bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localization of phytosiderophore release and of iron uptake along intact barley roots
Authors: Marschner Horst , Römheld Volker , Kissel Margit 
Published: May 2006

Under iron deficiency the release of so‐called phytosiderophores by roots of barley plants (Hordeum vulgare L. cv. Europa) was greater by a factor of 10 to 50 compared to iron‐sufficient plants. This enhanced release occurred particularly in apical zones of the seminal roots and in the lateral root zones. Under iron deficiency, uptake rates for iron, supplied as FeIII phytosiderophore, increased by a factor of ca 5 as compared to iron‐sufficient plants. This enhanced uptake rate for iron was also much more pronounced in apical than in basal root zones. In contrast, with supply of the synthetic iron chelate, FelII EDDHA (ferric diaminoethane‐N, N‐di‐o‐hydroxyphenyl acetic acid), the Fe deficiency‐enhanced uptake rates for iron were only small and similar along the roots, except for the lateral root zones. The high selectivity of barley roots for uptake and translocation of FeIII phytosiderophores compared with FeIII EDDHA is reflected by the fact that, at the same external concentration (2 μM), rates of uptake and translocation of iron from FeIII phytosiderophores were between 100 (Fe‐sufficient) and 1 000 times higher (Fe‐deficient plants) than from FeIII EDDHA. The relatively high rates of uptake and particularly of translocation of iron supplied as FeIII EDDHA in the zone of lateral root formation strongly suggest an apoplastic pathway of radial transport of the synthetic iron chelate into the stele in this root zone.The results demonstrate that apical root zones are the main sites both for Fe deficiency‐enhanced release of phytosiderophores and for uptake and translocation of iron supplied as FeIII phytosiderophores.
An automatic device to record the force necessary to compensate plant movements
Authors: Zachariassen Eli , Johnsson Anders 
Published: May 2006

A device, which automatically and continuously keeps moving plants in fixed positions, has been constructed. The apparatus is based on optical detection of any movements of the plant organ under study. The plant organ is kept in the desired position by means of wires, and the force necessary to apply to the wires to achieve this is recorded. The force reflects any tendency of the plant organ to move. The system is controlled by an Apple II computer. The device can work in one or two dimensions and record compensation forces in a wide range. In the experiments mentioned below, the magnitude of the forces necessary to keep the plants in a fixed position was of the order of 10‐4N.Circadian leaf movements of Oxalis regnellii Mig. were studied in the device. The leaf rhythm continued, although the leaflets were clamped and the light input on the leaf therefore constant. Circumnutation of hypocotyls of Helianthus annus L. cv. Californicus were drastically reduced in amplitude when the hypocotyls were kept in vertical position by the wires. Since the gravitropic input signal to this system was zeroed by the equipment, the results demonstrated that in the absence of gravitropic inputs the circumnutation reactions drastically diminish. This confirmed that circumnutations of these hypocotyls are influenced by gravity. Finally, the apparatus was used to study phototropic reactions: By clamping phototropically stimulated coleoptiles of Avena sativa L. cv. Seger no gravitational stimulations were involved and the phototropic reaction without interference from gravity could be studied.
Salinity effects on growth and carbon balance in Lycopersicon esculentum and L. pennellii
Authors: Taleisnik Edith L. 
Published: May 2006

The effects of salinity on growth and carbon balance in the cultivated tomato Lycopersicon esculentum (L.) Mill. cv. VF 234 and in a wild, salt‐tolerant relative, L. pennellii (Correll) D'Arcy accession Atico, were compared. The level of salinity that significantly reduced growth and affected morphology was lower for the cultivated than for the wild species.Net CO2 fixation, stomatal conductance and the specific activity of ribulose bisphosphate carboxylase (EC 4.1.1.39) were more decreased by salinity in the wild tomato than in the cultivated. In both species, the salinity‐associated decrease in assimilation was related to a decrease in net photosynthesis and to carbon reallocation favoring heterotrophic organs.
Effect of defoliation on tracheid production and the level of indole‐3‐acetic acid in Abies balsamea shoots
Authors: Sundberg Björn , Little C. H. Anthony 
Published: May 2006

