Die Photomodulation der Akkumulationsrate von Ascorbinsäure beim Senfkeimling (Sinapis alba L.) durch Phytochrom

Summary Ascorbic acid accumulation in the mustard seedling is controlled by P _fr(active phytochrome). Kinetic studies demonstrate that P _frexerts a rapid and fully reversible control over the steady state rate of ascorbic acid accumulation. Following the terminology of Weisz (1967) for this type of metabolic control the term photomodulation by P _fr is used.—The control by P _fris independent of RNA synthesis. Therefore regulation of gene activity is probably not involved in photomodulation of the rate of ascorbic acid accumulation.—There is only a limited period within which P _frcan control ascorbic acid accumulation. This period is fixed by the time pattern of primary differentiation in the seedling. There is no interaction between photomodulation by P _frand control by primary differentiation of ascorbic acid accumulation.     

Evaluation of malondialdehyde as an index of lead damage in rat brain homogenates

Lipid peroxidation in vitro homogenates of brain was examined as sequela of lead toxicity. The levels of malondialdehyde (MDA) in homogenates of rat brain (1 ml, 5% w/v) treated with lead (50 g) alone or in combination with ascorbic acid (100 g), alphatocopherol (100 g) or hydroquinone (100 g) were evaluated. The levels of MDA were consistently evoked by lead in a dose-related manner. The toxicity of lead was further advanced by the action of the pro-oxidant drug ascorbic acid on the brain. However, the anti-oxidant drugs alphatocopherol and hydroquinone decreased the toxic effect of lead on the brain. These results clearly show that the enhanced lipid peroxidation may provide a basis of lead-induced neurotoxicity.     

Effect of senescence and hormone treatment on the activity of a β-1,3-glucan hydrolase in Nicotiana glutinosa leaves

Summary A high level of activity of a -1,3-glucan hydrolase is present in leaves of Nicotiana glutinosa and the enzyme is also present in the roots, midribs, petioles and stems. By comparison, very low levels of -1,4-glucan hydrolase are found throughout the plant. The activity of the -1,3-glucan hydrolase in leaves aged on the plant was found to increase 14-fold during the course of leaf senescence and to reach a maximum in yellow-green leaves. Detached leaves and leaf discs floated on water in the dark showed similar patterns of change.The increase in -1,3-glucan hydrolase activity during senescence is apparently not due to the loss of an inhibitor from young green leaves or to the formation of an enzyme activator in yellow leaves. The enzyme in yellow leaves was electrophoretically indistinguishable from that in green leaves. The hydrolase is not firmly attached to the cell walls and is not present in the particulate fraction sedimenting at 105400xg for 60 min. Within the leaf cell it is therefore likely to be located either in the cytoplasm or in an easily disrupted structure such as a vacuole.The relationship of the hydrolase to leaf senescence was investigated by examining the effect of plant hormones on the changes in level of hydrolase, protein and chlorophyll in leaf discs during senescence. IAA (10 M) and GA₃ (50 M) did not alter the normal patterns of change, whilst Kin (50 M) delayed the loss of protein and chlorophyll and also delayed and decreased the rise in hydrolase activity. In contrast, ABA (190 M) which increased the rate of loss of protein and chlorophyll, also caused a decrease in the rate and extent of the rise in hydrolase.Possible functions of the hydrolase in the leaf are discussed.Abbreviations used throughout text CM-pachyman carboxymethyl pachyman - CM-cellulose carboxymethyl cellulose - BSA bovine serum albumin - ABA abscisic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - Kin kinetin     

Distribution of magnesium in wheat (Triticum aestivum L.) in relation to supply

The aims of this study were to describe the distribution of magnesium (Mg) and its retranslocation within wheat, in order to develop diagnostic procedures for Mg deficiency. Plants were grown in solution culture with both constant supply (0, 5, 10, 20, 40, 80, 160 MMg) and discontinued supply (40 M and 160 M decreased to nil).Magnesium was depleted from old leaves when Mg supply to the roots was halted. However, initial deficiency symptoms occurred on young leaves under constant but inadequate supply, contrasting with previous reports. Magnesium concentrations were also lower in young leaves compared to old leaves. Symptoms of yellowing and necrosis occurred if the leaf tissue contained <1194 gg^–1, irrespective of leaf age. The minimum Mg concentration in whole shoots associated with maximum shoot weight was 932 gg^–1; for the youngest emerged blade (YEB) it was 861 gg^–1. Symptoms were apparent on the young leaf before a reduction in shoot weight was measurable. The concentration of Mg in the YEB and whole shoot were better related to solution Mg concentration than was the Mg concentration in the old leaf.     

