bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunochemical characterization and localization of nitrate reductase in norflurazon‐treated soybean cotyledons
Authors: Vaughn Kevin C. , Duke Stephen O. , Funkhouser Edward A.
Published: April 2006

Immunochemical procedures were used to characterize and localize NADH:nitrate reductase (NR; EC 1.6.6.1) in cotyledons of norflurazon‐treated soybeans [Glycine max (L.) Merr. cv. ‘Hill’]. Antiserum prepared to NR isolated from Chlorella strongly reacted against NR from norflurazon‐treated cotyledons. This serum inhibited the NR activity in crude extracts of norflurazon‐treated soybean cotyledons by 98% even at a 1:2000 dilution of crude serum. Pre‐immune serum had no effect on the activity. These data indicate that there are similar antigenic determinants at the active site of both Chlorella and norflurazon‐treated soybean NR. Whole cotyledons were homogenized in lithium dodecyl sulfate‐containing buffer, electrophoretically separated and blotted to nitrocellulose. When the blots were reacted with the anti‐NR serum only a single protein (Mr= 98 kdalton) was visualized. Immunofluorescence studies on fixed tissue sections revealed intense fluorescence in the cytoplasm. Weaker reactions were associated with organelles tentatively identified as plastids. Pre‐immune serum controls were completely unstained using immunocytochemical procedures.
Interaction of respiratory and photosynthetic electron transport, and evidence for membrane‐bound pyridine‐nucleotide dehydrogenases in Anabaena variabilis
Authors: Stürzl Erwin , Scherer Siegfried , Böger Peter
Published: April 2006

Membranes isolated from vegetative cells of Anabaena variabilis (ATCC 29413) oxidine NADPH and NADH in a cyanide‐sensitive reaction, NADPH being the better donor. In addition, both act as reductants for photosystem I in the light and in the presence of DCMU. An NADH‐regenerating system has been introduced experimentally, functioning as donor system for photosystem I of Anabaena membranes. This NADH dehydrogenation is strictly light‐dependent, sensitive to DBMIB, establishes a transhydrogenase system with NADP+ was hydrogen acceptor and competes with oxygen. Kinetic analysis of oxygen uptake with reference to nucleotide concentration exhibited different Km‐ and Vmax‐values for NADPH and NADH in the light and in the dark.
Effects of ultraviolet‐B radiation on plants during mild water stress. III. Effects on photosynthetic recovery and growth in soybean
Authors: Teramura Alan H. , Perry Mark C. , Lydon John , McIntosh Marla S. , Summers Edwin G.
Published: April 2006

Soybean {Glycine max (L.) Merr. ev. Essex} was grown from seed in a greenhouse under ultraviolet‐B (UV‐B, 280–320 nm) radiation supplied by filtered FS‐40 sunlamps. On a weighted, total daily dose basis these plants received either 0 (control) or 2875 effective J m−2 day−1 UV‐BBE. When weighted with the generalized plant action spectrum (Caldwell 1971), this simulated the solar ultraviolet‐B irradiance expected to occur at College Park, Maryland, USA (39°N) in the event the global stratospheric ozone column is reduced by 23%. The effects of ultraviolet radiation on the photosynthetic recovery from water stress were measured with an infrared gas analyzer. These effects were examined in plants which were either well‐watered or previously preconditioned to water stress, during two distinct phenological stages of development. During the early stages of soybean growth, enhanced levels of UV‐B reduced net photosynthesis by 25%, and water stress also reduced photosynthesis to nearly the same extent (by 20%). The combination of these two stresses resulted in smaller biomass than that produced by plants exposed to either stress independently. Photosynthesis in older, larger plants was much more sensitive to water stress and was reduced by as much as 50–60% in non‐preconditioned plants. Although non‐irradiated, non‐preconditioned (control) plants recovered to only within 60% of their prestressed value, preconditioned plants recovered to within 70–80% during the 3 day recovery period. Both water stress and UV‐B radiation affected non‐stomatal conductance, while stomatal conductance was primarily affected by water stress.
The growth and gravitropic responses of wild‐type and auxinresistant mutants of Arabidopsis thaliana
Authors: Mirza Javed I. , Olsen Gunn M. , Iversen Tor‐Henning , Maher E. Paddy
Published: April 2006

Growth and gravitropism have been studied in three mutant strains of Arabidopsis thaliana L, that are resistant to auxin‐herbicide. Two of the mutations are allelic and recessive (aux‐1 and aux‐2) and are unlinked to a dominant mutation, Dwf, which confers a very high level of auxin‐resistance and is apparently lethal when homozygous. The aux‐1 and Dwf strains have altered response to gravity whereas aux‐2 appears to be gravitropically normal.

After 96 h in the normal, vertical position only minor differences in elongation were observed between roots of wild‐type, aux‐1 and aux‐2, but the hypocotyls of aux‐1 were significantly retarded compared with the gravitropically normal aux‐2 and wild‐type. In the progeny of selfed Dwf plants, where both normal (dwf) and agravitropic (Dwf) seedlings are present, the Dwf seedlings had much longer roots and shorter hypocotyls than dwf+. During 22 h of continuous stimulation the optimum angle for gravitropism in wild‐type roots and hypocotyls was 135° (i.e. the organ points obliquely upwards), with decreasing responses in the order 90° and 45°. The agravitropic nature of the roots of aux‐1 was confirmed as no significant response was obtained at any of the stimulation angles. In marked contrast, the negative gravitropic response of aux‐1 hypocotyls was greater than the wild‐type response in terms of the final angle attained at 22 h, but between 6 and 22 h the elongation rate was lower in aux‐1. After varying stimulation periods in the horizontal position, the curvature which had developed, decreased rapidly and almost disappeared during ensuing rotation on clinostats (2 and 4 rpm). Rotation on the clinostats had no effect on the agravitropic behaviour of aux‐1.
Ultrastructure and movements of cell organelles in the root cap of agravitropic mutants and normal seedlings of Arabidopsis thaliana
Authors: Olsen Gunn M. , Mirza Javed I. , Maher E. Paddy , Iversen Tor‐Henning
Published: April 2006

