, suggesting that how SEA reactive lymphocytes traffic between lymphoid tissues and the granuloma is critical to a better understanding of the mechanisms of granulomatous inflammation and its modulation.
Polyspecific malaria antibodies present at the time of infection inhibit the development of immunity to malaria but antibodies specific for the malaria merozoite surface protein, MSP1, facilitate immunity
Authors: Zhang Wenbao , Liu Xue Qin , Xu Huji , Good Michael F.
Published: March 2003

Serum taken from mice immune to malaria as a result of infection and drug cure, or from mice immunized with a recombinant form of the merozoite surface protein, MSP1, can provide passive protection of recipient mice against the lethal parasite, Plasmodium yoelii YM. However, recipients of MSP1‐immune serum go on to develop long‐term immunity, whereas recipients of serum from mice naturally immune to malaria rapidly lose their resistance to infection. We demonstrate that ‘infection/cure’ serum suppresses the development of both antibody and cell‐mediated parasite‐specific responses in recipients, whereas these develop in recipients of MSP1‐specific antibodies. These data have profound implications for our understanding of the development of malaria immunity in babies who passively acquire antibodies from their mothers.
Vaccination of calves againstOstertagia ostertagiwith cysteine proteinase enriched protein fractions
Authors: Geldhof P. , Claerebout E. , Knox D. , Vercauteren I. , Looszova A. , Vercruysse J.
Published: March 2003

Cysteine proteinase enriched fractions obtained by thiol‐sepharose chromatography ofOstertagia ostertagimembrane‐bound protein extract (S3‐thiol) or total adult excretory–secretory (ES‐thiol) products were tested in a vaccination experiment to evaluate their protective efficacy againstO. ostertagiin cattle. Calves were vaccinated three times and subsequently challenged with a trickled infection of 25 000 infective larvae in total over 25 days (1000 L3/day, 5 days/week). Geometric mean cumulative egg counts in the ES‐thiol group were reduced by 60% during the 2‐month period between the first challenge infection and necropsy, compared to the control group (P < 0·002). No reduction in egg output was observed in the S3‐thiol group. At necropsy, calves immunized with ES‐thiol had a significantly higher percentage of inhibited L4 larvae (9·8%) and had in total 18% less worms than the control calves, but this reduction was not statistically significant. Both the female and male adult worms were significantly smaller in the ES‐thiol group than in the control group. Although no significant difference was observed in the number of eggs per female worm between the groups, there was a trend to less eggs per female worm in the ES‐thiol group. Number of worms, size of adult worms and number of eggs per female worm were not significantly different between the S3‐thiol group and the control group. Systemic immunization with QuilA as adjuvant induced a significant rise inOstertagia‐specific antibody levels in the abomasal mucosa.Ostertagia‐specific local antibody levels showed a significant negative correlation with the size of the adult worms, the number of eggs per female worm and the cumulative faecal egg counts. However, these correlations were quite weak and did not appear to be isotype‐specific.
Production of a recombinant version of a Heligmosomoides polygyrus antigen that is preferentially recognized by resistant mouse strains
Authors: Hoselton Scott , Piche Lisa , Gustad Thomas , Robinson Michael
Published: March 2003

Protective immunity to the mouse nematode parasite, Heligmosomoides polygyrus, has been characterized and found to be composed of the Th2 type. However, many inbred mouse strains cannot produce this protective immune response during a primary infection. A possible reason for this lack of protection in poor responding strains could be due to lack of recognition of specific protective antigens by these strains. Recently, evidence suggests that specific antigens exist that are only recognized by fast responding strains during a primary infection. Using monoclonal antibodies to screen an H. polygyrus cDNA library enabled the production of a recombinant protein, 3A4, which is antigenically similar to those found in the excretory/secretory antigens (E/S) of both L4 and adult parasites. Protein 3A4 shares approximately 70% sequence homology with an E/S protein that induces protection to Trichostrongylus colubriformis in guinea‐pigs. Antibodies that bind to 3A4 are preferentially produced in SWR compared to BALB/c mice following immunization with L4 homogenate, although both strains of mice were able to produce comparable levels of specific antibodies after immunization with 3A4 protein. It is believed that 3A4 may have considerable importance in dissecting out the nature of the immune response to H. polygyrus infection, particularly in mouse strains of differing response phenotype.
The effects of injection of amphetamine on female insemination in the black blow fly, Phormia regina (Diptera: Calliphoridae)
Authors: EVANS B. P. , STOFFOLANO J. G. , YIN C.‐M. , MEYER J. S.
Published: March 2003

