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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fructose analog, psicose, and glucose analog, mannose, inhibited root growth of lettuce seedlings. Psicose is phosphorylated by hexokinase and fructokinase (EC 2.7.1.4) to psicose-6-phosphate with no known capacity for further metabolism. Mannose is phosphorylated by hexokinase (EC 2.7.1.1) to mannose-6-phosphate which is further metabolized very slowly. Hexokinase is known to have a sugar-sensing function and possibly triggers a signal cascade resulting in changes of several gene expressions. It was determined, compared with the behaviour of mannose, whether psicose inhibits the root growth through this system. The addition of phosphate into the growth medium of lettuce seedlings did not affect the inhibition by psicose and mannose, and both sugars did not reduce adenosine triphosphate (ATP) level in the roots, suggesting that the inhibition is not due to phosphate starvation and ATP depletion. The inhibiting effects of psicose and mannose were overcome by adding sucrose into the medium, which suggests that the inhibition is not caused by accumulation of psicose-6-phosphate or mannose-6-phosphate in the seedlings. Mannoheptulose, a specific competitive inhibitor of hexokinase, defeated the mannose-induced inhibiting but was not able to relieve the psicose-induced inhibition. Thus, the phosphorylation of mannose by hexokinase may trigger a signal cascade resulting in the growth inhibition of lettuce roots, which is consistent with the hypothesis established in Arabidopsis. However, psicose cannot inhibit the growth of lettuce roots via a hexokinase-mediated pathway, and the phosphorylation of psicose by fructokinase might trigger a hexokinase-independent signal cascade resulting in the growth inhibition.
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 107 (1999), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to clarify the effect of abscisic acid (ABA) on anaerobic tolerance in alfalfa (Medicago sativa L.), the seedlings were subjected to anaerobic stress after pretreatment with ABA. At concentrations〉 1 μM, ABA pretreatment increased the root viability of the seedlings to anaerobic stress and the viability increased with increasing ABA doses. At 100 μM ABA, the viability was 2.5-fold greater as compared with that of control seedlings. Roots of the seedlings rapidly lost ATP under the anaerobic stress; however, the decrease in ATP was much slower in the ABA-pretreated seedlings than the control seedlings. At 12 h after onset of the stress, ATP concentrations in the roots of 100 and 10 μM ABA-pretreated seedlings were 2.7- and 2.0-fold that of the control seedlings, respectively. During the period of ABA pretreatment under aerobic condition, ABA increased alcohol dehydrogenase (ADH, EC 1.1.1.1) activity in the roots until 12 h and then leveled off. The maximum ADH activities were 4.3- and 2.8-fold that in the roots of the control seedlings for 100 and 10 μM ABA-pretreated seedlings, respectively. After being subjected to the anaerobic stress, both ADH activities in the roots of the ABA-pretreated and the control seedlings increased but the differences in their activity remained. These results suggest that ABA pretreatment may maintain ATP level due to induction of ADH activity, which may be one of the causes of increasing anaerobic tolerance in the seedlings.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The ability to avoid the ethanol-induced injury was evaluated in rice (Oryza sativa L.) and oat (Avena sativa L.) coleoptiles. The growth of the rice and oat coleoptiles was inhibited by ethanol exogenously applied at concentrations greater than 200 and 30 mM, respectively. At 300 mM ethanol, oat coleoptiles were brown and flaccid but rice coleoptiles did not show any visible symptoms of toxicity. The acetaldehyde level in rice and oat coleoptiles was increased by exogenously applied ethanol and the increases were greater in oat than in rice coleoptiles under aerobic and anaerobic conditions. At 300 mM ethanol, the acetaldehyde concentrations in the rice and oat coleoptiles were 46 and 87 nmol g−1 FW under aerobic conditions, respectively, and 52 and 124 nmol g−1 FW under anaerobic conditions, respectively. The activity of alcohol dehydrogenase (ADH; EC 1.1.1.1) in the direction of ethanol to acetaldehyde was greater in oat than in rice coleoptiles and ADH protein in oat coleoptiles was more induced by exogenously applied ethanol than that in rice coleoptiles. These results suggest that in vivo conversion rate of ethanol to acetaldehyde by ADH is lower in rice than oat coleoptiles, which may be one of the reasons that ethanol sensitivity of rice is much lower than that of oat coleoptiles. The great ability of rice to avoid the ethanol-induced injuries may contribute its anoxia tolerance when glycolysis and ethanolic fermentation replace the Krebs cycle as the main source of energy under anaerobic conditions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 86 (1992), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of 3-hydroxy-β-ionone on the growth of hypocotyls of dark-grown dwarl bean (Phaseolus vulgaris L. cv. Morocco) and tall bean (cv. Kentucky Wonder) were examined. 