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  • 1
    ISSN: 1573-5044
    Keywords: Salix ; dormant reproductive buds ; in vitro culture ; flowering process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flowering process in a female tree ofSalix tetrasperma was analysed by culturing its reproductive buds at different developmental stages during the dormant period on a chemically defined medium and examining the nature of sprouts produced by them. Buds at the upper eight nodes of the actively growing shoots developing in an acropetal sequence were cultured in separate lots. While all the buds collected from the 1st and 2nd nodes of the branches from the top downwards were vegetative and produced shoots, a considerable number of those collected from the 3rd and 4th nodes were reproductively determined and produced catkins. All the buds obtained from the 5th node and below were reproductive. Reproductive buds were cultured at regular time intervals during the dormant period. Freshly formed buds cultured in March during the spring growth flush produced catkins and were therefore reproductively determined. However, such a determination was not tantamount to flowering, as the floral meristems present in the axils of catkin bracts remained quiescent. Floral meristems of the buds cultured during April to August developed into small vegetative shoots. This was followed by the crucial period during September to December when the hitherto vegetative sprouts of the floral meristems showed a gradual transition into ovaries (female flowers) resulting in fertile catkins. Catkins produced from buds cultured in January and February produced well-developed ovaries.
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  • 2
    ISSN: 1573-5044
    Keywords: triticale ; rye ; immature embryos ; plant regeneration ; chlorophyll variants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Callus cultures were established from the scutellum, scutellar node and radicle region of immature embryos of rye and octoploid triticale on modified Murashige-Skoog basal medium supplemented with various growth regulators. 2, 4-D, 2, 4, 5-T and 2, 4, 5-Cl, POP were found suitable for initiation and maintenance of callus cultures. Cytokinins had no or inhibitory effect on callus induction and growth. On basal medium containing 5 mg/l of 2,4,5-Cl3 POP, 16% of triticale and 17% of rye primary cultures exhibited shoot bud regeneration after 3–4 weeks. Transfer of such cultures to basal medium supplemented with zeatin or zeatin in combination with IAA further promoted shoot elongation and plantlet formation. Plantlets were rooted on basal medium containing 1 mg/l NAA and were eventually transferred to soil. Chlorophyll variants were observed in about 6% of triticale cultures.
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  • 3
    ISSN: 1573-5044
    Keywords: Pelargonium xhortorum ; geranium ; callus cultures ; cell selection ; toxin insensitivity ; bacterial blight resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments were designed to determine whetherXanthomonas campestris pv.pelargonii produces a toxin which induces symptoms of bacterial blight in geranium, and is active at the cellular level. Culture filtrates ofX. c. pv.pelargonii were prepared by ethyl acetate extraction and ultrafiltration of the aqueous fraction. Culture filtrates adjusted to several pH values induced maximum disease ratings on geranium seedlings in the pH range 7–10. Geranium callus growth was significantly reduced by the filtrate in the same pH range. An active fraction could also be isolated from diseased tissue. A thin-layer chromatography-callus bioassay system detected toxin activity in the culture filtrate and in extracts of geranium stems inoculated withX. c. pv.pelargonii. Callus growth inhibition was located at Rf = 0.2–0.3 for both sources of toxin. These results suggest thatX. c. pv.pelargonii produces a toxin which causes disease symptoms, is present in diseased tissues, and inhibits callus growth. This opens the possibility of developing resistance to this pathogen by selecting cells insensitive to the toxin and regenerating plants from these cells.
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  • 4
    ISSN: 1573-5044
    Keywords: Ipomoea ; morning glory ; cell culture ; acid phosphatases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two acid phosphatases isolated from culturedIpomoea (moring glory) cells were separated by column chromatography on DEAE-cellulose. The two acid phosphatases have different pH optima (pH 4.8–5.0 and 6.0) and do not require the presence of divalent ions. The enzymes possess high activity toward pyrophosphate,p-nitrophenylphosphate, nucleoside di- and triphosphates, and much less activity toward nucleoside monophosphates and sugar esters. The two phosphatases differ from each other in Michaelis constants, in the degree of inhibition by arsenate, fluoride and phosphate and have quantitative differences of substrate specificity. In addition, they also differ in their response to various ions.
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  • 5
    ISSN: 1573-5044
    Keywords: Dioscorea bulbifera ; yam ; tissue culture ; multiple shoot formation ; diosgenin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nodal stem segments ofDioscorea bulbifera were induced to form plantlets in vitro. Rooted plantlets were obtained on Murashige-Skoog [14] revised medium supplemented initially with 5 mg 1−1 kinetin and subsequently with 5 mg l−1 indole-butyric acid. By increasing the kinetin concentration from 5 mg l−1 to 10 mg l−1, the number of shoots forming per node was increased from five to eight. When kinetin was substituted with 6-benzylaminopurine at only 1 mg l−1, nine shoots formed on each node. Each shoot could be excised from the node and induced to form a new crop of multiple shoots. Rooted plantlets could be successfully transferred to in vivo conditions.
