bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of the outer tissue in abscisic acid‐mediated growth suppression of etiolated squash hypocotyl segments
Authors: Wakabayashi Kazuyuki , Sakurai Naoki , Kuraishi Susumu 
Published: May 2006

Exogenously applied abscisic acid (ABA) substantially suppressed the elongation of hypocotyl segments of etiolated squash (Cucurbita maxima Duch. cv. Houkou‐Aokawaamaguri) after a 3 h lag period, without changes in the osmolalities of the apoplastic and symplastic solutions in the segment.Segments with the outer tissues removed elongated more rapidly than unpeeled segments (whole segments). ABA did not suppress the elongation of peeled segments. When the segments were incubated in [14C]‐glucose, radioactivity was more effectively incorporated into the cell wall fractions of the outer than into those of the inner tissue. ABA significantly inhibited the incorporation of radioactivity into hermicellulose and cellulose of the outer tissue prior to the suppression of segment elongation, but it did not inhibit the incorporation into the pectic traction of the outer tissue or into any of the cell wall fractions of the inner tissue. These results indicate that ABA primarily affected the outer tissue, in which it specifically reduced the synthesis of hemicellulose and cellulose prior to the ABA‐mediated suppression of growth.
Photocontrol of the hypocotyl hook opening of Sinapis alba seedlings. Involvement of phytochrome and a high irradiance response
Authors: Baumgartner Nicole , Fondeville Jean‐Claude 
Published: May 2006

Baumgartner, N. and Fondeville, J. C. 1989. Photocontrol of the hypocotyl hook opening of Sinapis alba seedlings. Involvement of phytochrome and a high irradiance response.A statistical evaluation of the hypocotyl hook opening (hook opening index) was used for measurement of the hook angle in lots of etiolated Sinapis alba L. cv. Albatros seedlings. Studies of the kinetics for hook opening were carried out in continuous fluorescent white, blue and red light (6, 15 and 40 μmol m‐2s‐1) with 2‐day‐old dark‐grown seedlings. At the beginning of the irradiation period the photoresponse in red light was the opposite to that in blue (low photon fluences). Blue rapidly induced the hook opening (in less than 20 min), while red produced hook tightening (photon fluences up to 70 mmol m‐2), which precedes the normal progressive hook opening. For low fluences, the data were consistent with the involvement of phytochrome and a specific blue light photoreceptor. A phytochrome effect was observed in the hook opening, dependent upon a high irradiance response (HIR). This HIR (like that for the inhibition of the hypocotyl elongation) was characterized by a wavelength response curve with maxima in the blue and far‐red regions of the spectrum.
Effect of the auxin, 2‐(2‐methyl‐4‐chloro‐phenoxy)propionic acid, on cell cycle regulation in maize embryonic tissues
Authors: Baíza Ana María , Sànchez‐de‐Jiménez Estela 
Published: May 2006

During seed maturation, cells from embryonic tissues stop division at different phases of the cell cycle. In maize, neither these phases nor the effect of exogenous auxin on them are known. Disinfected whole maize (Zea mays L. Mexican commercial hybrid H30) seeds or sectioned embryonic axes were incubated in Murashige and Skoog medium, with or without 2‐(2‐methyl‐4‐chlorophenoxy)propionic acid (MCPP), a synthetic auxin. For some in vitro experiments, radioactive [3H]‐thymidine was also added. After the stated incubation period, meristems of mesocotyl, primary and seminal roots from embryonic axes were dissected, fixed, and analyzed under a microscope. The percentage of mitotic indices was recorded. In the labeling experiments, labeled and non‐labeled percentage of mitotic figures (MI %) were determined. It was found that cell division is a programmed event in the meristematic tissues of maize embryonic axes. Populations of cells entering cell division were obseved during the germination process. The mesocotyl was the first tissue to divide, followed by seminal and primary roots.Meristematic cells from dry embryos are arrested during the G2 and G1 phases of the cell cycle. MCPP has a differential effect, stimulating G2 cells to enter cell division. It is concluded that MCPP might regulate the cell cycle at specific points.
Relation of cell wall peroxidase activity with growth in epicotyls of Cicer arietinum. Effects of calmodulin inhibitors
Authors: Sanchez Oskar J. , Pan Alberto , Nicolás Gregorio , Labrador Emilia 
Published: May 2006

