bluuebunny/crossref_metadata_2025 huggingface dataset:
Free and conjugated polyamines during de novo floral and vegetative bud formation in thin cell layers of tobacco
Authors: Torrigiani Patrizia , Altamura Maria Maddalena , Pasqua Gabriella , Monacelli Barbara , Serafini‐Fracassini Donatella , Bagni Nello
Published: May 2006

The concentrations of three classes of polyamines, trichloroacetic acid‐soluble (free), TCA‐soluble conjugated (to small molecules) and TCA‐insoluble conjugated (to macromolecules), was examined during de novo floral and vegetative bud formation in thin cell layers of Nicotiana tabacum L. cv. Samsun. Explants (consisting of 5–6 layers of epidermal, subepidermal and parenchyma cells) were excised either from floral pedicels or from stem internodes at the unripe fruit stage and cultured on the same medium. In the former, the first de novo formed flower buds appeared on day 8 of culture, while in the latter the first vegetative domes appeared on day 10. In both cases the number of floral and vegetative buds increased up to day 12 and 15, respectively. Changes in dry weight were determined throughout the culture period. Free and conjugated putrescine titer increased 5–60 times in both types of culture and in the three classes of polyamines examined; spermidine content also increased, while spermine, when present, did not show significant changes. TCA‐soluble conjugated polyamines were most abundant, being about 2‐fold the TCA‐insoluble conjugated ones and 10‐fold the free ones. The major increment in putrescine and spermidine content occurred in stem internode explants developing vegetative buds. In pedicel explants the maximum putrescine level was reached before or on day 8 in culture (emergence of the first flower buds with calyx initials), while in stem internode explants the maximum level was reached on day 12, at the emergence of the first vegetative buds with leaf primordia. While spermidine prevailed on day 0, putrescine was the most abundant polyamine during both differentiation processes. The putrescine content rapidly increased immediately after the onset of culture. Thus conjugated polyamines, especially putrescine, and not only the free ones, seem to be involved in both the reproductive and vegetative phases of tobacco growth and development.
Characterization of the plasmalemma ATPase activity from roots of Plantago major ssp. pleiosperma, purified by the two‐phase partitioning method
Authors: Staal Marten , Hommels Cees , Kuiper Daan
Published: May 2006

A purified plasmalemma preparation from roots of Plantago major L. ssp. pleiosperma (Pilger) was obtained by the two‐phase partitioning method, using 6.5% (w/w) of Dextran T‐500 and polyethylene glycol 3350, respectively. The distribution of murker enzymes proved the purity of the plasmalemma fraction. The ATPase activity was characterized by determining its sensitivity to anions, cations and inhibitors. The Mg2+‐dependent ATPase activity peaked at pH 7.25, K+‐stimulation at pH 6.75, and the Cl− ‐stimulation both at pH 6.75 and 7.5 (all in the presence of 3 mM MgSO4). The plasmalemma preparations hydrolyzed preferentially ATP (in the presence of Mg2+), although they were less specific for ATP at pH 7.5 than at pH 6.75. The Cl− ‐ stimulated ATPase is probably associated with and located on the plasmalemma. The question if the Cl− ‐stimulated activity is due to an ATPase distinct from the classical K+‐stimulated ATPase is considered.
Effects of UV‐C radiation on membrane potential and electric conductance in internodal cells of Nitellopsis obtusa
Authors: Stolarek Jan , Karcz Waldemar
Published: May 2006

Effects of 253.7 nm ultraviolet radiation on membrane potential and conductance in internodal cells of Nitellopsis obtusa were studied. The radiation caused transient depolarization of plasmalemma and tonoplast and simultaneous increase in electric conductance. These effects were partly reversible and the degree of the recovery depended on the duration of the exposure. In cells with potential difference (between vacuole and external medium) more negative than – 140 mV, the radiation induced an action potential. The hyperpolarized state created by visible light and indole‐3‐acetic acid was fully suppressed by the radiation. The results are discussed taking into account the data for Chara corallina obtained by C. J. Doughty and A. B. Hope. It is suggested that 253.7 nm radiation inhibits electrogenic proton pumps in the plasmalemma and activates the Cl− channels.
Respiration of barley roots: Assessment of activity of the alternative path using SHAM
Authors: Bingham I. J. , Farrar J. F.
Published: May 2006

The activity of the alternative path of O2 consumption in detached and intact roots of barley [Hordeum distichum (L.) Lam. cv. Maris Mink] was determined by titration with salicylhydroxamic acid (SHAM) in the presence and absence of cyanide. In the absence of cyanide, only high concentrations were inhibititory (> 5 mM). whilst in its presence low SHAM concentrations (2.5–5.0 mM) gave maximum inhibition: the resulting ϱ Valt plots were non‐linear. A SHAM‐stimulated peroxidase could readily be washed from these roots, but non‐linearity cannot be explained in terms of SHAM‐stimulation of this peroxidase as it is not active in the absence of an exogenous supply of NADH. In detached roots the degree of inhibition of respiration with 25 mM SHAM was nearly double the capacity of the alternative path (measured as the degree of inhibition by SHAM in the presence of cyanide), suggesting non‐specific inhibition. Effects of SHAM on cytochrome path activity in intact roots were examined by reverse titration with cyanide in the presence and absence of SHAM. At 5 mM SHAM had no effect on the cytochrome path, but at 25 mM it inhibited. We conclude that the only factor causing non‐linearity of ϱValt plots in barley roots is non‐specific inhibition of the cytochrome path by high concentrations of SHAM; consequently only low concentrations of SHAM (2.5–5.0 mM) are suitable for estimating alternative path activity in barley roots.
Auxin‐stimulated ethylene production in fern gametophytes and sporophytes
Authors: Tittle Forrest L.
Published: May 2006