To simulate feeding by the spruce budworm (Choristoneura fumiferana Clem.), the apical current‐year shoots on 1‐year‐old branches in the uppermost whorl of 6‐year‐old balsam fir [Abies balsamea (L.) Mill.] trees were either removed completely by debudding before the start of the growing season or defoliated 0, 50, 90 or 100% shortly after budbreak. Debudded branches were treated at the apical end with 0, 0.1 or 1.0 mg of indole‐3‐acetic acid (IAA) (g lanolin)−1. Ninety % of the 1‐year‐old needles were also removed from some of the experimental branches. After ca 4 weeks of growth, the radial width of new xylem and the level of IAA were determined in the 1‐year‐old internode. The IAA content was measured by radioimmunoassay.The removal or defoliation of current‐year shoots inhibited tracheid production and decreased the IAA level. Exogenous IAA stimulated tracheid production and increased the IAA level in debudded branches. Current‐year shoot defoliation also inhibited current‐year shoot elongation. The inhibitory effect of current‐year needle removal on all parameters generally increased with increasing intensity of defoliation. The removal of 1‐year‐old needles did not affect the IAA level or current‐year shoot elongation, nor did it influence tracheid production in branches with current‐year shoots. However, removal of 1‐year‐old needles inhibited tracheid production in debudded branches supplied with exogenous IAA. The results indicate that (1) IAA is involved in the control of tracheid production in the 1‐year‐old internode, (2) IAA is supplied primarily by current‐year shoots, and (3) defoliation by the spruce budworm inhibits tracheid production partly by decreasing the supply of IAA.
Regulation of membrane phospholipid catabolism in senescing carnation flowers
Authors: Paliyath Gopinadhan , Lynch Daniel V. , Thompson John E. 
Published: May 2006

Evidence has been obtained for the involvement of μM levels of Ca2+ in phospholipid catabolism during petal senescence by following the breakdown of [U‐14C]‐phosphatidylcholine by microsomal membranes from cut carnation (Dianthus caryophyllus L. cv. White‐sim) flowers. Phospholipid degradation was mediated by three membrane‐associated lipases, viz. phospholipase D (EC 3.1.4.4), phosphatidic acid phosphatase (EC 3.1.3.4) and lipolytic acyl hydrolase. The activities of phospholipase D and phosphatidic acid phosphatase were stimulated by 30 and 100%, respectively, in the presence of 40 μM free Ca2+, and the Ca2+‐stimulation of phosphatidic acid phosphatase was calmodulin‐dependent. When L‐3‐phosphatidyl‐[2‐3H]‐inositol and L‐3‐phosphatidyl‐[N‐methyl‐3H]‐choline were used as substrates, inositol and choline accounted for 95 and 99%, respectively, of the water‐soluble radiolabelled products. This suggests a predominance of phospholipase D activity over phospholipase C activity in these membranes.Breakdown of membrane phospholipids in senescing carnations is known to be accelerated by treatment of young flowers with ethylene. To determine whether this involves a specific turnover of phosphatidylinositol as observed in animal systems in response to certain agonists, young flowers pre‐labelled with 32PO3‐4 were treated with 10 ppm ethylene. All phospholipids incorporated the label, but no enhanced turnover of phosphatidylinositol was observed. Inositol 1,4,5‐triphosphate did not release Ca2+ from preloaded microsomal vesicles at concentrations known to be effective in animal systems (i.e. < 5 μM) although release of Ca2+ was observed when a higher (20 μM) concentration was used.
Dependence of the quality and the in vitro translation capacity of pine ribosome assemblies on the isolation procedure
Authors: Kupila‐Ahvenniemi Sirkka , Muhonen Aija , Malinen Paula 
Published: May 2006