The root anatomy and ultrastructure of the agravitropic Arabidopsis thaliana L. mutants Dwf and aux‐1 were compared with the gravitropic mutant aux‐2 and the wild type (WT) in an attempt to find an explanation for the lack of response to gravity. No differences were found in the organization of the root cap. The central part of the cap (columella) contains 5 storeys of developing, functioning and degenerating statocytes. Their ultrastructure is very similar in all four types of plant. Particular attention was paid to the distribution of rough endoplasmie reticulum (ER). Both in the WT and the mutants the ER is concentrated in the distal part at the “floor” of the cell.

Light micrographs were used to compare the sedimentation rates of movable cell structures in normal and agravitropic root statocytes. A longitudinal movement of amyloplasts and nuclei was observed when the roots were inverted. In WT and aux‐2 the rates were on average 6.3 μm h−1 (amyloplasts) and 2.1 μm h−1 (nucleus). In aux‐1 the sedimentation rates were significantly lower: 2.4 and 0.6 μm h−1, respectively. Based on magnified electron micrographs of normal and inverted statocytes a morphometrical analysis of the distribution and redistribution of amyloplasts, nuclei, mitochondria, vacuoles and ER was made. The only significant difference was found in the redistribution of amyloplasts between aux‐1 and the gravitropical normal types.
Chilling syndrome in light‐exposed maize leaves and its easing by low doses of DCMU
Authors: Mustárdy L. A. , Sz‐Rózsa Zsuzsa , Faludi‐Dániel Ágnes
Published: April 2006

When maize plants (Zea mays L. line ps‐lye) were subjected to chilling (at 8 ± 2°C, 80% relative humidity for 24 h under illumination by 80 W m2 between 400–700 nm), the leaves were wilted and photosynthetic membranes were permanently damaged. This was shown by the swelling of grana thylakoids and a deerease in the charging capacity of the electron transport chain. Water loss and photosynthetic dysfunction were connected in the process of a chilling‐induced increase of stomatal aperture. Chilling injury could be eased to a considerable extent by a mild treatment with DCMU preventing stomatal opening, wilting, and the irreversible loss of CO2 fixation capacity.
Resolution and characterization of multiple cytosolic phosphatases capable of hydrolyzing fructose‐1,6‐bisphosphate in spinach and soybean leaves
Authors: Pharr David M. , Huber Steven C.
Published: April 2006

The apparent activity of cytoplasmic fructose bisphosphatase (EC 3.1.3.11) in crude extracts of spinach (Spinacia oleracea L.) and soybean (Glycine max [L.] Merr.) leaves was only partially dependent on Mg2+. At least two major non‐chloroplastic fructose bisphosphatases that differed in dependence on Mg2+ were chromatographically resolved from spinach leaves. The Mg2+‐dependent enzyme had an apparent Michaelis constant of 4 μM for fructose‐1,6‐P2, was highly specific, and was strongly inhibited by fructose‐2,6‐P2. Enzyme activity was inhibited by physiological levels of fructose‐6‐P.

Both species also contained at least one major enzyme, the activity of which was independent of Mg2+. These enzymes had pH optima near neutrality, Michaelis constants of 25 to 30 μM for fructose‐1,6‐P2, and were inhibited by AMP. Although hexose monophosphates were not metabolized, the enzymes were not specific for fructose‐1,6‐P2: phosphate was released from phosphoenolpyruvate and ribulose‐1, 5‐P2, and with fructose‐1,6‐P2, as substrate, Pi release was about 1.5‐fold greater than fructose‐6‐P production. It is concluded that only the Mg2+‐dependent fructose bisphosphatase, previously characterized, functions in the photosynthetic sucrose formation pathway. Inhibition of the Mg2+‐dependent enzyme by fructose‐6‐P may be involved in regulation of sucrose formation.
Evidence that brassinosteroid stimulates auxin‐induced ethylene synthesis in mung bean hypocotyls between S‐adenosylmethionine and 1‐aminocyclopropane‐1‐carboxylic acid
Authors: Schlagnhaufer Carl , Arteca Richard N. , Yopp John H.
Published: April 2006

Brassinosteroid (BR) stimulation of auxin‐induced ethylene production and the particular step at which BR acts to promote such synthesis were studied in mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. Increasing concentrations of methionine alone and in combination with 3 μM BR and 10 μM IAA had a minimal effect on ethylene production. With increasing concentrations of 1‐aminocyclopro‐pane‐1‐carboxylic acid (ACC), however, ethylene production increased. BR or IAA further enhanced ethylene production with maximum rates occurring when these compounds were added together with ACC. The addition of 10 μM CoCl2 in conjunction with BR and/or IAA resulted in 85–97% inhibition of ethylene production. When 20 μM cycloheximide was used in conjunction with BR and/or IAA there was a complete inhibition of ethylene production. Total inhibition also resulted when 1.0 μM aminoethoxy‐vinylglycine (AVG) was used in combination with BR and/or IAA. AVG alone had no effect on ACC conversion to ethylene.
Phosphorus nutrition of barley, buckwheat and rape seedlings. I. Influence of seed‐borne P and external P levels on growth, P content and 32P/31P‐fractionation in shoots and roots
Authors: Schjørring Jan K. , Jensén Paul
Published: April 2006

Schjørring, J. K. and Jensén, P. 1984. Phosphorus nutrition of barley, buckwheat and rape seedlings. I. Influence of seed‐borne P and external P levels on growth, P content and 32P/31P‐fractionation in shoots and roots.