The auxins indole‐3‐acetic acid (IAA) and 2,4‐dichlorophenoxyacetic acid (2,4‐D) stimulated ethylene production from gametophytes of the fern Pteridium aquilinum (L.) Kuhn. var. latiusculum (Desv) underw. ex Heller and sporophytes of the ferns Matteuccia struthiopteris (L.)Todaro and Polystichum munitum (Kaulf.) Presl. Treatment with Co2+ or l‐α ‐(2‐aminoethoxyvinyl)‐glycine (AVG) eleminated or significantly reduced the stimulatory effects of IAA. Treatment with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) resulted in significantly greater rates of ethylene production from all tissues tested. Based on their response to auxin, ACC, AVG and Co2+, the ethylene biosynthetic pathway in these three lower vascular plants appears similar to that existing in angiosperms.
Inhibition of photosynthetic activities under slow water stress measured in vivo by the photoacoustic method
Authors: Havaux Michel , Canaani Ora , Malkin Shmuel
Published: May 2006

A slow water stress over several days was imposed on tobacco plants (Nicotiana tabacum L. var. Xanthi) by withholding water from the soil. Photosynthesis was measured in leaves from those water‐stressed plants by the photoacoustic method. Slow drought induced marked changes in the photoacoustic signals, which were largely similar to those observed previously in leaves subjected to rapid desiccation in air (over 3–4 h), reflecting two simultaneous changes: 1) Modification of the heat and oxygen diffusion characteristics of the leaves due to changes in their anatomical structure [shown by the change in the slope of the plot of the oxygen (AOX) to photothermal signal (APT) ratio vs the square root of the modulation frequency]; 2) Inhibition of gross photosynthesis measured by the extrapolation of the AOX/APT ratio to zero frequency. However, in contrast to rapid water stress in detached leaves, where it was shown that mainly the oxidizing side of photosystem II (PS II) was damaged, we found a slower and more complex phenomenology having largely biphasic kinetics. During the first 6 days, there was a strong reduction in the photochemical energy storage, but the inhibition of oxygen evolution was relatively mild. The Emerson enhancement in state 1 dropped considerably, indicating lowering of the apparent absorption cross‐section of PS II. Fluorescence measurements suggest that PS II reaction center itseIf may be the primary site of the damage. PS I activity, judged by cytochrome f photooxidation, remained largely intact. The subsequent days were associated with a further spectacular decrease in the oxygen evolution quantum yield with both photosystems damaged. The photochemical energy storage continued to decrease further. The Emerson enhancement ratio of the remaining activities in both State 1 and 2 showed a marked increase, indicating the reestablishment of a strong imbalance in the distribution of excitation energy within the photochemical apparatus in favor of PS II. All the photoacoustic changes observed in response to drought were completely reversible within 2–3 days upon rewatering of the soil.
Photosynthetic 14CO2 fixation and [15N]‐ammonia assimilation during UV‐B radiation of Lithodesmium variabile
Authors: Döhler Günter , Worrest Robert C. , Biermann Irene , Zink Joachim
Published: May 2006

Uptake of [15N]‐ammonia was more sensitive to UV‐B exposure than the total 14CO2 fixation rate of Lithodesmium variabile Takano. Short‐term UV‐B radiation (15 min) had practically no effect on the kinetics of [15N]‐ammonia, whereas there was an effect on [14C]‐bicarbonate uptake rate. A significant reduction was found after 30 and 60 min UV‐B stress. The time course of photosynthetic uptake of 15NH4Cl at several wavelengths was markedly depressed at shorter wavelengths (irradiation with WG 280). A short‐term (11 min) exposure to ultraviolet radiation had no influence on the [14C]‐labeled photosynthetic products. However, the [15N]‐label of several amino acids and the ratio of [15N]‐glutamine to [15N]‐glutamic acid varied after irradiation with different ultraviolet wavebands. The results are discussed with reference to UV damage to the key enzymes of nitrogen metabolism.
Vessel differentiation along different tissue polarities
Authors: Gersani Mordechai
Published: May 2006

Organized vessel differentiation in an isolated system was studied on a quantitative basis. An auxin source was oriented on isolated pieces of turnip storage root (Brassica campestris cv. Rapifera) to allow diffusion a) in the direction of, b) at right angle to, and c) opposite to the original polarity. New vessel members differentiated within 44 h, and a minimum average auxin (IAA) concentration of 3.10−6M was required to induce initial vessel differentiation. The differentiation rates in three experimental orientations were 167, 60 and 43 cells h−1 at 10−3M IAA, and 1445, 1346 and 838 cells (log IAA concentration)−1 after 96 h, respectively. The difference between the differentiation rates in the original polarity orientation (a) and in the orientation at right angle (b) is interpreted as reflecting reorientation itself, which requires a minimum time.
The role of ethylene in the regeneration of Helianthus annuus (sunflower) plants from callus
Authors: Robinson Karol E. Paterson , Adams Douglas O.
Published: May 2006

