bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diel patterns of reproductive activities in the tomato fruit fly, Neoceratitis cyanescens
Authors: Brevault T. , Quilici S. 
Published: March 2003

SummaryWe describe the diurnal temporal and spatial patterns of reproductive activities (mating and ovipositing) of adult tomato fruit flies, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae), under laboratory, field‐cage and field conditions. The distribution pattern of flies in the different habitats (host and non‐host plants) showed temporal, physiological and sexual differences. Mature females were observed to frequent host plants preferentially, particularly in the late afternoon. By contrast, immature females preferred to rest on non‐host plants throughout the day. Males frequented mainly non‐host plants but some were observed on host fruits in the morning. Mating activity took place preferentially on non‐host plants, in the morning. In laboratory cages, females showed a strong daily propensity to engage in mating behaviour; the mean percentage of mating females was 88 ± 5%. Time allotted to this activity (4 h 52 min ± 1 h 23 min in laboratory cages and at least 3 h for the mating pairs observed in the field) appeared considerable compared to the time required to satisfy feeding or oviposition activities. Except for a few ovipositing females observed in the morning, oviposition activities occurred mainly in the late afternoon.
Anthocorid predators learn to associate herbivore‐induced plant volatiles with presence or absence of prey
Authors: Drukker Bas , Bruin Jan , Sabelis Maurice W. 
Published: March 2003

SummaryWe investigated how the plant‐inhabiting, anthocorid predator, Anthocoris nemoralis, copes with variation in prey, host plant and associated herbivore‐induced plant volatiles and in particular whether the preference for these plant odours is innate or acquired. We found a marked difference between the olfactory response of orchard‐caught predators and that of their first generation reared on flour moth eggs in the laboratory, i.e. under conditions free of herbivory‐induced volatiles. Whereas the orchard‐caught predators preferred odour from psyllid‐infested pear leaves, when offered against clean air in a Y‐tube olfactometer, the laboratory‐reared first generation of (naive) predators did not. The same difference was found when a single component (methyl salicylate) of the herbivore‐induced plant volatiles was offered against clean air. After experiencing methyl salicylate with prey, however, the laboratory‐reared predators showed a pronounced preference for this volatile. This acquired preference did not depend on whether the volatile had been experienced in the juvenile period or in the adult phase, but it did depend on whether it had been offered in presence or absence of prey. In the first case, they were attracted to the plant volatile in subsequent olfactometer experiments, but when the volatile had been offered during a period of prey deprivation, the predators were not attracted. We conclude that associative learning is the most likely mechanism underlying acquired odour preference.
Food availability controls the onset of metamorphosis in the dung beetle Onthophagus taurus (Coleoptera: Scarabaeidae)
Authors: Shafiei Majid , Moczek Armin P. , Nijhout H. Frederik 
Published: March 2003

SummaryIn nature, larvae of the dung beetle Onthophagus taurus (Schreber 1759) are confronted with significant variation in the availability of food without the option of locating new resources. Here we explore how variation in feeding conditions during the final larval instar affects larval growth and the timing of pupation. We found that larvae respond to food deprivation with a reduction in the length of the instar and premature pupation, leading to the early eclosion of a small adult. To achieve pupation, larvae required access to food for at least the first 5 days of the final instar (= 30% of mean third‐instar duration in control individuals), and had to exceed a weight of 0.08 g (= 58% of mean peak weight in control individuals). Larvae that were allowed to feed longer exhibited higher pupation success, but increased larval weight at the time of food deprivation did not result in increased pupation success except for larvae weighing > 0.14 g. Larvae responded to food deprivation by initiating and undergoing the same sequence of developmental events, requiring the same amount of time, as ad libitum‐fed larvae once those had reached their natural peak weight. Our results reveal a striking degree of flexibility in the dynamics and timing of larval development in O. taurus. They also suggest that premature exhaustion of a larva's food supply can serve as a cue for the initiation of metamorphosis. Premature metamorphosis in response to food deprivation has been documented in amphibians, but this is, to the best of our knowledge, the first time such a behaviour has been documented for a holometabolous insect. We discuss our findings in the context of the natural history and behavioural ecology of onthophagine beetles.
Multiple mechanisms control the expression of abscisic acid (ABA)‐requiring genes in tomato plants exposed to soil water deficit
Authors: Cohen A. , Moses M. S. , Plant Á. L. , Bray E. A. 
Published: March 2003