Change in the amino-acid content during male gametophyte formation of Datura metel in Situ

Summary Determination of the free and bound aminoacids during microsporogenesis of Datura metel showed that the principal amino-acids were proline, glutamic acid, aspartic acid, threonine-serine and alanine. Of these, only proline showed a consistent increment during pollen development. In contrast, aspartic acid and lysine decreased in the later stages of microsporogenesis. The amounts of other amino-acids did not show any consistent pattern. Four amino-acids, namely proline, glutamic acid and threonine-serine constituted nearly 85% of the free amino-acid pool in the developed anther (stage IV). Proline accumulation, relative to the total free amino-acid pool in mature anthers, was correlated with the water-content. The results were discussed in view of possible relationships between metabolic activity and free and bound amino-acid concentrations.Abbreviations ABA -Aminobutyric acid - mol/g micromoles of each amino-acid per gram of dry material     

Relationship between peroxidase activity and organogenesis in Panax ginseng calluses

The changes of redox status during culture and their effect on organogenesis were investigated in ginseng callus cultures. Three kinds of Panax ginseng calluses (non-organogenic calluses, root-forming and bud-forming calli) 21 were obtained from each of the three examined auxins (2,4-D, IBA and NAA) at 2 mg l^–1 (9.05 M 2,4-D; 9.84 M IBA; 10.74 M NAA) concentration and 0.1 mg l^–1 (0.46 M) kinetin over 5 weeks. Peroxidase in the soluble fraction, which indicates oxidative status and shows a correlation with differentiation, was higher in bud-forming calluses cultured in the three types of auxins. On the other hand, reducing capacity (overall reducing capacity of glutathione, ascorbic acid, tocoferol, carotenoids and phenol) which indicates reductive status, was higher when these calluses grew on media containing 2,4-D but specially so in the case of non-organogenic calluses. With the three types of auxin used, the reducing capacity was always higher in non-organogenic calluses and lower in calluses with more organogenic capacity. It seems that organogenesis of calluses is conditioned by a high peroxidase activity in soluble fraction (equal to or more than 0.8 A430/mg protein per min) and therefore a low reducing capacity (less than 0.3 A760/g DW). On the other hand 2,4-D promotes proliferation whereas NAA promotes morphogenesis.     

Protection against UVB inactivation (in vitro) of rat lens enzymes by natural antioxidants

Oxidative damage, through increased production of free radicals, is believed to be involved in UV-induced cataractogenesis (eye lens opacification). The possibility of UVB radiation causing damage to important lenticular enzymes was assessed by irradiating 3 months old rat lenses (in RPMI-1640 medium) at 300 nm (100 Wcm-2) for 24 h, in the absence and presence of ascorbic acid, -tocopherol acetate and -carotene. UVB irradiation resulted in decreased activities of hexokinase, glucose-6-phosphate dehydrogenase, aldose reductase, and Na, K- ATPase by 42, 40, 44 and 57% respectively. While endopeptidase activity (229%) and lipid peroxidation (156%) were increased, isocitrate dehydrogenase activity was not altered on irradiation. In the presence of externally added ascorbic acid, tocopherol and -carotene (separately) to the medium, the changes in enzyme activities (except endopeptidase) and increased lipid peroxidation, due to UVB exposure, were prevented. These results suggest that UVB radiation exerts oxidative damage on lens enzymes and antioxidants were protective against this damage.     

Ferulic acid may prevent infection of Cicer arietinum by Sclerotium rolfsii

High performance liquid chromatography analysis of different parts of Sclerotium rolfsii-infected and healthy seedlings of chickpea (Cicer arietinum) was carried out to examine the status of phenolic compounds. Three major peaks that appeared consistently were identified as gallic, vanillic and ferulic acids. Gallic acid concentrations were increased in the leaves and stems of infected plants compared to healthy ones. Vanillic acid detected in stems and leaves of healthy seedlings was not detected in infected seedlings. There was a significant increase of ferulic acid in those stem portions located above the infected collar region compared to minimal amounts in the roots of healthy seedlings. In vitro studies of ferulic acid showed significant antifungal activity against S. rolfsii. Complete inhibition of mycelial growth was observed with 1000 g of ferulic acid/ml. Lower concentrations (250, 500 and 750 g/ml) were also inhibitory and colony growth was compact in comparison with the fluffy growth of normal mycelium. Higher amounts of phenolics were found in the stems and leaves of S. rolfsii-infected seedlings in comparison to the healthy ones. A role for ferulic acid in preventing infections by S. rolfsii in the stems and leaves of chickpea plants above the infection zone is therefore feasible.     

