bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of gibberellin A3 and cytokinins on natural and post‐harvest, ethylene‐induced pigmentation of Satsuma mandarin peel
Authors: Garcia‐Luis A. , Fornes F. , Guardiola J. L.
Published: May 2006

Natural and post‐harvest ethylene‐induced pigment changes in the rind of Satsuma mandarin (Citrus unshiu Marc.) fruits respond differently to the exogenous application of growth regulators. Both gibberellin A3 and the synthetic cytokinins N6‐benzyladenine and kinetin opposed the ethylene‐induced chlorophyll destruction, while the loss of chlorophyll during natural maturation was retarded by the gibberellin but not by the cytokinins. This different behaviour suggests that ethylene may not be playing a central role in the endogenous control of ripening. Carotenoid accumulation during natural maturation is apparently controlled through a different mechanism than chlorophyll loss since it is reduced both by the cytokinins and gibberellin A3.

Kinetin and gibberellin A3 increased to a similar extent the accumulation of reducing sugars and free amino acids, and reduced that of non‐reducing sugars in the peel during natural maturation. Their differential effect on chlorophyll loss may not be explained through their effects on sugar accumulation.
Activities of some peptidases and proteinases in germinating kidney bean, Phaseolus vulgaris
Authors: Mikkonen Anita
Published: May 2006

The activities of aminopeptidase (EC 3.4.11), dipeptidase (EC 3.4.13), carboxypeptidase (EC 3.4.16), naphthylamidase (EC 3.4.11) and proteinases (EC 3.4.21) were assayed in extracts from the cotyledons and the axial tissues of resting and germinating kidney beans (Phaseolus vulgaris L. cv. Processor).

The activities of the alkaline peptidases (aminopeptidase hydrolyzing Leu‐Tyr at pH 9.2 and dipeptidase acting on Ala‐Gly at pH 8.5) and naphthylamidases (hydrolyzing Leu‐β‐naphthylamide at pH 6.4) were high in the cotyledons of resting seeds, but decreased during germination. This decrease was faster than the loss of the total nitrogen. On the contrary, the activities of carboxypeptidase (hydrolyzing carbobenzoxy‐Phe‐Ala at pH 5.9) and proteinases (acting on haemoglobin at pH 3.7 and on casein at pH 5.4 and 7.0) were low in the resting seeds, but increased during germination reaching their maximal values when the mobilization of nitrogen was highest. It has been suggested that the breakdown of storage proteins is initiated inside the protein bodies by acid proteinases and carboxypeptidases. Although the activities of the alkaline peptidases and naphthylamidases decreased during germination, these were still relatively high and enough for the completion of the proteolytic breakdown. Thus, it is suggested that, as a final step in a chain of events, the main role for the alkaline peptidases in the cotyledons of germinating seeds is to provide amino acids for the growth of the seedling.
Properties of NADP+‐malic enzyme from pod walls of chickpea (Cicer arietinum)
Authors: Das Suchitra , Sood D. R. , Sawhney S. K. , Singh Randhir
Published: May 2006

NADP+‐malic enzyme (l‐malate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.40) from pod walls of chickpea was purified 51‐fold by ammonium sulphate fractionation, DEAE‐ cellulose chromatography and gel filtration through Sepharose 4B. The purified enzyme required a divalent cation, either Mn2+ or Mg2+, for its activity. Km values at pH 7.8 for malate, NADP+ and Mn2+ were 4.0, 0.031 and 0.71 mM, respectively. Mn2+‐dependent activity was inhibited by heavy metal ions such as Cd2+, Zn2+, Hg2+, and to a lesser extent by Pb2+ and Al3+. Among the organic acids examined, sodium salts of oxalate and oxaloacetate were inhibitory. Kinetics of the reaction mechanism showed sequential binding of malate and NADP+ to the enzyme. Products of reaction, viz. pyruvate, bicarbonate and NADPH, inhibited the enzyme activity. At limiting concentrations of NADP+, pyruvate and bicarbonate induced a positive cooperative effect by malate. It is proposed that the activity of NADP+‐malic enzyme is controlled by intracellular concentrations of substrates and products.
Regulation of ammonium/methylammonium transport by ammonium in the cyanobacterium Anabaena variabilis
Authors: Rai A. N. , Singh D. T. , Singh H. N.
Published: May 2006

The ammonium transport system of Anabaena variabilis Kütz ATCC 29413 was studied with regard to its repression and derepression using [14C]‐methylammonium as an analogue for ammonium. Whereas N2‐grown cells showed an active ammonium transport system, the latter was repressed in ammonium‐grown cells. Repression of the ammonium transport system by ammonium did not require ammonium assimilation or de novo protein synthesis, suggesting that ammonium itself was the repressor signal. The derepression of the ammonium transport system however, required de novo protein synthesis and glutamine synthetase activity.
Reduction of nitrate in the perennial tissues of aerial parts of Alnus glutinosa
Authors: Pizelle G. , Thiery G.
Published: May 2006

In vivo nitrate reductase (NR, EC 1.6.6.1.) activity was measured in leaves, branches and trunk of field‐grown Alnus glutinosa (L.) Gaertn. All of the assayed tissues enzymatically reduced nitrate with a decreasing activity [μmol NO2− (g dry weight)−1 h−1] in the order: leaves > branch bark > inner branch tissues > trunk xylem. The NR activity of the various tissues of excised branches was inhibited by tungstate added to the transpiration stream. Part of the nitrate added to the feeding solution (0.2, 0.5 or 1 mM KNO3) of excised branches disappeared during its transport via the transpiration stream in the perennial tissues. This disappearance was enzymatic since it was decreased by tungstate.

