bluuebunny/crossref_metadata_2025_split huggingface dataset:
FITC‐dextran for measuring apoplast pH and apoplastic pH gradients between various cell types in sunflower leaves
Authors: Hoffmann Bernd , Kosegarten Harald 
Published: May 2006

The liquid in the free space of leaf cell walls, the apoplast, is in direct contact with the plasma membrane and its nutrient uptake systems. Therefore, the pH of the apoplast is of utmost interest. We have elaborated a non‐destructive method by which excised sunflower leaves (Helianthus annuuscv. Erika) were perfused with fluorescein isothiocyanate‐dextran (FITC‐dextran) (4 000 Da) via the transpiration stream. We showed that leaf apoplast pH can be measured by using the fluorescence ratio technique together in conjunction with this dye. Evidence is provided that FITC‐dextran does not penetrate the plasma membrane over a period of ca 17 h from the beginning of dye perfusion. Dye enrichment in the leaf apoplast did not cause an ‘inner filter effect’ and thus the fluorescence ratio was only dependent on pH. In vivo calibration yielded a pKa of 5.92, which was virtually identical to the pKa of 5.93 calculated for dye solutions. Hence, FITC‐dextran can be detected in complex environments and covers a pH range prevailing in the leaf apoplast.Based on this method we developed a microscope image technique visualizing pH gradients between various cell types. The pH in the lumen of the xylem vessel was ca 0.3–0.5 units lower than that of the apoplast of surrounding cells. Nitrate present in the leaf apoplast caused an increase in pH, especially in the dark. Under these conditions, in the intercostal area, the apoplast pH around the stomata was ca 0.5–1.0 units higher than that of the surrounding epidermal cells.
Effect of abscisic acid on stomatal opening in isolated epidermal strips of abi mutants of Arabidopsis thaliana
Authors: Roelfsema M. Rob G. , Prins Hidde B. A. 
Published: May 2006

Abscisic acid‐insensitive mutants of Arabidopsis thaliana L. var. Landsberg erecta were selected for their decreased sensitivity to ABA during germination. Two of these mutants, abi‐1 and abi‐2, display a wilty phenotype as adult plants, indicating disturbed water relations. Experiments were undertaken to find out if this results from insensitivity of mutant stomates to ABA.Growth conditions and methods to isolate epidermal strips were optimized to study stomatal movement. Wild type stomates required external ionic conditions comparable to those found for other species such as Commelina communis. The largest light‐induced opening of A. thaliana stomates was found at an external KCl concentration of 50 mM. Stomatal apertures were increased by lowering external Ca2+ to 0.05 mM. The apertures of stomates incubated with 10 μM ABA were not altered by changes in Ca2+ from 0.05 to 1.0 mM.Stomates of all abi mutants showed a light‐stimulated stomatal opening. The opening of wild type and abi‐3 stomates was inhibited by ABA, while stomates of abi‐1 and abi‐2 did not respond to ABA. The insensitivity of abi‐1 and abi‐2 stomates to ABA may thus explain the observed disturbed water relations.
Sugar degradation during autoclaving: Effects of duration and solution volume on breakdown of glucose
Authors: Wang Xiao‐Jia , Hsiao Ke‐Cheng 
Published: May 2006

As the autoclaving of a sugar together with other nutrient components enhances its degradation with the associated formation of toxic products, it is advisable to autoclave it separately from other medium components. In such cases, and to prepare growth media of consistent quality, it may also be necessary to adjust the duration of autoclaving according to the volume of the sugar solution. The results of an attempt to fine‐adjust the autoclaving procedure are presented.Glucose, used as model sugar in this investigation, was autoclaved for 20,32 or 44 min in volumes of 0.25. 1.2 and 5 1. The rise in temperature of the solutions was monitored by thermocouples. Glucose degradation was estimated by the rate of cyanide‐initiated oxygen consumption. The rates were found to be inversely proportional to the volumes in a semilogarithmic plot. The T‐t (temperature‐time) value, the area under the solution temperature vs time curve, was found to be an independent variable from which the extent of glucose degradation could be deduced. For a chosen level of thermodegradation of glucose, the duration of autoclaving for solutions of different volumes could be determined graphically from a T‐t value vs time plot.
Effect of temperature on biomass allocation in tomato (Lycopersicon esculentum)
Authors: Heuvelink E. 
Published: May 2006

