bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasts between Citrus species in response to salinisation: An analysis of photosynthesis and water relations for different rootstock‐scion combinations
Authors: Lloyd Jon , Kriedemann P. E. , Aspinall D. 
Published: May 2006

Leaf gas exchange, water relations and ion content were measured on two‐year‐old Valencia orange (Citrus sinensis [L.] Osbeck), Washington Navel orange (C. sinensis) and Marsh grapefruit (C. parodisi Macfad) scions budded to either Trifoliata (Poncirus infoliata [L] Raf) or Cleopatra mandarin (C. reticuLua Blanco) rootstoeks. Trees were watered with dülute nutrient solution containing either 0 or 50 mM NaCl for 77 days. Leaf chloride concentrations (cell sap basis) were higher in all scions budded on “Trifoliata but sodium levels were lower than in equivalent foliage budded on Cleopatra mandarin rootstock. Foliar salt levels also varied according to scion. Leaves of Marsh grapefruit had higher levels of both sodium and chloride than leaves of either Valencia orange or Washington Navel orange on both rootstocks. Accumulation of sodium and chloride in salinised leaves caused a reduction in leaf osmotic potential of 0.2–1.4 MPa. and leaf water potential declined by as much as 0.5 MPa. Turgor pressure in salinised leaves was thus maintained at or above the control level. Osmotic potentials determined by psychrometry compared with pressure‐volume curves were taken to imply that some accumulation of sodium or chloride in the apoplast of salinised leaves may have occurred.Despite turgor maintenance both co2 assimilation and stomatal conductance were reduced by salinity. Following onset of leaf response to salinisation, gas exchange was impaired to a greater extent in scions budded to Cleopatra mandarin compared to those on Trifoliata. Amongst those scions. leaves of salt‐treated Marsh grapefruit showed greater reductions in gas exchange than Valencia orange or Washington Navel orange budded on either rootstock. Increased sensitivity of 1Marsh grapefruit was correlated with a higher foliar sodium and chloride content in this scion. Scion differences in sensitivity of leaf gas exchange to solute concentration were independent of rootstock and appeared unrelated to leaf prolinebetaine concentrations. This implies an inherent difference between scion species with respect to salt tolerance, rather than variation in their capacity to acquire that type of compatible solute.In terms of rootstock effects, all scions proved more sensitive to salinity when budded to Cleopatra mandarin compared with Trifoliata. That response was attributed to a disproportionately higher concentration of leaf sodium in scions on Cleopatra mandarin.
Induction of peroxidases in cucumber hypocotyls by wounding and fungal infection
Authors: Svalheim Øystein , Robertsen Børre 
Published: May 2006

The induction of peroxidases (EC 1.11.1.7) during elicitation of lignification by α‐1,4‐linked oligogalacturonides in cucumber hypocotyl segments (Cucumis sativus L. cv, Wisconsin SMR 58) was investigated. The wounding associated with the preparation of hypocotyl segments induced a 19‐fold increase in peroxidase activity during the following 72 h. The increase was partially due to an increase in activity of a constitutive peroxidase with a pI of 8.9 and partially due to the expression of new peroxidase isozymes with pIs of 3.8, 5.4, 6.2, 9.1 and 9.4. The oligogalacturonides did not induce any peroxidase activity in addition to the wound‐induced activity. These results suggest that either the constitutive peroxidase isozyme (pI 8.9) of intact hypocotyls or some of the wound‐induced peroxidases are involved in the oligogalacturonide‐induced lignification.Induction of the peroxidases by wounding was inhibited by cycloheximide. This indicates that they accumulate as a result of de novo protein synthesis. Actinomycin D caused only a modest inhibition of the wound‐induction peroxidases, indicating that the process is regulated at the level of translation.Peroxidase activity increased more rapidly in resistant than in susceptible cucumber hypocotyls after inoculation with the pathogen Cladosporium cucumerinum Ellis & Arthur. The pattern of isozymes which was induced by fungal infection of resistant hypocotyls was similar to the pattern of isozymes induced by wounding. This suggests that similar induction mechanisms may be involved in the two processes.
Influence of extraction solvent (buffer, methanol, acetone) and time on the quantification of indoIe‐3‐acetic acid in plants
Authors: Sundberg Björn 
Published: May 2006