3-Hydroxy-β-ionone inhibited growth of the hypocotyl of both cultivars at doses higher than 3 ng per plant. Seedlings of the tall cultivar responded to a slightly lesser extent to 3-hydroxy-β-ionone than those of the dwarf cultivar. Changes in the levels of 3-hydroxy-β-ionone in hypocotyls of both cultivars 24 h after the onset of light irradiation, were determined by high-performance liquid chromatography and the results compared with the results of light-induced inhibition of growth. The difference in levels of 3-hydroxy-β-ionone between the two cultivars was considerable, and the changes in its levels in the hypocotyls of each cultivar reflected the light-induced inhibition of growth of the hypocotyls of the respective cultivars. These results suggest that the endogenous growth inhibitor. 3-hydroxy-β-ionone, may play an important role in the inhibition by light of hypocotyl growth of the two cultivars and may serve to distinguish the growth habits of these cultivars.
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 109 (2000), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: According to the Davies–Roberts hypothesis, plants primarily respond to oxygen limitation by a burst of lactate production and the resulting pH drop in the cytoplasm activates ethanolic fermentation. To evaluate this system in lettuce (Lactuca sativa L.), seedlings were subjected to anoxia and in vitro activities of alcohol dehydrogenase (ADH, EC 1.1.1.1), pyruvate decarboxylase (PDC, EC 4.1.1.1) and lactate dehydrogenase (LDH, EC 1.1.1.27) and concentrations of ethanol, acetaldehyde and lactate were determined in roots of the seedlings. The in vitro activities of ADH and PDC in the roots increase in anoxia, whereas no significant increase was measured in LDH activity. At 6 h, the ADH and PDC activities in the roots kept in anoxia were 2.8- and 2.9-fold greater than those in air, respectively. Ethanol and acetaldehyde in the roots accumulated rapidly in anoxia and increased 8- and 4-fold compared with those in air by 6 h, respectively. However, lactate concentration did not increase and an initial burst of lactate production was not found. Thus, ethanol and acetaldehyde production occurred without an increase in lactate synthesis. Treatments with antimycin A and salicylhydroxamic acid, which are respiratory inhibitors, to the lettuce seedlings in the presence of oxygen increased the concentrations of ethanol and acetaldehyde but not of lactate. These results suggest that ethanolic fermentation may be activated without preceding activation of lactate fermentation and may be not regulated by oxygen concentration directly.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 116 (2002), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The catalytic direction of pyrophosphate:fructose-6-phosphate 1-phosphotransferase (PFP; EC 2.7.1.90) in coleoptiles of rice (Oryza sativa L.) seedlings subjected to anoxia stress is discussed. The stress greatly induced ethanol synthesis and increased activities of alcohol dehydrogenase (ADH; EC 1.1.1.1) and pyruvate decarboxylase (PDC; EC 4.1.1.1) in the coleoptiles, whereas the elevated PDC activity was much lower than the elevated ADH activity, suggesting that PDC may be one of the limiting factors for ethanolic fermentation in rice coleoptiles. Anoxic stress decreased concentrations of fructose 6-phosphate (Fru-6-P) and glucose 6-phosphate, and increased concentration of fructose 1,6-bisphosphate (Fru-1,6-bisP) in the coleoptiles. PFP activity in rice coleoptiles was low in an aerobic condition and increased during the stress, whereas no significant increase was found in ATP:fructose-6-phosphate 1-phosphotransferase (PFK; EC 2.7.1.11) activity in stressed coleoptiles. Fructose 2,6-bisphosphate concentration in rice coleoptiles was increased by the stress and pyrophosphate concentration was above the Km for the forward direction of PFP and was sufficient to inhibit the reverse direction of PFP. Under stress conditions the potential of carbon flux from Fru-6-P toward ethanol through PFK may be much lower than the potential of carbon flux from pyruvate toward ethanol through PDC. These results suggest that PFP may play an important role in maintaining active glycolysis and ethanolic fermentation in rice coleoptiles in anoxia.