Abstract. An earlier study on the blowfly Phormia regina (Meigen) demonstrated that the injection of amphetamine (12 μg) depletes biogenic amine levels in the CNS. In the present study, P. regina females were injected with amphetamine (12 μg), each female was placed with three males and insemination success was determined. Amphetamine inhibited female insemination by 43.3% at 2–90 min post‐injection and by 70% at 10–60 min post‐injection. At 180–270 min post‐injection, there was no significant inhibition of female insemination. This study indicates a possible role in insects for the biogenic amines in female insemination.
Effects of low temperature on diapause termination and body colour change in adults of a stink bug, Plautia stali
Authors: KOTAKI TOYOMI
Published: March 2003

Abstract. Diapause adults of Plautia stali Scott maintained at 20°C under short day conditions (LD 12:12 h) were exposed to four temperatures of 5–20°C to examine the effect on diapause development which was assessed in terms of oviposition. Diapause adults kept at 20°C under short day conditions changed their body colour gradually from brown to green and started egg laying after a prolonged preoviposition period. Those transferred to either 10 or 15°C also showed colour change but did not lay eggs. Bugs exposed to 5°C underwent neither body colour change nor oviposition and died more rapidly than those kept at higher temperatures. When 30‐day‐old diapause adults were chilled at 5, 10 or 15°C for 30 or 60 days and returned to 20°C and long day conditions (LD 16:8 h), the preoviposition period varied primarily depending on the chilling, but not on the temperature. On the other hand, when 60day‐old diapause adults chilled for 30 days were observed at 20°C and long day conditions, their preoviposition period tended to be longer as the chilling temperature was lower In this case, a temperature of 10°C appeared to intensify diapause. Therefore, the effect of chilling on diapause development varied depending on the age at which insects were chilled. When chilled bugs were transferred to short day conditions at 20°C, most females failed to lay any eggs and some turned green, then after a while, some green bugs changed to brown again. These results indicate that bugs remained sensitive to short day conditions even after a 60‐day chilling at 10 or 15°C.
Duration of behaviour patterns during oviposition by the bruchid beetle, Callosobruchus maculatus
Authors: PARR MARTIN , TRAN BRUNO , SIMMONDS MONIQUE , CREDLAND PETER
Published: March 2003

The behaviour of insects between making contact with a potential oviposition site and the act of oviposition itself determines the conditions in which their progeny begin development and, in many cases, whether a crop or commodity is damaged. In this paper the behaviour of female cowpea seed beetles, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae), during this period has been examined. The duration of discrete behaviour patterns within this period and the transitional frequencies between them have been used to compare the behaviour of beetles on two different hosts. In a 30‐min period, beetles laid more eggs on mung than adzuki beans and rejected mung as an oviposition site much less frequently.

A log‐linear contingency table analysis of the transitional frequencies indicated a highly significant interaction between successive behaviours and between the second of the two behaviours and the host seed, indicating that the sequence of behaviours is partially determined by the host seed. Grooming, departure from the seed and loops in behavioural sequences occur more often on adzuki than mung and are indicative of a less acceptable host. Discriminant analysis showed that the total time spent exhibiting different behaviour patterns was significantly different on the two hosts. Mann–Whitney tests revealed small but significant differences in the mean durations of only three behaviour patterns on the two seed types.

Measurement of the duration of each behavioural pattern confirms what can be deduced about host acceptability by observing the simple occurrence of different behavioural patterns and the determination of the frequency of transitions between them. Differences in acceptability were predominantly reflected in the frequency of certain behaviour patterns and of particular transitions from one pattern to another, not in the mean duration of each exhibition of a defined behaviour pattern. It is argued that the utility of measuring the duration of behavioural elements could only be demonstrated because behavioural patterns or categories were precisely defined.
Diversity in gas exchange and muscular activity patterns in insects studied by a respirometer‐actograph
Authors: Tartes Urmas , Kuusik Aare , Vanatoa Alo
Published: March 2003

Different events in insect gas exchange and muscular activity are described by a new system of automatic respirometers, a differential electrolytic microrespirometer‐actograph. This is very sensitive to volumetric changes caused by insect respiration and/or body movements. In this system, oxygen generation and its regulation are combined in the same current circuit. According to this principle, the oxygen consumed by the insect is continuously replaced by equal amounts of electrolytically produced oxygen. This simple laboratory‐made apparatus records simultaneously metabolic rate, the cyclicity of external gas exchange, rhythms of muscular ventilating and the pattern of other body movements, including abdominal pulsations not observable with the naked eye. The respirometer‐actograph described here is applicable also to the recording of the respiration of other terrestrial arthropods or other living organisms or tissues.
Geographic variation in cold hardiness of eggs and neonate larvae of the yellow‐spotted longicorn beetle Psacothea hilaris
Authors: Shintani Yoshinori , Ishikawa Yukio
Published: March 2003