Hypocotyl‐derived callus from the Helianthus annuus L. inbred line SS415B regenerated significantly more plants if the seedlings were grown in the light. The difference between light‐ and dark‐grown seedlings was not correlated with differences in seedling ethylene production, but seemed to be due to a difference in sensitivity to ethylene at a specific time during seedling growth. Treating 3‐day‐old dark‐grown seedlings with 10 μM aminoethoxyvinylglycine (AVG) effectively inhibited ethylene production for at least 7 days. Hypocotyl callus derived from AVG‐treated seedlings gave the same amount of regeneration as callus from light‐grown seedlings. Promotion of regeneration by AVG was not seen unless the 3‐day‐old seedlings were grown for 4 additional days prior to culturing hypocotyl explants. The effects of AVG could be reversed by treatment with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) during these 4 days. After the 4 days, ACC was no longer effective.
Localization of phytosiderophore release and of iron uptake along intact barley roots
Authors: Marschner Horst , Römheld Volker , Kissel Margit
Published: May 2006

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

The results demonstrate that apical root zones are the main sites both for Fe deficiency‐enhanced release of phytosiderophores and for uptake and translocation of iron supplied as FeIII phytosiderophores.
Levels of endogenous indole‐3‐acetic acid in the vascular cambium region of Abies balsamea trees during the activity ‐ rest ‐ quiescence transition
Authors: Sundberg Björn , Anthony Little C. H. , Riding Richard T. , Sandberg Göran
Published: May 2006

Indole‐3‐acetic acid (IAA) levels in the cambial region were measured by radioimmunoassay during the annual cambial activity ‐ rest ‐ quiescence transition at the crown top (current‐year shoots) and at the middle and base of the stem of two 21‐year‐old Abies balsamea (L.) Mill. trees about 7.5 m in height. The IAA level declined throughout the experimental period (July 24 ‐ December 3) at all positions in both trees. The earlywood ‐ latewood transition, which occurred throughout each tree about the end of July, was associated in time with the largest decrease in the absolute amount of IAA. Tracheid production ceased towards the end of September, the cessation occurring earlier at the top of the tree than at the base. The cessation of tracheid production was only poorly correlated in time and space with the decline in IAA level, and it was not prevented by exogenous IAA. The results suggest that IAA level is involved in the control of tracheid radial enlargement, but not in the regulation of the cessation of tracheid production.
An automatic device to record the force necessary to compensate plant movements
Authors: Zachariassen Eli , Johnsson Anders
Published: May 2006

A device, which automatically and continuously keeps moving plants in fixed positions, has been constructed. The apparatus is based on optical detection of any movements of the plant organ under study. The plant organ is kept in the desired position by means of wires, and the force necessary to apply to the wires to achieve this is recorded. The force reflects any tendency of the plant organ to move. The system is controlled by an Apple II computer. The device can work in one or two dimensions and record compensation forces in a wide range. In the experiments mentioned below, the magnitude of the forces necessary to keep the plants in a fixed position was of the order of 10‐4N.

Circadian leaf movements of Oxalis regnellii Mig. were studied in the device. The leaf rhythm continued, although the leaflets were clamped and the light input on the leaf therefore constant. Circumnutation of hypocotyls of Helianthus annus L. cv. Californicus were drastically reduced in amplitude when the hypocotyls were kept in vertical position by the wires. Since the gravitropic input signal to this system was zeroed by the equipment, the results demonstrated that in the absence of gravitropic inputs the circumnutation reactions drastically diminish. This confirmed that circumnutations of these hypocotyls are influenced by gravity. Finally, the apparatus was used to study phototropic reactions: By clamping phototropically stimulated coleoptiles of Avena sativa L. cv. Seger no gravitational stimulations were involved and the phototropic reaction without interference from gravity could be studied.
Ornithine decarboxylase activity in Helianthus tuberosus
Authors: D'Orazi Dario , Bagni Nello
Published: May 2006

Ornithine decarboxylase (ODC, EC 4.1.1.17) was studied in crude extracts of parenchyma slices of dormant tubers activated for 12 h, tuber shoots and shoot apices. It was highest in shoot apices. The enzyme activity was measured by the production of 14CO2 from labelled ornithine; Vmax was 450 nmol (mg protein)‐1h‐1, Km for ornithine and pyridoxal phosphate were, respectively, 30 mM and 5μM. Only when partially purified, the 14CO2 production was inhibited by α‐difluoromethylornithine, while in crude extracts dithiothreitol was inhibitory. Ornithine and arginine decarboxylase (ADC, EC 4.1.1.19) activities from parenchyma tubers were not greatly altered by exogenously supplemented ornithine, even though its endogenous pool increased. Exogenously supplemented arginine enhanced ornithine decarboxylase activity, whereas putrescine decreased it slightly. The possibility of artifactual activities in the crude extract is also discussed.
The role of endogenous gibberellin in seed and fruit development of tomato: Studies with a gibberellin‐deficient mutant
Authors: Groot Steven P. C. , Bruinsma Johan , Karssen Cees M.
Published: May 2006

The role of endogenous gibberellin (GA) in seed and fruit development was studied with the use of the GA‐deficient ga‐1 mutant of tomato (Lycopersicon esculentum Mill. cv. Moneymaker). Flowers of the ga‐1 mutant were abnormal and sterile, but parthenocarpic fruit development was observed occasionally on the dwarf plants. A single application of GA4+7 restored the fertility of the mutant flowers and resulted in seed set. Development of GA‐producing and GA‐deficient seeds in GA‐deficient fruits was compared by pollination of ga‐1/ga‐1 flowers with wild‐type or ga‐1 pollen, respectively. In ga‐1/ga‐1 seed dehydration started about 1 week earlier than in Ga‐1/ga‐1 seeds. Ultimate fresh and dry weights of mature Ga‐1/ga‐1 seeds were higher than those of ga‐1/ga‐1 seeds and showed negative correlations with the total number of seeds per fruit. Total content and composition of seed proteins were not influenced by the GA‐deficiency. Germination of the mature seeds depended on embryonal GA synthesis and was not influenced by maternal GA production. Final fresh weight of the ga‐1/ga‐1 fruits was positively correlated with the number of seeds per fruit. In these fruits, the minimum number of seeds for growth above the parthenocarpic level was about 10 or 35 in the presence of Ga‐1/ga‐1 or ga‐1/ga‐1 seeds, respectively. Fruits containing GA‐producing seeds reached a higher fresh weight than those containing GA‐deficient seeds, and their ripening was delayed by one week. It is concluded that gibberellin is indispensable for the development of fertile flowers and for seed germination, but only promoting in later stages of fruit and seed development.
Nickel and rubidium uptake by whole oat plants in solution culture
Authors: Aschmann S. G. , Zasoski R. J.
Published: May 2006

