bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stomatal acclimation over a subambient to elevated CO2 gradient in a C3/C4 grassland
Authors: Maherali H. , Reid C. D. , Polley H. W. , Johnson H. B. , Jackson R. B. 
Published: March 2003

AbstractAn investigation to determine whether stomatal acclimation to [CO2] occurred in C3/C4 grassland plants grown across a range of [CO2] (200–550 µmol mol−1) in the field was carried out. Acclimation was assessed by measuring the response of stomatal conductance (gs) to a range of intercellular CO2 (a gs–Ci curve) at each growth [CO2] in the third and fourth growing seasons of the treatment. The gs–Ci response curves for Solanum dimidiatum (C3 perennial forb) differed significantly across [CO2] treatments, suggesting that stomatal acclimation had occurred. Evidence of non–linear stomatal acclimation to [CO2] in this species was also found as maximum gs (gsmax; gs measured at the lowest Ci) increased with decreasing growth [CO2] only below 400 µmol mol−1. The substantial increase in gs at subambient [CO2] for S. dimidiatum was weakly correlated with the maximum velocity of carboxylation (Vcmax; r2 = 0·27) and was not associated with CO2 saturated photosynthesis (Amax). The response of gs to Ci did not vary with growth [CO2] in Bromus japonicus (C3 annual grass) or Bothriochloa ischaemum (C4 perennial grass), suggesting that stomatal acclimation had not occurred in these species. Stomatal density, which increased with rising [CO2] in both C3 species, was not correlated with gs. Larger stomatal size at subambient [CO2], however, may be associated with stomatal acclimation in S. dimidiatum. Incorporating stomatal acclimation into modelling studies could improve the ability to predict changes in ecosystem water fluxes and water availability with rising CO2 and to understand their magnitudes relative to the past.
Transient releases of acetaldehyde from tree leaves − products of a pyruvate overflow mechanism?
Authors: Karl T. , Curtis A. J. , Rosenstiel T. N. , Monson R. K. , Fall R. 
Published: March 2003

AbstractEmissions of acetaldehyde from tree leaves were investigated by proton‐transfer‐reaction mass spectrometry (PTR‐MS), a technique that allows simultaneous monitoring of different leaf volatiles, and confirmed by derivatization and high‐performance liquid chromatography analysis. Bursts of acetaldehyde were released by sycamore, aspen, cottonwood and maple leaves following light–dark transitions; isoprene emission served as a measure of chloroplastic processes. Acetaldehyde bursts were not accompanied by ethanol, but exposure of leaves to inhibitors of pyruvate transport or respiration, or anoxia, led to much larger releases of acetaldehyde, accompanied by ethanol under anoxic conditions. These same leaves have an oxidative pathway for ethanol present in the transpiration stream, resulting in acetaldehyde emissions that are inhibited in vivo by 4‐methylpyrazole, an alcohol dehydrogenase (Adh) inhibitor. Labelling of leaf volatiles with 13CO2 suggested that the pools of cytosolic pyruvate, the proposed precursor of acetaldehyde bursts, were derived from both recent photosynthesis and cytosolic carbon sources. We hypothesize that releases of acetaldehyde during light–dark transitions result from a pyruvate overflow mechanism controlled by cytosolic pyruvate levels and pyruvate decarboxylase activity. These results suggest that leaves of woody plants contribute reactive acetaldehyde to the atmosphere under different conditions: (1) metabolic states that promote the accumulation of cytosolic pyruvate, triggering the pyruvate decarboxylase reaction; and (2) leaf ethanol oxidation resulting from ethanol transported from anoxic tissues.
Temperature dependence of two parameters in a photosynthesis model
Authors: Leuning R. 
Published: March 2003

AbstractThe temperature dependence of the photosynthetic parameters Vcmax, the maximum catalytic rate of the enzyme Rubisco, and Jmax, the maximum electron transport rate, were examined using published datasets. An Arrehenius equation, modified to account for decreases in each parameter at high temperatures, satisfactorily described the temperature response for both parameters. There was remarkable conformity in Vcmax and Jmax between all plants at Tleaf < 25 °C, when each parameter was normalized by their respective values at 25 °C (Vcmax0 and Jmax0), but showed a high degree of variability between and within species at Tleaf > 30 °C. For both normalized Vcmax and Jmax, the maximum fractional error introduced by assuming a common temperature response function is < ± 0·1 for most plants and < ± 0·22 for all plants when Tleaf < 25 °C. Fractional errors are typically < ± 0·45 in the temperature range 25–30 °C, but very large errors occur when a common function is used to estimate the photosynthetic parameters at temperatures > 30 °C. The ratio Jmax/Vcmax varies with temperature, but analysis of the ratio at Tleaf = 25 °C using the fitted mean temperature response functions results in Jmax0/Vcmax0 = 2·00 ± 0·60 (SD, n = 43).
Causes of variation in cold hardiness among fast‐growing willows (Salix spp.) with particular reference to their inherent rates of cold hardening
Authors: Lennartsson M. , Ögren E. 
Published: March 2003