ABSTRACTElevated levels of abscisic acid (ABA) are required for the expression of several genes during water deficit. The expression patterns of the ABA‐requiring genes, le4, le16, le25 and his1‐s, differed during a 4 d period of water deficit and a 24 h recovery period in intact tomato plants. During water deficit, a strong correlation between ABA content and mRNA accumulation was observed for le16, with only a moderate or poor correlation observed between the accumulation of ABA and the other mRNAs. The regulation of le4 and le16 can be accounted for by an increase in transcription rate, while components of post‐transcriptional regulation are implicated in the regulation of the le25 and his1‐s genes. A strong correlation between leaf ABA content and the transcription rate of le4 and le16 during the stress and recovery periods was observed. Protein synthesis was not necessary for the expression of the four genes. However, the mRNA content of le25 increased in the presence of translation inhibitors plus ABA, implicating inhibition of a transcriptional repressor. The regulation of gene expression in response to stress is complex; although ABA was required for the regulation of the genes in this study, there must be additional control mechanisms that interact with components of the ABA regulatory machinery.
Adaptive nature of the transition phases in development: the case of Sorghum bicolor
Authors: Amzallag G. N. 
Published: March 2003

ABSTRACTAn increase in tolerance to salinity is induced in Sorghum bicolor by exposure to a sublethal concentration of NaCl during early vegetative development. The phase of competence for induction of this response, termed salt adaptation, is well defined in time and it coincides with the emergence of the first adventitious roots. The link between these events was investigated. Competence for salt adaptation varies among genotypes. It is shown that competence is especially high for genotypes in which the link between the seminal root and the shoot is reduced during emergence of the adventitious root. These data relate the capacity for salt adaptation with development in the absence of NaCl, suggesting that: (i) functional integration of the adventitious roots within the whole plant has an adaptive nature in normal development; (ii) salt adaptation results from an integration of the environmental constraint (NaCl) during this developmental readjustment. It is concluded that perturbations generated by emergence of a new organ are the cause of rapid variations in sensitivity required to open a competence window.
Phosphate uptake in Chara: membrane transport via Na/Pi cotransport
Authors: Reid R. J. , Mimura T. , Ohsumi Y. , Walker N. A. , Smith F. A. 
Published: March 2003

ABSTRACTPhosphate uptake in the freshwater charophyte plant Chara corallina was found to be strongly dependent on the presence of Na in the external medium. Based on the reciprocal stimulations of 32Pi uptake by Na and 22Na uptake by Pi, the logical mechanism for Pi uptake appears to be a nNa/Pi symport with a half‐maximal stimulation (Km) for Na of approximately 300 μM and a Km for Pi of approximately 10 μM. Comparison of the stimulations of 32Pi and 22Na influxes at pH 6 gives a stoichiometry of Na : Pi of 5·68. The reduction in Pi influx with increasing pH is consistent with the transported species being the monovalent H2PO4−. In voltage‐clamp experiments, currents elicited by Pi in the presence of Na were equivalent to an influx of positive charge which exceeded the measured influxes of 32P by a factor of 6·26. Intracellular perfusion was used to examine the dependence of Pi influx on ATP and Na. In perfused cells, Pi influx was low when ATP was absent from the internal medium or Na was absent from the external medium. Addition of ATP alone had little effect whereas addition of Na alone increased the 32Pi influx slightly. Addition of both ATP and Na together restored Pi influx to rates comparable to those of intact cells. It is suggested that the ATP is required for membrane hyperpolarization which in turn drives the highly electrogenic flux of Pi with up to 6 Na. However, consideration of the electrochemical potential differences for Na and Pi at pH less than 6 shows that nNa/Pi would not be feasible. It is suggested that at low pH, H+ may substitute for Na.
Susceptibility to photoinhibition of three deciduous broadleaf tree species with different successional traits raised under various light regimes
Authors: Kitao M. , Lei T. T. , Koike T. , Tobita H. , Maruyama Y. 
Published: March 2003