Sánchez, O.J., Pan, A., Nicolás, G. and Labrador, E. 1989. Relation of cell wall peroxidase activity with growth in epicotyls of Cicer arietinum. Effects of calmodulin inhibitors.Peroxidases are bound ionically to cell walls in epicotyls of Cicer arietinum L. cv. Castellana. The cell wall peroxidase activity increases during the growth of epicotyls, being the lowest in 3‐day‐old epicotyls with high growth capacity. The cell wall phenolic compounds, postulated natural substrates of cell wall peroxidases, also increase during growth.The calmodulin inhibitors chlorpromazine and trifluoperazine decrease the elongation rate of epicotyls of Cicer arietinum. These inhibitors also cause an increase in the cell wall peroxidase activity and in the level of phenolic compounds. A possible regulatory effect of calmodulin on peroxidase activity is postulated.
Effect of nitrogen starvation on ammonium assimilation by Chlamydomonas reinhardtii
Authors: Menacho Alberto , Vega José M. 
Published: May 2006

In nitrogen‐starved Chlamydomonas reinhardtii, wild type, strain 21 gr cells, consumption of nitrate, nitrite and ammonium may occur in the dark in the absence of an added carbon source. Consumption of ammonium in the dark was about 25% higher than in the light, while consumption of nitrate or nitrite in the dark was lower than in the light.N starvation produced a linear increase with time in the intracellular level of glutamine synthetase (GS, EC 6.3.2.1) and glutamate synthase (NADH‐GOGAT, EC 1.4.1.14 and ferredoxin‐GOGAT, EC 1.4.7.1) activities in C. reinhardtii. The effect on GS1 (3‐fold) and NADH‐GOGAT (4.5‐fold) was higher than that on GS2 (1.5‐fold) and ferredoxin‐GOGAT (1.5‐fold).Experiments with methylammonium, L‐methionine‐D, L‐sulfoximine (MSX) and azaserine suggest that: 1) Ammonium itself decreases the intracellular levels of glutamine synthetase and ferredoxin‐glutamate synthase activities; and 2) a metabolite resulting from ammonium assimilation by the alga may be a negative modulator of NADH‐glutamate synthase activity.
The effect of salt stress on polyamine biosynthesis and content in mung bean plants and in halophytes
Authors: Friedman Ra'anan , Altman Arie , Levin Nitsa 
Published: May 2006

The activity of L‐arginine decarboxylase (EC 4.1.1.19) and L‐ornithine decarboxylase (EC 4.1.1.17), polyamine content, and incorporation of arginine and ornithine into polyamines, were determined in mung bean [Vigna radiata (L.) Wilczek] plants subjected to salt (hypertonic) stress (NaCl at 0.51–2.27 MPa). Changes in enzyme activity in response to hypotonic stress were determined as well in several halophytes [Pulicaria undulata (L.), Kostei, Salsola rosmarinus (Ehr.) Solms‐Laub, Mesembryanthemum forskahlei Hochst, and Atriplex halimus L.].NaCl stress, possibly combined with other types of stress that accompanied the experimental conditions, resulted in organ‐specific changes in polyamine biosynthesis and content in mung bean plants. The activity of both enzymes was inhibited in salt‐stressed leaves. In roots, however, NaCl induced a 2 to 8‐fold increase in ornithine decarboxylase activity. Promotion of ornithine decarboxylase in roots could be detected already 2 h after exposure of excised roots to NaCl, and iso‐osmotic concentrations of NaCl and KCl resulted in similar changes in the activity of both enzymes. Putrescine level in shoots of salt‐stressed mung bean plants increased considerably, but its level in roots decreased. The effect of NaCl stress on spermidine content was similar, but generally more moderate, resulting in an increased putrescine/spermidine ratio in salt‐stressed plants. Exposure of plants to NaCl resulted also in organ‐specific changes in the incorporation of both arginine and ornithine into putrescine: incorporation was inhibited in leaf discs but promoted in excised roots of salt‐stressed mung bean plants.In contrast to mung bean (and several other glycophytes), ornithine and arginine decarboxylase activity in roots of halophytes increased when plants were exposed to tap water or grown in a pre‐washed soil—i.e. a hypotonic stress with respect to their natural habitat. NaCl, when present in the enzymatic assay mixture, inhibited arginine and ornithine decarboxylase in curde extracts of mung bean roots, but did not affect the activity of enzymes extracted from roots of the halophyte Pulicaria.Although no distinct separation between NaCl stress and osmotic stress could be made in the present study, the data suggest that changes in polyamines in response to NaCl stress in mung bean plants are coordinated at the organ level: activation of biosynthetic enzymes concomitant with increased putrescine biosynthesis from its precursors in the root system, and accumulation of putrescine in leaves of salt‐stressed plants. In addition, hypertonic stress applied to glycophytes and hypotonic stress applied to halophytes both resulted in an increase in the activity of polyamine biosynthetic enzymes in roots.
Diagnostic parameters for selecting against novel spruce (Picea abies) decline: III. Response of photosynthesis and transpiration to O3 exposures
Authors: Saxe Henrik , Murali N. S. 
Published: May 2006