No evidence was obtained for the presence of nitrate in natural xylem sap nor for a significant correlation between nitrate content of soil and leaf NR activity. These results indicate that in the field‐grown black alder, the nitrate not reduced in the roots could be reduced in the perennial tissues of aerial parts. Since the leaf NR activity does not reflect the actual in situ nitrate reduction, the existence of a constitutive NR activity in Alnus leaves is suggested.
A burst of CO2 from photosynthesizing leaves after a temperature decrease under constant light conditions
Authors: Tarlowski Jan , Bzdȩga Tomasz , Łoboda Tadeusz , Nalborczyk Emil
Published: May 2006

A transient CO2 burst from seedlings of some plant species was observed after a rapid temperature decrease. The magnitude of the CO2 release depended on initial temperature, oxygen concentration and light intensity. To obtain a maximal value of CO2 release, the temperature had to decrease by more than 8°C. The phenomenon was detected only in the light, and was confined to C3 species. It was inhibited by low oxygen concentration, indicating its possible connection with photorespiration.
Direct versus indirect effects of p‐chloromercuribenzenesulphonic acid on sucrose uptake by plant tissues: The electrophysiological evidence
Authors: M'Batchi Bertrand , El Ayadi Rachida , Delrot Serge , Bonnemain Jean‐Louis
Published: May 2006

The short‐term effects of p‐chloromercuribenzenesulphonic acid (PCMBS) on the transmembrane potential difference (PD) of broad bean (Vicia faba L. cv. Aguadulce) cotyledon cells and on sugar beet (Beta vulgaris L. cv. Klein E.) leaf cells were studied by the electrophysiological method. These effects were compared with that of the permeant thiol reagents N‐ethylmaleimide and HgCl2. N‐Ethylmaleimide and HgCl2 markedly and rapidly depolarised the PD of all the material studied, while PCMBS caused either a slight depolarisation (cotyledon cells) or no depolarisation (leaf cells) during the first 30 min of treatment. In cotyledons, PCMBS markedly inhibited sucrose uptake (89%) and the sucrose‐induced depolarisation associated with the proton‐sucrose symport (67%), while it decreased the proton‐motive force only marginally (7%). It is concluded that during short treatments (30 min or less). PCMBS inhibits sucrose uptake directly by blocking the sucrose carrier, and not the proton pump. For longer treatments, indirect effects cannot be excluded.
Auxins of non‐flowering plants. I. Occurrence of 3‐indoleacetic acid and phenylacetic acid in vegetative and fertile fronds of the ostrich fern (Matteucia struthiopteris)
Authors: Schneider Elonora A. , Wightman Frank
Published: May 2006

Gas chromatography‐mass spectrometry evidence is presented for the presence of both phenylacetic acid (PAA) and 3‐indoleacetic acid (IAA) in vegetative and fertile tissues of the sporophyte of the ostrich fern [Matteucia struthiopteris (L.) Todaro]. 3‐Indolepropionic acid, tryptamine and 3‐indoleacetonitrile were not found in tissue extracts, although small amounts of 3‐indolebutyric acid and tryptophol may have been present. PAA was present in amounts higher than those found in flowering plants, while LAA levels fall within the angiosperm range. The levels of both auxins were higher in the younger vegetative tissues than in mature vegetative or fertile pinnae. Recent evidence for the occurrence of angiosperm growth hormones in ferns is discussed.
The effect of the high lysine genes of the barley mutants Risø 1508 and 527 on embryo development
Authors: Deggerdal A. , Klemsdal S. S. , Olsen O.‐A.
Published: May 2006

Dry weight of 34‐day‐old embryos from barley (Hordeum vulgare L.) cv. Bomi and high lysine mutants 527, 1508 and the double mutant 527/1508 were 1.00, 1.13, 1.56 and 2.22 mg, respectively. Embryos of the four lines were compared by light and electron microscopy and two dimensional gel electrophoresis. Morphological differences were restricted to the scutellar tissue, which had an irregular form in 1508 and the double mutant. Average scutellar cell volumes in 34‐day‐old embryos from cv. Bomi, mutants 527, 1508, and 527/1508 were 4 200, 8 300, 4 900 and 23 400 μm3. respectively. The starch content of the scutellar parenchyma cells was slightly higher in mutant 527 than in cv. Bomi, and considerably higher in mutant 1508 and the double mutant. The two dimensional gel electrophoretic examination showed that seven of the embryo protein spots were of a significantly different size in the mutants relative to those from cv. Bomi. Among these seven proteins, one was apparent only in the double mutant, four were more abundant in the mutants than in cv. Bomi and two were less abundant. The isoelectric points and the molecular weights of these proteins do not correspond exactly to those of proteins previously described in barley seeds.
Effects of sodium diethyldithiocarbamate, solvent, temperature and plant extracts on the stability of indoles
Authors: Ernsten Arild , Sandberg Göran , Crozier Alan
Published: May 2006

A study has been made of the effects of solvent, temperature, and the antioxidant, sodium diethyldithiocarbamate, on the breakdown of indole‐3‐pyruvic acid to indole‐3‐acetic acid (IAA). In addition, the degradation of tryptophan, tryptamine, indole‐3‐pyruvic acid, indole‐3‐acetaldehyde and indole‐3‐ethanol to IAA during the purification and analysis of extracts from Pinus sylvestris L. needles, in the presence and absence of sodium diethyldithiocarbamate, has been investigated. The data obtained indicate that if the antioxidant is supplied throughout the analytical sequence there is a marked reduction in the spontaneous formation of IAA from other indolic compounds and, by inference, the stability of indoles in general is enhanced.
Responses of Pinus clausa, Pinus serotina and Pinus taeda seedlings to anaerobic solution culture. I. Changes in growth and root morphology
Authors: Topa Mary A. , McLeod Kenneth W.
Published: May 2006