The effect of extraction solvent and time on the measured indole‐3‐acetic acid (IAA) level was investigated in plant materials having different contents of lAA‐conjugates, Tissues from pine (Pinus sylvestris L.). tobacco (Nicotiana tabacum L.), and maize (Zea mays L.) were extracted for 1–9 h with Na‐phosphate buffer (pH 7.5). 80% methanol and 70% acetone. IAA was measured by combined gas chromatography‐selected ion minitoring‐mass spectromctry (GC‐SIM‐MS) with [13C6]‐IAA as an internal standard.Extraction of maize seedlings with buffer gave a higher estimate of free IAA than did extraction with methanol or acetone, which produced similar values. The increase in free IAA after buffer extraction was paralleled by a stoichiometric decrease in lAA‐ester conjugates, indicating that free IAA was formed during buffer extraction by hydrolysis of these conjugates, which are abundant in maize seedlings. The amount of hydrolysis during a 1‐h extraction period was estimated to be ca 3% of the total lAA‐ester pool. However, in the pine extraxylary tissues and tobacco in‐ternodes which lack a significant lAA‐ester pool, buffer extraction resulted in the same IAA estimate as extraction with the organic solvents, but produced a cleaner extract. For all the plant materials investigated, a 1‐h extraction period was sufficient for equilibrating the internal standard with the endogenous IAA pool.
Inhibition and labeling of red beet uridine 5′diphospho‐glucose: (1,3)‐β‐glucan (callose) synthase by chemical modification with formaldehyde and uridine 5′diphospho‐pyridoxal
Authors: Mason Theresa L. , Read Stephen M. , Frost David J. , Wasserman Bruce P. 
Published: May 2006

The effects of the lysine‐reactive chemical modification reagents, uridine 5’ diphospho (UDP)‐pyridoxal and formaldehyde (HCHO), on the activity of membrane‐bound and solubilized UDP‐Glc: (1,3)‐β‐D‐glucan synthase (callose synthase) from red beet (Beta vulgaris L.) storage tissue were compared. Exposure to micromolar levels of UDP‐pyridoxal, or millimolar levels of HCHO in the presence of NaCNBH3, resulted in complete enzyme inactivation. Conditions for inhibition of membrane‐bound enzyme activity by the two reagents were markedly similar; divalent cations were required for inactivation, and complete protection of activity was obtained with EDTA or EGTA. The substrate, UDP‐Glc, protected membrane‐bound callose synthase against inactivation by UDP‐pyridoxal or HCHO, but protected the solubilized enzyme only against inhibition by UDP‐pyridoxal, suggesting that the lysine residue modified by both these reagents is at the enzyme active site, and that the site is more open or has a certain conformational flexibility in the solubilized enzyme.Potential UDP‐Glc‐binding polypeptides of callose synthase were identified by a two‐step labeling procedure. First, nonessential lysine residues were blocked by irreversible modification reaction with HCHO or UDP‐pyridoxal in the presence of UDP‐Glc to protect lysines at UDP‐Glc‐binding sites. In the second step, proteins were recovered, reacted with [14C]‐HCHO in the absence of UDP‐Glc, and polypeptide labeling patterns analyzed by SDS‐polyacrylamide gel electrophoresis and fluorography. This procedure reduced incorporation of label by 5‐ to 8‐fold compared to a procedure omitting the preblocking step, and with enzyme partially purified by solubilization in CHAPS followed by product entrapment, labeling was limited to a small set of polypeptides. Taken together with the results of other studies, the data suggest that one or more polypeptides migrating in the 54–57 kDa region are good candidates for the UDP‐Glc‐binding components of callose synthase.
Internode length in Lathyrus odoratus. Effects of mutants l and lb on gibberellin metabolism and levels
Authors: Ross John J. , Davies Noel W. , Reid James B. , Murfet Ian C. 
Published: May 2006

After the application of [13C3H]‐gibberellin A20 to wild‐type (tall) sweet peas (Lathyrus odoratus L.) labelled gibberellin A1 (GA1), GA8, GA29 and 2‐epiGA29 were identified as major metabolities by gas chromatography‐mass spectrometry after high performance liquid chromatography. By contrast in genetically comparable dwarf (II) plants only labelled GA29 and 2‐epiGA29 were produced in significant amounts, although evidence was obtained for trace amounts of labelled GA1 and GA8. The apical portions of dwarf plants contained 8–10 times less GA1 than those of tall plants but at least as much GA20 (measured using di‐deuterated internal standards). In conjunction with previous data these results strongly indicate that in genotype ll internode length is reduced and leaf growth altered by a reduction in GA1 levels attributable to a partial block in the 3β‐hydroxylation of GA20 to GA1.In contrast to dwarf plants, semidwarf plants (genotype lblb) contained more GA1 in the apical portion than wild‐type counterparts. This is consistent with the suggestion that lb alters some aspect of GA sensitivity.
Organic acids and cellular changes in the endosperm of Euphorbia lambii seedlings
Authors: Groeneveld H. W. , Idzinga T. M. , Elings J. C. 
Published: May 2006