Nickel and rubidium uptake by oat plants (Avena sativa L. cv. Victory) were examined in relation to solution temperature, solution concentrations, metabolic inhibitors, anaerobic root conditions, transpiration and time. Over a 4‐h period, uptake rates for both Ni2+ and Rb+ remained constant at 23°C. Decreasing temperatures to 2°C, 20 μM concentrations of 2,4‐dinitrophenol (DNP), or anaerobic root conditions decreased Ni2+ and Rb+ uptake rates by 97 to 86% in whole plants. Treatment of excised roots with 20 μM DNP decreased Ni2+ uptake by 93%. Nickel and Rb+ uptake rates measured as a function of the external solution concentration followed a typical parabolic curve. Km (0.012 mM) and Vmax [2.72 μmol (g dry weight)‐1 h‐1] values for Ni2+ were nearly 7 times lower than those for Rb+ [0.09 mM and 19.2 μmol (g dry weight)‐1 h‐1]. In all experiments, Ni2+ and Rb+ showed qualitatively similar uptake patterns, but Rb+ uptake was quantitatively more sensitive than Ni2+ to experimental manipulations.
Abscisic acid in dormant apple seed tissues ‐ a rapid purification scheme using pre‐packed columns and GCMS‐SIM quantitation
Authors: Subbaiah Thilak , Powell Loyd
Published: May 2006

A rapid small scale procedure has been developed for quantitative abscisic acid (ABA) determination by gas chromatography ‐ mass spectrometry with selected ion monitoping (GCMS‐SIM). Extracts of apple seeds (Malus domestica cv. Northern Spy) were passed first through 3 ml C18 columns, and then through 3 ml silica gel columns. GCMS‐SIM quantitation of ABA was done by adding an internal standard, hexadeuterated ABA. Ten sample extracts could be purified and analyzed by GCMS in 5 to 6 h, offering a quick and precise method to laboratories equipped with GC‐MS instrumentation. The endosperm membrane and seed coat of apple seeds contained 2.5‐3 times the ABA concentration found in the embryonic axis and cotyledons, supporting the hypothesis that it may be the ABA content of the membrane and seed coat that explains their inhibitory qualities with respect to seed germination.
Non‐phytotoxicity of the aluminum sulfate ion, AlSO+4
Authors: Kinraide Thomas B. , Parker David R.
Published: May 2006

Aluminum is a phytotoxic element in many soils and occurs in a variety of chemical species. In order to determine whether AlSO+4 is toxic, seedlings of wheat (Triticum aestivum L. cv. Tyler) and red clover (Trifolium pratense L. cv. Kenland) were transferred to solutions containing controlled activities of Al3+, AlSO+4, Na+ and Ca2+. Root elongation was inhibited by Al3+ (or mononuclear hydroxy‐Al species that are in equilibrium with Al3+), but not by AlSO+4. We assumed a formation constant (KAlSO+4= {AlSO+4}/[{Al3+} {SO2‐4}]; braces indicate activities} of 103.2 for AlSO+4 in the computation of ionic activities, but use of KAlSO+4 values ranging from 102.8 to 103.6 had very little effect on the computed toxicities of Al3+ and AlSO+4. Sulfate did not promote the formation of polynuclear Al complexes in our experiments. A practice in studies of Al phytotoxicity has been to attribute toxicity to mononuclear Al, but now it would seem advisable to exclude AlSO+4. That AlSO+4 is non‐toxic, or is at least 10‐fold less toxic than Al3+, has implications for the physiology of Al toxicity and for the use of sulfate salts in experimental work and in agriculture.
Salinity effects on growth and carbon balance in Lycopersicon esculentum and L. pennellii
Authors: Taleisnik Edith L.
Published: May 2006

The effects of salinity on growth and carbon balance in the cultivated tomato Lycopersicon esculentum (L.) Mill. cv. VF 234 and in a wild, salt‐tolerant relative, L. pennellii (Correll) D'Arcy accession Atico, were compared. The level of salinity that significantly reduced growth and affected morphology was lower for the cultivated than for the wild species.