Seedlings of barly (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus ev. Line) were grown at 8 or 10 different external P levels in the range 0‐2000 μM. Apart from P, the nutrient solutions were complete. In some experiments with barley and rape, 32P‐labelled phosphate was used. Root fresh weights of buckwheat and rape decreased when the external P supply exceeded the level required for maximal root development. In all three species, the roots constituted a decreasing proportion of the total plant fresh weight as the external P level increased. The shoot/root fresh weight ratio increased linearly with the P concentration of the roots. The ratio between the P concentration in shoots and roots increased with the P status of the seedlings grown at low to intermediate external P levels, but decreased at higher P levels. The proportion of total seedling‐P held in roots consequently reached a minimum value and thereafter increased as the P status of the seedlings increased. This indicates that some control mechanism counteracted the accumulation of harmful P levels in the shoots. 32P‐Phosphate uptake by seedlings of barley and rape grown in solutions with 2 μM P overestimated the actual net phosphorus uptake by a factor of 6 to 7, indicating a marked fractionation of 32P and 31P. For seedlings grown in solutions with 25 μM P (barley) or 50 μM (rape) no fractionation occurred. The relative excess of 32P in high P seedlings accumulated in the roots. It is suggested that the fracionation was caused by efflux of low specific activity phosphorus and by diffusion of free phosphate ions across the plasmalemma of the root cells in response to a difference in the concentration gradient between the two P isotopes.
Non‐steady state xylem transport of fifteen elements into the tomato leaf as measured by gamma‐ray spectroscopy: A model
Authors: Wolterbeek H. Th. , van Luipen J. , de Bruin M.
Published: April 2006

A model describing the transport of elements through the xylem vessels into the leaf of a red cherry tomato (Lycopersicon esculentum Mill cv. Tiny Tim) in a non‐steady state situation is presented. The model describes the upward movement of ions as a mass‐flow of the xylem fluid with dissolved elements, with lateral ion escape represented by a first‐order process. The model is fitted to data obtained in an experiment in which 15 elements were applied in a solution to a cut stem part with attached leaf and were measured simultaneously by gamma‐ray spectroscopy. The model is in good agreement with the transport into the leaf of K+ Na+, Rb+, Cs+, Yb3+, Sm3+ Zn2+, Co2+, Cu2+, Sb(SO4)2 AsO3+4, WO2+4; and Mo7O6+24.

Only indirect data could be obtained for Cd2+ and La3+ because of their apparently high affinity for charged sites in the cell walls and high escape constant, respectively. The escape constants were relatively low for all anions, probably due to the presence of a large number of negative charges in the cell walls.
Photosporogenesis ofCoprinus congregatus: Correlations between the physiological age of lamellae and the development of their potential for renewed fruiting
Authors: Bastouill‐Descollonges Y. , Manachère G.
Published: April 2006

When the hymenial lamellae ofCoprinus congregatusBull ex Fr. are used as implants, their potential for renewed fruiting varies according to the photocontrolled meiosis and the consecutive sporogenesis. In the case of young lamellae, whose basidia are still at the dikaryon stage, one can observe immediate start of mycelial growth all around the lamellae and production of the first mature sporophores directly on the lamellae (direct fruiting). Simultaneously, meiosis does not occur in hymenial cells. Conversely, in the case of implantation of the oldest lamellae, whose basidia are characterized by meiotic nuclei beyond prophase 1 and rather near telophase 2 (tetranucleate stage), vegetative growth starts slowly and the first mature sporophores are not produced on the lamellae but on the surrounding vegetative mycelium (indirect fruiting). When the lamellae are isolated from photoindifferent primordia – for instance, 12 h before maturity – sporogenesis in hymenial cells proceeds normally until autolysis of the isolated lamellae. Such isolated lamellae no longer show direct fruiting where the first flush is concerned.
Compartmentation of phenylacetic and cinnamic acid synthesis in spinach
Authors: Bitsch Annette , Trihbes Rainer , Schultz Gernot
Published: April 2006

Applying labelled phenylalanine or tyrosine to purified intact spinach chloroplasts, only the corresponding phenylacetic acids but not the cinnamic acids could be detected. The addition of mercaptoethanol or dl‐dithiothreitol and the variation of light conditions had only a slight effect. However, cinnamic acids could be found together with phenylacetic acids in leaf homogenates indicating the presence of phenylalanine and/or tyrosine ammonia lyase outside the spinach chloroplasts. Similar results were obtained with barley leaf homogenates, where cinnamic acids were the main products. Reviewing recent findings on amino acid synthesis in spinach leaves, it may be concluded that the synthesis of aromatic amino acids is restricted to the chloroplast, whereas the metabolism of secondary aromatic compounds is predominantly localized outside the chloroplasts.
Sources of proline‐nitrogen in water‐stressed soybean (Glycine max). II. Fate of 15N‐labelled protein
Authors: Fukutoku Yasuo , Yamada Yoshio
Published: April 2006

