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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To elucidate the mechanism by which white fluorescent light (5 W m-2) stimulates the formation of diferulic acid (DFA) in cell walls, the effect of light on phenylalanine-and tyrosine-ammonia-lyase (PAL, EC 4.3.1.5 and TAL, EC 4.3.1.5) and peroxidase activities was studied using coleoptiles of maize (Zea mays L. cv. Cross Bantam T51). Growth rate of dark-grown coleoptiles was highest at the basal zone and decreased towards the tip, while continuous irradiation caused an inhibition of growth, especially at the basal zone. Light decreased the cell wall extensibility in all zones of the coleoptile. The amounts of DFA, ferulic acid (FA) and p-coumaric acid (p-CA) increased by severalfold in cell walls of light-grown maize coleoptiles as compared with those grown in the dark. Strong correlations were observed between the increase in the contents of either DFA, FA or p-CA and the decrease in cell wall extensibility. Light decreased the wall-bound peroxidase activity. No correlation was found between DFA content and peroxidase activity. The activities of PAL and TAL were enhanced upon white light irradiation. The increment in either DFA, FA or p-CA content was correlated with an increase in PAL activity, but not with that in TAL activity. White light may promote DFA formation in the cell walls of maize coleoptiles by enhancing PAL activity.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 118 (2003), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The present study was conducted to investigate the mechanism inducing the difference in the cell wall extensibility of rice (Oryza sativa L. cv. Koshihikari) coleoptiles grown under various temperature (10–50°C) conditions. The growth rate and the cell wall extensibility of rice coleoptiles exhibited the maximum value at 30–40°C, and became smaller as the growth temperature rose or dropped from this temperature range. The amounts of cell wall polysaccharides per unit length of coleoptile increased in coleoptiles grown at 40°C, but not at other temperature conditions. On the other hand, the molecular size of hemicellulosic polysaccharides was small at temperatures where the cell wall extensibility was high (30–40°C). The autolytic activities of cell walls obtained from coleoptiles grown at 30 and 40°C were substantially higher than those grown at 10, 20 and 50°C. Furthermore, the activities of (1→3),(1→4)-β-glucanases extracted from coleoptile cell walls showed a similar tendency. When oat (1→3),(1→4)-β-glucans with high molecular mass were incubated with the cell wall enzyme preparations from coleoptiles grown at various temperature conditions, the extensive molecular mass downshifts were brought about only by the cell wall enzymes obtained from coleoptiles grown at 30–40°C. There were close correlations between the cell wall extensibility and the molecular mass of hemicellulosic polysaccharides or the activity of β-glucanases. These results suggest that the environmental temperature regulates the cell wall extensibility of rice coleoptiles by modifying mainly the molecular mass of hemicellulosic polysaccharides. Modulation of the activity of β-glucanases under various temperature conditions may be involved in the alteration of the molecular size of hemicellulosic polysaccharides.
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  • 3
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in the amount and composition of cell wall constituents in response to continuous hypergravity stimuli were studied in wheat (Triticum aestivum L.) coleoptiles. The lengths of coleoptiles grown under hypergravity (300 g) conditions for 2–4 days from germination stage were 60–70% of those of 1 g control. However, the net amounts of hemicellulosic polysaccharides and cellulose in hypergravity-treated coleoptiles increased progressively as much as those in the control coleoptiles. As a result, their contents per unit length of coleoptile largely increased under hypergravity conditions. In the hemicellulose fraction, the amounts of arabinose and xylose, the major components of the fraction, prominently increased in response to hypergravity. When hemicellulosic polysaccharides were separated into neutral and acidic polymers by an anion-exchange column, the amounts of the acidic fraction consisting of (glucurono)arabinoxylans were higher in hypergravity-treated coleoptiles than in control coleoptiles. The amounts of cell wall-bound ferulic acid and diferulic acid (DFA) increased dramatically in both 1 g control and hypergravity-treated coleoptiles. Particularly, the amounts of DFA in hypergravity-treated coleoptiles were significantly higher than those in control coleoptiles during the incubation period. These results suggest that continuous hypergravity increases the rigid network structures via arabinoxylan–hydroxycinnamate cross-links within cell wall architecture in wheat coleoptiles. These structures may have a load-bearing function and contribute to construct the stable cell wall against the gravitational force.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 121 (2004), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The protein fraction extracted with a high ionic strength buffer from the cell wall preparation of oat (Avena sativa L.) coleoptiles and first leaves contained starch-degrading (amylase) activity. The activity of apoplastic amylase in the coleoptiles and first leaves continued to increase in parallel with organ growth. One of the apoplastic amylases recovered from shoot cell wall preparations was purified by sequential ion exchange and gel filtration chromatography, and the catalytic properties of the enzyme were analysed. The purified enzyme gave a single 25 kDa protein band on SDS-PAGE. The enzyme exhibited maximum activity at pH 5.0 against maltooligosaccharides. The purified enzyme hydrolysed soluble starch and maltooligosaccharides larger than tetraose at maltose unit, but did not hydrolyse β-limit dextrin or p-nitrophenyl-α-d-glucopyranoside. These results as well as the findings that the molecular size and the catalytic properties of the purified enzyme are different from those of known amylases obtained from Gramineae caryopses suggest that this enzyme is a novel type of β-amylase present in cell walls of vigorously elongating Gramineae shoot organs.