The in vitro translation capacity of total ribosome assemblies isolated from the vegetative buds of small Scots pine (Pinus sylvestris L.) plants depends on the isolation procedure. Good yields and high values for protein synthesis were obtained in experiments in which polyvinyl pyrrolidone (PVP) was added to the grinding buffer. The polysome profiles obtained after sucrose density gradient centrifugation indicated the presence of polysomes in all samples. In addition, large ribosome aggregates were visible in the scanning electron micrographs. The use of an RNase inhibitor (RNasin) together with PVP did not improve the results, and treatment with ribonuclease (RNase, EC 3.1.27.5) destroyed the ability to synthesize protein.D, L‐Dithiothreitol (DTT) and mercaptoethanol, if used instead of or together with PVP, gave low yields and also DTT destroyed the in vitro translation capacity of the ribosome assemblies. The polysome profiles had a high peak indicating dimers and often a descending series of peaks indicating polymers. A study of the scanning electron micrographs gave the impression that the largest polymers and aggregates had broken down.Protease K (EC 3.4.21.14) when added to the grinding buffer also destroyed the ability of the ribosomes to maintain protein synthesis in vitro. In this case, the shape of the polysome profiles gave the impression of successful isolation. Clumps of ribosomes, presumably originating from large aggregates, were visible in the scanning electron micrographs. Triton X‐100 and 0.25 M NaCl in the grinding buffer extracted chromatin, which affected the results. The material lost during the extraction and purification processes consisted mainly of monosomes and their sub‐units.On the basis of the above results it was concluded that the preservation of large polysomes and ribosome aggregates in the isolated ribosome assemblies is necessary if they are to maintain a high translation capacity. The content of the assemblies was best revealed in the scanning electron micrographs. The shape of the polysome profiles did not always correlate with the ability of the isolated ribosomes to synthesize proteins.
Ethylene and wound‐induced cyanide‐resistant respiration climaxes in potato: The synergistic role of CO2 and the selective role of lycorine
Authors: Laties George G. 
Published: May 2006

When treated with ethylene in O2, conditioned potato (Solanum tuberosum L. cv. Russet Burbank) tubers – that is, tubers kept at room temperature for 10 days or more – yield slices that are CN− resistant. Ten % CO2 in the gas mixture not only synergizes the effect of ethylene, but replaces the need for conditioning as well. The response to CO2 is more pronounced with increasing time from harvest. By contrast fresh slices from untreated tubers are CN− sensitive, as are slices from tubers incubated in O2 or O2 plus CO2. The suggestion is made that CN− resistance is constitutive, and that treatment with ethylene/CO2 in O2 confers on potato tuber tissue a resistance to the extensive degradation of membrane phospholipids that normally attends slicing and leads to the loss of CN− resistance. In this connection respiration inhibition by imidazole, an inhibitor of fatty acid α‐oxidation, is extensive in slices of untreated tubers, and sharply diminished in slices of ethylene‐treated tubers in proportion to their CN− resistance.The coextensive rise of respiration rate and CN− resistance in aged potato slices has led to the presumption that the CN−‐resistant path mediates the respiration climax. Accordingly the alkaloid, lycorine, has been considered to inhibit the development of CN− resistance in aging potato slices because it curtails the wound‐induced respiration. A comparison was carried out on the effect of lycorine on CN−‐sensitive and CN−‐resistant fresh slices – the latter obtained from ethylene/CO2‐treated tubers. Lycorine suppressed the development of the wound‐induced respiration without restricting the development of CN− resistance.
Mg2+‐ATPase activity in wheat root plasma membrane vesicles: Time‐dependence and effect of sucrose and detergents
Authors: Bérczi Alajos , Møller Ian M. 
Published: May 2006