The absorption of nitrate, protein metabolism and the source of nitrogen for proline synthesis were studied in soybean (Glycine max L. cv. Akisengoku) with 15N tracer technique under water stress conditions. The absorption of nitrate was sensitive to water stress and the flow of nitrate into the leaves completely ceased under severe stress conditions. Net protein loss from the water‐stressed leaves was attributable to both a decrease in synthetic activity and a stimulation of protein degradation. Proline and asparagine accumulated extensively in the severely water‐stressed plant tissues, especially in the younger green leaves. Fifty four % of the loss of leaf protein‐15N during the stress period was balanced by a gain in 15N in the free amino acids, 41% being found in proline and asparagine. The increase in 15N content of the free proline was 3 times greater than the decrease in 15N content of the protein‐bound proline in the leaf. The results indicate that the accumulation of proline in response to water stress was caused by enhanced synthesis and that the nitrogen source for this proline is the leaf protein. The possible association of these findings with stress tolerance is discussed.
Najas marina in Israel: It is a halophyte or a glycophyte?
Authors: Agami Moshe , Eshel Amram , Waisel Yoav
Published: April 2006

In Israel Najas marina L. grows mainly in fresh water habitats. The halophytic nature of a population from one such habitat was investigated. NaCl had a positive effect on the growth of Najas, with an optimal concentration of 37–55 μM. Germination percentage was only slightly reduced by NaCl up to a concentration of 74 μM. It is thus concluded that the populations of Najas in Israel retain their halophytic nature. In fresh water habitats, Najas grows under suboptimal NaCl concentrations.
Roles of ethylene and 1‐aminocyclopropane‐1‐carboxylic acid in pollination and wound‐induced senescence of Petunia hybrida flowers
Authors: Whitehead Charles S. , Halevy Abraham H. , Reid Michael S.
Published: April 2006

Normal senescence of Petunia hybrida L. (cv. Pink Cascade) was associated with a 10‐fold increase in their ethylene production. Soon after pollination wounding of the stigma of detached flowers there was a burst of ethylene production by the gynoecium, which reached a maximum after 3 h. A subsequnt more gradual rise in ethylene production by the flowers was accompanied by blueing, wilting, and senescence of the corolla. Treatment with 1 μl ethylene 1−1 accelerated the onset of senescence as measured first by color change and then by wilting of the corolla. These changes were further accelerated by using older flowers or higher concentrations of ethylene. Senescence was also hastened by supplying 1‐aminocyclopropane‐1‐carboxylic acid (ACC) through the flower pedicel. Petunia pollen contained high concentrations of ACC (300 nmol g−1); treatment of stigmas with ACC (1 mM) caused a 4‐fold increase in their ethylene production. Senescence, whether natural or hastened by pollination or piercing, was delayed by treating the flowers with the anionic silver thiosulfate complex.
Effects of water stress on enzymes of ammonia assimilation in root nodules of alfalfa (Medicago sativa)
Authors: Becana M. , Aparicio‐Tejo P. M. , Sánchez‐Díaz M.
Published: April 2006

Protein content and activities of the enzymes glutamine synthetase (EC 6.3.1.2), NADH‐glutamate synthase (EC 1.4.1.14), NADH‐glutamate dehydrogenase (reductive amination (EC 1.4.1.2) and NAD+‐glutamate dehydrogenase (oxidative deamination) (EC 1.4.1.2) from the plant fraction of root nodules of alfalfa (Medicago sativa L. cv. Aragon) were determined under water stress. Only NADH‐glutamate synthase activity was inhibited during drought. The results indicate that the glutamine synthetase/NADH‐glutamate synthase cycle was fully operational in alfalfa nodules of control or even mildly stressed plants when N2‐fixation was not inhibited, but that the coupling between glutamine synthetase and NADH‐glutamate synthase was lost as drought progressed. Patterns of glutamine synthetase and NADH‐/NAD+‐gluta‐mate dehydrogenase activities reflect changes in ammonia content of nodules and/or availability of carbon substrates, and indicate that nodules maintain sufficient enzyme activity for ammonia assimilation throughout water stress.
Absorption and translocation of Cd in bush beans (Phaseolus vulgaris)
Authors: Hardiman R. T. , Jacoby B.
Published: April 2006

A series of experiments was conducted to examine some factors affecting the absorption and translocation of Cd in young bean plants (Phaseolus vulgaris L. cv. Bulgarian). Absorption of Cd by roots was reduced in the presence of other cations of increasing valency or ionic radii. Reduced absorption was also found in the presence of EDTA. Concentration of Cd in exudates from excised stems increased with increased passage of Cd solutions and approached the concentration in the external medium (4.5 μM Cd). This was apparently associated with saturation of adsorption sites in the stems. The stem behaved as a cation exchange column resulting in a chromatographic distribution of Cd towards the top of the plant. These experiments indicate that Cd existed in the xylem fluid as a free or weakly complexed cation. Additional experiments showed that the total amount of Cd absorbed by bean plants was elevated by inducing higher transpiration rates. The effect of water flux on Cd transport indicated apoplastic flow to the stele.
Betaine accumulation in salt‐stressed sorghum
Authors: Grieve C. M. , Maas E. V.
Published: April 2006

Two analytical methods for measuring betaine were compared in a study of betaine accumulation in salt‐stressed sorghum. Spectrophotometric determination of betaine as the p‐bromophenacyl ester is highly sensitive and specific. However, a periodide assay was found to be more convenient for screening numerous plant samples without undue sacrifice in accuracy.

The accumulation of betaine in grain sorghum [Sorghum bicolor (L.) Moench] cvs NK 265 and Double TX was measured in salt‐stressed plants grown hydroponically and in the field and in drought‐stressed potted plants. Neither drought nor mild salinity (‐0.2 MPa) stress was effective in stimulating betaine accumulation. However, when the osmotic potential of the culture solution was lowered to ‐0.8 MPa, betaine levels in the shoots rose rapidly for 12 days after initiation of salination, and then declined, apparently because of dilution by plant growth. In young leaf blades, betaine was strongly accumulated up to 70–75 μmol (g dry weight)−1; the concentration in leaf sheaths was less than 6 μmol (g dry weight)−1.