Cold hardiness of eggs and neonate larvae of the yellow‐spotted longicorn beetle, Psacothea hilaris (Pascoe) was examined using six geographical populations in Japan. Particular attention was paid to cold hardiness of eggs and neonate larvae of the subtropical population (Ishigaki), because the east Japan populations are considered to have been introduced from a subtropical area, and the overwintering stage in the east Japan populations is incidentally shifted from the original mature larval stage to the egg or neonate larval stages. When the eggs were exposed to low temperatures for 1 h, the decrease in hatchability became significant at –12°C in the southernmost two populations (Ishigaki and Naze), and at –16°C in the northern populations. After 1 h exposure to –20°C, few eggs could hatch in the Ishigaki population, whereas 27–55% of the eggs survived in the northern populations. Pre‐chilling of the eggs at 10°C for 10 days enhanced the cold hardiness in all populations. This effect was particularly distinct in the subtropical population; the eggs of the Ishigaki population became as cold hardy as those of the northern populations after acclimation. These results suggest that the subtropical population is capable of establishing itself in east Japan, where the winter is cold.
Localization of the photoreceptor for photoperiodism in the stink bug, Plautia crossota stali
Authors: Morita Akihiro , Numata Hideharu
Published: March 2003

The brown‐winged green bug Plautia crossota stali Scott (Heteroptera: Pentatomidae) shows a long‐day photoperiodic response with respect to the control of adult diapause. The location of the photoreceptor for this response was examined by surgical removal of putative photoreceptor organs. Even after both ocelli were removed, the insects responded normally to the photoperiod. After bilateral removal of the compound eyes, the insects developed reproductive organs and the volume of the corpus allatum increased regardless of photoperiod. Therefore, the compound eyes play a major role in the reception of photic information for photoperiodism in P. c. stali. However, because removal of the bilateral compound eyes did not completely prevent the response to photoperiod, photoreceptors other than the compound eyes can also receive photic information for photoperiodism.
Real‐time measurement of pheromone release from individual female moths and synthetic dispensers in a wind tunnel by recording of single receptor‐neurone responses
Authors: Valeur Peter G. , Hansson BilL. S. , Löfstedt Christer
Published: March 2003

Measurements of single neurone activity in the peripheral pheromone receptors of male Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) were performed in a wind tunnel using a portable electrophysiological recording unit. Filter paper and rubber septa loaded with synthetic sex pheromone, as well as individual conspecific female glands, were used as pheromone sources. Recordings, up to 3 h long, were analysed for temporal variation in spiking activity. The recordings were performed 2 m downwind of the source, where the pheromone plume had a width of approximately 12 cm, as could be measured with the single cell preparations. The system allowed reliable measurements of relative pheromone concentration with a 20‐s time resolution. The release rate from rubber septa loaded with pheromone was more or less constant over time, whereas the release rate from filter paper loaded with pheromone decreased to one tenth of the initial value within 6 min from the application of the pheromone. The release of pheromone from female pheromone glands was pulsed with an interval of 2–10 min between bursts. This pulsing was not caused by retraction of the gland, as the glands were forcibly extruded during the entire experiment, but should reflect variation in transport of pheromone to the gland surface and subsequent release. The demonstrated stability of the preparations using tungsten electrodes, the reliable monitoring of female‐produced pheromone plumes at several metres distance, and the time resolution obtained are important steps towards field monitoring of natural pheromone plumes, as well as pheromone concentration and distribution in applications for mating disruption.
Respiratory physiology and water relations of three species of Pogonomyrmex harvester ants (Hymenoptera: Formicidae)
Authors: Quinlan Michael C. , Lighton JohN. R. B.
Published: March 2003

The respiratory physiology and water relations of three harvester ant species (Pogonomyrmex rugosus Emery, P. occidentalis[Cresson] and P. californicus[Buckley]) were examined at three temperatures (15, 25 and 35°C) using a flow‐through respirometry system. As intact ants tended to be active during testing, we performed a parallel set of experiments on individuals rendered motionless by decapitation. Both intact and decapitated ants exhibited discontinuous ventilation. Decapitation caused metabolic rate (V˙CO2) and burst frequency to decrease in all three species. Burst volume either remained constant or increased after removal of the head, though mass‐specific V˙CO2 was unaffected except in P. rugosus. Mass‐specific V˙CO2s of headless harvesters were comparable with published values derived from motionless specimens of other ant species. The mean Q10 for intact ants of all three species was 2.37; for decapitated insects the mean was 2.32. Respiratory water constituted a small (< 5%) fraction of total loss, and we believe that discontinuous ventilation does not act to conserve water in these organisms, although it may serve other functions.
Flight activity of three Spodoptera spp., Spodoptera litura, S. exigua and S. depravata, measured by flight actograph
Authors: Saito Osamu
Published: March 2003