Purified plasma membrane vesicles were isolated in the presence of 250 mM sucrose from 7‐day‐old roots of Triticum aestivum L. cv. Drabant by aqueous polymer two‐phase partitioning. When added to a low‐salt medium containing 9‐aminoacridine (9‐AA), the vesicles caused a much larger total decrease in 9‐AA fluorescence when sucrose was absent than when sucrose was present. A slow component of the decrease was also larger in the absence of sucrose. Triton X‐100 reduced the decrease in 9‐AA fluorescence upon vesicle addition and abolished completely the slow component of the decrease. There was no correlation between the time‐dependence of 9‐AA fluorescence and that of the Mg2+‐ATPase described below.The time course of Mg2+‐ATPase activity was followed by sampling at short intervals (down to 10 s) and analyzing for P, released. In the absence of detergent, the rates of P, release were linear from zero minutes, whether 250 mM sucrose was present or not, but the rate was 10−50% higher in the absence of sucrose than in its presence. Sucrose (250 mM) added during a minus‐sucrose assay lowered Mg2+‐ATPase activity within 2 min to the level observed with 250 mM sucrose present from the start. The effect of 25‐1 100 mM sucrose was tested and there was little or no effect below KM) mM. Above 100 mM sucrose the rate of P, release decreased drastically; at 1 100 mM sucrose the rate was ca 20% the rate at 25 mM sucrose. The inhibitory effect of sucrose was not alleviated by increased concentrations of Mg2+ and/or ATP. nor was it affected by the presence or absence of Triton X‐100. We conclude that sucrose somehow inhibits the Mg2+‐ATPase directly or affects the conformation of the plasma membrane in such a way as to inhibit the enzyme.The presence of detergents increased Mg2+‐ATPase activity in the order Triton X‐100 (4–5‐fold) > Zwittergent 3–14 = Na‐cholate = octylglucoside > digitonin (2‐fold). In all cases optimal activity was observed at detergent concentrations at or below the critical micellar concentration. The detergent concentration curves could be simulated by the sum of a stimulatory and an inhibitory reaction. At the optimal concentration, digitonin gave a linear time‐course of P, release, whereas all the other detergents showed a distinct lag of 1–3 min before maximal rates were attained. The problems of using detergents in polarity assays are discussed.
Phenolamides during the ripening of dormant and non‐dormant seeds in different Petunia lines
Authors: Jassey Yves , Monin Jeannine 
Published: May 2006

Phenolamides were extracted from reproductive organs and different capsule parts (fruit wall, placenta and seeds) of dormant and non‐dormant lines derived from the species Petunia hybrida hort,. Petunia axillaries Lam. B.S.P. and Petunia parodii Steere. The different compounds were separated by high‐pressure liquid chromatography and analyzed before pollination, during ripening, at ripeness and after 2 weeks of after‐ripening of the seeds. The extracts were examined particularly for the presence of an alkaline compound (X), which is a phenolic derivative of tryptophanamide and appears to be a biochemical marker for the dormancy of ripe dry seeds of Petunia. During capsule growth and seed ripening, compound X was not a marker for dormancy, although it occurred in the reproductive organs of seed‐parent plants. After pollination and fertilization, accumulation of compound X started mainly in the fruit wall, but in ripe dry capsules it was present entirely in the seeds. In contrast to compound X, neutral phenolamides were not detected in extracts from the fruit wall: and from the early stages of the capsule growth substantial accumulation took place only in the seeds.Absence of compound X from ripe dry seeds appears as a necessary but not a sufficient condition for non‐dormancy.
The regulation of respiration and growth of potato tuber callus by endogenous ethylene. Suppression of ethylene action by 2,5‐norbornadiene
Authors: Gude Henk , Rietveld Ellen , van der Plas Linus H. W. 
Published: May 2006

The growth (fresh and dry weight increase) of potato tuber (Solanum tuberosum L. cv. Bintje) callus discs was stimulated by incubation in air with 500 ppm 2,5‐norbornadiene (NBD, a competitive inhibitor of ethylene action) and inhibited by incubation in air with 4 000 ppm NBD. Ethylene formation by the callus was stimulated by NBD. The development of the alternative pathway, measured in isolated mitochondria was inhibited by NBD in a concentration‐dependent way. The alternative pathway capacity, measured in vivo, was inhibited by 4 000 ppm NBD, but not by 500 ppm. Uninhibited in vivo respiration, which consists of cytochrome path activity and alternative path activity, was stimulated by the treatment with 500 ppm NBD. The main contribution to this stimulation was made by the cytochrome pathway. In 4 000 ppm NBD‐treated callus, uninhibited respiration seemed to be unaffected as a consequence of an inhibited cytochrome path activity, which was compensated by a stimulated alternative path activity. Both in 500 and 4 OIK) ppm NBD‐treated callus the alternative path activity in vivo was stimulated.The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth.
ABA‐induced proline accumulation in barley leaf segments: Dependence on protein synthesis
Authors: Pesci Pierantonio 
Published: May 2006