In the field, betaine levels in salt‐stressed sorghum increased 6‐ to 7‐fold over the basal level of the control plants. In a comparable study of two wheat species (Triticum aestivum L. cv. Probred and T. durum Desf. cv. 1000‐D), betaine increased only 3‐ to 4‐fold over unstressed plants.
Occurrence of esterified triterpenoid alcohols in the leaves of Pilosella officinarum
Authors: Karunen P. , Hakala K. , Heinonen S.
Published: April 2006

The mature winter leaves of Pilosella officinarum coll. Schultz and Schultz contained 29 mg esterified triterpenoid alcohols (g dry weight)−1, of which over 80% was esterified with long‐chain (C16‐C18) fatty acids. The major fatty acids were 16:0, 18:2ω6 and 18:3ω3 and their amounts varied according to the season and stage of leaf development. In mature leaves the amount of triterpenoid alcohols esterified with long‐chain fatty acids varied only slightly with the season. The changes in the fatty acid proportions in late winter‐early spring, however, indicated a turnover in the esterified triterpenoid alcohol pool. In late winter after the snow had melted a 50% decrease occurred in the amount of triterpenoid alcohols esterified with short‐chain fatty acids. The amount of esterified triterpenoid alcohols in immature leaves was relatively low [4 mg (g dry weight)−1].

In the mature leaves esterified triterpenoid alcohols were found in globules whose appearance varied greatly according to the season. The globules were partly dissolved in late winter, and this together with the activation of respiration, suggests that the globules function as short‐term energy reservoirs. Relationships between the appearance of lipid globules and the amount of esterified triterpenoid alcohols are discussed.
Chloroplast glutathione reductase: Purification and properties
Authors: Kalt‐Torres Willy , Burke John J. , Anderson James Michael
Published: April 2006

Glutathione reductase was partially purified from isolated pea chloroplasts (Pisum sativum L. cv. Progress #9). A 1600‐fold purification was obtained and the purified enzyme had a specific activity of 26 μmol NADPH oxidized (mg protein)−1 min−1. The enzyme had a native molecular weight of approximately 156 kdalton and consisted of two each of two subunits of about 41 and 42 kdalton. The Km for oxidized glutathione was 11 μM and the Km for NADPH was 1.7 μM. Enzyme activity was affected by the ionic strength of the assay medium, and maximum activity was observed at an ionic strength of between 60 and 100 mM. The enzyme was inactivated by sulfhydryl modifying reagents and the presence of either oxidized glutathione or NADPH affected the extent of inactivation. Chloroplast glutathione reductase probably serves in the removal of photosynthetically derived H2O2 by reducing dehydroascorbate for ascorbate‐linked reduction of H2O2. Intermediates of this reaction sequence, dehydroascorbate, ascorbate, reduced glutathione, and NADPH had no effect on enzymic activity.
Photoautotrophic potato cells: Transition from heterotrophic to autotrophic growth
Authors: LaRosa P. Christopher , Hasegawa Paul M. , Bressan Ray A.
Published: April 2006

Cells of potato (Solanum tuberosum L.) were obtained which were capable of photoautotrophic growth in liquid suspension culture under a photon flux density of 90–110 μmol m−2 s−1 PAR and in an atmosphere enriched with 2% CO2. These photoautotrophic cells contained between 100 to 200 μg Chl (g fresh weight)−1 and fixed CO2 at a maximum rate of 16 μmol CO2 (g fresh weight)−1h−1. In order to obtain cells capable of photoautotrophic growth it was necessary to adapt highly chlorophyllous heterotrophic cells (>50 μg Chl (g fresh weight)−1) for growth in medium with 2.5 g sucrose 1−1 (photomixotrophic cells). The photomixotropic cells had a Chl content of ca 100 μg Chl (g fresh weight)−1 and were capable of photosynthetic activity which allowed them to survive after sugars had been depleted from the medium. It was from the photomixotrophic cells that cells capable of photoautotrophic growth were obtained.

Heterotrophic cells initially established in liquid medium with 25 g sucrose I−1 from chlorophyllous callus contained about 50 to 150 μg Chl (g fresh weight)−1. However, after 5 to 10 passages the Chl content decreased to a maximum of 15 μg Chl (g fresh weight)−1. These cells could not be adapted to photomixotrophic or photoautotrophic growth. These cells also were not able to regain Chl or initiate high rates of CO2 fixation during the stationary phase of growth as did photomixotrophic cells or chlorophyllous heterotrophic cells. The loss of Chl exhibited by the cells during adaption to heterotrophic growth could be attributed at least in part to unbalanced growth (when cell division and growth exceeds Chl accumulation). Sucrose appeared to have an inhibitory effect directly on photosynthesis independent of Chl accumulation.
Sequential and non‐sequential pattern of monocarpic senescence in two rice cultivars
Authors: Mondal W. A. , Choudhuri M. A.
Published: April 2006