Temperature may influence dry matter partitioning between fruits and vegetative plant parts either directly or indirectly through its influence on development, flower and/or fruit abortion. The objective of the present work was to investigate whether there is any direct effect of temperature on dry matter partitioning between fruits and vegetative plant parts in tomato. A greenhouse experiment was conducted, with alternating 3‐week periods of high (23°C) and low (18°C) temperature setpoint. Dry matter partitioning during these 3‐week periods was determined from destructive plant harvests at two levels of fruit pruning (3 and 7 fruits per truss). Indirect temperature effects on dry matter partitioning were excluded by fruit pruning.On average, the fraction of dry matter distributed to the fruits during a 12‐week period, starting with the flowering of the fifth truss (28 days after planting), was 0.53 (3 fruits per truss) and 0.70 (7 fruits per truss). These ratios were also calculated for every 3‐week period separately and did not depend on the average temperature (18–24°C) during that period.It is concluded that dry matter distribution in tomato is not significantly affected by temperature directly, which means that the temperature effect (18–24°C) on the generative sink strength is not much different from the temperature effect on the vegetative sink strength.
Effect of apex excision and replacement by 1‐naphthylacetic acid on cytokinin concentration and apical dominance in pea plants
Authors: Li C.‐J. , Guevara E. , Herrera J. , Bangerth F. 
Published: May 2006

As known from literature lateral buds from pea (Pisum sativum) plants are released from apical dominance when repeatedly treated with exogenous cytokinins. Little is known, however, about the endogenous role of cytokinins in this process and whether they interact with basipolar transported IAA, generally regarded as the main signal controlling apical dominance. This paper presents evidence that such an interaction exists.The excision of the apex of pea plants resulted in the release of inhibited lateral buds from apical dominance (AD). This could be entirely prevented by applying 1‐naphthylacetic acid (NAA) to the cut end of the shoot. Removal of the apex also resulted in a rapid and rather large increase in the endogenous concentrations of zeatin riboside (ZR), isopentenyladenosine (iAdo) and an as yet unidentified polar zeatin derivative in the node and internode below the point of decapitation. This accumulation of ZR and iAdo, was strongly reduced by the application of NAA. The observed increase in cytokinin concentration preceded the elongation of the lateral buds, suggesting that endogenous cytokinins play a significant role in the release of lateral buds from AD. However, the effect of NAA on the concentration of cytokinins clearly demonstrated the dominant role of the polar basipetally transported auxin in AD. The results suggest a mutual interaction between the basipolar IAA transport system and cytokinins obviously produced in the roots and transported via the xylem into the stem of the pea plants.
Solute leakage, lipid peroxidation, and protein degradation during the senecence of Iris tepals
Authors: Celikel Fisun G. , van Doorn Wouter G. 
Published: May 2006

A colour change and inrolling of the tepal edges are the first symptoms of senescence of Iris flowers (Iris x hollandica Tub., cv. Blue Magic). Tepals showed an increase in leakage of both ions and anthocyanins, prior to the visible senescence symptoms. Increased leakage occurred irrespective of the time at which the tepals were severed and placed in water, indicating that the senescence process is inherent in the tepal cells. Net loss of proteins in the tepal edges started after flower opening, and after two more days, when the first symptoms of senescence were observed, the protein level was only 20% of that at harvest. Cycloheximide delayed senescence and resulted in a lower rate of protein loss. Phenylmethylsulfony fluoride (PMSF), a protease inhibitor, had a similar effect on protein levels but did not affect the time to visible senescence, and also several other protease inhibitors did not affect the time to senescence.During senescence the rate of respiration of the tepals remained unchanged and their rate of ethylene production decreaased. The rate of ethane production, an indicator of lipid peroxidation, was very low and remained unaltered. Antioxidants (lascorbic acid, benzoic acid, butylated hydroxytoluene, diphenylamine, propyl gallate, propyl‐p‐hydroxybenzoate and sodium benzoate) had no effect on the time to tepal senescence. It is concluded that tepal wilting is due to transfer of solutes from the symplast to the apoplast. Although net protein degradation occurs early during the senescence process, its inhibition is not correlated with a delay in the time to senescence. Furthermore, the results do not support the hypothesis that the increase in solute leakage is due to (free radical‐mediated) peroxidation of membrane lipids. The present results are in contrast with the ethylene‐regulated petal senescence of carnation, which is accompanied by lipid peroxidation.
Expression of chloroplastic and cytosolic glutamine synthetase in barley leaves after cold‐sensitive blocking of β‐carotene synthesis by amitrole or mutation
Authors: Zito Francesca , Gough Simon , Marcato Caterina , Rascio Nicoletta , Casadoro Giorgio 
Published: May 2006