The dose‐ and time‐response effects of single 4 h day‐time exposures of 0.064, 0.166, 0.336, 0.452 or 0.693 μl l−1 (ppm) O3 followed by single 4 h night‐time exposures of 0.078, 0.198, 0.378, 0.502 or 0.747 μl l−1 O3 on photosynthesis, transpiration and dark respiration were examined for nine Carpatho‐Ukrainian (‘Rachovo’) half‐sib families and for two populations. ‘Westerhof’ from the FRG and ‘Schmiedefeld’ from the GDR, of Norway spruce [Picea abies (L.) Karst.], all in their 4th growing season. Needles were scorched by 4 h exposures to 0.336 μl l−1 O3 and higher.The lag before photosynthesis and transpiration responded significantly to O3 decline took from a few minutes at the highest concentration to several hours at the lower concentrations. Recovery of photosynthesis and transpiration was absent or extremely slow. Photosynthesis of the different spruce types was affected significantly differently, the most sensitive spruce having its photosynthesis suppressed 1.9 times and its transpiration 1.6 times more than the most tolerant spruce. The physiological responses of ‘Westerhof’ were less sensitive than the average ‘Rachovo’ half‐sibs. Neither night transpiration nor dark respiration were affected by high doses of night O3, preceded by day O3 exposures.The gradients of different photosynthesis and transpiration sensitivities of the young half‐sibs (and ‘Westerhof’) demonstrated a significant, positive, mutual correlation, and significant positive correlations with the gradient of novel decline symptoms of their parents growing in Danish forests. The relative photosynthesis and transpiration sensitivities may thus serve as diagnostic parameters in laboratory tests for selection against novel spruce decline.
On the possible control of ultraviolet‐B induced response in growth and photosynthetic activities in higher plants
Authors: Kulandaivelu G. , Maragatham S. , Nedunchezhian N. 
Published: May 2006

When Vigna sinensis L.cv. Walp seedlings were grown under control (from four 40 W white fluorescent tubes) and enhanced ultraviolet‐B (UV‐B) radiation (four 40 W white fluorescent tubes plus one Philips 20W/12 sun lamp) a large inhibition in seedling growth, particularly shoot eelongation and leaf expansion, was observed under enhanced UV‐B radiation. The UV‐B radiation also reduced the overall photosynthetic activity as measured by chlorophyll fluorescence induction. In order to check whether UV‐B causes any destruction of auxins, seedlings with either their shoot tip or primary leaves were covered with black paper and kept under both light conditions. Both the fully exposed and shoot tip‐covered seedlings showed a similar negative response on growth characteristics and physiological activities. Leaf‐covered seedlings showed well preserved photosynthetic activity under both light conditions. However, in these seedlings the pigment content decreased more than under other treatment conditions.Our experiments provide evidence for distinguishing between the UV‐B induced responses on growth and physiological activities; while the former may be controlled through auxins, the latter is probably by direct action on the organelles.
Growth and development of Brassica genotypes differing in endogenous gibberellin content. I. Leaf and reproductive development
Authors: Zanewich Karen P. , Rood Stewart B. , Williams Paul H. 
Published: May 2006