Two rice (Oryza sativa L.) cultivars viz. Ratna (dwarf, photoperiod insensitive) and Masuri (tall, photoperiod sensitive) were selected to analyse their mode of senescence. At the vegetative stage, leaf senescence, expressed as the loss of chlorophyll and protein and a decline in the activities of catalase and alkaline pyrophosphatase, was found to be a function of chronological age (sequential) in both cultivars. With advancing reproductive development, cultivar Masuri retained this sequential mode but cultivar Ratna showed a non‐sequential mode of senescence where the flag leaf senesced earlier than the older second leaf, unlike that observed at the vegetative stage. Masuri showed a more rapid senescence than Ratna. In both cultivars, excision of any leaf during anthesis initially retarded the senescence of the remaining leaves on the defoliated plants but soon after, at the grain maturation stage, the leaf senescence started at a higher rate compared with that of the intact control plant. In Ratna, when either the second or the third leaf was removed, the flag leaf senesced faster than that of the unexcised control plant. In Masuri, when either the flag or the third leaf was removed, the second leaf senesced earlier than that of the intact control. In both cultivars, excision of the third leaf showed the least detrimental effect on yield. The greatest detrimental effect on grain yield per plant was observed in Ratna when the flag leaf was removed and in Masuri when the second leaf was removed. Mobilization of metabolites from the source leaf to the sink and the consequent depletion in the leaf as the cause of senescence is discussed.
Auxin effects on rooting in pea cuttings
Authors: Eliasson Lennart , Areblad Karin
Published: April 2006

Light‐grown stem cuttingss of Pisum sativum L. cv. Weibull's Marma were rooted in a nutrient solution. The presence of 10 μM indolylacetic acid (IAA) in the solution for 24 h or longer periods decreased the number of roots subsequently formed to about 50% of control, provided IAA was present in the solution during any of the 4 first 24 h periods. Treatment for 6 h or shorter periods caused no or small response. IAA did not appreciably change the time needed for root formation, the time course of root appearance or the pattern of root distribution along the basal internode. IAA at 100 μM usually increased the number of roots although variable results were obtained with this IAA concentration.

The number of roots was strongly increased by treatment with indolylbutyric acid (IBA) or 2,4‐dichlorophenoxyacetic acid (2,4‐D). None of these or other synthetic auxins decreased the number of roots in suboptimal concentrations. Experiments with 10 μM IBA showed that stimulation of rooting was obtained only if the auxin was present in the rooting solution for several days. Simultaneous treatment with IAA decreased the stimulating effect of IBA to some extent, whereas no such response was obtained if IAA was combined with 2,4‐D.

IAA applied in lanolin to the stem of intact cuttings decreased the number of roots formed. Decapitation and debudding of the cuttings decreased the number of roots formed. If at least 2 leaves were left this decrease was efficiently counteracted by an optimal IAA dose applied to the upper part of the stem. A five times higher dose was less effective, indicating a negative effect on rooting also by IAA applied to the shoots.
Rhizobial polysaccharide‐degrading enzymes from roots of legumes
Authors: Solheim Bjórn , Fjellheim Karl E.
Published: April 2006

The surface structure and chemistry of symbiotic bacteria from the genus Rhizobium are probably important for the outcome of the infection of legume hosts. Exopolysaccharide, capsular polysaccharide, lipopolysaccharide and a low‐molecular‐weight polysaccharide were isolated from R. trifolii UTC 110‐1 and R. leguminosarum UTC 114‐5 and partially characterized. No or only minor differences in sugar composition could be found for the corresponding fractions from the two organisms. A general method to measure low activities of polymer‐degrading enzymes was developed, and used to determine enzyme activities in root extracts of Trifolium repens L. cv. Lena and Pisum xativiini L. cv. Little Marvel against the isolated rhizobial polysaccharides. An enzyme preparation from T. repens partially degraded all polysaccharides isolated from its symbiont R. trifolii while polysaccharides from R. leguminosarum, symbiont of P. sativum, were degraded to a much lesser extent. Correspondingly, an enzyme preparation from P. sativum degraded all polysaccharides isolated from both its symbiont R. leguminosarum and its non‐symbiont R. trifolii. The amount of symbiont polysaccharides degraded was larger than the amount of polysaccharides degraded from the non‐symbiont R. trifolii.
Fractionation and partial characterization of cell walls from normal and non‐ripening mutant tomato fruit
Authors: Gross Kenneth C.
Published: April 2006

Cell walls extracted from cv. Rutgers, 7711 (ripening inhibited), and nor (non‐ripening) tomato (Lycopersicon eseulentum Mill.) pericarp tissue at various stages of post‐maturation development have been separated into four distinct fractions and their carbohydrate composition characterized. The amount of ionically‐associated, chelator‐soluble (CDTA, cyclohexanediaminetetraacetic acid) uronic acid in ‘Rutgers’ fruit cell walls remained constant during ripening, whereas the amount of residual pectin, which was extracted with cold alkali (Na2CO3) and was apparently covalently bound, decreased. These changes did not occur in rin and nor mutant fruit at a similar chronological age. The galactose content in pectic polysaccharide preparations extracted from tomato cell walls with CDTA and Na2,CO3, decreased by 65% during ripening. A similar but diminished decrease also occurred in rin and nor fruit. A non‐cellulosic polysaccharide(s) was present in walls which resisted extraction with Na‐acetate/CDTA, Na2CO3, and 4 M KOH. In ‘Rutgers’ fruit, the content of galactose in this polysaccharide(s) decreased 44% during ripening, whereas little or no significant change was observed in rin or nor mutant fruit.
Flowering requirements in Bromus inermis, a short‐long‐day plant
Authors: Heide Ola M.
Published: April 2006

