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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 25 (1968), S. 104-106 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The occurrence of a synaptinemal complex in yeast was demonstrated by an electron-microscopical examination of meiotic prophase I. The complex is formed during the interval between the maximum of meiotic DNA synthesis and the first division.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 129 (1981), S. 47-48 
    ISSN: 1432-072X
    Keywords: Adenylate energy charge ; Phosphate ; Saccharomyces ; Sporulation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The induction of sporulation in yeast is generally accompanied by a sharp increase in energy metabolism which is evidenced by a rise of the adenylate energy charge by that time. The energy charge can be held at a low level by limitation of the phosphate supply in the growth medium. Ascus formation remains unaffected by this treatment. This suggests that the rise in ATP production normally encountered during early sporulation is not essential for the initiation of sporulation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 102 (1975), S. 117-122 
    ISSN: 1432-072X
    Keywords: Actinomycin ; Allomyces ; Gametogenesis ; Nuclear Cap ; Polyribosomes ; RNA Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Synchronous gametogenesis in the water mold Allomyces arbuscula is blocked by actinomycin D added at the onset of the process. Formation of the male gametangium can be selectively inhibited by administering actinomycin one hr after the induction of gametogenesis. The polyribosome pattern obtained after density gradient centrifugation remains virtually unchanged throughout gametogenesis until a stage immediately preceding maturation of the gametes. When ribosomes from gametes and swarming zygotes are analyzed on gradients, some RNase-sensitive material is found to band in the heavier portion of the gradient. Its presence suggests that some messenger RNA associated with ribosomes is conserved in the swarming cells. During gametogenesis RNA is de novo synthesized and becomes associated with the polyribosomes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 76 (1989), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relation between root differentiation and accumulation of biocidal thiophenes was studied in stem calli of two Tagetes species. Disorganized tissues of T. erecta were low in thiophene production. A sharp rise in thiophene content coincided with the emergence of roots on the calli. Root regeneration and the amount of thiophenes produced were found to be quantitatively related. Callus tissues of T. minuta did not differentiate into organs. Nevertheless, they accumulated thiophenes throughout the incubation period. Light at 12 W m- stimulated thiophene production in T. erecta without having an apparent effect on root regeneration. In T. minuta even low irradiance levels (2 W m∼2) strongly inhibited thiophene accumulation. Under favorable conditions thiophene concentrations in calli of both species were comparable to or somewhat lower than the levels in roots on the plants and in excised, cultured roots of T. erecta. We conclude that in calli of T. erecta thiophene accumulation is coupled to root regeneration whereas a different control mechanism allowing for accumulation in disorganized tissues is operative in T. minuta.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 74 (1988), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Benzyladenine (BA) was found to regulate the number of flower buds regenerated in vitro from pedicel tissue of tobacco. Flower bud induction was particularly sensitive to BA levels in the range of 0.45 to 1.0 μM, where a two-fold increase in concentration caused a threefold rise in the number of buds. When tissues were fed radioactive BA for 24h, only 9–12% of the counts were recovered in the original compound. The rest was present in metabolites, tentatively identified as the mono-, di- and triribotides, 7- and 9-glucosides and 9-riboside of BA. The amount of growth regulator taken up and the quantities of BA and its metabolites in the explants were all linearly related to the concentration of the medium. The internal BA concentration was ca 60% of the level in the medium after 24 h. When the concentration in the medium was raised, relatively more BA remained in the non-conjugated form. However, this change in the equilibrium between BA and the conjugates is too small to account for the steep rise in the curve representing concentration vs effect between 0.45 and 1.0 μM.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract After germination, pollen grains of Lilium longiflorum became very sensitive to short periods of heat stress as shown by the greatly reduced germination percentages upon subsequent incubation at the optimal temperature. Addition of proline to the incubation medium made pollen more resistant to heat. It was demonstrated that in a short time a large amount of proline was taken up by the cell. Germination and metabolic functions were completely or partially protected from heat damage by proline treatment. As well, it was shown that proline treatment at least partially protected pollen grains from cold stress. These results suggest that the high proline concentrations found in pollen of many species may confer resistance to germinating pollen grains at unfavourable temperatures thereby enhancing the chances of successful fertilization.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Germination and protein synthesis of lily pollen subjected to a short heat shock after imbibition are strongly inhibited. The proteins synthesized after the heat shock were analysed by polyacrylamide gel electrophoresis. The patterns obtained from heat-treated pollen are strikingly different from those of control samples. The difference is nearly completely climinated by a high concentration of proline in the incubation medium. This proline effect correlates with the protection of pollen germination from high temperature by the amino acid.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 61 (1984), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The in vitro development of flower buds was studied on tissue explants of epidermis and subepidermal cortex from the flower stalks of Nicotiana tabacum L. cv. Samsun. The number of flower buds formed depended mainly on cytokinin concentration. Auxin acted as a modifier in a complex way. In early development, NAA at 1 μM decreased the number of buds initiated and delayed bud emergence. At a later stage, auxin promoted bud outgrowth at the same concentration. Optimal results were obtained when explants were first incubated at low auxin concentration for 3–5 days and subsequently transferred to an elevated auxin level. Physiological processes that lead to flower bud initiation start very soon after the onset of incubation. This was inferred from experiments whereby explants were first cultured at an inductive cytokinin concentration and then transferred to a non-inductive hormone level.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 78 (1990), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this paper the effects of indole-3-acetic acid (IAA) on growth of Tagetes patula hairy root cultures and secondary product formation are presented. The biosynthesis of thiophenes, sulfurous compounds with nematicidal activity, was inhibited by IAA application, as was evident from a decrease of [35S] sulfur incorporation. The inhibition only occurred after the roots had developed numerous laterals as a result of auxin action. However, in roots cultured in the absence of IAA, there was no significant correlation between branching and thiophene accumulation. Therefore, development of lateral roots is not a sufficient condition for a low capacity to synthesize thiophenes. The highest rate of thiophene accumulation in the roots culture is at its maximum. Hence, growth and the production of thiophenes appear to be compatible in T. Patula hair roots.
    Type of Medium: Electronic Resource
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