3‐Amino‐ 1,2,4‐triazole (amitrole) provided to germinating barley at 20°C in the light led to bleached seedling leaves and photodynamic destruction of chloroplast structure, whereas normal greening and chloroplast ultrastructure was obtained when the seedlings developed in the presence of amitrole in the light at 30°C. Mass spectrometric analysis of the extractable herbicide demonstrated the same content of amitrole in leaves developed at 20 and 30°C. A very similar temperature‐sensitive syndrome is characteristic for the nuclear gene mutant ligrina‐o34 in barley. Amitrole and the mutation were shown to inhibit the cyclization of lycopene, leading to severe deficiencies in β‐carotene and its xanthophyll derivative lutein. Besides accumulation of lycopene, also its precursors phytoene, phytofluene and ξ‐carotene accumulated. Inhibition of carotenoid biosynthesis by amitrole and the mutation at 20°C in the light led to a strong reduction of both transcript and protein levels for chloroplastic glutamine synthetase (GS2) while transcript amount and protein of the cytosolic isoenzyme (GS1) were unaffected. At 30°C increased levels of mRNA for the chloroplastic isoform GS2 were observed in wild type, mutant and amitrole‐treated seedlings, but protein levels remained unchanged. Turnover rates of the GS2 protein were the same at 20 and 30°C. This extensive translational control of chloroplastic GS2 synthesis was also observed in a heat shock experiment, which revealed transiently increased mRNA levels for chloroplastic GS2 but unchanged protein levels.Permissive synthesis of β‐carotene and chloroplastic glutamine synthetase (GS2) at 30°C in the presence of amitrole or the tigrina‐o34 mutation might be due to two alternative pathways of ionone ring formation using either lycopene or neurosporene as substrates for cyclization.
Phosphatidylcholine biosynthesis and cell growth in Apium graveolens
Authors: Parkin Edward T. , Goad L. John , Rolph Carole E. 
Published: May 2006

Xenobiotics directed against sterol biosynthesis have proved to be useful tools in the determination of which sterol molecules are necessary for successful plant cell growth. However, the exact mode of action by which sterols are able to trigger cell growth remains to be elucidated. Previous studies using the triazole paclobutrazol, demonstrated that in Apium graveolens (cv. New Dwarf White) suspension cultures, sterol and phosphatidylcholine biosynthesis are co‐ordinately regulated (C. E. Rolph and L. J. Goad 1991, Physiol. Plant. 83: 605–610). The studies presented herein, were designed to investigate the possible role of phosphatidylcholine in the stimulation of plant cell growth.Sterol biosynthesis, and hence cell growth, was inhibited by the use of the azole xenobiotic miconazole. Treatment of the cultures with miconazole lead to compositional changes in the free sterol content of the cells. For example, 30 μM miconazole treatment led to a reduction in the stigmasterol/sitosterol ratios from 1.53 to 1.24. In contrast, the phospholipid content of the cells remained relatively unchanged with phosphatidylcholine accounting for approximately 25% of the total phospholipids present in both control and miconazole‐treated cells. The cytostatic effect of miconazole could be partially counteracted by supplementation of the growth medium with the phytosterol stigmasterol and/or the unsaturated fatty acids oleate and linoleate.The activity of CTP:cholinephosphate cytidylyltransferase (EC 2.7.7.15), a rate‐limiting enzyme in phosphatidylcholine biosynthesis, was significantly reduced in cells whose growth had been arrested by miconazole treatment. In miconazole‐treated cultures whose growth had been partially restored by supplementation with either specific sterols or unesterified fatty acids, the activity of this key enzyme was increased. In the case of stigmasterol, oleate and linoleate supplementation, the microsomal activity was found to be similar to that exhibited by control cultures.From these studies, it may be concluded that certain phytosterols and unsaturated fatty acids play key roles with respect to phosphatidylcholine biosynthesis and that phosphatidylcholine biosynthesis via the CDP‐base pathway is an important pre‐ and/or co‐requisite for successful culture growth.
Proteinase inhibitor II is developmentally regulated in Nicotiana flowers
Authors: Ausloos G. R. J. , Proost P. , van Damme J. , Vendrig J. C. 
Published: May 2006