Seedling of Euphorbia lambii Svent. were grown in the dark, and the levels of organic acids in the endosperm were monitored during the 6–7 day period in which all the reserves were depleted. Glycolate, glyoxylate, succinate, fumarate and 2‐oxoglutarate occurred in traces only, the citrate concentration remained rather constant (0.4 μmol endosperm−1), malate varied from 0.2 to 0.4 μmol endosperm−1, but malonate appeared to be the major organic acid in the endosperm ranging from 0.75 to 1.25 μmol endosperm−1. Radioactive malonate was easily taken up by the cotyledons of growing seedlings, and up to 11.2% of the label proceeded to the sterols, the triterpenes and triterpene esters in a 48 h incorporation period. No label from [14C]‐malonate was built into the triacylglycerols in the seedling. Maximum uptake values of 0.6 μmol malonate seedling−1 day−1 were measured, and this value was not altered by a simultaneous uptake of sucrose. Conversely, the uptake of labeled sucrose and its subsequent conversion into sterols and (latex) triterpenes was not altered by a simultaneous uptake of low concentrations of malonate. Increased amounts (from 0.25 μmol malonate seedling−1 and up) caused a 75–90% reduction of both uptake and conversion of sucrose into neutral lipids. To maintain a daily uptake of 4 μmol of sucrose by the cotyledons (required to maintain seedling growth) the simultaneous in vivo uptake of malonate from the endosperm was supposed not to exceed 0.2 μmol seedling−1 day−1.Thin sections of the endosperm revealed the morphology of the process of reserve depletion. The occurrence of vacuoles 2 days after germination, coincided with the increase in the malonate level. The protein bodies first disappeared completely from the outer layers, whereas the triacylglycerols gradually disappeared from the entire endosperm. About 80% of the endosperm cells contained a large vacuole until the stage of complete depletion, probably serving as the major site of malonate storage.
Identification of polypeptides specific to rachis abscission zone cells of Sambucus nigra
Authors: McManus Michael T. , Osborne Daphne J. 
Published: May 2006

Specific polypeptides and antigenic determinants in abscission zone cells of the leaf rachis of Sambucus nigra L. (elderberry) were identified. Extracts from abscission zone tissue (OZ) and from ethylene‐treated abscission zone tissue after separation (Zone) were probed, using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and immunological techniques, for unique peptide components absent from neighbouring non‐zone mid‐rachis tissue (MR). Ouchterlony immuno‐diffusion revealed differences in the spectrum of antigenic determinants possessed by each tissue type when challenged with antiserum raised against OZ. Immuno‐electrophoresis showed a basic polypeptide which is expressed preferentially in the abscission zone.Immune‐competition of OZ, MR and Zone extracts using immuno‐affinity column chromatography has identified polypeptides of ca 34, ca 32, and ca 28 kDa which are (up to the limits of detection) abscission‐cell specific. An antibody raised against the ca 34 kDa polypeptide recognises a peptide of ca 34 kDa present in OZ and Zone. This peptide is absent from MR.These results suggest that the specific positional differentiation of ethylene‐responsive target cells which constitute the leaf rachis abscission zone in S. nigra is accompanied by the expression of zone‐cell‐specific antigenic determinants which are not expressed by non‐target neighbouring tissue.
Characterization of a shiitake mutant strain producing ballshaped fruiting bodies
Authors: Itävaara Merja 
Published: May 2006