Seedlings of pond pine (Pinus serotina Michx.), sand pine [P. clausa (Engelm.) Sarg.] and two edaphic seed sources of loblolly pine (P. taeda L., dry‐ and wet‐site seed sources) were grown in non‐circulating, continuously flowing solution culture under aerobic (250 μM O2) and anaerobic (≤ 23 μM O2) conditions. Survival was 100% for all seedlings at 11 weeks. Although shoot height, biomass and leaf emergence of loblolly and pond pine seedlings were not significantly affected by 15 or 30 days of anaerobic growth conditions, root biomass was significantly reduced. Sand pine suffered the largest reduction in biomass, showing extensive root dieback and shoot chlorosis with retarded leaf development. These anaerobically induced symptoms of flooding injury were less severe in dry‐site loblolly pine, and absent in wet‐site loblolly and pond pine seedlings. Adventitious or new, secondary roots, and stem or taproot lenticels were particularly abundant under the 30‐day anaerobic treatment in wet‐site loblolly and pond pine seedlings, present to a lesser degree in dry‐site loblolly pine, and nearly absent in sand pine seedlings. These results indicate that much of the immediate damage from flooding is due to the anoxic condition of the root rather than to the build‐up of phytotoxins or soil nutrient imbalances. On the basis of overall seedling vigor, root plasticity and growth, we suggest the following flooding‐tolerance/intolerance species (seed source) gradient: pond pine ≥ wet‐site loblolly pine > dry‐site loblolly pine > sand pine.
Role of the testa epidermis in the leakage of intracellular substances from imbibing soybean seeds and its implications for seedling survival
Authors: Duke Stanley H. , Kakefuda Genichi , Henson Cynthia A. , Loeffler Nancy L. , Van Hulle Nancy M.
Published: May 2006

The effects of testa epidermal cracks on imbibition induced soybean (Glycine max [L.] Merr.) seed damage, as measured by the leakage of intracellular constituents, and on subsequent seedling survival were examined. Testa epidermal cracking increased with increasing seed surface area and this was caused by periods of dry seed hydration as short as 1 min followed by air drying. As compared to slow imbibition in germination paper, rapid imbibition of seeds caused by submersion in distilled H2O for 6 h at 25°C greatly increased the leakage of intracellular substances during imbibition and greatly decreased the survival of seeds with intact testae, testa epidermal cracks, and without testae. Seeds that were aerated during rapid hydration germinated as poorly and leached solutes as profusely as seeds not aerated. This indicates that anoxia is not a significant factor in rapid hydration effects on soybean seeds. Seeds with testa epidermal cracks had higher levels of leakage of intracellular substances and lower rates of seedling survival than seeds with intact testae. This was true regardless of rate of hydration. Testa tissues other than the epidermis had no effect on seedling survival after slow imbibition but greatly decreased seed leakage during rapid imbibition and increased subsequent survival. Studies with individual seeds indicated that the leakage of intracellular substances during rapid hydration is greatest from seeds that are killed or severely injured by imbibition or that are dead before imbibition, regardless of testa condition. These results indicate that soybean seed testa epidermis is extremely important in protecting the seed from injury by rapid and slow hydration and in maintaining seed viability.
Root hair formation and elongation of primary maize roots
Authors: Jaunin Françoise , Hofer Rose‐Marie
Published: May 2006

In maize (Zea mays L. cv. LG 11) roots cultured in humid air, the presence of hairs was not related to root growth. However, maximum hair length and length of the hair zone could be correlated to the elongation rate of the primary root. Under the growth conditions used, the emergence of root hairs always took place in the extending zone. In more basal regions, rhizodermal cells could not give rise to root hairs. Results were similar for roots preincubated in a buffer solution.
Seasonal variation in the ultrastructure of the cambium in young stems of willow (Salix viminalis) in relation to phenology
Authors: Sennerby‐Forsse Lisbeth
Published: May 2006

The growth period of Salix viminalis L. (clone 683) plants near Stockholm, Sweden, (59.5°N, 18.3°E) started in April with flowering and ended in October with abscission of the shoot tips. Cell divisions in the vascular cambium started almost two months before sprouting and ceased at about the same time as the elongation growth of the shoots. Phloem cells were apparently produced before flowering, while new xylem production started at the time of flushing. Cytodifferentiation in immature xylem continued until November. Thick‐walled cells with protoplasm were observed adjacent to xylem mother cells in the cambium during the winter. The number of radially arranged cells in the cambial zone increased from 3–4 during dormancy to about 18 during the mitotic maximum in July. Seasonal variation was apparent in vacuolization, wall thickness and presence of storage material in the cells. Lipid bodies and protein bodies occurred in both fusiform and ray initials, while starch was observed in ray initials, ray cells and in the phloem. In September the ultrastructure of the cambium showed anatomical features characteristic for both active and dormant cells. Dictyosomes with vesicles and rough ER were present in thick‐walled cells that contained lipid bodies and starch granules. Nuclear divisions in the cambium ended in October.
Characterization of NADP+‐isocitrate dehydrogenase from the host plant cytosol of lucerne (Medicago sativa) root nodules
Authors: Henson Cynthia A. , Duke Stanley H. , Collins Michael
Published: May 2006