ABSTRACTThe susceptibility to photoinhibition of tree species from three different successional stages were examined using chlorophyll fluorescence and gas exchange techniques. The three deciduous broadleaf tree species were Betula platyphylla var. japonica, pioneer and early successional, Quercus mongolica, intermediate shade‐tolerant and mid‐successional, and Acer mono, shade‐tolerant and late successional. Tree seedlings were raised under three light regimes: full sunlight (open), 10% full sun, and 5% full sun. Susceptibility to photoinhibition was assessed on the basis of the recovery kinetics of the ratio of vaviable to maximum fluorescence (Fv/Fm) of detached leaf discs exposed to about 2000 μmol m−1 s−1 photon flux density (PFD) for 2 h under controlled conditions (25 to 28 °C, fully hydrated). Differences in susceptibility to photodamage among species were not significant in the open and 10% full sun treatments. But in 5% full sun, B. platyphylla sustained a significantly greater photodamage than other species, probably associated with having the lowest photosynthetic capacity indicated by light‐saturated photosynthetic rate (B. platyphylla, 9·87, 5·85 and 2·82; Q. mongolica, 8·05, 6·28 and 4·41; A. mono, 7·93, 6·11 and 5·08 μmol CO2 m−1 s−1for open, 10% and 5% full sun, respectively). To simulate a gap formation and assess its complex effects including high temperature and water stress in addition to strong light on the susceptibility to photoinhibition, we examined photoinhibition in the field by means of monitoring ΔF/F′m on the first day of transfer to natural daylight. Compared with ΔF/F′m in AM, the lower ΔF/F′m in PM responding to lower PFD following high PFD around noon indicated that photoinhibition occurred in plants grown in 10 and 5% full sun. The diurnal changes of ΔF/F′m showed that Q. mongolica grown in 5% full sun was less susceptible to photoinhibition than A. mono although they showed little differences both in photosynthetic capacity in intact leaves and susceptibility to photoinhibition based on leaf disc measurements. These results suggest that shade‐grown Q. mongolica had a higher tolerance for additional stresses such as high temperature and water stress in the field, possibly due to their lower plasticity in leaf anatomy to low light environment.
Cell growth analysis during steady and non‐steady growth in leaves of perennial ryegrass (Lolium perenne L.) subject to defoliation
Authors: Schäufele R. , Schnyder H. 
Published: March 2003

ABSTRACTThe effect of defoliation on leaf elongation rate (LER) and on the spatial distribution of epidermal cell lengths in the leaf growth zone was studied in vegetative main tillers of perennial ryegrass (Lolium perenne L. cv Modus) grown in a controlled environment. A new material approach was used to analyse the responses of epidermal cell expansion and production during the initial, non‐steady growth phase following defoliation. The analysis involved assigning an identity to individual expanding cells, assessing the displacement and estimating the expansion of cells with assigned identity during day 1 and day 2 after defoliation. LER decreased by 34% during the first 2 d after defoliation and did not recover to the pre‐defoliation rate within the 14 day regrowth period. Decreased LER on day 1 and day 2 after defoliation was associated with (i) a decrease in the length of the leaf growth zone; (ii) a decrease in the length at which epidermal cells stopped expanding; (iii) a reduced expansion of cells at intermediate growth stages; and (iv) a reduction in cell production (i.e. division) and an associated decrease in the number of expanding cells in the growth zone. However, defoliation had no effect on the expansion of cells located in the proximal part of the growth zone. Reduced LER at 14 d after defoliation was associated with a reduced cell production rate (27% lower than the pre‐defoliation rate) and decreased final cell size (− 28%).
Evidence implicating a novel thiol methyltransferase in the detoxification of glucosinolate hydrolysis products in Brassica oleracea L.
Authors: Attieh J. , Kleppinger‐Sparace K. F. , Nunes C. , Sparace S. A. , Saini H. S. 
Published: March 2003