Flight activities of three Spodoptera species were measured by the aid of flight actograph: S. litura and S. exuiga being regarded as long‐distance migratory insects, and S. depravata being non‐migratory and diapause‐inducible species. In all species tested, flight activities were observed only in scotophase, males showed far higher activities than females, being several times higher at the time of maximum flight activity, which was observed within 2 days after adult eclosion. Total flight activity in males was highest in S. litura, some being flyable even 12 days after eclosion, followed by S. exigua being one‐third compared to the former species, while in S. depravata flight activity was nearly half of that of the second species and most ceased to fly within a week after eclosion. There occurred species‐specific daily rhythms in flight activity during respective scotophase. In S. litura, both females and males exhibited a peak of flight activity shortly after light‐off and exhibited the second flight activity in late scotophase, the females slightly but the males more actively compared to early scotophase. In S. exigua, both sexes did not respond to light‐off, did not show a peak of flight activity in early scotophase, whereas males, but not females prominently increased activity toward the end of scotophase. In S. depravata, both sexes exhibited a peak of flight activity in early scotophase, and the males revived flight activity, being maximum shortly before light‐on, but the females did not show a clear rhythm in flight activity. These features observed in flight activity were discussed in relation with migratory capability.
Body movements and their role as triggers of heartbeats in pupae of the Colorado potato beetle Leptinotarsa decemlineata
Authors: Kuusik Aare , Tartes Urmas , Vanatoa Alo , Hiiesaar Külli , Metspalu Luule
Published: March 2003

Rhythmic body movements and their role as triggers of intermittent heartbeats were studied in pupae of Leptinotarsa decemlineata Say. Heartbeats and body movements were recorded simultaneously by means of an optical method (infra‐red cardiography) combined with respirometry. IR‐cardiography allows heartbeats and body movements to be distinguished on the basis of their different rates (40–80 min−1 and 4–8 min−1, respectively) and amplitude.

In the mid‐interecdysial period, abdominal movements in the pupae were always accompanied by heart activity beginning after the first 5–12 abdominal strokes. Simultaneous periods of abdominal movements and heartbeats lasted 2–5 min, while the intervening pause ranged from 40 to 72 min at 24°C.

Experiments of forced heart activity showed that a slight external tactile stimulus (prodding once with a single hair), applied prior to an expected heartbeat bout, evoked abdominal movements followed soon afterwards by contractions of the dorsal vessel. Repeated prodding with a hair evoked body rotating movements (1–3 strokes) at any time with heartbeats starting at the first movement.

We surmise that rhythmic body movements play an active role in the triggering of heart activity in pupae according to the principle of cardiac reflex response. This is a possible mechanism for synchronizing periods of heart activity with periods of rhythmic body movements. Haemolymph circulation in pupae is favoured when heartbeat bouts are accompanied by active body movements.
Divergent nutrition‐related adaptations in two cockroach populations inhabiting different environments
Authors: Mira Alex , Raubenheimer David
Published: March 2003

Developmental, reproductive and size‐related variables were compared between two ecologically different strains of Periplaneta americana (L.). One strain was a laboratory‐reared culture, and the other a feral strain inhabiting an urban environment. The feral population was originally founded by escapees from the culture, but may also include immigrants from other urban populations. Both final‐instar nymphs and adults of the feral insects were heavier than their equivalents from the cultured population, this weight difference being due to a higher capacity for the storage of water and heavier fat‐free carcasses. Feral cockroaches also had heavier oothecae, which contained heavier offspring than those from cultured females. Feral animals had one or two more larval stadia and higher growth rates. Size‐related differences persisted in first and second filial generations reared under laboratory conditions on a nutritionally balanced diet, but were not apparent in first filial insects reared on a vegetable diet. Greater resistance to starvation was found in feral animals, and this was attributed primarily to their larger water stores. Feral animals were found to harbour a higher density of endosymbiotic bacteria in the fat body, which are known to enhance the efficiency of protein utilization. The data suggest that the characteristics of feral animals have been selected in the nutritionally harsh feral environment compared with the more benign culture conditions, with water availability playing a role.
Transpiration and stomatal behaviour of Quercus ilex plants during the summer in a Mediterranean carbon dioxide spring
Authors: Tognetti R. , Longobucco A. , Miglietta F. , Raschi A.
Published: March 2003