AbstractCauses of variation in cold hardiness in the autumn were assessed among closely related, fast‐growing clones of willow of northern/continental and southern/maritime origins, under controlled regimes and natural conditions. Cold hardiness was assessed by controlled freezing followed by injury analysis, based on measurements of chlorophyll fluorescence (stems) and electrolyte leakage (leaves). During growth at a given temperature, the cold hardiness of the clones' stems was negatively correlated with their rate of growth. This apparently phenotypic variation was independent of temperature and, hence, the absolute growth rate. At later stages, cold hardiness of stems varied mainly with respect to genetic differences in the timing and rate of cold hardening. Cold hardening began up to 7 weeks earlier in northern/continental clones, and their rates of hardening in cool temperature regimes were up to three times higher than in southern/maritime clones. Ranking of clones with respect to rates was essentially the same whether natural or abrupt reductions of day length were used to trigger cold hardening. Results closely agreed with those of a previous field trial. Comparisons of rates at cool and warm temperatures suggest that cold hardening became increasingly dependent on cool temperatures with time. Increasing sucrose‐to‐glucose ratios, and especially dry‐to‐fresh weight ratios, paralleled early cold hardening. Before leaves were shed in the autumn they underwent cold hardening in parallel with stems, eventually allowing them to tolerate temperatures down to −10 °C.
Effect of chilling on antioxidant enzymes and DPPH‐radical scavenging activity of high‐ and low‐vigour cucumber seedling radicles
Authors: Kang H.‐M. , Saltveit M. E. 
Published: March 2003

AbstractThe chilling tolerance of cucumber seedling radicles was influenced by their relative levels of vigour. Radicles of high‐vigour seedlings grew to 20 mm in length in 36 h at 25 °C, whereas it took 60 h for low‐vigour seedling radicles to reach that length. Chilling at 2·5 °C for 48 h inhibited the subsequent growth of high‐ and low‐vigour seedlings by 39 and 68%, respectively. The 2,3,5‐triphenyltetrazolium chloride (TTC) viability index, and α,α‐diphenyl‐β‐picrylhydrazyl (DPPH)‐radical scavenging activity were higher in high than low‐vigour radicles. Higher ascorbate peroxidase (APX) and catalase (CAT) enzyme activity, DPPH‐radical scavenging activity, and recovery of CAT activity after chilling in high‐vigour radicles corresponded with their higher level of chilling tolerance in comparison with low‐vigour radicles. In contrast, elevated levels of superoxide dismutase, glutathione reductase and guaiacol peroxidase appear to be correlated with chilling injury since they only showed substantial increases in activity in the more chilling‐­sensitive low‐vigour radicles after chilling. Manipulation of APX, CAT, and/or DPPH activity could produce plants with superior and persistent chilling tolerance.
Regulation of root respiration in two species of Plantago that differ in relative growth rate: the effect of short‐ and long‐term changes in temperature
Authors: Covey‐Crump E. M. , Attwood R. G. , Atkin O. K. 
Published: March 2003