ABSTRACTThe physiological relevance of a novel thiol methyltransferase from cabbage, and its possible role in sulphur metabolism have been investigated. The enzyme was absent from the chloroplast, the site of sulphate reduction, and was localized in the cytosol. Potential substrates were initially screened on the basis of their ability to inhibit the methylation of iodide, a previously known substrate for the enzyme. Thiocyanate, 4,4′‐thiobisbenzenethiol, thiophenol, and thiosalicylic acid were identified as possible substrates. Methylation of these thiols by the purified enzyme using [Methyl‐3H]S‐adenosyl‐
L‐methionine confirmed their nature as substrates. The purified enzyme strongly preferred thiocyanate as a methyl acceptor. The enzyme had Km values of 11, 51, 250 and 746 mmol m−3 for thiocyanate, 4,4′‐thiobisbenzenethiol, thiophenol and thiosalicylic acid, respectively. The identity of methylthiocyanate as the product of thiocyanate methylation by the purified enzyme was confirmed by mass spectrometry. The enzyme was strictly associated with glucosinolate‐containing plants. Thiol substrates of the enzyme are known products of glucosinolate hydrolysis. Our observations indicate that this enzyme could be involved in the detoxification of reactive thiols produced upon glucosinolate degradation in these plants.
Detopping causes production of intercellular space occlusions in both the cortex and infected region of soybean nodules
Authors: James E. K. , Iannetta P. P. M. , Deeks L. , Sprent J. I. , Minchin F. R. 
Published: March 2003

ABSTRACTA structural analysis was conducted to determine whether glycoprotein‐containing intercellular space occlusions are involved in medium‐term regulation of O2 diffusion in soybean (Glycine max) nodules. Alterations in O2 diffusion were induced by a 3 h detopping treatment, and glycoprotein was immunolocalized with the monoclonal antibodies MAC236 and MAC265. Western blots of unstressed nodules revealed that these antibodies recognize antigens with two different molecular weights in soybean nodules. Tissue printing of halved nodules showed that both antigens were present in fresh nodules from control and 3 h detopped plants. The main localization appeared to be the inner cortex, but some immunolabelling also occurred in the infected region. ELISAs demonstrated a significant increase in total nodule concentration of intercellular glycoprotein following detopping, and cryosections of fresh nodules from this treatment also showed localization of antigens within the intercellular spaces of the infected region. The production of intercellular space occlusions in both the mid‐cortex and infected regions after 3 h detopping was confirmed by light microscopy and silver‐enhanced immunolabelling; cortical changes were quantified by image analysis techniques. Electron microscopy revealed that the occlusions within the infected region were less dense and less heavily labelled than those in the cortex. These results are discussed in relation to O2 diffusion regulation in soybean nodules
Why are higher plants green? Evolution of the higher plant photosynthetic pigment complement
Authors: Nishio J. N. 
Published: March 2003

ABSTRACTThe physiological reason that higher plants are green is unknown. Other photosynthetic organisms utilize pigments that strongly absorb green light; therefore, there must have been natural forces that ‘selected’ the photosynthetic pigments found in higher plants. Based on previously published data and our recent findings about green light and photosynthesis within leaves (Sun et al.), a specific functional role is described for the primary photosynthetic pigments of higher plants, that were derived from green algal progenitors. The particular absorptive characteristics of chlorophylls a and b appear to perform two contradictory, but necessary functions in higher plants. Firstly, chlorophylls a and b absorb light for maximum utilization under non‐saturating conditions, a function that is well understood. Secondly, they can act as protective pigments under over‐saturating light conditions, when absorbed light is dissipated as heat. Under such conditions, a significant portion of light can also be efficiently utilized, especially in the bottom portion of the leaf, that is mainly illuminated by green light and not down‐regulated. The second function may have been the selective force that gave rise to the extremely successful terrestrial plants, that evolved from green algae.
Source metabolism dominates the control of source to sink carbon flux in tuberizing potato plants throughout the diurnal cycle and under a range of environmental conditions
Authors: Sweetlove L. J. , Hill S. A. 
Published: March 2003