The effect of in vitro pretreatments on subsequent shoot organogenesis from excised Rubus and Malus leaves

Shoot regeneration from Rubus leaves was obtained on a medium containing MS salts, vitamins and sugars, Staba vitamins, casein hydrolysate (100 mg l^–1) and 10 M thidiazuron. Shoot regeneration from Malus leaves was obtained on N⁶ rice anther medium with 5 M thidiazuron. In vitro pretreatment of source shoots with either colchicine or thidiazuron enhanced the organogenic potential of detached leaves of two Rubus hybrids. The response to colchicine was quadratic and occurred at non-mutagenic concentrations (75–250 M). The response to thidiazuron was exponential between 0 and 5 M. When applied as a pretreatment, the effectiveness of several different cytokinins (benzyladenine, thidiazuron, zeatin) at enhancing Malus and Rubus organogenesis was related to the shoot proliferation activity of the cytokinin and to treatment-induced variation in leaf and petiole size.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IBA indolebutyric acid - MS Murashige & Skoog basal medium devoid of plant growth regulators - OI organogenesis-initiating subculture - PTI colchicine pretreatment subculture - PTII cytokinin pretreatment subculture - NAA naphthaleneacetic acid - TDZ thidiazuron - zeatin trans-zeatin     

Induction of systemic acquired resistance in cotton by BTH has a negligible effect on phytophagous insects

Whether or not chemical changes in plants in response to pests (insects and pathogens) are general or specific remains unclear. Some evidence indicates that an induced response (IR) to arthropods via the octadecanoid pathway represents a distinct mechanism from the salicylic acid-based pathway of systemic acquired resistance (SAR) to pathogens. To further test this hypothesis, young cotton seedlings were activated with benzo (1,2,3) thiadiazole-7-carbothioic acid (S) methyl ester (BTH), an elicitor of SAR. The enzymatic activities of a number of pathogenesis-related (PR) proteins in young and old leaves of control and BTH treated plants were measured. BTH applications elicited marked increases in the activity levels of chitinase, peroxidase, and -1,3-glucanase both locally and systemically. The highest levels of induction were detected systemically in young leaves. Except for some local effects on whitefly oviposition, the induction of SAR by BTH had no effect on either host preference of whiteflies Bemisia tabaci (Gennadius) or on feeding efficiency of cotton bollworms Helicoverpa armigera (Hübner). We conclude that SAR induction via the salicylic acid pathway in Acala cotton has negligible effect on the tested insect herbivores.     

Analysis of an ABA-responsive rice gene promoter in transgenic tobacco

We have analyzed in transgenic tobacco the expression of a chimeric gene containing 5 sequences of the rice rab-16B gene fused to the -glucuronidase (GUS) reporter gene. This construct, a translational fusion (–482 to +184) including 14 amino acids of the RAB-16B protein, is expressed only in zygotic and pollen-derived embryos. In zygotic embryos, GUS activity begins to accumulate 10 days after flowering (daf), and increases until seed maturation at 25 daf. Immunological measurements of endogenous abscisic acid (ABA) accumulation in these seeds showed a close parallel between hormone levels and GUS activity. However, GUS activity could not be reproducibly induced by treatment of immature embryos with ABA (10 M). Neither GUS activity nor GUS mRNA could be detected in leaves of transgenic tobacco even after ABA treatment. In contrast, GUS activity could be induced to high levels in pollen-derived embryos by treatment with ABA. Our results show that 482 bp of 5 sequences of the rice rab-16B promoter can confer in transgenic tobacco developmentally regulated expression in embryos but not ABA-responsive expression in vegetative tissues.     