Net CO2 fixation, stomatal conductance and the specific activity of ribulose bisphosphate carboxylase (EC 4.1.1.39) were more decreased by salinity in the wild tomato than in the cultivated. In both species, the salinity‐associated decrease in assimilation was related to a decrease in net photosynthesis and to carbon reallocation favoring heterotrophic organs.
The role of glucose on the enzymes involved in the release of mature spores of Chlorella fusca
Authors: Walter Joachim K. , Rickert Mechthild , Aach H. G.
Published: May 2006

An enzyme with carbohydrate‐releasing activity (CRA) plays a key role in the release of the mature autospores of Chorella fusca Shihira et Krauss var. vacuolata SAG 211‐8B. CRA liberates oligomeric carbohydrates from isolated sprorangia walls and furthermore splits p‐nitrophenyl‐β‐d‐fucopyranoside. Observations on mixotrophically cultivated C. fusca and on isolated CRA indicated that in vitro the β‐d‐fucosidase activity is inhibited by glucose. In vivo glucose induces the well‐known gigantism of the algal cells by blocking sporulation, and this leads to the formation of giant sporangia containing up to 128 spores. Glucose and fucose were the only inhibitors of CRA isolated from the homogenate of C. fusca cells.
Effect of an endogenous factor on arginase activity in germinating Bengal gram (Cicer arietinum) seeds
Authors: Pawashe Aruna B. , Srivastava S. K.
Published: May 2006

Arginase (EC 3.5.3.1) activity increased in the cotyledon, while it declined rapidly in the embryonic axis of Bengal gram (Cicer arietinum L. cv. Desi type) seeds during germination. The decrease in enzyme activity in the embryonic axis was accompanied by changes in the properties of arginase in vitro such as decreased stability, increased heat lability and failure to bind to DEAE‐cellulose. These alterations were due to the presence of a low‐molecular‐weight factor in the extract, which was purified and identified as a hexose derivative. During germination the concentration of the factor increased in the embryonic axis, while no detectable level of the factor was present in the cotyledons. We postulate that the factor may have a role in the regulation of arginase activity in vivo.
Dynamics of indole‐3‐acetic acid and indole‐3‐ethanol during development and germination of Pinus sylvestris seeds
Authors: Sandberg Göran , Ernstsen Arild , Hamnede Marianne
Published: May 2006

Indole‐3‐acetic acid (IAA) and indole‐3‐ethanol (IEt) were identified in immature seeds of Pinus sylvestris L. by combined gas chromatography‐mass spectrometry. Indole‐3‐methanol was tentatively identified using multiple ion monitoring. Anatomical investigations of seeds, as well as measurements of free and alkali‐hydrolysable IAA and IEt, were made during seed development and germination. Levels of free IAA and IEt decreased during seed development. In the later stages of seed maturation most IAA and IEt were present in alkali‐hydrolysable forms. Bound IAA and bound IEt rapidly decreased during germination, while levels of free IAA and IEt increased dramatically for a short period.
Lipid composition of pine needle chloroplasts and apple bark tissue as affected by growth temperature and daylength changes. 1. Phospholipids
Authors: Ketchie D. O. , Bervaes J. C. A. M. , Kuiper P. J. C.
Published: May 2006

Phospholipid (PL) and fatty acid composition of chloroplasts of pine needles (Pinus sylvestris L.) and apple bark tissue (Malus sylvestris Mill. cv. Golden Delicious) was determined in a series of experiments in which growth temperature and daylength were changed. Trees were exposed to 0 and 20°C and to daylength conditions of 9 and 14 h. All 16 possible combinations were investigated by transfer of the trees from the original condition to each of the other conditions. There was no direct relation between cold hardiness and PL composition in apple bark and pine chloroplasts, when temperature and/or daylength were changed. PL composition seemed to be strongly determined by the sequence of the imposed sets of daylength and temperature. The effect of these environmental factors on PL composition strongly differed from that for cold hardiness. The correlation between the levels of PL (and phosphatidylcholine) and cold hardiness, as reported in the literature, was also evident in this experiment, when treatments, presenting the normal seasonal order, were compared. It seems that the yearly cycle of temperature and daylength is important in determining the PL composition of apple bark and pine chloroplasts.
Lipid composition of pine needle chloroplasts and apple bark tissue as affected by growth temperature and daylength changes. 2. Glycolipids, neutral lipids and chlorophyll
Authors: Bervaes J. C. A. M. , Ketchie D. O. , Kuiper P. J. C.
Published: May 2006

Glycolipids, neutral lipids and chlorophyll of chloroplasts of pine needles (Pinus sylvestris L.) and apple bark tissue (Malus sylvestris Mill. cv Golden Delicious) were determined in a series of experiments in which growth temperature and daylength were changed. Trees were exposed to 0 and 20°C and to daylength conditions of 9 and 14 h. All 16 possible combinations were studied by transfer of the trees from the original condition to each of the other conditions. There was no direct relation between cold hardiness and glycolipid composition in apple bark and pine chloroplasts, when temperature and/or daylength were changed. Glycolipid and neutral lipid composition seemed to be strongly determined by the sequence of the imposed sets of daylength and temperature, and the effects of these factors on lipids strongly differed from that on cold hardiness. When the treatments were given in seasonal order, the corresponding changes in chloroplast glycolipids matched those reported in the literature for needles collected in the forest the year around. Glycolipid synthesis could well be under phytochrome control.
Effect of defoliation on tracheid production and the level of indole‐3‐acetic acid in Abies balsamea shoots
Authors: Sundberg Björn , Little C. H. Anthony
Published: May 2006

To simulate feeding by the spruce budworm (Choristoneura fumiferana Clem.), the apical current‐year shoots on 1‐year‐old branches in the uppermost whorl of 6‐year‐old balsam fir [Abies balsamea (L.) Mill.] trees were either removed completely by debudding before the start of the growing season or defoliated 0, 50, 90 or 100% shortly after budbreak. Debudded branches were treated at the apical end with 0, 0.1 or 1.0 mg of indole‐3‐acetic acid (IAA) (g lanolin)−1. Ninety % of the 1‐year‐old needles were also removed from some of the experimental branches. After ca 4 weeks of growth, the radial width of new xylem and the level of IAA were determined in the 1‐year‐old internode. The IAA content was measured by radioimmunoassay.