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice (Oryza sativa L.). Rice seedlings inhibited the growth of cress (Lepidium sativum L.) and lettuce (Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 µM, respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non-husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk-treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 98 (1996), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Dark-grown, 10-day-old bean seedlings (Phaseolus vulgaris L. cv. Morocco) were transferred to continuous light, and the resulting changes in growth rate and concentration of 3-hydroxy-β-ionone, an endogenous growth inhibitor, were monitored. The growth rate of the first internodes of the seedlings decreased rapidly and leveled off 20 h after onset of light. This plateau value was about 25% of the growth rate of the non-irradiated control. The concentration of 3-hydroxy-β-ionone in the internodes of the irradiated seedlings increased rapidly and reached a plateau value after 16 h. This increased level of the inhibitor was about 5 times the level in the non-irradiated control. The changes in the levels of the inhibitor in the internodes reflected the light-induced growth inhibition of the internodes. The longitudinal distribution of the growth inhibitor along the first internodes of the seedlings was closely correlated with the light-induced growth inhibition of the corresponding region of the internodes. The present results suggest that the endogenous growth inhibitor 3-hydroxy-β-ionone may play an important role in the inhibition by light of internode growth of bean seedlings.
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  • 9
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Dark-grown, 4-day-old seedlings of dwarf bean (Phuseolus vulgaris L. cv. Morocco) and tall bean (cv. Kentucky Wonder) were transferred to conditions of continuous light at various fluence rates, and the resulting changes in growth rates and concentration of 3-hydroxy-β-ionone, a novel endogenous growth inhibitor, were monitored. The light-induced inhibition of growth and the levels of the inhibitor concentration were dependent on the fluence rate of light applied. The growth rate of hypocotyls of both cultivars decreased rapidly and reached a plateau 18 h after the onset of light. However, the more noticeable changes were the marked inhibition of growth of the hypocotyls of the dwarf cultivar. The concentration of 3-hydroxy-β-ionone in the hypocotyls of both cultivars increased after a 20-min lag and reached plateau values after 12 h. The concentration of the inhibitor in the hypocotyls of the dwarf cultivar increased to about 4 to 8 times the level in the nonirradiated controls, while that in the hypocotyls of the tall cultivar increased only about 2- to 3-fold under the same conditions. The high concentration of 3-hydroxy-β-ionone in the dwarf cultivar under steady-state conditions in continuous light, as compared with that in the tall cultivar, may determine the growth habit of these cultivars.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 20 (1994), S. 315-319 
    ISSN: 1573-1561
    Keywords: Allelopathy ; Avena sativa ; oat ; l-tryptophan ; root exudates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract l-Tryptophan caused growth inhibition of roots and hypocotyls (or coleoptiles) of cockscomb (Amaranthus caudatus L.), lettuce (Lactuca sativa L.), cress (Lepidium sativum L.), timothy (Phleum pratense L.), rice (Oryza sativa L.), wheat (Triticum aestivum L.), and oat (Avena sativa L.), increasing the dose ofl-tryptophan increased the inhibition. The concentrations for 50% inhibition of the root growth were 0.14, 0.15, 0.21, 0.79, 0.95, 1.7, and 2.4 mM for cockscomb, cress, lettuce, timothy, rice, wheat, and oat, respectively; the concentrations for 40% inhibition of the hypocotyl (or coleoptile) growth were 0.28, 0.33, 0.43, 2.7, 4.5, 7.2, and 15 mM for cockscomb, cress, lettuce, timothy, rice, wheat and oat, respectively. The levels ofl-tryptophan in oat seedlings and in its root exudates were 29.3 mg/kg fresh wt and 0.25 mM under light conditions, and 21.1 mg/kg fresh wt and 0.18 mM under dark conditions, respectively. The presence ofl-tryptophan in the root exudates coupled with its effect on growth suggested thatl-tryptophan may play an important role in the growth inhibition of other plants in nature.
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