Leaf and reproductive development were compared in 3 rapid cycling Brassica rapa genotypes grown for 4 weeks under greenhouse conditions. The dwarf mutant, rosette (ros), is gibberellin (GA)‐deficient, while the tall mutant, elongated internode (ein), has enhanced endogenous GA levels. Germination was delayed in ros and a selection of a more severe form of ros, named dormant (do), has even more retarded germination and some seeds entirely fail to germinate. Seeds of do and ros respond to exogenous GA, by rapid germination.The 3 genotypes, ros, normal and ein, displayed similar developmental sequences, although floral bud formation and subsequent floral development and anthesis were delayed in ros. Conversely, anthesis was slightly accelerated in ein. Individual leaf areas were reduced in both ros and ein relative to the normal genotype, but leaf numbers were similar in all 3 genotypes. Differences in leaf morphology (heterophylly) were also observed; the normal genotype and ein plants possessed uniform leaf shapes and relatively smooth leaf margins, although petiole length was increased in ein. The mutant ros had scalloped leaf margins and convoluted leaf blades in addition to shortened petioles. These phenotypes suggest a role for GA in the regulation of germination and reproductive and leaf development in Brassica.
The development of dormancy in bulblets of Lilium speciosum generated in vitro. II. The effect of temperature
Authors: Delvallée Isabelle , Paffen Annie , De Klerk Geert‐Jan 
Published: May 2006

Upon harvest, lily (Lilium speciosum Thunb. cv. Rubrum) bulblets generated in vitro under standard conditions (11 weeks at 20°C) were dormant and needed a cold treatment prior to planting. During culture in vitro at 20°C, the bulblets proceeded through three phases: (1) at first they were non–viable and non‐dormant (up to 5 weeks), (2) then viable and non‐dormant (5–9 weeks) and (3) finally viable and dormant (from 9 weeks onwards). At 15°C, the bulblets became viable but did not develop dormancy, even after protracted culture. The results suggest that the development of dormancy depends upon an accumulation of‘heat units’occurring at temperatures higher than 15°0. At 25°C, the succession of the three phases occurred more rapidly than at 20°C and heat units were accumulated more rapidly. During the third period, the chilling requirement increased showing that heat units continued to be accumulated during this period.Dormancy connotes an arrest of growth. In lily bulblets, however, the number of scales continued to increase after the induction of dormancy at 20 or 25°C. Many of the scales initiated before the onset of dormancy were formed by swelling of a petiole, whereas, after the onset of dormancy, all scales were formed directly from a primordium. We conclude that the development of dormancy corresponds to a switch in the development of the primordium. Thus, after the induction of dormancy the primordium lost the ability to become a leaf and always developed into a scale.
Slow‐phase chlorophyll fluorescence characteristics of the donor plant leaf tissue as a predictive parameter of protoplast survival potential in vitro
Authors: Cassells Alan C. , Hurley Deirdre H. 
Published: May 2006

Variation in the steady state (FT) to fluorescence peak (FP) ratio of Nicotiana tabacum L. cv. Xanthi‐nc leaves in relation to their position on the plant were correlated with the survival in vitro of protoplasts isolated. The FT/FP ratio detected variation in the protoplast survival potential in individual plants in a batch and between batches of donor plants. Deliberately waterlogged and droughted plants had increased FT/FP values and decreased protoplast survival potential.The use of slow‐phase chlorophyll fluorescence characteristics as a predictive parameter of protoplast survival potential is discussed and compared with the use of stress ethylene and stress ethane measurements for the same purpose.
Role of ethylene in auxin‐induced flower bud formation in tobacco explants
Authors: Smulders M. J. M. , Kemp A. , Barendse G. W. M. , Croes A. F. , Wullems G. J. 
Published: May 2006