Growth characteristics of a spontaneous mutant of shiitake Lentinula edodes (Berk.) Pegler were studied. The mutant was first detected as a result of changes in the growth habit of the normal strain in the liquid medium. Abundant formation of aerial hyphae was distinctive. In sawdust logs the mutant strain produced abnormal basidiocarps, lacking stipe, gill and spore formation.Growth rates of the normal and the mutant strain were compared in two liquid media: malt‐yeast extract and Leatham's medium. The increase in dry weight of the mutant's mycelium was much higher than that of the wild type in both media, which indicated better adaptation to liquid culture. In the sawdust, however, growth of the mutant was slower than that of the normal strain. The mutant's intracellular protein content was lower than that of the normal strain. The pH of the liquid cultures differed: the wild type decreased the pH during growth, while the mutant increased the pH. Comparison of the protein and esterase isoenzyme profiles of the vegetative hyphae of both strains indicated profound differences. One protein (pI 6.5, 39 kDa), which in earlier studies has been found to be typical of L. edodes species, was absent from the mutant's profile. Differences in the esterase profile were also clear.
The role of extracellular carbonic anhydrase for accumulation of inorganic carbon in the green alga Chlamydomonas reinhardtii. A comparison between wild‐type and cell‐wall‐less mutant cells
Authors: Palmqvist Kristin , Ramazanov Zakir , Samuelsson Göran 
Published: May 2006

The role of extracellular carbonic anhydrase (CAex) for dissolved inorganic carbon (DIC) accumulation in the green alga Chlamydomonas reinhardtii was investigated. It was found that when algal cells were bubbled with ambient air, cell‐wall‐less mutant cells exhibited the same high photosynthetic affinity for CO2 as wild‐type cells despite a 10 times lower activity of CAex. It was also found that the affinity for CO2 was further increased when the total DIC concentration of the algal medium was reduced from that in equilibrium with ambient air to even lower levels. This increased affinity was not correlated with any further increase in the CAex activity.Dextran‐bound sulfonamide (DBS. 100 μM bound ligand) completely inhibited the activity of CAex in intact, low‐DIC grown, wild‐type cells, while photosynthesis at <2 μM CO2(aq) proceeded at a far greater rate than could be maintained by CO2 supplied from the spontaneous dehydration of HCO−3. DBS‐inhibition of CAex, during the induction of the DIC‐accumulating mechanism in previously high‐DIC grown cells, only caused a 50% inhibition of photosynthesis at 10 μM CO2(aq) after 1 h of low‐DIC acclimation. It was also shown that 50 μM acetazolamide (AZ) inhibited photosynthesis at low DIC concentrations to a relatively higher degree than DBS, suggesting that AZ inhibited intracellular CA as well.Taken together, these results suggest that low‐DIC grown cells of C. reinhardtii have the ability to transport HCO−3 across the plasma membrane in addition to the CAex‐mediated, facilitated diffusion and/or transport of CO2. It is also suggested that the relative importance of these two fluxes (CO2 or HCO−3) is dependent on the growth and experimental conditions. Facilitated CO2 uptake seems to be most prevalent, supported by HCO−3‐transport under more or less extreme situations, such as a reduction of CO2 to extremely low concentrations, leakage of CAex to the medium as in cultures of cell‐wall‐less mutant cells or when the activity of CAex has been artificially inhibited.
Changes in gene expression of Scots pine buds during the winter and under experimentally altered light and temperature conditions
Authors: Nuotio S. , Häggman H. , Kupila‐Ahvenniemi S. 
Published: May 2006

Vegetative buds of Scots pine (Pinus sylvestris L.) were collected during the apparently dormant phase in January and February and at the beginning of the growth phase in May. Wintering Scots pine plants were placed in climate chambers in which either the daily photoperiod or the temperature simulated the situation in early spring, whereas the other conditions were characteristic of midwinter.The amount of total ribosome populations and their in vitro translation capacities were independent of the height of the tree or place of collection, but both were dependent on the season; the amount of ribosomes per fresh weight of buds was lower in spring than in winter, whereas the translation capacity in spring exceeded that in winter. Poly(A)+ RNA was purified from the ribosomes and translated in vitro and the translation products were separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The polypeptide patterns proved that changes in gene expression can occur in plants growing outdoors even during the season of severe cold. In the climate chamber experiments, lengthening of the daily photoperiod increased the in vitro translation capacity of the buds within 7 days even at temperatures below 0°C, whereas a rise in temperature seemed to cause a more transient stress effect. Both treatments induced alterations in the pattern of in vitro polypeptide synthesis. It is suggested that while improvements in both light and temperature hastened the development of the buds under experimental growth conditions, the lengthening of the day may be the factor which induces a change in wintertime metabolism under natural conditions.
Alterations of gene expression in potato (Solanum commersonii) during cold acclimation
Authors: Tseng M. J. , Li P. H. 
Published: May 2006