Variations in the water relations and stomatal response of Quercus ilex were analysed under field conditions by comparing trees at two locations in a Mediterranean environment during two consecutive summers (1993 and 1994). We used the heat‐pulse velocity technique to estimate transpirational water use of trees during a 5 month period from June to November 1994. At the end of sap flow measurements, the trees were harvested, and the foliage and sapwood area measured. A distinct environmental gradient exists between the two sites with higher atmospheric CO2 concentrations in the proximity of a natural CO2 spring. Trees at the spring site have been growing for generations in elevated atmospheric CO2 concentrations. At both sites, maximum leaf conductance was related to predawn shoot water potential. The effects of water deficits on water relations and whole‐plant transpiration during the summer drought were severe. Leaf conductance and water potential recovered after major rainfall in September to predrought values. Sap flow, leaf conductance and predawn water potential decreased in parallel with increases in hydraulic resistance, reaching a minimum in mid‐summer. These relationships are in agreement with the hypothesis of the stomatal control of transpiration to prevent desiccation damage but also to avoid ‘runaway embolism’. Trees at the CO2 spring underwent less reduction in hydraulic resistance for a given value of predawn water potential. The decrease in leaf conductance caused by elevated CO2 was limited and tended to be less at high than at low atmospheric vapour pressure deficit. Mean (and diurnal) sap flux were consistently higher in the control site trees than in the CO2 spring trees. The degree of reduction in water use between the two sites varied among the summer periods. The control site trees had consistently higher sap flow at corresponding values of either sapwood cross‐sectional area or foliage area. Larger trees displayed smaller differences than smaller trees, between the control and the CO2 spring trees. A strong association between foliage area and sapwood cross‐sectional area was found in both the control and the CO2 spring trees, the latter supporting a smaller foliage area at the corresponding sapwood stem cross‐sectional area. The specific leaf area (SLA) of the foliage was not influenced by site. The results are discussed in terms of the effects of elevated CO2 on plant water use at the organ and whole‐tree scale.
How does a gymnosperm branch (Pseudotsuga menziesii) assume the hydraulic status of a main stem when it takes over as leader?
Authors: Spicer R. , Gartner B. L.
Published: March 2003

In most gymnosperms, resistance to the flow of water per unit path length through the main stem is less than that of lateral branches. Using branches, leaders, and branches that have replaced missing leaders (‘branch‐leaders’), we tested the hypothesis that branch‐leaders are at a hydraulic disadvantage. Reduced xylem transport efficiency in branch‐leaders relative to leaders could be expected both because of an initial disparity in hydraulic capacity, and because of the relatively impermeable compression wood formed in branch‐leaders during shoot reorientation. By subsampling branch‐leaders, we also tested the hypothesis that opposite wood (formed directly opposite compression wood) is more permeable than normal wood, and could, therefore, compensate for the presence of compression wood at the whole shoot level. Fifteen months after leader removal, branch‐leaders were intermediate between branches and leaders in their ability to supply foliage with water, suggesting a transition towards leader status that was not yet complete. Increased hydraulic capacity in branch‐leaders was the result of increased xylem cross‐sectional area per unit foliage, rather than an increase in permeability. Among subsampled wood types from basal branch‐leader segments, opposite wood was significantly less permeable than normal wood, suggesting that it does not compensate for the presence of compression wood.
Variation in the components of relative growth rate in 10Acaciaspecies from contrasting environments
Authors: Atkin O. K. , Schortemeyer M. , McFarlane N. , Evans J. R.
Published: March 2003

In this study we assessed the inherent relative growth rate (RGR) under controlled environment conditions of 10 contrastingAcaciaspecies from semi‐arid and mesic environments. For several of the species, compound pinnate leaves produced early in the seedling stage, were gradually replaced by phyllodes (expanded petioles that form simple lamina). Other species either did not form phyllodes, or only did so to a minor degree by the end of the study. Phyllode production was dominant in the four slow‐growingAcaciaspecies from semi‐arid environments (A. aneura, A. colei, A. coriaceaandA. tetragonophylla), with leaf production being exclusive or dominant in five (A. dealbata, A. implexa, A. mearnsii, A. melanoxylonandA. irrorata) of the six faster‐growing species from mesic environments. The exception wasA. salignawhich was fast growing but did produce phyllodes. From a carbon economy perspective, slow growth in the semi‐arid species was not associated with lower net assimilation rates or less plant mass allocated to foliage. Rather, the primary factor associated with their slow growth was a smaller foliage area per unit foliage mass. This was true for comparisons based on the mean over all harvests or at set plant masses. The production of phyllodes by the semi‐arid species substantially reduced foliage area per unit foliage mass, as this was lower for phyllodes than leaves in all species. To assess the impact that phyllode production had on ontogenetic changes in RGR, we modelled the situation where only leaves were formed. This analysis showed that changing from leaves to phyllodes substantially reduced the RGR. There was little difference in plant nitrogen concentration or the ratio of foliage nitrogen to plant nitrogen between the species. This resulted in foliage nitrogen productivity (dry mass gain per unit foliage nitrogen and time) being directly proportional to foliage area per unit foliage mass between species. We concluded that a smaller foliage area per unit foliage mass and phyllode production are the primary factors associated with lower RGR in contrastingAcaciaspecies.
Gas exchange and chlorophyll fluorescence responses of three south‐westernYuccaspecies to elevated CO2and high temperature
Authors: Huxman T. E. , Hamerlynck E. P. , Loik M. E. , Smith S. D.
Published: March 2003