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  • 6
    ISSN: 1573-5044
    Keywords: Lolium multiflorum ; ryegrass ; tissue culture ; somatic embryogenesis ; inflorescence ; node
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When cultured on agar-solidified media (based on Murashige and Skoog's formula), immature inflorescences and nodes ofLolium multiflorum underwent several different pathways of morphogenesis. The pathway expressed was dependent upon the type of explant, its age and the composition of the culture medium. Immature inflorescences generally produced either leaves and roots or embryoids whereas nodes produced axillary shoots or embryoids. Embryogenesis from both explant sources occurred from a firm, white, opaque, proliferating tissue. The embryoids could be cultured individually and induced to produce plantlets capable of transfer to soil. Generally the plantlets formed from newly isolated tissues were green, but chlorophyll-deficient plantlets arose infrequently (up to about 5%). However, this frequency increased as the embryoid-producing tissues were propagated by subculture.
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  • 7
    ISSN: 1573-5044
    Keywords: suspension cultures ; growth pattern ; nutrient changes ; cytoplasmic volume ; transport properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth characteristics and nutrient changes in medium and cells of batch-grown sugarcane cultures were investigated over a period of 14 days. Amino acids, PO 4 3− and K+ were substantially removed from the medium during the first seven days of culture; a strong preference for uptake of organic nitrogen over inorganic nitrogen was observed. Sodium uptake increased during the time when K+ was becoming deficient in the medium. The main anions taken up were SO 4 2− and PO 4 3− . Strong acidification and a virtually total extracellular hydrolysis of sucrose in the medium during the first seven days of culture were also observed. Tapering off of the rapid growth phase was accompanied by an increase of intra-cellular sucrose and a decrease of intracellular protein. As cells went from rapid growth into stationary phase, cytoplasmic space of the cells decreased slightly in favor of vacuolar space. Overall cell volume stayed constant throughout the growth cycle, except during a short period before onset of rapid growth. Transport of the glucose analog 3-O-methyl glucose remained constant in terms of Km value but the Vmax was slightly higher in rapidly growing cells.
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  • 8
    ISSN: 1573-5044
    Keywords: cassava ; mosaic disease ; meristem-tip culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods previously established for the propagation of cassava plants free from cassava mosaic disease have been applied to Nigerian clones. Meristem tips from diseased plants subjected to heat treatment for not less than 30 days at 35°–38°C were cultured on modified Murashige-Skoog medium. Concentration ranges of benzyladenine in combination with α-naphthalene acetic acid and gibberellic acid were investigated and, at optimal levels, 36% of the meristems regenerated. Regenerants, with callus and shoots only, were rooted with 80% efficiency by sub-culturing following a dip in a hormone rooting powder. All plants raised from heat-treated meristems were free of the disease as judged by visual inspection of the leaves, rooted explants and assay for the suspected pathogenic agent of the disease.
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  • 9
    ISSN: 1573-5044
    Keywords: single cell suspensions ; immobilized plant cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fine, almost single cell, suspensions were produced from both existing suspension cultures containing large cell clumps and from chopped callus pieces by immobilizing the cells in 4–5 mm diameter calcium alginate beads. The immobilized cells continued to divide inside the beads and at the bead surface, and after 2–3 weeks' culture, fine cell suspensions were formed as a result of loss of the surface cells into the medium. After removal of the cell suspensions by filtration, subsequent culture of the beads in fresh medium resulted in the further production of homogeneous cell suspensions after 1–2 weeks. In this way an almost continuous supply of fine cell suspensions could be obtained from cultures containing large clumps of cells. The cells produced by this method remained in this state for at least one culture period, although in some instances repeated subculture resulted in an increase in the size of cell groups. The technique has been successfully applied to the production of fine cell suspensions ofCatharanthus roseus, Nicotiana tabacum andDaucus carota.
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  • 10
    ISSN: 1573-5044
    Keywords: Bougainvillea ; clonal propagation ; shoot apex culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shoot apices ofBougainvillea glabra ‘Magnifica’ were induced to regenerate an average of ten shoots from their bases in response to BAP (0.5 mg/l) plus IAA (1.5 mg/l). All the isolated shoots from such cultures were rooted in a medium containing 0.1 mg/l each of IBA and 2,4,5-T and lacking BAP. Plantlets were then successfully grown in potted soil where they flowered normally.
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