NADP+‐isocitrate dehydrogenase (EC 1.1.1.42) was purified more than 1500‐fold from the host‐plant cytosol ofMedicago sativaL. cv. Saranac root nodules by ion exchange and affinity chromatography. The forward reaction was characterized. The enzyme exhibited an absolute requirement for a divalent cation (preferably Mn2+), had a broad activity optimum from pH 7.5 to 9.0, and was most stable at pH 7.5. The apparent Arrhenius energy of activation was 70.7 kJ mol−1(20 to 30°C) indicating that the reaction rate of the enzyme was relatively sensitive to temperature. The Kmfor isocitrate was 20 μMand for NADP+10.7 μM. Initial velocity and end product inhibition studies of the forward reaction indicate a random bi ter mechanism. End product studies indicated that NADPH was a competitive inhibitor and α‐ketoglutarate was a non‐competitive inhibitor with respect to isocitrate and NADP+. Citrate was a competitive inhibitor with respect to isocitrate. Glutamine was identified as a positive effector when assays were conducted at non‐saturating isocitrate concentrations. The potential significance of glutamine regulation of α‐ketoglutarate production in a dinitrogen‐fixing tissue is discussed.
Calcium ion dependency of ethylene production in segments of primary roots of Zea mays
Authors: Hasenstein Karl Heinz , Evans Michael L.
Published: May 2006

We investigated the effect of Ca2+ on ethylene production in 2‐cm long apical segments from primary roots of corn (Zea mays L., B73 × Missouri 17) seedlings. The seedlings were raised under different conditions of Ca2+ availability. Low‐Ca and high‐Ca seedlings were raised by soaking the grains and watering the seedlings with distilled water or 10 mM CaCl2, respectively. Segments from high‐Ca roots produced more than twice as much ethylene as segments from low‐Ca roots. Indoleacetic acid (IAA; 1 μM) enhanced ethylene production in segments from both low‐Ca and high‐Ca roots but auxin‐induced promotion of ethylene production was consistently higher in segments from high‐Ca roots. Addition of I‐aminocyclopropane‐I‐carboxylic acid (ACC) to root segments from low‐Ca seedlings doubled total ethylene production and the rate of production remained fairly constant during a 24 h period of monitoring. In segments from high‐Ca seedlings ACC also increased total ethylene production but most of the ethylene was produced within the first 6 h. The data suggest that Ca2+ enhances the conversion of ACC to ethylene. The terminal 2 mm of the root tip were found to be especially important to ethylene biosynthesis by apical segments and, experiments using 45Ca2+ as tracer indicated that the apical 2 mm of the root is the region of strongest Ca2+ accumulation. Other cations such as Mn2+, Mg2+, and K+ could largely substitute for Ca2+. The significance of these findings is discussed with respect to recent evidence for gravity‐induced Ca2+ redistribution and its relationship to the establishment of asymmetric growth during gravitropic curvature.
Effect of solar near ultraviolet radiation on growth of Chlorella cells
Authors: Manabe Eichi , Hirosawa Takayasu , Tsuzuki Mikio , Miyachi Shigetoh
Published: May 2006

Cells of Chlorella regularis (Artari) Oltmanns (S‐50) were grown under solar radiation in Tokyo, using a newly constructed outdoor culture system. The maximum specific growth rate (log2 unit h−1) was about 0.3, which was a little lower than the highest value reported using artificial light in the laboratory. The near ultraviolet light, consisting mostly of UV‐A, inhibited the growth from 10 to 40% in summer mornings; the inhibition was not significant in the afternoon. The percentage inhibition was correlated with the total dose of the ultraviolet radiation.
Effect of light intensity on proton extrusion by roots of intact maize plants
Authors: Schubert S. , Mengel K.
Published: May 2006

Shading of maize plants (Zea mays L. cv. Blizzard) reduced net H+ extrusion by roots and increased K+ release, whereas there was no significant effect on anion efflux in deionized water. With lower light intensity the concentrations of carbohydrates in the roots decreased, but ATP levels and energy charge remained unchanged. Also, shading raised the tissue pH of roots and made the cytoplasmic pH of root cells drop. There was a significant influence of light intensity on H+ uptake by roots from an acidified test solution and CCCP (carbonylcyanide‐3‐chlorophenylhydrazone)‐in‐duced H+ uptake was modified by shading.

It is concluded that low light intensity does not limit active H+ release by plasmalemma ATPase activity in the root cells, but that a reduced carbohydrate supply brings about a change in biochemical reactions which alter the membrane permeability for protons. An increased passive reflux of H+ into the cells rather than a reduced H+ ATPase activity explains the decrease of net H+ release by roots of intact maize plants under low light intensity.
Carbon dioxide assimilation during postharvest removal of astringency from persimmon fruit
Authors: Pesis Edna , Ben‐Arie Ruth
Published: May 2006

Application of anaerobic conditions with CO2 or N2 atmospheres to remove astringency from harvested persimmon fruit (Diospryros kaki L. cv. Triumph), caused production of more acetaldehyde under CO2 than under N2, 14CO2 applied in a 100% CO2 atmosphere, for 48 h to astringent persimmon fruits was incorporated mainly into malate and very little into other metabolites, such as carbohydrate or amino acids. Application of malate or pyruvate to pulp discs of astringent persimmons caused an immediate rise in acetaldehyde production. The higher levels of acetaldehyde produced by whole fruits held in a CO2 atmosphere, than by fruits held in a N2 atmosphere, can be explained through fixation of atmospheric CO2 into malate, leading to acetaldehyde production.
Secondary dormancy in Avena fatua: Induction and characteristics in genetically pure dormant lines
Authors: Symons Stephen J. , Naylor James M. , Simpson Graham M. , Adkins Stephen W.
Published: May 2006