Smooth bromegrass plants (Bromus inermis Leyss.) have a dual photoperiodic requirement for flowering. At temperatures ranging from 6 to 24°C, short days (SD) are necessary for primary induction while a transition to long days (LD) is required for initiation of flower primordia, culm elongation and flower development (secondary induction). Critical photoperiods for primary induction (50% flowering) were 13.5 h (15°C) and 12 h (24°C) in the American cv. Manchar and 14.5 and 13 h, respectively, in the Norwegian cv. Löfar. For the secondary induction the respective critical photoperiods were 14 and 15 h in ‘Manchar’ and 16 and 17.5 h in ‘Löar’, which also appeared to be better adapted to low temperatures. Low temperature vernalization in LD for up to 16 weeks at 3°C was unable to cause primary induction and temperatures below 12°C also strongly reduced the SD effect. At optimum temperature (15‐2TC) 4 to 6 weeks of 8‐10 h SD treatments were needed for optimal primary induction effect. A minimum of 8 LD cycles of 24 h were required for complete secondary induction in ‘Manchar’, while more than 16 cycles were needed in ‘Löfar’. Seedlings grown in SD developed a rosette type of growth with shoots growing in a decumbent position, while those in LD grew upright and formed elongated vegetative culms. Rate of leaf initiation was enhanced by about 60% by LD while tillering was promoted by SD.
Changes in cell wall polysaccharides during elongation in a 2, 4‐D free medium in a carrot suspension culture
Authors: Masuda Hiroshi , Ozeki Yoshihiro , Amino Shin‐ichi , Komamine Atsushi
Published: April 2006

Cell elongation occurred when carrot (Daucus carota L. ev. Kurodagosun) cells subcultured through sieving (Y. Ozeki and A. Komamine, Physiol. Plant. 53: 570‐577. 1981) were transferred to a medium lacking auxin, while the cells showed no elongation in a medium containing 2, 4‐D. Changes in polysaccharides of the cell walls and in their sugar composition during elongation were investigated. All wall components, EDTA‐soluble pectic substance, 5 and 24%, KOH‐soluble hemicelluloses and cellulose increased markedly during elongation. The increase of hemicelluloses correlated especially with elongation. In the 5% KOH‐soluble hemicellulose, galactose and arabinose contents in the walls increased significantly both in amounts (per fresh weight) and relative contents (% in total neutral sugars) during elongation, while the relative contents of glucose and xylose decreased rapidly in the 5 and 24% KOH‐soluble hemicelluloses. The methylation analysis tentatively indicated that larger amounts of galactan and/or arabinogalactan and lower amount of xyloglucan were found as components of the two hemicelluloses of elongating cells than those of non‐elongating cells. The amounts of total carbohydrate and of uronic acid of extracellular polysaccharides secreted into the medium increased to a larger extent in the elongation culture than in the non‐elongation culture. The contents of galactose and arabinose in extracellular polysaccharides increased rapidly in the elongation culture. The biochemical aspects of cell elongation in the absence of auxin were discussed from the viewpoint of the results obtained here.
Thigmomorphogenesis: On the mechanical properties of mechanically perturbed bean plants
Authors: Jaffe Mordecai J. , Telewski Frank W. , Cooke Paul W.
Published: April 2006

The mechanical properties of control and mechanically perturbed (MP) bean stems (Phaseolus vulgaris L., ev. Cherokee wax) were compared. The rubbed plants were greatly hardened against mechanical rupture by previous MP. This hardening was due to a dramatic increase in the flexibility of the stems, but not in their stiffness. The MP‐plants were able lo bend more than 90° without breaking, whereas the control plants broke after just slight bending. A comparison with other work reveals that different species utilize different tactics for achieving similar resistance to rupture due to mechanical stress.
Floral morphogenesis in thin‐layer tissue cultures of Nicotiana tabacum
Authors: van den Ende G. , Crocs A. F. , Kemp A. , Barendse G. W. M. , Kroh M.
Published: April 2006

The morphological changes in thin‐layer tissues of Nicotiana labacum L. cv. Samsun, cultured on Murashige and Skoog medium with 1 μ M each of naphthalene acetic acid (NAA) and benzyladenine (BA), were studied during the first 8 days of culture with light and scanning electron microscopy. The first three days of culture arc characterized by enlargement of all cells and cell divisions starling in the cortical parenchyma cells adjacent to the medium. Between days 3 and 6, epidermal and/or subepidermal cells start to divide, resulting in division centers, which lead to flower bud formation. The hormones NAA and BA in different concentrations affect the formation and distribution of flower buds, bud morphology and callus formation. BA influences particularly bud formation and bud morphology, while NAA affects callus formation in particular. In addition, polarity may occur in the formation of both callus and flower buds, the degree of which depends upon the hormone concentrations.
Allantoinase and asparaginase activities in maturing fruits of nodulated and non ‐nodulated soybeans
Authors: Gomes M. A. F. , Sodek L.
Published: April 2006

Immature fruits of soybean (Glycine max L. Merr. cv. Santa Rosa) were found to contain high ureide/amino acid ratios for plants dependent on atmospheric nitrogen (nodulated), but low ratios for plants cultivated on NO−3 (non‐nodulated). The pod tissue was responsible for almost all this difference, which reflects the N metabolism of these plants (nodulated:urcide‐based; NO−3 dependent: asparagine based). The capacity of fruit tissues to utilize ureides and asparagine via allantoinase (EC 3.5.2.5) and asparaginase (EC 3.5.1.1) was investigated during fruit development. Both enzymes were present in crude desalted extracts of all parts of the fruit analysed (pod, cotyledon and seed coat). Asparaginase was detected in pod tissue only at early stages and with very low activities, whereas high activities of allantoinase (up to 20 [imol pod−1 h−1) were present after this organ reached full expansion. The cotyledons contained most of the allantoinase and asparaginase activities of the seed, the highest activities being recorded during the period of rapid protein accumulation. There was little difference in the activity patterns for nodulated and NO−3‐grown plants, despite the large difference in nitrogen nutrition of the fruits.
Identification of the photosynthetic CO2 fixation inhibitors in isolated pine chloroplasts as resin acids
Authors: Martin Björn , Malmberg Gunilla , Gref Rolf , Öquist Gunnar
Published: April 2006