AbstractThis study investigates the effect of short‐ and long‐term changesin temperature on the regulation of root respiratory O2 uptakeby substrate supply, adenylate restriction and/or the capacityof the respiratory system. The species investigated were the lowland Plantagolanceolata L. and alpine Plantago euryphylla Briggs, Carolin& Pulley, which are inherently fast‐ and slow‐growing, respectively. Theplants were grown hydroponically in a controlled environment (constant23 °C). The effect of long‐term exposure to lowtemperature on regulation of respiration was also assessed in P.lanceolata using plants transferred to 15/10 °C(day/night) for 7 d. Exogenous glucose and uncoupler (CCCP)were used to assess the extent to which respiration rates were limitedby substrate supply and adenylates. The results suggest that adenylatesand/or substrate supply exert the greatest control overrespiration at moderate temperatures (e.g. 15–30 °C)in both species. At low temperatures (5–15 °C),CCCP and glucose had little effect on respiration, suggesting thatrespiration was limited by enzyme capacity alone. The Q10 (proportionalincrease of respiration per 10 °C) of respirationwas increased following the addition of CCCP and/or exogenousglucose. The degree of stimulation by CCCP was considerably lowerin P. euryphylla than P. lanceolata. This suggeststhat respiration rates operate much closer to the maximum capacity in P.euryphylla than P. lanceolata. When P. lanceolata wastransferred to 15 °C for 7 d, respirationacclimated to the lower growth temperature (as demonstrated by an increasein respiration rates measured at 25 °C). In addition,the Q10 was higher, and the stimulatory effectof exogenous glucose and CCCP lower, in the cold‐acclimated rootsin comparison with their warm‐grown counterparts. Acclimation of P.lanceolata to different day/night‐time temperatureregimes was also investigated. The low night‐time temperature wasfound to be the most important factor influencing acclimation. The Q10 valueswere also higher in plants exposed to the lowest night‐time temperature.The results demonstrate that short‐ and long‐term changes in temperaturealter the importance of substrate supply, adenylates and capacityof respiratory enzymes in regulating respiratory flux.
Metabolic regulation of genes encoding cytochromecand cytochromecoxidase subunit Vb inArabidopsis
Authors: WELCHEN E. , CHAN R. L. , GONZALEZ D. H. 
Published: March 2003

AbstractIn this study an analysis of the expression of fourArabidopsisnuclear genes encoding components of the mitochondrial cyanide‐sensitive respiratory pathway: two genes encoding cytochromecoxidase subunit Vb (COX5b) and two genes encoding cytochromec(Cytc), was carried out. Northern blot analysis indicated that these genes are expressed in several organs. Incubation of plants in solutions containing metabolizable sugars produced an increase in transcript levels. The effect of carbohydrates showed the same time and concentration dependence for the four genes, suggesting the operation of a common regulatory mechanism. Light produced an increase in transcript levels, although smaller than that produced by sugars. Incubation of plants in solutions with different nitrogen sources also produced changes in expression. In the presence of ammonium, higher transcript levels were observed with respect to plants treated with either nitrogen‐free or nitrate solutions. Nitrate, on the other hand, produced a slight decrease in transcript levels and abolished the inducing effect of ammonium. Reporter enzyme activity in transgenic plants carrying a fusion of aCytcgene promoter with the beta‐glucuronidase coding region was increased by the inclusion of sucrose and ammonium in the culture medium. The present results suggest that carbon and nitrogen metabolites act in concert to regulate the expression of different components of the cyanide‐sensitive respiratory pathway.
Long‐distance transport in non‐vascular plants
Authors: RAVEN J. A. 
Published: March 2003

ABSTRACTMany macroalgae have significant spatial differentiation involving higher rate resource use at a site than of acquisition of that resource from the environment at that site. Long‐distance symplasmic transport of solutes occurs in some large green algae where the solutes are moved in streaming cytoplasm. In some large brown algae there is evidence of long‐distance symplasmic transport of organic C and other solutes. Structural and physiological data suggest that while the transport in ‘sieve tubes’ of Macrocystis might be by a Munch pressure flow mechanism the transport in many other brown algae is less likely to be by this mechanism. Less is known of long‐distance symplasmic transport in red algae. In terrestrial bryophytes transpiration occurs and in some liverworts and many mosses (but not in hornworts) there are files of dead cells in their tissues which may, and in some cases certainly, function in long‐distance apoplasmic water transport. The hydraulic conductivity of these conduits is poorly characterized. Long‐distance symplasmic transport in some mosses have been characterized both structurally and physiologically, but in other mosses and in liverworts the evidence is only structural. Most of these symplasmic transport pathways seem to have a high resistance to flow.
Cope's Rule and the evolution of long‐distance transport in vascular plants: allometric scaling, biomass partitioning and optimization
Authors: ENQUIST B. J. 
Published: March 2003