The kinetics of proline accumulation in barley (Hordeum vulgare L. cv. Georgie) leaf segments showed a lag phase of ca 3 h when the increase was induced by abscisic acid (ABA), but not when the accumulation of the imino acid was promoted by isobutyric acid (IBA). Cycloheximide (CHI) supplied together with ABA, either from the beginning of the treatment or some time before the end of the lag phase, completely abolished ABA‐induced proline accumulation, whereas no block was observed when the inhibitor was supplied after the lag phase. Cordycepin (COR) exibited a similar effect. The IBA‐induced increase in proline was not influenced by CHI for at least 5 h.When segments were pretreated with ABA for a period longer than the lag phase in the absence of salts in the external medium, there was no significant increase in proline. If KCI was added to the incubation medium after such a pretreatment, however, proline increased even after removal of the hormone from the external medium. This increase in proline occurred without any lag phase, and was only partially inbibited by CHI and rapidly and totally blocked by fusicoccin (FC). These results suggest that some protein, characterized by a fast turnover and possibly conferring the sensitivity to KCI, is synthesized during the early hours (lag phase) of the ABA treatment.The synthesis of this protein(s) does not seem to be involved in the increase in proline induced by IBA and is thus a peculiar aspect of that mediated by ABA.
Mobilisation of reserves and the earliest synthesis of sterols and latex triterpenes during germination and early seedling growth of Euphorbia lathyris
Authors: Groeneveld Henri W. , Elings Jopie C. , Koops Andries J. 
Published: May 2006

Seedlings of Euphorbia lathyris L. were grown in the dark at 25°C. Levels of amino acids, sugars and soluble phosphate in the endosperm increased upon germination after 4 days of imbibition, while the amounts of mineral reserves Mg2+ and K+ started decreasing. Ca2+ was not translocated from the endosperm to the seedling. Maximum values for amino acids were found on day 7, and the highest amounts of sugars were present on day 10. The endosperm was completely depleted by day 12.Before germination (days 1–3) a low level of sterol synthesis in the embryo was detected with labeled sucrose and serine and to a lesser extent with labeled pyruvate. The label of [2‐14C]‐mevalonate proceeded exclusively to squalene. Laticifers started the synthesis of their triterpenes upon germination (day 4), using sucrose as a main substrate. A concurrent increase of sterol synthesis outside the laticifers was traced with labeled serine. Radioactive triterpenes, 4 α‐methylsterols and sterols were detected in growing seedlings after [14C]‐mevalonate uptake, but most of its label accumulated in squalene. The use of labeled mevalonate in sterol synthesis in growing seedlings is discussed.
NAD(P)H oxidase and peroxidase activities in purified plasma membranes from cauliflower inflorescences
Authors: Askerlund Per , Larsson Christer , Widell Susanne , Møller Ian M. 
Published: May 2006

An NAD(P)H oxidase activity stimulated by phenolic compounds has been investigated in purified plasma membranes (pm) and in an intracellular membrane (icm) fraction depleted in plasma membranes, both obtained from a microsomal fraction from cauliflower inflorescences (Brassica oleracea L.). The phenolic compounds salicylhydroxamic acid (SHAM), ferulic acid, coniferyl alcohol, n‐propyl gallate, naringenin, kaempferol and caffeic acid all strongly stimulated the activity. Peroxidase (EC 1.11.1.7), or a peroxidase‐like enzyme, was responsible for the NAD(P)H oxidase activity, which proceeded through a free‐radical chain reaction and was inhibited by catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and KCN. Most of the total activity was soluble; however, the membrane‐bound activity was highly enriched in the pm compared to the icm. The catalase activity was 6 times higher in the icm‐fraction than in the pm‐fraction, but this was not the reason for the much lower phenol‐stimulated NADH oxidase activity in the icm. Peroxidase activity measured with o‐dianisidine and H2O2 had about the same specific activities in the pm‐and icm‐fractions.Neither the phenol‐stimulated NADH oxidase nor the peroxidase activity could be washed away from the pm even by 0.7 M NaCl, indicating that these activities are truly membrane‐bound. SHAM as well as the other phenolic compounds capable of stimulating the NADH oxidase reaction were potent inhibitors of blue light‐induced cytochrome b‐reduction in the pm fraction.