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The correlation of white light-induced changes in osmotic concentration in the coleoptile and the first leaf and the growth rate of these organs in maize seedlings, was examined in relation to sugar distribution and invertase activity. One hour irradiation with white light decreased the osmotic concentration in basal zones of the coleoptile and increased it in the apical zones of the first leaf. The change in the osmotic concentration was positively correlated with the growth rate of both organs. The amount of total osmotic solutes in each zone was highly correlated with that of soluble sugars. Light decreased the activity of wall-bound invertase in the coleoptile, but increased it in the first leaf. A high correlation existed between the content of soluble sugars and invertase activity in both organs. During 1 h incubation in the light, ca 2 µmol of soluble sugars per seedling was lost from the coleoptile and gained in the first leaf. Light promoted sugar exudation from the excised coleoptile, but the amount of soluble sugar exuded represented 5% of sugar loss from the coleoptile in intact seedlings.These results indicate that in maize seedlings white light controls the growth rate of the coleoptile and the first leaf through the osmotic concentration. Light may have an osmoregulatory function in the control of sugar distribution between the coleoptile and the first leaf by regulating the activity of wall-bound invertase.
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  • 6
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: When white light irradiation inhibits shoot growth in derooted pea (Pisum sativum L. cv. Alaska) cuttings, it decreases tissue tension, a driving force for shoot growth, by making the cell wall of the inner tissues mechanically rigid. To elucidate the mechanism by which light affects the mechanical properties of the cell wall in the inner tissues, its effect on the chemical properties of the cell walls was studied by analyzing qualitatively and quantitatively cell wall polysaccharides in the epdidermis and inner tissue of pea epicotyls grown in both dark and light. The amount of polysaccharides per subhook in the cell walls of both tissues increased during a 4-h dark incubation. Light suppressed the increase in hemicellulosic (HC)-II and cellulosic polysaccharides in the inner tissues, while it did not affect the increase in other wall fractions in either the epidermal or subepidermal tissues. No light effect was observed on the neutral sugar compositions of pectin, HC-I or HC-II fractions in either of the tissues. Light increased the mass-average molecular mass of xyloglucan and rhamnoarabinogalactan in HC-II fractions in the inner tissues, while such an effect was not observed in the epidermis. These facts suggest that the light-induced decrease in the tissue tension in pea epicotyls is caused by an increase in the molecular size of xyloglucan, rhamnoarabinogalactan in the HC-II fraction and/or the suppression of the synthesis of HC-II and cellulosic polysaccharides in the inner tissues.
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  • 7
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The growth rate of maize (Zea mays L. cv. Cross Bantam T51) coleoptiles in the dark was highest at the basal zone and decreased towards the tip. Growth was strongly inhibited by white fluorescent light (5 W m−2), especially in the basal zone of coleoptiles. Light irradiation caused an increase in the values of stress-relaxation parameters, the minimum stress-relaxation time and the relaxation rate and a decrease in the extensibility (strain/stress) of the cell walls at all zones. In addition, during growth, the accumulation of osmotic solutes was strongly inhibited by white light irradiation, resulting in an increased osmotic potential. The influences of white light on the mechanical properties of the cell wall and the osmotic potential of the tissue sap were most prominent in the basal zone. Significant correlations were observed between the increment of coleoptile length and the mechanical properties of the cell walls or the osmotic potential of the tissue sap and osmotic solutes content. Furthermore, light inhibited the outward bending of split coleoptile segments. These facts suggest that white light inhibits elongation of maize coleoptiles by modifying both the mechanical properties of the cell walls and cellular osmotic potential, which control the rate of water uptake.