Thus far all attempts to isolate CO, fixing chloroplasts from pine have failed. In this paper it is proposed that resin acids present in pine needles partition into membranes during chloroplast isolation and interfere with specific reactions of the Calvin cycle. CO, fixation by isolated spinach chloroplasts was strongly inhibited by the introduction of a suspension of chloroplasts isolated from Pinus sylvestris L. A partially purified organic extract obtained from chloroplasts of this pine species also strongly inhibited CO, fixation by the spinach chloroplasts. The major inhibitory compounds from the organic extract were identified as a mixture of resin acids by gas‐liquid chromatography and mass spectrometry. Two resin acids, abietic acid and dehydroabietic acid, were tested for inhibitory activity. Both resin acids were potent inhibitors of photosynthetic CO2fixation, with dehydroabietic acid being about three times more potent than abietic acid.
Ethylene and apical dominance
Authors: Yeang A. Y. , Hillman J. R.
Published: April 2006

Ethylene is involved in at least two discrete mechanisms in the control of apical dominance: the release of lateral buds from inhibition and their subsequent growth and development. Generally, high levels of freely diffusible ethylene in the apical region of the shoot are conducive to lateral‐bud‐outgrowth, while high ethylene levels in the region of the lateral buds themselves tend to be inhibitory. Threshold ethylene levels concerned with the release of buds from inhibition and with the growth that follows may differ between species. Thus, in some species (e.g. Gossypium) lateral‐bud growth proceeds in the continuing presence of ethylene supplied to the whole plant, whereas in others (e.g. Petunia) the growth of the released lateral buds occurs only when the ethylene is remaved.

When ethylene production in Pisum nodal sections is enhanced by exomgenous auxin, growth of the attached buds is suppressed. In the intact plant system, unequivocal evidence has not been established for a role of endogenous ethylene acting directly on lateral buds to effect their inhibition. Apical dominance is not affected by the apptication of ethylene antagonists to the lateral buds of intact plants. Results from different studies have been inconsistent regarding the changes in endogenous ethylene levels in the node/lateral‐bud tissue when the plant is decapitated or when auxin is applied to the stump of the decapitated plant to maintain lateral bud inhibition.

While exogenous ethylene supplied to the lateral bud generally increases inhibition, the availability of ethylene, regulated endogenously, is essential to the released bud on the decapitated plant in order to sustain its subsequent development into a lateral shoot. There is evidence that, in certain instances, endogenous ethylene may also be essential in the initial stages of bud development, e.g. in thee early growth that is promoted bmy auxin in Phaseolus or by kinetin in Avena.
Glycerol‐3‐phosphate dehydrogenase (EC 1.1.1.8) from Dunaliella tertiolecta. I. Purification and kinetic properties
Authors: Haus M. , Wegmann K.
Published: April 2006

A rapid purification procedure for glycerol‐3‐phosphate dehydrogenase from Dunaliella tertiolecta (strain 19‐6 of the algal collection of the Univ. of Göttingen), the initial enzyme in the glycerol cycle, has been developed on the basis of affinity chromatography on Blue Sepharose and subsequent desalting by Sephadex G‐50. The achieved purification was 126‐fold. The pH optimum of dihydroxyacetone phosphate reduction is 7, that of glycerol‐3‐phosphate oxidation is about 9. The in vitro enzymatic activity obtained from cell extracts is higher than the required activity for the observed glycerol production rates under osmotic stress in vivo.
Rapid isolation of plant peroxidase. Purification of peroxidase a from Petunia
Authors: van den Berg Bartel M. , van Huystee Robert B.
Published: April 2006

A rapid isolation procedure was developed for purification of peroxidase a from Petunia hybrida. Rapid isolation was possible since about 15% of the extracellular protein from stem tissue obtained by vacuum infiltration followed by centrifugation of the tissue represents peroxidase. Purification of peroxidase a from intercellular fluid was achieved by two acetone precipitation steps followed by DEAE‐cellulose chromatography.

Three different forms of peroxidase were eluted from DEAE‐cellulose at different NaCl concentrations. Isoelectric focusing showed, however, a pI of 3.8 for all three forms of peroxidase a. Only part of the peroxidase a enzymes bound to Concanavalin A indicating heterogeneity in the carbohydrate part. Homology of peroxidase a to the peroxidase G1 group from tobacco is discussed.
Changes in cell wall constituents during the cell cycle in a synchronous culture of Catharanthus roseus
Authors: Amino Shin‐ichi , Takeuchi Yuichi , Komamine Atsushi
Published: April 2006

Changes in cell wall constituents during the cell cycle were investigated using a synchronous culture of Catharanthus roseus (L.) G. Don which was obtained by the double phosphate starvation method (S. Amino et al. 1983. Physiol. Plant. 59: 393–396). Cell walls isolated from the cells in each phase of the cell cycle were fractionated into EDTA‐soluble (pectin), 5 and 24% KOH‐soluble (hemicellulose) and 24% KOH‐insoluble (cellulose) fractions. Their sugar compositions were investigated by gas chromatography and methylation analysis. The following changes were observed: (1) a significant increase in total cell walls in the G1 phase after cell division, (2) a temporary increase in the relative amount of the EDTA‐soluble fraction during cytokinesis, (3) an increase in the relative amount of galactose, probably 4‐linked galactose, in the EDTA‐soluble fraction prior to cytokinesis, (4) a temporary increase in the relative amount of 3‐linked glucose during cytokinesis, (5) little change in the composition of polysaccharides throughout the cell cycle in the 24% KOH‐soluble fraction, which consisted mainly of xyloglucan. The changes observed are discussed in relation to the progression and physiological significance of each phase of the cell cycle.