Experimental myocardial necrosis in rats: Role of arjunolic acid on platelet aggregation,coagulation and antioxidant status

Arjunolic acid, a new triterpene and a potent principle from the bark of Terminalia arjuna, has been shown to provide significant cardiac protection in isoproterenol induced myocardial necrosis in rats. To further explore the mechanism of action of arjunolic acid, antiplatelet activity, anticoagulant assays, electrocardiographic changes, serum marker enzymes, antioxidant status, lipid peroxide and myeloperoxidase (MPO) have been measured and the results are compared with a potent cardioprotective drug, acetyl salicylic acid (ASA). Administration of isoproterenol produces electrocardiographic changes such as decreased R amplitude and increased ST segment elevation and has resulted in an increase in serum marker enzyme levels as well as a decrease in enzymatic and nonenzymatic antioxidant levels. Arjunolic acid at an effective dosage of 15 mg/kg body weight (pre and post treatment),when administered intraperitoneally (i.p.), effects a decrease in serum enzyme levels and the electrocardiographic changes get restored towards normalcy. Arjunolic acid treatment is also shown to prevent the decrease in the levels of superoxide dismutase, catalase, glutathione peroxidase, ceruloplasmin, -tocopherol, reduced glutathione (GSH), ascorbic acid, lipid peroxide, MPO and the cardioprotection is confirmed by the histopathological studies.This study shows that the cardioprotection of arjunolic acid pre and post treatment could possibly be due to the protective effect against the damage caused by myocardial necrosis.     

Effect of Metabolites of γ-Aminobutyric Shunt on Activities of NAD- and NADP-Isocitrate Dehydrogenases and Aconitate Hydratase from Higher Plants

We studied the influence of metabolites of -aminobutyric shunt of the tricarboxylic acid cycle on the activities of aconitate hydratase (EC.4.2.1.3) as well as NAD- and NADP-specific isocitrate dehydrogenases (EC.1.1.1.41 and EC.1.1.1.42, respectively) using purified enzyme preparations from pea leaves (Pisum sativum L.) and maize scutellum (Zea mays L.). -Aminobutyric acid and succinate proved to have no significant effect on these enzymes, while 0.1–0.2 mM glutamate markedly activated NADP isocitrate dehydrogenase from both sources, especially at unsaturating concentrations of the substrate. Succinic semialdehyde stimulated the activities of aconitate hydratase and NADP isocitrate dehydrogenase. The obtained data point to a similar pattern of the effect of intermediates of -aminobutyric shunt on the studied enzymatic activities for both photosynthetic tissues (pea leaves) and those with acidifying, transport, and digestive functions (maize scutellum). However, the absence of pronounced control effects of most metabolites on the studied enzymes allows us to assign them to a relatively inert pool of metabolites.     

The inhibition of phenolic biosynthesis in damaged and undamaged birch foliage and its effect on insect herbivores

Summary 1. The leaves of Betula pendula Roth trees were damaged artificially, or by insect-grazing. Both induced an increase in phenolic levels in damaged leaves, larger in the case of insect attack.-2. Some of the damaged trees were sprayed with an inhibitor of phenolic biosynthesis, (aminoxy) acetic acid, which led to a reduction in phenolic levels in both undamaged and damaged leaves. Hence both the effects of damage per se and damage-induced changes in foliage phenolic levels on insect feeding preference could be examined using this technique.-3. Herbivore feeding preferences were assessed in the laboratory by comparing damaged and undamaged leaves, with or without phenolic inhibition, using caterpillars of a natural birch feeder, Apocheima pilosaria D. & S. (Lepidoptera: Geometridae) and a non-birch feeder, Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae). Neither species showed any significant preferences and appeared indifferent to damage, irrespective of whether the trees had their damage-induced phenolic synthesis blocked.-4. The implications of these results for induced defense theory are discussed.     

Effect of regular training on the myocardial and plasma concentrations of taurine andα-amino acids in thoroughbred horses

Summary Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 ± 1.2mol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 ± 0.9 and 7.7 ± 0.69mol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1mol/g wet weight (4.6 ± 0.25 and 1.7 ± 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 ±1.1mol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.     