The induction of secondary dormancy in caryopses of genetically pure dormant lines of Avena fatua L. is described. Seeds harvested from mature plants were after‐ripened under controlled conditions (26°C, 25% relative humidity) until fully non‐dormant. Secondary dormancy was then induced into these caryopses by incubation on moist filter papers in an aspirated nitrogen atmosphere at 20°C over periods from 3 h to 14 days. These caryopses failed to germinate when returned to an aerobic environment. The dose‐response curves for gibberellic acid, sodium azide, sodium nitrite, sodium nitrate and ethanol show that all of these treatments can overcome the induced secondary dormancy. Drying increased the sensitivity of secondary dormant caryopses to these treatments. These treatments overcame secondary dormancy at all times, indicating the presence of only one of the two known blocks to germination that exist during primary dormancy. Similarities between primary and secondary dormancy in A. fatua are discussed.
Effect of darkness and CO2starvation on NH4+and NO3−assimilation in the unicellular algaCyanidium caldarium
Authors: Di Martino Rigano Vittoria , Vona Vincenza , Di Martino Catello , Rigano Carmelo
Published: May 2006

Cyanidium caldarium(Tilden) Geitler, a non‐vacuolate unicellular alga, resuspended in medium flushed with air enriched with 5% CO2, assimilated NH4+at high rates both in the light and in the dark. The assimilation of NO3−, by contrast, was inhibited by 63% in the dark. In cell suspensions flushed with CO2‐free air, NH4+assimilation decreased with time both in the light and in the dark and ceased almost completely after 90 min. The addition of CO2completely restored the capacity of the alga to assimilate NH4+. NO3−assimilation, by contrast, was 33% higher in the absence of CO2and was linear with time. It is suggested that NO3−and NH4+metabolism inC. caldariumare differently controlled in response to the light and carbon conditions of the cell.
Comparison of the properties of plasmalemma vesicles purified from wheat roots by phase partitioning and by discontinuous sucrose gradient centrifugation
Authors: Bérczi Alajos , Møller Ian M.
Published: May 2006

Plasmalemma vesicles were purified from 7‐day‐old wheat (Triticum aestivum L. cv. Drabant) roots by a) discontinuous sucrose gradient (SG), b) aqueous polymer two‐phase partitioning (PP) and c) SG followed by PP (SG + PP). SG‐purified plasmalemma preparations were 2‐3 fold more contaminated with mitochondria (cytochrome c oxidase, EC 1.9.3.1) when compared to PP and (SG + PP)‐purified plasmalemma. The electrostatic surface properties, as measured by 9‐aminoacridine fluorescence, were similar in PP and (SG + PP)‐purified plasmalemma and different from SG‐purified. The latency of the MG‐ATPase measured with Triton X‐100 was 51, 81 and 82% for SG‐, PP‐ and (SG + PP)‐purified plasmalemma vesicles, respectively. The higher latency of the ATPase (and lower specific activity in the absence of Triton X‐100) in PP‐purified and (SG + PP)‐purified preparations was not due to an effect of PEG, since exposure of SG‐purified preparations to PEG either in the wash medium or in the ATPase assay medium did not change ATPase activity. It is concluded that SG‐purified plasmalemma vesicles are more contaminated than PP‐purified preparations and that the former are likely to be leaky. They are, therefore, less suitable for use in studies of transport across the plasmalemma.
Separation and partial characterization of two alkaline peptidases from cotyledons of resting kidney beans, Phaseolus vulagaris
Authors: Mikkonen Anita , Mikola Juhani
Published: May 2006

Extracts prepared from cotyledons of resting kidney beans (Phaseolus vulgaris L., cv. Processor) rapidly hydrolyzed two dipeptides, Leu‐Tyr and Ala‐Gly, with pH optima at 9.2 and 8.5, respectively. On ion exchange chromatography on DEAE‐Sephacel the two activities eluted as separate peaks, showing that they were due to two different peptidases. The extracts also hydrolyzed Leu‐β‐naphthylamide optimally at pH 6.4; this activity eluted as a third peak berween the other peaks. The activity peak acting on Leu‐Tyr and Ala‐Gly rapidly hydrolized two tripeptides, showing that it was an aminopeptidase, whereas the Ala‐Gly hydrolyzing peak acted only on dipeptides. The activities against Leu‐Tyr and Ala‐Gly were also separated by gel chromatography on Sephacryl S‐300 with elution positions corresponding to M, values of about 360 000 and 105 000. The aminopeptidase was inhibited by bestatin, and the dipeptidase was inhibited by p‐hydroxymercuribenzoate. Both enzymes were inhibited by o‐phenanthroline. In most of their properties the two kidneys bean enzymes resembled the alkaline aminopeptidase and the dipeptidase earlier characterized from barley grains.
Adventitious root formation in green cuttings of Populus tremula: Characterisation of the effect of vitamin D3 and indolylbutyric acid
Authors: Pythoud F. , Buchala A. J. , Schmid A.
Published: May 2006

Indolyl‐3‐butyric acid and vitamin D3 enhance adventitious root formation in green cuttings of Populus tremula L. A significant synergistic effect is observed between these two substances. The number of roots formed on application of the individual substances and on simultaneous application depends on the growth substance concentration, the timing of application, the age of the cuttings and the number of leaves. Of the vitamin D3 animal metabolites tested, only 1,25‐dihydroxyvitamin D3 markedly promoted adventitious rooting, and this to a lesser extent than vitamin D3 itself. The 3‐O‐glucopyranosides of vitamin D3 and the vitamin D3 animal metabolites, promoted rooting to the same extent as the parent compounds.
Leaf respiration during early plastidogenesis in light‐grown barley seedlings
Authors: Owen John H. , Laybourn‐Parry Johanna E. M. , Wellburn Alan R.
Published: May 2006