ABSTRACTRecent advances in allometric theory have proposed a novel quantitative framework by which to view the evolution of plant form and function. This general theory has placed strong emphasis on the importance of long‐distance transport in shaping the evolution of many attributes of plant form and function. Specifically, it is hypothesized that with the evolutionary increase in plant size natural selection has also resulted in vascular networks that minimize scaling of total hydrodynamic resistance associated with increasing transport distances. Herein the central features of this theory are reviewed and a broad sampling of supporting but yet preliminary empirical data are analysed. In particular, subtle attributes of the scaling of tracheid and vessel anatomy are hypothesized to be crucial for the evolution of increased plant size. Furthermore, the importance of minimizing hydrodynamic resistance associated with increased transport distances is also hypothesized to be reflected in an isometric scaling relationship between stem mass,MSand root mass,MR(i.e.MS ∝ MR). Preliminary data from multiple extant and fossil plant taxa provide tantalizing evidence supporting the predicted relationships. Together, these results suggest that selection for the minimization of the scaling of hydrodynamic resistance within plant vascular networks has in turn allowed for the enormous diversification in vascular plant size.
Presence in Leptosphaeria maculans populations of isolates virulent on resistance introgressed into Brassica napus from the B. nigra B genome
Authors: Brun H. , Ruer D. , Levivier S. , Somda I. , Renard M. , Chèvre A. M. 
Published: March 2003

The resistance carried by chromosome 4 of the Brassica B genome confers on the Brassica napus–B. nigra addition line ‘LA4+’ a high level of resistance to Leptosphaeria maculans isolates at the cotyledon stage under controlled conditions and at all growth stages under field conditions. This resistance has never been used commercially in B. napus varieties. To determine the potential durability of this new resistance, it is necessary to investigate whether it exerts selective pressure on fungus populations. A study of the pathogenicity of 57 single ascospore isolates of L. maculans on this line at the cotyledon stage was carried out to examine possible race specificity of the resistance. Two isolates were clearly virulent and three had intermediate aggressiveness on the ‘LA4+’ line. Two B‐group isolates and 53 A‐group isolates, including isolates from darkening tissue of resistant plants of the ‘LA4+’ line and cv. Junius (B. nigra), were virulent on the susceptible isogenic ‘LA–’ line. These results demonstrate that: (i) the resistance of the ‘LA4+’ oilseed rape line, conferred on B. napus by B. nigra chromosome 4, is race specific at the cotyledon stage; and (ii) the resistant material can act as a reservoir of virulent isolates for susceptible oilseed rape lines.
Detection of Xylophilus ampelinus in grapevine cuttings using a nested polymerase chain reaction
Authors: Botha W. J. , Serfontein S. , Greyling M. M. , Berger D. K. 
Published: March 2003

A sensitive and specific assay was developed to detect bacterial blight of grapevine caused by Xylophilus ampelinus (Panagopoulos, 1969) comb. nov. in grapevine cuttings. The 16S−23S rDNA intergenic spacer region of X. ampelinus was sequenced and pathogen‐specific primers were designed from a region in the spacer between the tRNA (Ala) and the 23S genes. A nested PCR (n‐PCR) reaction was applied with a first‐stage PCR using universal primers within the ends of the 16S and 23S genes, followed by a second‐stage PCR with nested primers specific to the X. ampelinus spacer region. A 277‐bp fragment was amplified from 38 Xylophilus strains tested, but not from saprophytes associated with grapevine or phylogenetically related phytobacteria. The 277‐bp product was shown to be derived from the X. ampelinus spacer region by restriction with Dra I, Sau 3AI, Taq I and Msp I, Southern hybridization and genomic DNA dot blots. When the (n‐PCR) procedure was applied in the absence of nontarget DNA, the limit of detection was less than 10 colony‐forming units (CFU) per µL. The same number of X. ampelinus CFU could be detected in the presence of 1·5 × 105 CFU µL−1 of Erwinia herbicola cells using the n‐PCR procedure.
Gas chromatography–mass spectrometry analyses of volatile organic compounds from potato tubers inoculated with Phytophthora infestans or Fusarium coeruleum
Authors: De Lacy Costello B. P. J. , Evans P. , Ewen R. J. , Gunson H. E. , Jones P. R. H. , Ratcliffe N. M. , Spencer‐Phillips P. T. N. 
Published: March 2003