The removal or defoliation of current‐year shoots inhibited tracheid production and decreased the IAA level. Exogenous IAA stimulated tracheid production and increased the IAA level in debudded branches. Current‐year shoot defoliation also inhibited current‐year shoot elongation. The inhibitory effect of current‐year needle removal on all parameters generally increased with increasing intensity of defoliation. The removal of 1‐year‐old needles did not affect the IAA level or current‐year shoot elongation, nor did it influence tracheid production in branches with current‐year shoots. However, removal of 1‐year‐old needles inhibited tracheid production in debudded branches supplied with exogenous IAA. The results indicate that (1) IAA is involved in the control of tracheid production in the 1‐year‐old internode, (2) IAA is supplied primarily by current‐year shoots, and (3) defoliation by the spruce budworm inhibits tracheid production partly by decreasing the supply of IAA.
Nucleolar size at early stages of cotton fiber development in relation to final fiber dimension
Authors: Peeters M.‐C. , Voets S. , Dayatilake G. , De Langhe E.
Published: May 2006

Changes in nucleolar size and nucleolar vacuolation at early stages of fiber development and final fiber dimensions were determined for cotton of different species: Gossypium hirsutum L. cv. B49, Gossypium barbadense L. cv. Menoufi and Gossypium arboreum L. cv. Virnar. Size of the nucleolus in combination with its vacuolation at an early stage of development was found to be clearly associated with the final result of fiber development.
Heat inactivation of electron transport reactions in photosystem II particles
Authors: Inoué Hiroshi , Kitamura Tohru , Noguchi Munenori
Published: May 2006

Heat inactivation of diphenylcarbazide (DPC)‐supported 2,6‐dichloroindophenol (DCIP) photoreduction by photosystem II (PS II) particles and non‐oxygen‐evolving PS II core complex isolated from spinach (Spinacia oleracea L. cv. Kyoho) was suppressed under annealing conditions, and accelerated in the presence of EDTA or high concentration of divalent cations. After heating at 45°C for 10 min, half‐maximal annealing effects occurred at 35°C. Minimum acceleration was observed in the presence of 1 mM Mg2+, implying the existence of a cation‐specific site in the vicinity of the PS II reaction center. The acceleration depended on the temperature at which EDTA was added to PS II particles. Half‐acceleration by EDTA occurred at 35°C. Glutaraldehyde stabilized PS II particles against heat inactivation of PS II photochemical reactions.
Lupin peroxidases. I. Isolation and characterization of cell wall‐bound isoperoxidase activity
Authors: Barceló Alfonso Ros , Muñoz Romualdo , Sabater Francisco
Published: May 2006

Cell wall fragments, isolated from dark‐grown Lupinus albus L. (cv. multolupa) hypocotyls, and purified by washing with Triton X‐100, did not show detectable contamination by enzyme markers of cytosol or endoplasmic reticulum in which peroxidase activity was also located by electron microscopy. Peroxidase (EC 1.11.1.7) isoenzymes, solubilized from these cell wall fractions by high saline forces, showed a high affinity towards guaiacyl type substrates, whereas syringyl type substrates were not oxidized. On the other hand, both the isoenzyme patterns and the substrate specificity of these cell wall isoperoxidases could be altered by chromatographic and denaturating/renaturating procedures, which break the protein‐phenol interactions, and this suggests the presence of phenol‐induced conformers. These results draw attention to the origin of the enzymatic polymorphism, and catalytic properties, of the peroxidase activity located in the cell wall.
Effects of nitrogen source on betacyanin accumulation and growth in suspension cultures of Phytolacca americana
Authors: Sakuta Masaaki , Takagi Tsutomu , Komamine Atsushi
Published: May 2006

In suspension cultures of Phytolacca americana L., betacyanin accumulation per cell increased with increasing total nitrogen concentration (initial NH+4:NO−3 ratio 1:2) in the range 0–40 mM and then remained almost constant in the range 40–80 mM. Increasing ammonium increased growth while betacyanin accumulation was reduced. On the other hand, betacyanin accumulation increased when nitrate was increased while growth was almost constant in the concentration range examined. A time‐course study of ammonium and nitrate concentration changes in the medium showed that betacyanin accumulation was associated with nitrate uptake.
Influence of cytokinins on growth of Phycomyces blakesleeanus and on the activities of the glyoxylate cycle enzymes isocitrate lyase and malate synthase
Authors: Botz Thomas , Hilgenberg Willy
Published: May 2006

Treatment of the 1 + strain of Phycomyces blakesleeanus Bgff. with various cytokinins resulted in a stimulation of growth. The magnitude of growth stimulation depended on both the structure of the hormone used and the carbon source in the culture medium. Most of the cytokinin derivatives were active effect in glucose and oleic acid cultures. Benzyladenine (BA) and benzyladenosine stimulated the fungal growth only when oleic acid was the sole carbon source, while they had no effect in glucose cultures within the tested range of concentrations. [14C]‐BA was accumulated by the mycelium of oleic acid cultures. Therefore, differences in BA uptake between glucose and oleic acid cultures could account mainly for the specific growth‐promoting effect of BA. In oleic acid cultures isocitrate lyase (EC 4.1.3.1) and malate synthase (EC 4.1.3.2) activities were enhanced by 40 and 34%, respectively, in the presence of BA. A time course of the hormone effect suggests that BA is not involved in induction, but in the regulation of the mentioned enzymes in Phycocmyces. In contrast, acetate when presented as the sole carbon source or after addition to a glucose culture medium, induced isocitrate lyase activity. This enzyme induction was prevented by simultaneous addition of cycloheximide.
Nitrate‐induced de novo synthesis and regulation of NAD(P)H nitrate reductase from Sphagnum
Authors: Deising Holger , Rudolph Hansjörg
Published: May 2006