Oxygen fluxes of protoplasts from different developmental regions of light‐grown (16 h day/8 h dark) barley (Hordeum vulgare L. cv. Patty) seedlings were studied using oxygen electrodes as well as with a more sensitive technique of oxygen exchange measurement, Cartesian‐diver microrespirometry. A pronounced increase in dark respiration of protoplasts from the region close to the intercalary meristem was observed, especially below the amyloplast region. In the dark this region also displayed the greatest activity of the alternative (cyanide‐insensitive) mitochondrial electron‐flow pathway, possibly due to high intracellular sugar levels and suitable cytosolic energy charge engaging the pathway. Etiolated protoplasts from similar regions of dark‐grown barley seedlings close to the intercalary meristem displayed a reduced dark respiratory rate which suggests that mitochondrial participation prior to normal plastid development is a partially light‐initiated process, probably acting through the agency of phytochrome and a blue light receptor. These results demonstrate that in normal light‐grown seedlings, just as in algal and etiolated greening systems, mitochondrial participation is vital for the very early stages of plastid development and may be controlled at least partly through phytochrome action as well as a blue light receptor.
Plant regeneration from seedling cotyledons, leaves and petioles of Glycine clandestina
Authors: Hammatt N. , Davey M. R. , Nelson R. S.
Published: May 2006

A B5‐based culture medium containing 4.4 μM N6‐benzyladenine (BA) and 0.025 μM indole‐3‐butyric acid (IBA) induced callus from seedling cotyledons, leaves and petioles of Glycine clandestina Wendl. Only hard, green, nodular callus tissues were capable of producing shoot buds and of five accessions examined, only two (G1231 and G1145) were morphogenetically competent. Callus that did not regenerate could often be induced to produce shoot buds after subculture to fresh regeneration medium. Buds developed into shoots following transfer of callus to a medium containing 0.9 μM BA and 0.025 μM IBA. Shoots were rooted in hormone‐free, half‐strength B5 medium supplemented with 0.2% activated charcoal. The application of these results is discussed in relation to somatic hybridisation between the cultivated soybean and wild Glycine species.
Changes in apoplastic and intracellular leaf sugars induced by the blocking of export in Vicia faba
Authors: Ntsika Gaspard , Delrot Serge
Published: May 2006

Sugar export by broadbean (Vicia faba L. cv. Aguadulce) was blocked by a cold jacket (1 cm‐width, 1°C) applied on the petiole of a mature leaf or by heat‐girdling the petiole. A time course study was made on the effects of these treatments on apoplastic and intracellular soluble sugars of the leaf in relation to phloem loading and photosynthesis. Blocking of export by heat‐girdling induced an inhibition of phloem loading within 10 min, an accumulation of starch within 30 min and a rise in apoplastic sucrose within 60 min. By contrast, apoplastic hexoses and photosynthesis were not affected by this treatment within 8 h and intracellular sugars were not affected within 2 h. The cold jacket also increased the sucrose content of the apoplast. The increase in apoplastic sucrose induced by the cold barrier is reversed upon rewarming and less marked when the sink/source ratio is increased by defoliating all but the leaves studied. The results are discussed in terms of sink/source relationships. They show that the increase in apoplastic sucrose resulting from inhibition of loading is not part of the events leading from blocking of transport to change in carbon partitioning.
The effects of phosphate supply on uptake of potassium ions, 2,4‐D and atrazine by wheat and maize
Authors: Zsoldos Ferenc , Haunold Ernst , Vashegyi Ágnes
Published: May 2006

The uptake of the auxin‐type herbicide 2,4‐D and of the non‐auxin‐type atrazine into seedlings of maize (Zea mays L.cv. SZeTC 505) and wheat (Triticum aestivum L.cv. GK Szeged) was investigated, as were their effects on the growth and K+ uptake under different nutrient conditions. A brief incubation of the roots in 0.01 mM 2,4‐D caused a marked herbicide influx only in the absence of Pi. Lowering the Pi concentration of the uptake solution led to an increased 2,4‐D influx into the roots, thereby inhibiting K+ uptake, growth and dry‐matter production of the plants. In the case of 0.01 mM atrazine, Pi‐supply in the external solution influenced neither the herbicide uptake nor the growth of the plants.
Temperature inducible protochlorophyllide reduction in darkness in a pigment mutant of Scenedesmus obliquus
Authors: Oh‐hama Tamiko , Kotzabasis Kiriakos , Senger Horst
Published: May 2006

Accumulation of chlorophyll and protochlorophyllide (PChlide) was followed during beterotrophic growth of the pigment mutant C‐2A′ of Scenedesmus obliquus L. in the darkness at 30 and 20°C. At 30°C the cells remained yellow with accumulation of protochlorophyllide, whereas they became green at 20°C with only traces of protochlorophyllide. The capacity of mutant cells to reduce PChlide to chlorophyllide (Chlide) in the dark with or without addition of 5‐aminolevulinic acid as measured in isolated membranes, was high in cells grown at 20°C but negligible at 30°C. The high capacity to reduce PChlide created in cells growing at 20°C was only slightly diminished by exposure of cells to 38°C for 3 h. Mechanisms of temperature‐sensitive chlorosis in algae and higher plants are discussed in relation to the results with pigment mutant C‐2A′ of Scenedesmus obliquus. It is assumed that either an activator of NADPH protochlorophyllide oxidoreductase (EC 1.6.99.1) or a different enzyme system can be activated by lower temperature as by light.
Responses of red alder and black cottonwood seedlings to flooding
Authors: Harrington Constance A.
Published: May 2006

Red alder (Alnus rubra Bong.) and black cottonwood (Populus trichocarpa Torr. & Gray) seedlings were monitored to evaluate response during a 20‐day period of artificial flooding and a 20‐day recovery period following flooding. During the flooding period, both species showed changes in nutrient uptake and transport, initiated stemderived adventitious roots that became aerenchymatous, and exhibited hypertrophied lenticels. Flooded red alder seedlings also showed reduced height and leaf area growth and developed lower‐stem hypertrophy. Flooded black cottonwood seedlings exhibited root dieback, aerenchyma in below ground root tips, and changes in root hydraulic conductance and xylem pressure potential. Contrary to expectations, however, stomatal closure following flooding was not observed in either species. Flooded red alder seedlings increased growth rapidly when drained, and by the end of the recovery period, formerly flooded and non‐flooded red alder seedlings differed only minimally in this respect. In contrast, several characteristics of black cottonwood – including growth rate and nutrient content – still differed between formerly flooded and non‐flooded seedlings at the end of the recovery period. Based on observed treatment differences at the end of the experiment, red alder seedlings were judged to be more tolerant of flooding than black cottonwood.
Partitioning of nitrogen from biological fixation and fertilizer in Phaseolus vulgaris
Authors: Hungria Mariangela , Neves Maria Cristina P.
Published: May 2006