Proteinase inhibitors (PI) are expressed in several members of the Solanaceae. According to species, PI can be both developmentally and environmentally regulated. We investigated the presence and developmental regulation of PI in the flowers of Nicotiana plumbaginifolia. By trypsin affinity chromatography a small protein, Np‐PI‐II, was isolated. This protein had an N‐terminus similar to a part of a Nicotiana alata PI‐II, and an inhibitory activity towards trypsin. Inhibitory activity is expressed at very early stages of floral development. No inhibitor is present in the vegetative meristems. The inhibitory activity remains high throughout flower maturation and rapidly declines in the ovary after pollination. In the stigma of mature Nicotiana tabacum flowers trypsin inhibitory activity is detected extracellularly. Proteinase inhibitor activity is not a regular feature of the stigmas of several solanaceous genera.Proteinase inhibitors apparently have no function in the development of floral structures and probably act as protective agents against fungal infection of and insect damage to the floral parts and the developing fruit.
Inhibitory effect of S‐carvone on wound healing of potato tuber tissue
Authors: Oosterhaven K. , Hartmans K. J. , Scheffer J. J. C. , van der Plas L. H. W. 
Published: May 2006

Wounded tuber tissue of potato (Solanum tuberosum L. cv. Gloria) exposed to the monoterpene S‐carvone did show neither suberization nor cambium layer formation, whereas these processes started after 2–4 days in control tissue. Suberized tissue was clearly visible 24 days after the start of the S‐carvone treatment, when the concentrations of S‐carvone and its bioconversion products in the tissue were almost zero and cambium layer formation had not yet started. The inhibition of wound healing coincided with a lack of induction of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34). The wounded potato tissue used as control, showed a transient induction of HMGR activity.In S‐carvone treated tissue, the activities of GR (glutathione reductase, EC 1.6.4.2) and AP (ascorbate peroxidase, EC 1.11.1.11) were induced, and the level of glutathione increased four‐ to five‐fold.
Diagnosis of damage to Norway spruce (Picea abies) through biochemical criteria
Authors: Wild Aloysius , Schmitt Volker 
Published: May 2006

Bioindication can be carried out at different hierarchical levels, eg. cell, organism, and ecosystem. While the monitoring of damage by visible criteria (e.g. loss of needles) is connected with the organism as a whole, the monitoring of damage by biochemical indicators is above all connected with cell metabolism.The degree of vitality of a tree can be ascertained through the integration of a number of biochemical parameters. Furthermore, a differential diagnosis of a particular stress pattern can be carried out because of the feedback pattern of several biochemical indicators. In order to describe and interpret biochemical or physiological changes that have been caused by a number of factors, multivariate statistical methods are being used more frequently. Apart from cluster and discriminant analysis, it is especially factor analysis which provides a helpful tool when dealing with problems in the field of environmental analysis. Factor analysis can be used for an integrating as well as a differentiating assessment.Within the framework of forest damage research, numerous changes at the level of cell metabolism have been detected to which a bioindicative character can be attached. A number of physiological and biochemical parameters with bioindicative character concerning Norway spruce are presented.
Photoperiodic control of endogenous gibberellins in seedlings of Salix pentandra
Authors: Olsen J. E. , Jensen E. , Junttila O. , Moritz T. 
Published: May 2006

In the temperate‐zone woody species Salix pentandra elongation growth is regulated by the photoperiod. Long days sustain active growth, whereas short days induce cessation of apical growth, which is a prerequisite for winter hardening. It is shown that this is correlated to quantitative changes in levels of endogenous GA19 GA20, and GA1. Within two short days the amount of the active GA1 and its immediate precursor GA20, decreased markedly in young leaves us well as in stem tissue. Also, the amount of GA19, declined, but the decrease was delayed relative to that of GA1 and GA20. The ability of S. pentandra seedlings to respond to exogenous GA19, decreased with increasing numbers of short days. Observations that support the hypothesis that the level of GA1 in S. pentandra is regulated by the photoperiod in a quantitative mode with conversion of GA19, to GA20, being one target for control.Different distribution of GAs in various plant parts was observed. The level of GA was higher in young leaves than in other plant parts, and the amount of GA19 was 5–10 times higher in stem tissue than in leaves and roots. The ratios of GA8 to GA1 and GA20, were higher in roots as compared with other parts, as rods contained very low levels of GA1 and GA20, but amounts of GA20 comparable with other parts.
Thiols of Cu‐treated maize plants inoculated with the arbuscular‐mycorrhizal fungus Glomus intraradices
Authors: Galli Ulrich , Schüepp Hannes , Brunold Christian 
Published: May 2006

