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The effects of jasmonic acid (JA) applied in the medium and its methylester (MeJA) applied either in the medium or as a vapour, on shoot growth and microtuber formation were evaluated in three important food yam species ( Dioscorea alata, D. cayenensis, and D. rotundata). Single nodes with leaves, derived from in vitro-multiplied material, were used as explants. When delivered at higher concentrations (10 or 50 μ m) both JA and MeJA suppressed node formation. Microtuberisation was supported in all three species by adding either JA or MeJA to the medium. Significant promotory effects were observed only when photoperiod, salt compositions and sucrose concentrations known to favour microtuberisation processes in yams were used. MeJA applied as a vapour strongly inhibited microtuber differentiation in D. alata on all media tested but in D. rotundata and D. cayenensis yams MeJA, also applied in the vapour phase, exhibited slight promotory effects on microtuberisation. [ABSTRACT FROM AUTHOR]

Using glasshouse-raised plants (1 month, 1 year and 5 years old), factors affecting shoot development from shoot nodes of two Brazilian and one Tanzanian elite selections of cashew ( Anacardium occidentale L.) were assessed. Sprouting of buds decreased strongly with increasing age of mother plants. Solidified media, mainly when purified agar was used, gave better results than liquid medium. Murashige and Skoog salts containing 1/2-strength macroelements were the most suitable for bud sprouting and shoot elongation. Vitamins and sucrose concentration did not have a significant effect but by replacing 20 g/l sucrose with glucose or maltose all estimated parameters were improved. Gibberellins supported bud sprouting and shoot elongation but blocked rooting. Shoots developed in the presence of cytokinins were short and produced axillary branches. Activated charcoal, cultivation of explants in darkness for the first 7 days and superoptimal temperature (35 °C) decreased bud sprouting and supported shoot elongation. Microshoots rooted in vitro at a frequency of 42% when cultured for 5 days with 100 μ μ indole-3-butyric acid. Over 40% of rooted microshoots survived weaning. [ABSTRACT FROM AUTHOR]

Embryogenic cultures were established from silver fir ( Abies alba Mill.) female megagametliophytes with developing embryos and from excised mature embryos after pollination with Abies cephalonica Lond. or Abies numidica DeLann pollea The frequency of embryogenic callus formation was dependent on genotype, collection time, medium and explants used. The embryogenic callus initiation potential of megagamethophytes with developing embryos in both hybrids was higher in early July and dropped as the zygotic embryos matured. Excised cotyledonary embryos were less suitable for induction of embryogenic cultures. SH medium supplemented with 1mg/l BAP was the most efficient for callus induction and maintenance. Cultures were composed of early somatic embryos with an embryonal mass formed of highly cytoplasmic cells, rich in cell organelles and a suspensor built up by vacuolated, strongly elongated cells. Maturation of embryos was detected with the formation of bipolar structures with shoot and root apices. Nutrition reserves were observed in cells of embryos cultured on DCR medium containing 1 or 10 mg/l ABA. Cotyledon formation, hypocotyl elongation and low frequency germination occured following transfer of the embryos to the same medium without ABA. [ABSTRACT FROM AUTHOR]

Embryogenic callus cultures of European black pine ( Pinus nigra Arn.) were established on megagametophytes containing zygotic embryos in early developmental stage. In addition to many elongated cells and disorganized growing clumps they contained early somatic embryos at various stages of development. At all stages of embryogenesis the embryos were organized as bipolar structures. Cell pairs composed of one isodiametric cell with dense cytoplasm and a second large vacuolated cell were the simplest bipolar system. The vacuolated cell underwent senescence. The cytoplasm-rich cell and its derivates divided transversally, resulting in several cytoplasmic cells arranged in row. An early embryonal cylindrical mass was formed by longitudinal division of the cells in a filament. Proximally localized cells in the early embryonal mass became vacuolized and elongated gradually giving rise to the secondary suspensor. Distal cells remained cytoplasmic in character and formed an embryonal mass along the axis of long early somatic embryos. Differences in the proportion of organelles and heterochromatin clumps, thickness of cell walls and number of plasmodesmata between cells at various stages of early somatic embryogenesis were described. [ABSTRACT FROM AUTHOR]