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  • 8
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seedlings of maize (Zea mays L. cv. Golden Cross Bantam T-51) were grown under microgravity conditions simulated by a three-dimensional clinostat. On the clinostat, maize shoots exhibited curvatures in three different portions: (1) the basal transition zone connecting roots and mesocotyls, (2) the coleoptile node located between mesocotyls and coleoptiles, and (3) the elongating region of the coleoptiles. Even non-clinostatted control shoots showed some degree of curvature away from the caryopsis in the transition zone and bending toward the caryopsis in the coleoptile node. Clinostat rotation greatly stimulated these curvatures. Control coleoptiles elongated almost straightly, whereas coleoptiles on the clinostat bent either away from or toward the caryopsis depending on the timing of rotation. The curvature in all three portions became larger with time, both in control and clinostatted seedlings. There was no difference in the osmotic concentration of the cell sap between the convex and the concave halves of any portion. However, in coleoptile nodes and coleoptiles, the faster-expanding convex side exhibited a higher extensibility of the cell wall than the opposite side, and this appears to be a cause of the curvature. Thus, changes in the cell wall metabolism may be involved in automorphosis, which governs the life cycle of plants under a microgravity environment.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 77 (1989), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Antiserum raised against the LiCl extract of maize shoot cell walls suppresses auxin-induced elongation of maize coleoptile segments. A series of polyclonal antibodies were raised against protein fractions separated from the LiCl extract of maize (Zea mays L. cv. B73 x Mo17) coleoptiles by SP-Sephadex and Bio-Gel P-150 chromatography. To understand the role of cell wall proteins in growth regulation, the effect of these antibodies on auxin-induced elongation and changes in the cell walls of maize coleoptiles was examined. Four of the fractions prepared reacted with the antiserum raised against the total LiCl extract and effectively suppressed its growth-inhibiting activity. Only these fractions contained the proteins responsible for eliciting growthinhibiting antibodies. The antibodies capable of growth inhibition of auxin-induced elongation of segments also inhibited auxin-induced cell wall loosening (decrease in the minimum stress-relaxation time of the cell walls) of segments. The antibodies raised against one of the protein fractions separated by SP-Sephadex inhibited the autolytic reactions of isolated cell walls and the auxin-induced decrease in (1→3), (1→4)-β-D-glucans in the cell walls. Thus, the degradation of β-D-glucans by cell wall enzymes may be associated with the cell wall loosening that is responsible for cell elongation. Because the other antibodies did not influence the auxin-induced degradation of (1→3), (1→4)-β-D-glucanses, β-D-glucanases and other cell wall enzymes may cooperate in regulation of cell elongation in maize coleoptiles.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Auxin-induced elongation of epicotyl segments of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) was suppressed by a fucose-binding lectin from Tetragonolobus purpureas Moench and by polyclonal antibodies raised against xyloglucan heptasaccharide (Xyl3Glc4) when the cuticle present in the outer surface of epicotyls was abraded. In contrast, elongation of non-abraded segments was not influenced by the lectin or the antibodies. Epicotyl segments, from which the epidermal and the outer cortical cells had been removed, elongated rapidly for 2 h and than only slowly. Auxin slightly stimulated elongation of the inner tissue segments in the phase of slow growth. Neither in the presence nor in the absence of auxin did the lectin or the antibodies affect elongation of the inner tissue segments. The split portions of outer surface-abraded epicotyl segments incubated in buffer extended outward, and auxininhibited this outward bending. The lectin and the antibodies reversed the effect of auxin on bending. The fucose-binding lectin pretreated with fucose or the immunoglobulin fraction obtained from preimmune serum exhibited little or no inhibitory effect on auxin-induced elongation of abraded or split segments. These results support the view that a breakdown of xyloglucans in the epidermal cell walls plays an essential role in auxin-induced elongation in dicotyledons.
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