Mycorrhizal colonization of roots, fresh weight, content of cysteine, γ‐glutamylcysteine (γEC). glutathione (GSH), thiol groups in Cu‐binding peptides (CuBP), and the uptake of Cu were measured in roots and shoots of maize (Zea mays L., cv. Honeycomb F‐1) grown in quartz sand, with Cu at 0, 4.5, 9, 15 and 30 μg g−1 added with or without inoculum of the arbuscular‐mycorrhizal fungus (AMF) Glomus intraradices. In control plants (no Cu added) AMF significantly reduced shoot growth, but did not affect root growth. At an external Cu supply of 9 μg (g quartz sand)−1 or higher, both mycorrhizal colonization and growth of roots and shoots of mycorrhizal and non‐mycorrhizal plants were significantly reduced.With up to 9 μg Cu g−1, mycorrhizal colonization increased the content of cysteine, γEC and GSH in the roots. However, the amount of thiols in CuBPs was not increased by mycorrhizal colonization in Cu‐treated plants and no differences in Cu uptake were detected between non‐mycorrhizal and mycorrhizal plants. A CuBP‐complex with a relative molecular mass of 7300 and a SH:Cu ratio of 1.77:1 was separated on a Sephadex G‐50 column from both non‐inoculated and inoculated roots of Cu‐treated plants. HPLC chromatography of the CuBPs of both non‐inoculated and inoculated roots resulted in a similar peak pattern, indicating that no additional CuBPs were formed by the fungus. In conclusion, our results do not support the idea that AMF protects maize from Cu‐toxicity.
Nitrate regulation of nitrate uptake and nitrate reductase expression in barley grown at different nitrate:ammonium ratios at constant relative nitrogen addition rate
Authors: Samuelson Mariann E. , Öhlén Elisabeth , Lind Maria , Larsson Carl‐Magnus 
Published: May 2006

Barley (Hordeum vulgareL. cv. Golf) was cultured using the relative addition rate technique, where nitrogen is added in a fixed relation to the nitrogen already bound in biomass. The relative rate of total nitrogen addition was 0.09 day−1(growth limiting by 35%), while the nitrate addition was varied by means of different nitrate: ammonium ratios. In 3‐ to 4‐week‐old plants, these ratios of nitrate to ammonium supported nitrate fluxes ranging from 0 to 22 μmol g−1root dry weight h−1, whereas the total N flux was 21.8 ± 0.25 μmol g−1root dry weight h−1for all treatments. The external nitrate concentrations varied between 0.18 and 1.5 μM. The relative growth rate, root to total biomass dry weight ratios, as well as Kjeldahl nitrogen in roots and shoots were unaffected by the nitrate:ammonium ratio. Tissue nitrate concentration in roots were comparable in all treatments. Shoot nitrate concentration increased with increasing nitrate supply, indicating increased translocation of nitrate to the shoot.The apparent Vmaxfor net nitrate uptake increased with increased nitrate fluxes. Uptake activity was recorded also after growth at zero nitrate addition. This activity may have been induced by the small, but detectable, nitrate concentration in the medium under these conditions. In contrast, nitrate reductase (NR) activity in roots was unaffected by different nitrate fluxes, whereas NR activity in the shoot increased with increased nitrate supply. NR‐mRNA was detected in roots from all cultures and showed no significant response to the nitrate flux, corroborating the data for NR activity. The data show that an extremely low amount of nitrate is required to elicit expression of NR and uptake activity. However, the uptake system and root NR respond differentially to increased nitrate flux at constant total N nutrition. It appears that root NR expression under these conditions is additionally controlled by factors related to the total N flux or the internal N status of the root and/or plant. The method used in this study may facilitate separation of nitrate‐specific responses from the nutritional effect of nitrate.