The effect of ethytene on in vitro flower bud formation in thin‐layer explants from tobacco pendicels (Nicotiana tabacum L. cv. Samsun) was studied Endogenous ethylene production was stimulated by l‐minocyclopropanc‐l‐carhoxylic acid (ACT), and inhibited by aminoethoxyviny lglycine (AVG). resulting in higher and lower ethylene accumulation. respectively. In the presence of an elevated ethylene concentration, the number of flower buds formed after 7 days of culture in explants was increased, compared with the control. Treatment with AVG or with AgNO3 which blocks ethylene action resulted in decreased bud numbers after 7 days of culture. A different effect of ethylene was visible after 14 days of culture, when regeneration was complete. Treatment with AgNO3 led to more bud regeneration, and increasing ethylene concentrations to lower bud numbers. The endogenous production of ethylene was enhanced by high concentrations of 1‐naphthaleneacetic acid (NAA).The inhibitory effect of applied ethylene was almost 100% in explants cultured at low concentrations of NAA (below 1 μM). but hardly visible at high concentrations (4.5 μM). As a consequence, the optimal NAA concentration shifted to a higher value in the presence of ethylene. These results are interpreted as a reduction in tissue sensitivity to auxin and in regenerative capability by ethylene. The effect of ethylene on auxin action is not exerted at the level of hormone concentration. Neither NAA uptake nor conversion to conjugates was effected by ethylene.
Oxidation of NADH by plant mitochondria: Kinetics and effects of calcium ions
Authors: Soole Kathleen L. , Dry Ian B. , Wiskich Joseph T. 
Published: May 2006

The kinetics of NADH oxidation by the outer membrane electron transport system of intact beetroot (Beta vulgaris L.) mitochondria were investigated. Very different values for Vmax and the Km for NADH were obtained when either antimycin A‐insensitive NADH‐cytochrome c activity (Vmax= 31 ± 2.5 nmol cytochrome c (mg protein)−1 min−1; Km= 3.1 ± 0.8 μM) or antimycin A‐insensitive NADH‐ferricyanide activity (Vmax= 1.7 ± 0.7 μmol ferricyanide (mg protein)−1 min−1; Km= 83 ± 20 μM) were measured. As ferricyanide is believed to accept electrons closer to the NADH binding site than cytochrome c, it was concluded that 83 ± 20 μM NADH represented a more accurate estimate of the binding affinity of the outer membrane dehydrogenase for NADH. The low Km determined with NADH‐cytochrome c activity may be due to a limitation in electron flow through the components of the outer membrane electron transport chain.The Km for NADH of the externally‐facing inner membrane NADH dehydrogenase of pea leaf (Pisum sativum L. cv. Massey Gem) mitochondria was 26.7 ± 4.3 μM when oxygen was the electron acceptor. At an NADH concentration at which the inner membrane dehydrogenase should predominate, the Ca2+ chelator, ethyleneglycol‐(β‐aminoethylether)‐N,N,‐tetraacetic acid (EGTA), inhibited the oxidation of NADH through to oxygen and to the ubiquinone‐10 analogues, duroquinone and ubiquinone‐1, but had no effect on the antimycin A‐insensitive ferricyanide reduction. It is concluded that the site of action of Ca2+ involves the interaction of the enzyme with ubiquinone and not with NADH.
Changes in the concentration of indole‐3‐acetic acid during the growth of etiolated lupin hypocotyls
Authors: Ortuño A. , Sánchez‐Bravo J. , Moral J. R. , Acosta M. , Sabater F. 
Published: May 2006

The longitudinal distribution of unaltered radioactive indole‐3‐acetic acid (IAA), after application of [5‐3H]‐IAA to decapitated etiolated lupin hypocotyls. exhibited a wave‐like pattern similar to that obtained with endogenous IAA. Waves of radioactive IAA were localizated both in the elongation zone and in the non‐growing basal region of the hypocotyl. These IAA waves were transient because of basipetal polar transport and metabolism of IAA.The level of endogenous IAA in different zones of the hypocotyl varied with age, following a wave‐like pattern. During the elongation period of each zone, IAA was parallel to the bell‐shaped curve of the growth rate. In addition, a role in secondary cell wall deposition is suggested for the other IAA wave that appeared after the cell elongation period, since an electron microscopic morphometric analysis of the cell wall showed that the cell wall thickness increased once the cell elongation ceased.As the oscillation of endogenous IAA level occured in both space (distribution along the hypocotyl) and time (variation with age), it is suggested that the level of IAA really depended on the growth status of the cells. The response of the cells to the positional information submitted by the auxin waves as regards the growth status of the cell is discussed.