The NO−3‐triggered induction of nitrate reductase (NR; EC 1.6.6.2) in the bryophyte Sphagnum magellanicum Brid. has been studied, using in vivo and in vitro assays as well as immunological methods. The time‐course of induction was triphasic with maximal NR activity after 6–8 h. Results obtained from Western blots show that NR is synthesized de novo after NO−3 application. The inhibitory effect of cycloheximide on NR induction corroborated this conclusion. Light enhanced the NO−3‐triggered NR induction. The enzyme activity, measured in vivo, increased more than the in vitro activity. No evidence for phytochrome control of NR was found. Nitrate uptake, in contrast to NR activity, showed no lag period after NO−3 application and, under the experimental conditions used, was not rate limiting for NR induction. Neither light nor a NO−3 pretreatment significantly affected NO−3 uptake.
Purity of Frankia preparations from root nodules of Alnus incana
Authors: Vikman Per‐Åke , Huss‐Danell Kerstin
Published: May 2006

Frankia vesicle clusters were prepared from Alnus incana (L.) Moench root nodules by a homogenization‐filtration procedure. The preparation was examined by transmission electron microscopy and computerized picture analysis to quantify contamination from the host plant. Special attention was paid to plant mitochondria. Mitochondria were only found in 30% of the 50 sections of clusters examined. In sections containing mitochondria the mean number of mitochondria per cluster section was 1.5. The relative volume of all objects found in the vesicle clusters was calculated. More than 98% of the volume of a preparation consisted of Frankia vesicles and hyphae, while only 0.4% of the volume was host plant mitochondria. The frequency of mitochondria in a preparation could be further decreased by osmotic shock. It is concluded that Frankia vesicle clusters, prepared from Alnus incana by the homogenization‐filtration technique used here, are sufficiently pure to be used for studies of Frankia metabolism.
Regulation of membrane phospholipid catabolism in senescing carnation flowers
Authors: Paliyath Gopinadhan , Lynch Daniel V. , Thompson John E.
Published: May 2006

Evidence has been obtained for the involvement of μM levels of Ca2+ in phospholipid catabolism during petal senescence by following the breakdown of [U‐14C]‐phosphatidylcholine by microsomal membranes from cut carnation (Dianthus caryophyllus L. cv. White‐sim) flowers. Phospholipid degradation was mediated by three membrane‐associated lipases, viz. phospholipase D (EC 3.1.4.4), phosphatidic acid phosphatase (EC 3.1.3.4) and lipolytic acyl hydrolase. The activities of phospholipase D and phosphatidic acid phosphatase were stimulated by 30 and 100%, respectively, in the presence of 40 μM free Ca2+, and the Ca2+‐stimulation of phosphatidic acid phosphatase was calmodulin‐dependent. When L‐3‐phosphatidyl‐[2‐3H]‐inositol and L‐3‐phosphatidyl‐[N‐methyl‐3H]‐choline were used as substrates, inositol and choline accounted for 95 and 99%, respectively, of the water‐soluble radiolabelled products. This suggests a predominance of phospholipase D activity over phospholipase C activity in these membranes.

Breakdown of membrane phospholipids in senescing carnations is known to be accelerated by treatment of young flowers with ethylene. To determine whether this involves a specific turnover of phosphatidylinositol as observed in animal systems in response to certain agonists, young flowers pre‐labelled with 32PO3‐4 were treated with 10 ppm ethylene. All phospholipids incorporated the label, but no enhanced turnover of phosphatidylinositol was observed. Inositol 1,4,5‐triphosphate did not release Ca2+ from preloaded microsomal vesicles at concentrations known to be effective in animal systems (i.e. < 5 μM) although release of Ca2+ was observed when a higher (20 μM) concentration was used.
Fructans
Authors: Nelson C. J. , Spollen W. G.
Published: May 2006

Fructans are a major form of stored carbohydrate in vegetative tissues of many plant species and may contribute other functions. Their chemical structures, distribution among plant families, metabolism and possible physiological significance are discussed.
Effects of aluminium on growth and nutrient uptake of Betula pendula seedlings
Authors: Göransson Anders , Eldhuset Toril Drabløs
Published: May 2006

The response to aluminium concentrations was evaluated for birch seedlings (Betula pendula Roth, formerly Betula verrucosa Ehrh.) by using a growth technique that provides stable internal concentrations of nutrients in plants. Aluminium was added as aluminium nitrate and aluminium chloride and pH was kept at 3.8±0.2 by adding HCl or NaOH. The seedlings were grown in two different series of nutrient treatments, either with near‐optimum conditions (relative addition rate 25% day−1) or with constant nutrient stress (relative addition rate 10% day−1) before the aluminium addition. Growth reduction occurred at aluminium concentrations greater than 3 mM, and lethal effects at aluminium concentrations greater than 15 mM. In plants subjected to near‐optimum conditions before aluminium addition, the internal nutrient concentrations decreased with increasing aluminium concentration for all macronutrients. The concentration of the macronutrients N, K and P decreased gradually with increasing aluminium concentration, while the concentration of Ca and Mg decreased fairly abruptly when aluminium concentrations exceeded 1 mM. The same tendency was observed in nutrient stressed birch seedlings, but the pattern was more scattered. Relative growth rate of the seedlings was not affected by a low Ca/Al ratio. In all treatments, the molar Ca/Al ratio in/on the roots was below 0.2 at the end of the experiments. As decrease in growth occurs only at high aluminium concentrations, there is no reason to suggest that aluminium in acid soils is growth limiting for natural birch stands.
Differential effects of chilling on the activity of C4 enzymes in two ecotypes of Echinochloa crus‐galli from sites of contrasting climates
Authors: Simon Jean‐Pierre
Published: May 2006