The ability of seedlings to tolerate temperature extremes is important in determining the distribution of perennial plants in the arid south‐western USA, and the manner in which elevated CO2impacts the ability of plants to tolerate high temperatures is relatively unknown. Whereas the effects of chronic high temperature (30–38°C) and elevated CO2are comparatively well understood, little research has assessed plant performance in elevated CO2during extreme (> 45 °C) temperature events. We exposed three species ofYuccato 360 and 700μmol CO2mol–1for 8 months, then 9 d of high temperature (up to 53 °C) to evaluate the impacts of elevated CO2on the potential for photosynthetic function during external high temperature. Seedlings of a coastal C3species (Yucca whipplei), a desert C3species (Yucca brevifolia), and a desert CAM species (Yucca schidigera), were used to test for differences among functional groups. In general,Yuccasexposed to elevated CO2showed decreases in carboxylation efficiency as compared with plants grown at ambient before the initiation of high temperature. The coastal species (Y.whipplei) showed significant reductions (33%) in CO2saturated maximum assimilation rate (Amax), but the desert species (Y.brevifoliaandY.schidigera) showed no such reductions inAmax. Stomatal conductance was lower in elevated CO2as compared with ambient throughout the temperature event; however, there were species‐specific differences over time. Elevated CO2enhanced photosynthesis inY. whippleiat high temperatures for a period of 4 d, but not forY. brevifoliaorY. schidigera. Elevated CO2offset photoinhibition (measured asFv/Fm) inY. whippleias compared with ambient CO2, depending on exposure time to high temperature. StableFv/FminY. whippleioccurred in parallel with increases in the quantum yield of photosystem II (ΦPSII) at high temperatures in elevated CO2. The value ofΦPSIIremained constant or decreased with increasing temperature in all other treatment and species combinations. This suggests that the reductions inFv/Fmresulted from thermal energy dissipation in the pigment bed forY. brevifoliaandY. schidigera. The greater efficiency of photosystem II inY. whippleihelped to maintain photosynthetic function at high temperatures in elevated CO2. These patterns are in contrast to the hypothesis that high temperatures in elevated CO2would increase the potential for photoinhibition. Our results suggest that elevated CO2may offset high‐temperature stress in coastalYucca, but not in those species native to drier systems. Therefore, in the case ofY. whipplei, elevated CO2may allow plants to survive extreme temperature events, potentially relaxing the effects of high temperature on the establishment in novel habitats.
Induction of the activity of glycolytic enzymes correlates with enhanced hydrolysis of sucrose in the cytosol of transgenic potato tubers
Authors: TRETHEWEY R. N. , GEIGENBERGER P. , HENNIG A. , FLEISCHER‐NOTTER H. , MÜLLER‐RÖBER B. , WILLMITZER L.
Published: March 2003

The aim of this work was to define the metabolic factors which regulate the respiratory pathways in trangenic potato tubers. We previously found that respiration is enhanced in transgenic tubers which express a yeast invertase and a glucokinase from Zymomonas mobilis. In this study we investigated glycolysis in three further transgenic potato lines with profound changes in the mobilization of sucrose. We studied antisense ADPglucose pyrophosphorylase lines which are characterized by a reduction in starch accumulation and a significant build up of sucrose and related metabolic intermediates. We also report the generation of two novel double transgenic lines where the yeast invertase is expressed specifically in tubers of the ADPglucose pyrophosphorylase antisense line, targeted to either the cytosol or apopolast. We evaluated whether the localization of sucrose cleavage had an impact on the glycolytic induction, and assessed if invertase expression in the high‐sucrose background had any further effects on glycolysis. We found that induction of the glycolytic enzymes only occurs when the invertase is targeted to the cytosol, and that the extent of this induction was comparable in the wild type and antisenseADPglucose pyrophosphorylase backgrounds. We conclude that the signal regulating glycolysis is directly linked to cytosolic sucrose hydrolysis.
Effects of elevated ozone on CO2 uptake and leaf structure in sugar maple under two light environments
Authors: BÄCK J. , VANDERKLEIN D. W. , TOPA M. A.
Published: March 2003