Volatile organic compounds (VOCs) collected from potato tubers inoculated with Phytophthora infestans (late blight), Fusarium coeruleum (dry rot) or sterilized distilled water (as a control) were analysed using gas chromatography–mass spectrometry (GC–MS) and gas chromatography–flame ionization detection (GC–FID). A total of 52 volatiles were identified by GC–MS in the headspaces above P. infestans‐ and F. coeruleum‐inoculated tubers after incubation for 42 days in the dark at 10°C. Of these VOCs, the six most abundant were common to both pathogens. These were benzothiazole (highest abundance), 2‐ethyl‐1‐hexanol (second highest abundance), and at approximately equal third abundance, hexanal, 2‐methylpropanoic acid‐2,2‐dimethyl‐1‐(2‐hydroxy‐1‐methylethyl)‐propyl ester, 2‐methylpropanoic acid‐3‐hydroxy‐2,4,4‐trimethyl‐pentyl ester and phenol. In addition, styrene also occurred at approximately equal third abundance in the headspace of F. coeruleum‐inoculated tubers, but at lower abundance in the headspace of P. infestans‐inoculated tubers. Some VOCs were specific to each pathogen. Butanal, 3‐methylbutanal, undecane and verbenone were found at low levels only in the headspace of tubers inoculated with P. infestans, while 2‐pentylfuran and copaene were found only in the headspace of tubers inoculated with F. coeruleum. Additionally GC–FID analysis identified ethanol and 2‐propanol in the liquid exudate from both P. infestans‐ and F. coeruleum‐inoculated tubers after incubation for 35 days, and in the headspace after incubation for 42 days. These data provide key information for developing a sensor‐based early warning system for the detection of postharvest diseases in stored potato tubers.
Development of a PCR‐based diagnostic test for Spongospora subterranea f.sp. nasturtii, the causal agent of crook root of watercress (Rorippa nasturtium‐aquaticum)
Authors: Down G. J. , Clarkson J. M. 
Published: March 2003

The polymerase chain reaction (PCR) technique was utilized to obtain internal transcribed spacer ribosomal DNA (ITS rDNA) and small‐subunit (18S) rDNA sequences from UK isolates of Spongospora subterranea f.sp. nasturtii, a plasmodiophorid pathogen of watercress (Rorippa nasturtium‐aquaticum). ITS sequence data obtained from S. subterranea isolated from a range of UK sites were found to be identical. PCR primers were designed using these sequences and were shown to be capable of specific amplification of S. subterranea f.sp. nasturtii DNA from plant tissue and from water samples containing zoospores of the pathogen. As little as 5 ng total genomic DNA from infected plant material, or 1000 zoospores, was required for consistently successful amplification of DNA. A filtration‐based method for obtaining pathogen DNA for PCR from watercress‐bed water was developed.
Dynamics of Polymyxa graminis and Indian peanut clump virus (IPCV) infection on various monocotyledonous crops and groundnut during the rainy season
Authors: Delfosse P. , Reddy A. S. , Thirumala Devi K. , Legrève A. , Risopoulos J. , Doucet D. , Shoba Devi P. , Maraite H. , Reddy D. V. R. 
Published: March 2003

The progress of Indian peanut clump virus (Hyderabad isolate; IPCV‐H) and its vector Polymyxa graminis in various monocotyledonous crops and groundnut was studied during the 1994, 1995 and 1996 rainy seasons in a naturally infested field in India. The roles of rainfall and temperature in the dynamics of infection by both the virus and its vector were analysed by exposing young seedlings for short periods in the field. Of the host crops studied, wheat, followed by barley, showed the highest virus incidence, although P. graminis was rarely observed in roots of wheat and was not detected in those of barley. The roots of maize, pearl millet and sorghum plants infected by P. graminis showed intense colonization by sporosori. IPCV accumulated in systemically infected maize plants; the sorghum and pearl millet cultivars studied showed a transient presence of IPCV‐H. Rice was seldom infected by the virus and P. graminis was not detected in its roots. Groundnut was a systemic host for the virus, although during these experiments no P. graminis was found in its roots. Groundnut appeared to be susceptible to infection, mostly in the early stages of crop development, and the rate of IPCV‐H transmission in groundnut seeds was highest (13%) for plants infected when young. The seed‐transmission rate quickly decreased in plants showing symptoms 1 month after sowing. Time of infection had little influence on groundnut pod yield, which was always reduced by >60% in infected plants. There was some evidence that the quantity and distribution of rainfall influenced the incidences of IPCV‐H and P. graminis: high rainfall resulted in high incidences of the virus and P. graminis, and a weekly rainfall of 14 mm was sufficient for P. graminis to initiate infection. Temperatures prevailing during the rainy season ranged from 23 to 30°C and were found to be conducive to natural virus transmission. These results suggest measures to be explored for controlling peanut clump disease.