ABSTRACTThe aim of this work was to investigate the effect of environmental conditions on the control of source to sink carbon flux in potato during tuberization. Top down metabolic control analysis was used to quantitatively determine the extent to which source and sink reactions control the flux from CO2 to the tuber. Under all conditions investigated (beginning of the dark period, low nitrogen availability, variation in temperature) source metabolism accounts for at least 80% of the control. In plants grown with limiting nitrogen, or when measurements were made at low temperature the extent to which source metabolism controls flux increased to 90%.
Influence of carbon dioxide enrichment, ozone and nitrogen fertilization on cotton (Gossypium hirsutumL.) leaf and root composition
Authors: Booker F. L. 
Published: March 2003

ABSTRACTThe objective of this study was to test whether elevated [CO2], [O3] and nitrogen (N) fertility altered leaf mass per area (LMPA), non‐structural carbohydrate (TNC), N, lignin (LTGA) and proanthocyanidin (PA) concentrations in cotton (Gossypium hirsutumL.) leaves and roots. Cotton was grown in 14 dm3pots with either sufficient (0·8 g N dm−3) or deficient (0·4 and 0·2 g N dm−3) N fertilization, and treated in open‐top chambers with either ambient or elevated (+175 and+350μmol mol−1) [CO2] in combination with either charcoal‐filtered air (CF) or non‐filtered air plus 1·5 times ambient [O3]. At about 50 d after planting, LMPA, starch and PA concentrations in canopy leaves were as much as 51–72% higher in plants treated with elevated [CO2] compared with plants treated with ambient [CO2], whereas leaf N concentration was 29% lower in elevated [CO2]‐treated plants compared with controls. None of the treatments had a major effect on LTGA concentrations on a TNC‐free mass basis. LMPA and starch levels were up to 48% lower in plants treated with elevated [O3] and ambient [CO2] compared with CF controls, although the elevated [O3] effect was diminished when plants were treated concurrently with elevated [CO2]. On a total mass basis, leaf N and PA concentrations were higher in samples treated with elevated [O3] in ambient [CO2], but the difference was much reduced by elevated [CO2]. On a TNC‐free basis, however, elevated [O3] had little effect on tissue N and PA concentrations. Fertilization treatments resulted in higher PA and lower N concentrations in tissues from the deficient N fertility treatments. The experiment showed that suppression by elevated [O3] of LMPA and starch was largely prevented by elevated [CO2], and that interpretation of [CO2] and [O3] effects should include comparisons on a TNC‐free basis. Overall, the experiment indicated that allocation to starch and PA may be related to how environmental factors affect source–sink relationships in plants, although the effects of elevated [O3] on secondary metabolites differed in this respect.
Molecular markers for ozone stress isolated by suppression subtractive hybridization: specificity of gene expression and identification of a novel stress‐regulated gene
Authors: Sävenstrand H. , Brosché M. , Ängehagen M. , Strid Å. 
Published: March 2003

ABSTRACTSuppression subtractive hybridization was used to identify genes regulated by ozone (100 nmol mol−1) in Pisum sativum. One novel gene (named PsUod1) was found. In addition, mRNA levels for four genes (encoding lipid transfer protein, pre‐hevein‐like protein, leucine‐rich repeat protein, and disease‐resistance response protein 230), which previously were shown to be regulated by biotic stress, increased. Finally, mRNA species for two genes (encoding extensin and pathogenesis‐related protein 4A), previously shown to be regulated by ozone in other species, were found to increase in abundance. The ozone‐specificity of the expression of these genes was studied by using UV‐B radiation. PsUod1 and the genes encoding extensin, leucine‐rich repeat protein, and disease‐resistance response protein 230, were differentially regulated when comparing ozone and UV‐B. Moreover, the mRNA levels for extensin, leucine‐rich repeat protein and disease‐resistance response protein 230 all increased under NaCl and aluminium stress and after wounding, whereas the message abundance for PsUod1 was unchanged under these stresses. Thus, in general, ozone caused changes similar to wounding, salt stress and aluminium stress, whereas UV‐B radiation regulated gene expression differently.