Nitrogen uptake, distribution and remobilization in the vegetative and reproductive parts of the plant were studied in bean (Phaseolus vulgaris L.) cultivars Negro Argel and Rio Tibagi inoculated with either Rhizobium strain C05 or 127 K‐17. Greenhouse grown plants were supplied with 2.5 mg N (plant)−1 day−1 as KNO3 or K15NO3 and the relative contribution to total plant nitrogen of mineral and symbiotically fixed nitrogen was determined. Control plants included those entirely dependent on fixed nitrogen as well as uninoculated plants supplied with 10 mg N (plant)−1 day−1. No differences were observed between inoculated treatments in total nitrate reductase activity and in the amount of mineral nitrogen absorbed, but there were considerable differences in the contribution of fixed nitrogen. Nitrogen fixation supplied from 58 to 72% of the total nitrogen assimilated during the bean growth cycle and the symbiotic combinations fixed most of their nitrogen (66 to 78% of total nitrogen) after flowering. Maximum uptake of mineral nitrogen was in the 15‐day‐period between flowering and mid‐podfill (47 to 58% of total mineral nitrogen). Nitrogen partitioning varied with Rhizobium strains, and inoculation with strain C05 increased the nitrogen harvest index of both cultivars. Applied mineral nitrogen had a variable effect and in cv. Negro Argel was more beneficial to vegetative growth, resulting in smaller nitrogen harvest indices. Seed yield was not increased by heavy nitrogen fertilization. In contrast, cv. Rio Tibagi always benefited from nitrogen applications. Among the various nitrogen sources supplying the grain, the most important one was the fixed nitrogen translocated directly from nodules or after a rapid transfer through leaves, representing from 60 to 64% of the total nitrogen incorporated into the seeds.
Membrane lipids in Ceratodon purpureus protonemata grown at high and low temperatures
Authors: Aro Eva‐Mari , Somersalo Susanne , Karunen Pirjo
Published: May 2006

Ceratodon purpureus (Hedw.) Brid. was grown at two temperatures, 20 and 4°C. The protonemata grown at 4°C fixed more CO2 at low temperatures; but their frost tolerance, tested as the recovery of photosynthesis after frost treatment, was not better than in the protonemata grown at 20°C. The effects of the growth temperature were studied on the membrane lipids of intact protonemata and on the lipid and protein contents of isolated thylakoid membranes. A large proportion, 70 to 90%, of the thylakoid membrane lipids was lost unless precautions were taken to inhibit the lipid‐degrading enzyme activities. The lipid content of the thylakoid membranes of protonemata grown at 20 and 4°C was 3.9 and 4.8 mol (mol chlorophyll)−1, respectively. Only minor differences were found in the lipid class composition. Monogalactosyldi‐acylglycerol constituted more than 50 mol‐% of the thylakoid membrane lipids at both 20 and 4°C. However, each lipid class had a higher average number of double bonds per lipid molecule in cold growth conditions. The protein content of the thylakoid membranes was low at both 20 and 4°C. These characteristics of the thylakoid membranes may be a prerequisite for the observed ability of protonemata to photosynthesize even at subzero temperatures.
Isolation and characterisation of developing chloroplasts from light‐grown barley leaves
Authors: Guillot‐Salomon Thérèse , Farineau Nicole , Cantrel Catherine , Oursel Annette , Tuquet Christiane
Published: May 2006

Developing chloroplasts were isolated from the basal region of green barley (Hordeum vulgare L. cv. Menuet) leaves and their ultrastructure and biochemical composition were compared to those of mature chloroplasts from the tip of the same leaves, using two methods of purification on sucrose and Percoll gradients.

When examined and compared to mature chloroplasts, the developing chloroplasts showed well‐developed grana stacks, but these last organelles were 2‐fold smaller and contained lower amounts of chlorohylls and polar lipids. Only traces of trans‐3‐hexadecenoic acid could be detected in phosphatidylglycerol of developing plastids. The protein content of these plastids was higher than in mature plastids and showed an increased proportion of polypeptides linked to P‐700 chlorophyll α‐protein. The photosynthetic activity of these plastids was about 2‐fold lower and their photosystem 1/photosystem II ratio higher than in mature chloroplasts.
Degradation of ribulose‐1,5‐bisphosphate carboxylase and chlorophyll in senescing barley leaf segments triggered by jasmonic acid methylester, and counteraction by cytokinin
Authors: Weidhase R. A. , Lehmann J. , Kramell H. , Sembdner G. , Parthier B.
Published: May 2006