Copper and cobalt uptake byHaumaniastrum species

Summary Herbarium specimens of the genus Haumaniastrum (mainly from Shaba Province Zaïre) were analysed for copper and cobalt.H. homblei showed elevated copper levels and indicated its tolerance to mineralized ground.H. robertii (previously-known as a copper flower) showed the expected high copper concentrations, but contained abnormally high concentrations of cobalt (av. 4304 g/g dry weight) far exceeding those of copper. This species has the highest cobalt content of any phanerogam and its distribution may be controlled by cobalt rather than by copper. re]19761220     

Rapid separation of the plastid,mitochondrial, and cytoplasmic fractions from intact leaf protoplasts of Avena

Purified intact protoplasts were isolated from etiolated and greening leaves of Avena sativa. They were ruptured by forcing them through a 20-m aperture nylon net and immediately thereafter fractionated into a pure pellet of plastids (well above 70% of total plastids), a layer of mitochondria only slightly contaminated by other cellular constituents (about 50% of total mitochondria), and a cytoplasmic supernatant. This was achieved within 60 s by an integrated method of homogenation of protoplasts and centrifugal filtration of the homogenate on a gradient of silicone oils, contained together with the nylon net in 450 l microtubes, and verified by comparing the levels of activity of specific markers within the three fractions obtained. With appropriate modifications to immediately quench metabolic reactions within the fractions, this method allows the determination of metabolite levels within plastids, mitochondria, and the cytoplasmic compartment of intact protoplasts. The applicability of this technique is demonstrated by the determination of ATP in the plastids, mitochondria, and the cytoplasm of protoplasts obtained from etiolated and greening primary leaves of Avena. The levels of ATP, corrected for contamination of the fractions by each other, exhibit a pronounced transient increase during greening, especially within the cytoplasm.Abbreviations BSA bovine serum albumin - Cyt c cytochrome c - EDTA ethylenediamine tetraacetic acid - HEPES N-2-hydroxyethyl-piperazine-N-2-ethane sulphonic acid - MES 2(N-morpholino) ethane sulphonic acid - PGA 3-phosphoglyceric acid - PEP phosphoenol pyruvic acid - RuBP ribulose-1.5-bis-phosphate     

Purification and characterization of antifreeze proteins from larvae of the beetle Dendroides canadensis

Summary Four antifreeze proteins (AFPs) were purified from larvae of the beetle Dendroides canadensis. The AFPs are similar in amino acid compositions, having high contents of hydrophilic amino acids (45–55 mol%) and cysteine (16 mol% Cys). Approximately half of the Cys residues form disulfide bridges, and both the disulfide bridges and free sulfhydryls are essential for activity. The N-terminals of the AFPs are blocked. The pH optimum of the AFPs is 7.8, but major loss of activity occurred only at very high pH (12.0). The detergents SDS and Triton X-100 did not inactivate the AFPs. Circular dichroism spectra indicate the presence of both and secondary structures in the AFPs, in addition to a large random structure component.Abbreviations AFP antifreeze protein - CD circular dichroism - DTT dithiothreitol - HPLC high pressure liquid chromatography - PAGE polyacrylamide gel electrophoresis - PAS periodic acid Schiff - SDS sodium dodecyl sulfate - TFA trifluoroacetic acid     

Somatic embryogenesis in callus culture of Mussaenda erythrophylla cvs. Queen Sirikit and Rosea

Somatic embryogenesis was achieved from mid-rib and internodal calluses of Mussaenda erythrophylla L. cvs. Queen Sirikit and Rosea cultured on Murashige and Skoog basal medium containing 8.9 M BA+0.57 M IAA+10 mg l^-1 ascorbic acid. Clumps of somatic embryos were separated and grown into complete plantlets when transferred to 1/2 MS medium+37 M adenine sulphate with 2% (w/v) sucrose.     

Callus induction and shoot regeneration in Sempervivum tectorum

Leaf and shoot explants of Sempervivum tectorum L., taken from 14- and 30-day-old plants germinated in vitro, have been studied by using Murashige-Skoog and White basal media with cytokinins (benzyladenine, kinetin) and auxins (indoleacetic acid, naphthaleneacetic acid, indolebutyric acid) in various concentrations. Explants taken from 14-day-old plants died but 30-day-old leaves and shoots produced yellow and soft, as well as green and hard calluses on Murashige-Skoog medium with 4.4–8.8 M benzyladenine and 0.57 M indoleacetic acid. Shoot organogenesis was induced from green, hard callus in a medium with 2.2 M benzyladenine plus either 1.1 M indoleacetic acid or 2.5 M indolebutyric acid. Whole plants were grown on Murashige-Skoog medium without plant growth regulators. On the other hand, White medium was not suitable for raising Sempervivum tectorum in vitro.Abbreviations BA benzyladenine - IAA indoleacetic acid - IBA indolebutyric acid - MS Murashige-Skoog - NAA napthaleneacetic acid - W White