Five‐week‐old plants of Echinochloa crusgalli (L.) Beauv. from Mississippi and from Québec grown under controlled conditions were subjected to dark chilling for 10 h at 5°C or light chilling treatments for 14 h at 7°C under hight light (1 000 μmol m−2 s−1). The activities of four C4 enzymes of Québec plants, measured 4 h after the completion of the cold treatment, were not affected by the chilling treatment in the dark. The activities of pyruvate, Pi dikinase (PPDK; EC 2.7.9.1) and NADP+‐malic enzyme (NADP+‐ME; EC 1.1.1.40), were significantly reduced in dark‐chilled Mississippi plants. Chilling under high light conditions elicited significant levels of reduction in the activities of the four enzymes from both ecotypes but the reductions were significantly less severe for Québec plants. The recovery of activities of phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) and PPDK for both ecotypes was completed within 36 to 60 hours following the chilling treatment, but NADP+‐malate dehydro‐genase (NADP+‐MDH; EC 1.1.1.82) and NADP+‐ME activities of chilled Mississippi plants remained below that of control plants at the end of the 5‐day monitoring period. PPDK was inactivated in vitro at 0 and 10°C and the rates of cold inactivation were significantly higher for PPDK extracted from Mississippi plants. The activity of PEPC of Mississippi extracts was slightly, but significantly reduced by a 60 min treatment at 0°C.
Biochemical, electrophoretic and immunological characterization of peroxisomal enzymes in three soybean organs
Authors: Stegink Steven J. , Vaughn Kevin C. , Kunce Christine M. , Trelease Richard N.
Published: May 2006

Biochemical, electrophoretic and immunological studies were made among peroxisomal enzymes in three organs of soybean [Glycine max (L.) Merr. cv. Centennial] to compare the enzyme distribution and characteristics of specialized peroxisomes in one species. Leaves, nodules and etiolated cotyledons were compared with regard to several enzymes localized solely in their peroxisomes: catalase (EC 1.11.1.6), malate synthase (EC 4.1.3.2), glycolate oxidase (EC 1.1.3.1), and urate oxidase (EC 1.7.3.3). Catalase activity was found in all tissue extracts. Electrophoresis on native polyacrylamide gels indicated that leaf catalase migrated more anodally than nodule or cotyledon catalase as shown by both activity staining and Western blotting. Malate synthase activity and immunologically detectable protein were present only in the cotyledon extracts. Western blots of denaturing (lithium dodecyl sulfate) gels probed with anti‐cotton malate synthase antiserum, reveal a single subunit of 63 kDa in both cotton and soybean cotyledons. Glycolic acid oxidase activity was present in all three organs, but ca 20‐fold lower (per mg protein) in both nodule and cotyledon extracts compared to leaf extracts. Electrophoresis followed by activity staining on native gels indicated one enzyme form with the same mobility in nodule, cotyledon and leaf preparations. Urate oxidase activity was found in nodule extracts only. Native gel electrophoresis showed a single band of activity. Novel electrophoretic systems had to be developed to resolve the urate oxidase and glycolate oxidase activities; both of these enzymes moved cathodally in the gel system employed while most other proteins moved anodally. This multifaceted study of enzymes located within three specialized types of peroxisomes in a single species has not been undertaken previously, and the results indicate that previous comparisons between the enzyme content of specialized peroxisomes from different organisms are mostly consistent with that for a single species, soybean.
Correlation between K+content, activities of arginine and ornithine decarboxylase, and levels of putrescine and nicotine in cultured tobacco callus
Authors: Piñol Ma T. , Palazón J. , Altabella T. , Serrano M.
Published: May 2006

In callus cultures ofNicotiana tabacumL. cv. Burley 21 we have examined the effect of two auxin concentrations (1 and 11.5 μMα‐naphthaleneacetic acid) in the culture medium on K+, putrescine and nicotine levels and activities of putrescine‐biosyn‐thetic enzymesl‐arginine decarboxylase (EC 4.1.1.19) andl‐ornithine decarboxylase (EC 4.1.1.17). The calli grown on the low‐auxin medium (with optimal auxin concentration for nicotine synthesis) had significantly lower concentrations of K+and higher concentrations of nicotine than those grown on the high‐auxin medium (with a supraoptimal auxin concentration). Furthermore, in the calli grown on both culture media, there was a positive correlation between the levels of HCIO4‐soluble free putrescine and nicotine, as well as a negative correlation between those of HCIO4‐soluble bound putrescine and the alkaloid. The results suggest that in tobacco callus K+uptake, the accumulation of HCIO4‐soluble free putrescine and nicotine synthesis are related processes that depend upon the concentration of auxin in the culture medium; a concentration of 1 μMNAA would increase HCIO4‐soluble free putrescine level to a greater degree than that of 11,5 μMNAA, and consequently lead to a higher production of the alkaloid. Although both putrescine‐biosynthetic enzymes are active in our callus cultures, ornithine decarboxylase activity was considerably greater. This interpretation is supported by the enhancement of the 35.5 kDa band and 38.9 kDa band (detected by SDS‐PAGE) which showed ornithine and arginine decarboxylase activity, respectively.