Barley (Hordeum vulgare L. cv. Salome) primary leaf segments responded to the application of a putative plant growth regulator, ± jasmonic acid methylester (JA‐Me). with accelerated senescence, as indicated by the loss of chlorophyll and the rapid decrease in activity and immunoreactive protein content of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBP carboxylase, EC 4.1.1.39). The senescence‐promoting action of JA‐Me differed in light and in darkness; e.g. the initial rates of chlorophyll and RuBP carboxylase breakdown were markedly higher in light than in darkness in the presence of 4.10−5M JA‐Me. Cytokinin (benzyladenine, 4.10−5M) stopped the loss of chlorophyll and RuBP carboxylase during senescence; however, the rapid drop induced by JA‐Me in the early phase of leaf segment senescence could not be prevented by concomitant or previous addition of BA. On the other hand, BA added 24 h after JA‐Me application resulted in a recovery of chlorophyll and RuBP carboxylase at the later stages, indicating a possible rapid inactivation of JA‐Me in the tissues. The activities of a number of other chloroplastic and cytosolic enzymes were not significantly altered in JA‐Me‐treated leaf segments compared with controls floated on water. Time‐dependent chlorophyll decrease in isolated chloroplasts did not change upon JA‐Me addition to the isolated organelles. It is suggested that JA‐Me acts on chloroplast senescence by promoting cytoplasic events which eventually bring about the degradation of chloroplast constituents.
Ethylene production by loblolly pine seedlings associated with water stress
Authors: Stumpff Nancy J. , Johnson Jon D.
Published: May 2006

Effects of water stress on production of ethylene and its precursor, 1‐aminocyclopropane‐1‐carboxylic acid (ACC), by loblolly pine (Pinus taeda L.) seedlings from a Texas drought‐hardy and a Virginia Coastal Plain source were investigated. Ethylene production rates in needles from the Virgnia source increased slightly with initial stress (‐1.3 MPa), declined until water potential reached ‐1.6 MPa and then increased sharply at ‐2.5 MPa. The ethylene production rates in needles from the Texas also increased slightly with initial stress, then decreased with decreasing water potential. Ethylene production by root tissue was two to three times higher than needle tissue and decreased with decreasing water potential. ACC concentrations in needles of both seed sources decreased as water potential began decreasing. Below ‐1.4 MPa, ACC levels started increasing (Texas source) or remained constant until ‐2.8 MPa (Virginia source) at which time its level increased three‐fold. Mean ACC levels in root tissue [122 nmol (g dry weight)−1] were slightly higher than the mean levels in the needle tissue [92 nmol (g dry weight) −1]; roots apparently were more efficient in converting it to ethylene since ethylene production was two to three times higher than needle tissue. The modulation of ethylene synthesis by ACC synthase and ethyleneforming enzyme appeared to be influenced by stress level, organ and seed source.
Changes at panicle emergence in the water relations of a wetland and a dryland Japonica rice cultivar under wetland conditions
Authors: Takami Shinichi , Ahmad Sayeed , Turner Neil C. , Kobata Tohru , O'Toole John C.
Published: May 2006

The diurnal and seasonal changes in plant water relations of two Japonica rice (Oryza sativa L.) cultivars, Nipponbare and Tachiminori, were studied under flooded conditions at Kyoto University. The dryland cv. Tachiminori maintained higher predawn and midday leaf osmotic potentials relative to the wetland cv. Nipponbare during the vegetative stage, but the ranking was reversed after flowering. The relationship between leaf water potential and leaf osmotic potential showed that prior to panicle emergence Nipponbare was able to adjust osmotically to maintain turgor, whereas after heading there was little turgor maintenance. Tachiminori showed little difference in osmotic adjustment before and after panicle emergence. Fertilizer treatment during panicle development also helped to maintain the degree of osmotic adjustment in both cultivars.
Evolution des glucides intratissulaires au cours de la néoformation des bourgeons par des explantats racinaires de Cichorium intybus cultivés in vitro
Authors: Vasseur J. , Lefebvre R. , Backoula E.
Published: May 2006

Variation of intratissular carbohydrates during bud formation in root explants of Cichorium intybus cultivated in vitro.

During the cellular activation that begins with excision of root explants from Cichorium intybus L. var. Witloof cv. Zoom cultured in vitro, hydrolysis of fructose polymers, in particular of the polyfructosans (inulin) takes place. The products of degradation are used to cover the energetic needs connected with the increase of the mitotic activity. After day 2 the intracellular carbohydrates (sucrose and reducing sugars) develop differently according to further development of the explants. When growth of unorganized callus is favoured and organ formation inhibited by medium supplemented with auxin, fructose is accumulated; but under bud‐forming conditions it is the amount of sucrose that increases. These differences were most notable between days 3 and 10 in culture, the period during which primordia occurred in the shoot‐forming callus
Frost tolerance in cell cultures of potato
Authors: van Swaaij A. C. , Talsma K. , Krigshekld H. , Jacobsen E. , Feestra W. J.
Published: May 2006

Different methods of freezing and of estimating frost damage in cell cultures of Solanum tuberosum L. and a number of wild Solanum species were compared. Frost‐killing temperatures (FKT, i.e. the temperature resulting in 50% of the maximum possible frost damage) in leaves of these species were ‐6°C (S. acaule), 5°C (S. me‐gistacrotobum), ‐4.5°C (S. commersonii) and ‐3°C (S. polytrichon and S. tubero‐sum) No appreciable species differences were found in FKT when cells were submerged in either buffer or medium and frozen. However, differences did exist when cells were frozen in a non‐submerged condition: S. acaule and S. commersonii callus were more sensitive to frost than suspensions, whereas suspensions of the other species were the most sensitive. Measurement of freezing damage by either electrolyte leakage or by 2,3,5‐triphenyltetrazolium chloride viability assays revealed similar FKT values. Cell cultures of S. acaule showed better frost tolerance than S. tuberosum (FKT values were ‐4.5 to ‐6°C and ‐2.5°C. respectively), however, frost tolerance of S. megistacrolobum and S. commersonii was only poorly expressed at the cell level (FKT values were between ‐2 and ‐3°C). Variant cell lines previously selected for resistance to the amino acid analogues hydroxyprotine, aminoethylcysteine and 5‐methyhryptophan appeared to be more tolerant to frost than the wild type S. tuberosum clone.