The interactive effects of ozone and light on leaf structure, carbon dioxide uptake and short‐term carbon allocation of sugar maple (Acer saccharum Marsh.) seedlings were examined using gas exchange measurements and 14C‐macroautoradiographic techniques. Two‐year‐old sugar maple seedlings were fumigated from budbreak for 5 months with ambient or 3 × ambient ozone in open‐top chambers, receiving either 35% (high light) or 15% (low light) of full sunlight. Ozone accelerated leaf senescence, and reduced net photosynthesis, 14CO2 uptake and stomatal conductance, with the effects being most pronounced under low light. The proportion of intercellular space increased in leaves of seedlings grown under elevated ozone and low light, possibly enhancing the susceptibility of mesophyll cells to ozone by increasing the cumulative dose per mesophyll cell. Indeed, damage to spongy mesophyll cells in the elevated ozone × low light treatment was especially frequent. 14C macroautoradioraphy revealed heterogeneous uptake of 14CO2 in well defined areole regions, suggesting patchy stomatal behaviour in all treatments. However, in seedlings grown under elevated ozone and low light, the highest 14CO2 uptake occurred along larger veins, while interveinal regions exhibited little or no uptake. Although visible symptoms of ozone injury were not apparent in these seedlings, the cellular damage, reduced photosynthetic rates and reduced whole‐leaf chlorophyll levels corroborate the visual scaling of whole‐plant senescence, suggesting that the ozone × low light treatment accelerated senescence or senescence‐like injury in sugar maple.
Interdependence of CO2 and inorganic nitrogen on crassulacean acid metabolism and efficiency of nitrogen use by Littorella uniflora (L.) Aschers
Authors: BAATTRUP‐PEDERSEN A. , MADSEN T. V.
Published: March 2003

The hypothesis is tested that crassulacean acid metabolism (CAM) in isoetids is a mechanism which not only conserves inorganic carbon but also plays a role in nitrogen economy of the plants. This hypothesis was tested in an outdoor experiment, where Littorella uniflora (L.) Aschers. were grown at two CO2 and five inorganic nitrogen concentrations in a crossed factorial design. The growth of Littorella responded positively to enhanced nitrogen availability at high but not at low CO2 indicating that growth was limited by nitrogen at high CO2 only. For the nitrogen‐limited plants, the capacity for CAM (CAMcap) increased with the degree of nitrogen limitation of growth and an inverse coupling between CAM and tissue‐N was found. Although this might indicate a role of CAM in economizing on nitrogen in Littorella, the hypothesis was rejected for the following reasons: (1) although CAMcap was related to tissue‐N no relationship between tissue‐N and ambient CAM activity (CAMambient) was found whereas a close relationship would be expected if CAM was regulated by nitrogen availability; (2) the photosynthetic nitrogen use efficiency for high CO2‐grown plants declined with increased CAMambient and with CAMcap; and (3) growth per unit tissue‐N per unit time declined with increased CAMambient and CAMcap.
Isoprene synthase activity and its relation to isoprene emission in Quercus robur L. leaves
Authors: LEHNING A. , ZIMMER I. , STEINBRECHER R. , BRÜGGEMANN N. , SCHNITZLER J. ‐P.
Published: March 2003

Pedunculate oak (Quercus robur L.) is known as a strong isoprene (2‐methyl‐1,3‐butadiene) emitter. Diurnal changes in isoprene emission were determined by branch enclosure measurements. In contrast to the diurnal cycle in emission rates, specific isoprene synthase activity in the leaves remained unchanged. Based on in vitro enzyme activity and its temperature dependency, an isoprene synthesis capacity at specific leaf temperatures was calculated. The comparison of these ‘leaf temperature‐dependent enzyme capacities’ and the measured emission rates revealed that the enzyme activity of isoprene synthase is comparable to the observed isoprene emission rates. In addition, variation in the isoprene synthase activity of the leaves due to changes in light intensity during leaf development was investigated. A 50% reduction of light intensity by shading of single branches reduced isoprene synthase activity by ≈ 60% compared with full sunlight. The calculation of isoprene synthesis capacities based on enzymatic data obtained under optimum reaction conditions, corrected for actual leaf temperature and related to leaf surface area, provides a sound basis for predicting the isoprene emission potential of plants.
Does elevated atmospheric CO2 concentration inhibit mitochondrial respiration in green plants?
Authors: DRAKE B. G. , AZCON‐BIETO J. , BERRY J. , BUNCE J. , DIJKSTRA P. , FARRAR J. , GIFFORD R. M. , GONZALEZ‐MELER M. A. , KOCH G. , LAMBERS H. , SIEDOW J. , WULLSCHLEGER S.
Published: March 2003