Plantlets of Solanum commersonii stem‐culture were acclimated at 5°C day/night temperature for 14 days. Cold hardiness increased from – 3.5°C to – 8.6°C. During the course of acclimation, the synthesis of polypeptides was investigated and poly (A+) RNA was isolated. Translation products of poly(A+) RNA in a rabbit rcticulocyte lysate system were then analyzed. During the 14 days of acclimation, 23 cold‐induced polypeptides were identified. Most of them disappeared following 1 day of de‐acclimation at a 20/15°C day/night regime. The synthesis of one group of polypeptides is prominent and stable throughout the acclimation period. The other group is transient. The most prominent and stable polypeptides have molecular weights of 21, 22, 31 and 83 kDa.Acclimation alters translatable mRNA population during the development of cold hardiness. Two mRNAs encoding in vitro translation products at 26 and 27 kDa were identified during the course of acclimation. These proteins may play important roles in the overall programming for the development of cold hardiness in tuber‐bearing S. commersonii.
Ethylene accelerates the breakdown of cytokinins and thereby stimulates rooting in Norway spruce hypocotyl cuttings
Authors: Bollmark Marie , Eliasson Lennart 
Published: May 2006

Cuttings were taken from 4‐week‐old seedlings of Norway spruce (Picea abies L. Karst.) raised at two different irradiation levels. Rooting experiments showed that root formation was increased by the ethylene formed by adding 1‐aminocyclopropane‐1‐carboxylic acid ACC or Ethrel, especially in the slowly rooting cuttings grown under high light (HL). Cobaltousion. an ethylene synthesis inhibitor, delayed rooting, especially in the easily rooted cuttings grown under low light (LL).Compounds isolated from the cuttings using immunoaffinity chromatography, on a column with antibodies against cytokinins, and separated by HPLC decreased in amount during the first week of the rooting period. An increase in ethylene production accelerated this process, especially in cuttings grown under HL, whereas cobaltous ion delayed it. We suggest that ethylene stimulates rooting by enhancing the degradation of cytokinins.
Indole‐3‐acetic acid uptake in isolated protoplasts of the moss Funaria hygrometrica
Authors: Geier Ulrike , Werner Olaf , Bopp Martin 
Published: May 2006

Protoplasts of the moss Funaria hygrometrica Hedw were used to study the mechanism of Indole‐3‐acetic acid (IAA) accumulation. Three main components appeared to be involved.1. The pH gradient between plasma and outer medium is the basis for an anion trap. The protonophores carbonylcyanide m‐chlorophenylhydrazone (CCCP) and carbonylcyanide p–trifluoromethoxyphenylhydrazone (FCCP) reduce IAA accumulation by destruction of the pH gradient.2 An intact efflux carrier could be demonstrated by an increase of IAA accumulation with the efflux inhibitors 2,3,5–trüodo‐benzoic acid (TIBA) and 1‐naphthy‐phthalamic acid (NPA). In efflux experiments, reduction of IAA efflux by the two inhibitors was directly demonstrated.3. The existence of an influx carrier was concluded from the strong stimulation of IAA accumulation by calcium in calcium‐deprived protoplasts. It is postulated that this carrier system transports IAA anions, protons and Ca2+. A computer simulation of the accumulation process with the three components, including internal IAA concentration determined by enzyme‐linked immunosorbent assay (ELISA), gave a highly accurate description of the data measured in the different experiments.
Cell wall localization of the natural substrate of a β‐galactosidase, the main enzyme responsible for the autolytic process of Cicer arietinum epicotyl cell walls
Authors: Dopico Berta , Nicolos Gregário , Labrador Emilia 
Published: May 2006

The Hw pectic fraction, extracted with hot water, is the major component of 4 days old epicotyl cell walls of Cicer arietinum L. cv. Castellana and is formed of arabinose and galactose, with smaller amounts of rhamnose, xylose, glucose and mannose. The cell wall 2βIII enzymatic fraction, with β‐galactosidase activity (EC 3.2.1.23) and the main enzyme responsible for the autolytic process, essentially acts on the Hw fraction, and is able to hydrolyze 560 μg of this fraction per g of epicotyls, releasing mainly galactose as monosaccharide.The 2βIII fraction acts very weakly on the other polysaccharide fractions of the cell wall, both pectic and hemicellulosic, releasing 80, 60 and 14 μg per g of epicotyls from the fractions extracted with oxalate (Ox), KOH 10% (KI) and KOH 24% (KII), respectively. It can be concluded that the natural substrate of this enzyme is the Hw pectic fraction, probably an arabinogalactan that is found in the cell wall in isolated form or as side chains of the rhamnogalacturonan I.