ATP, adenosine triphosphate Km, Michaelis‐Menton coefficient Ca, concentration of CO2 in the air (μmol mol–1) NAD, oxidized nicotin adenine dinucleotide NADH, reduced nicotin adenine dinucleotide NADP, oxidized nicotin adenine phosphate dinucleotide NADPH, reduced nicotine adenine phosphate dinucleotide R, rate of respiration per unit DW [μmol g  DW–1], Rubisco, ribulose‐1,5‐bisphosphate carboxylase/oxygenase Vc,max, maximum in vivo rate of carboxylation at Rubisco (μmol m–2 s–1)  There is abundant evidence that a reduction in mitochondrial respiration of plants occurs when atmospheric CO2 (Ca) is increased. Recent reviews suggest that doubling the present Ca will reduce the respiration rate [per unit dry weight (DW)] by 15 to 18%. The effect has two components: an immediate, reversible effect observed in leaves, stems, and roots of plants as well as soil microbes, and an irreversible effect which occurs as a consequence of growth in elevated Ca and appears to be specific to C3 species. The direct effect has been correlated with inhibition of certain respiratory enzymes, namely cytochrome‐c‐oxidase and succinate dehydrogenase, and the indirect or acclimation effect may be related to changes in tissue composition. Although no satisfactory mechanisms to explain these effects have been demonstrated, plausible mechanisms have been proposed and await experimental testing. These are carbamylation of proteins and direct inhibition of enzymes of respiration. A reduction of foliar respiration of 15% by doubling present ambient Ca would represent 3 Gt of carbon per annum in the global carbon budget.
A prolonged cold treatment‐induced cytochrome P450 gene from Arabidopsis thaliana
Authors: Bilodeau P. , Udvardi M. K. , Peacock W. J. , Dennis E. S.
Published: March 2003

The characterization of a full length cytochrome P450 (cyt P450) cDNA clone from Arabidopsis thaliana (CYP83A1) which showed a 2–4‐fold transcriptional induction in the shoot apex following a prolonged low temperature treatment is reported. CYP83A1 appears to be encoded by a single copy gene. The gene contains one intron in a position identical to that found in other class A P450 genes. Putative cis‐acting elements implicated in the regulation of phenylpropanoid/flavonoid biosynthetic genes (SBF‐1, MYB Ph3, and P‐MYB) were identified in the promoter region. The coding region was functional in yeast in binding carbon monoxide and tetcyclacis, suggesting that CYP83A1 was produced in its native state enabling it to interact properly with these two cyt P450 inhibitors. However, no activity could be detected when assayed in P450‐dependent reactions of gibberellin or phenylpropanoid biosynthesis. Transgenic Arabidopsis plants expressing sense and antisense transcripts did not show any abnormalities or altered flowering time with or without vernalization.
Age‐related decline in stand productivity: the role of structural acclimation under hydraulic constraints
Authors: Magnani F. , Mencuccini M. , Grace J.
Published: March 2003

The decline in above‐ground net primary productivity (Pa) that is usually observed in forest stands has been variously attributed to respiration, nutrient or hydraulic limitations. A novel model is proposed to explain the phenomenon and the co‐occurring changes in the balance between foliage, conducting sapwood and fine roots. The model is based on the hypothesis that a functional homeostasis in water transport is maintained irrespective of age: hydraulic resistances through the plant must be finely tuned to transpiration rates so as to avoid extremely negative water potentials that could result in diffuse xylem embolism and foliage dieback, in agreement with experimental evidence. As the plant grows taller, allocation is predicted to shift from foliage to transport tissues, most notably to fine roots. Higher respiration and fine root turnover would result in the observed decline inPa. The predictions of the model have been compared with experimental data from a chronosequence ofPinus sylvestrisstands. The observed reduction inPais conveniently explained by concurrent modifications in leaf area index and plant structure. Changes in allometry and shoot hydraulic conductance with age are successfully predicted by the principle of functional homeostasis.
Water movement between epidermal cells of barley leaves – a symplastic connection?
Authors: Fricke W.
Published: March 2003

Using the cell‐pressure probe the possibility of symplastic water flow between cells of the upper epidermis of barley leaves was investigated. Cells analysed had either an intact or a more or less damaged cellular environment. Cell damage caused large pressure differentials (0·9 MPa) between damaged and adjacent intact cells. Turgor in cells adjacent to damaged cells decreased significantly. Turgor decreases were the larger the more the adjacent, damaged cell was leaking (decreases by 2·5–4·4%). In cells surrounded by a patch of leaking cells, turgor decreased the most, by 18·1–20·4%. In contrast, half‐times of water exchange (T1/2) of cells were not affected by a damaged cellular environment. Assuming that in the barley leaf epidermis, plasmodesmata close at pressure‐differentials at or exceeding 0·2 MPa as shown for other plant cells (The Plant Journal 2, 741–750; Canadian Journal of Botany 65, 509–511), it is concluded that symplastic water flow contributes insignificantly to water exchange between cells. Mechanical damage to one individual cell is enough to induce significant turgor changes in neighbouring cells.