The Induction and Development of Potato Microtubers In Vitroon Media Free of Growth Regulating Substances

Reliable microtuber production has been obtained by culturingnodal explants of potato on Murashige and Skoog medium withoutthe addition of growth regulating substances. The use of sucroseat 8 %, as compared with 4 or 12%, advanced the initiation oftuberization and gave more and larger microtubers. A periodof 1 month under 16 h days, followed by transfer to 8 h photoperiodsgave most rapid microtuber development. A reduction in the totalnitrogen supply or an increase in the ratio of ammonium to nitratereduced the size and number of microtubers Potato, Solanum tubersum L;, microtubers, in vitro induction and development, sucrose, photoperiod, nitrogen nutrition     

The Effect of Environmental and Nutritional Factors on the Development of Flower Apices Cultured in vitro

Flower buds of Viscaria candida, excised at 1–2 mm inlength, have been grown to maturity in sterile culture, oftenproducing normal flower parts. The calyx and the corolla developedunder a wide range of conditions provided gibberellic acid waspresent. The development of the ovary and of the ovules tendedto be irregular and no consistent effects of treatment couldbe obtained. Pollen production was promoted by a temperatureof 15 °C as opposed to one of 25 °C, and by the additionof gibberellic acid to the medium; it was inhibited by the additionof kinetin or hydrolysed casein to the medium, and by growthin continuous darkness as compared with that in 8 or 16 h oflight daily.     

Development of Organized Structures in Callus Derived from Explants of Cocos nucifera L.

Clonal propagation of the coconut palm was attempted using tissueculture. Callus initiated from slices of seedling stem and fromthe rachillae of young inflorescences was maintained on agarmedium containing 2,4-D at 10^–4 M. Reduction of the 2,4-Dconcentration over several sub-cultures resulted in the developmentof nodular structures that resemble some of the stages in thedevelopment of the zygotic embryo. Cocos nucifera L., coconut palm, callus, organogenesis, embryogenesis, clonal propagation     

Effects of illumination source, culture ventilation and sucrose on potato (Solanum tuberosum) microtuber production under short days

The culture yield of a simple method of microtuber production of potato was increased by assessing the interactions of illumination source (Thorn Lighting (Philips) “Colour 84” lamps (TL‐84) or Grolux lamps (Sylvania) in a conventional growth room or natural light in a glasshouse cabinet), type of vessel closure (unventilated or ventilated) and sucrose concentration (1%, 2%, 4% or 8%). Microtuber initiation and growth in unventilated cultures was 100% at 8% sucrose falling to 40–50% at 4% sucrose and was absent at 1% or 2%. With ventilation, rapid tuberisation (90–100%) occurred at initial sucrose concentrations of 2–8%, but only when the medium was allowed to dry before transfer of cultures to short days. Water supplementation of cultures at day 28 prevented tuberisation at 1–4% sucrose up to day 56. The fresh weight and dry weight of microtubers per plant increased significantly with sucrose concentration, with ventilation of cultures and under natural light. In ventilated cultures, the mean number of usable microtubers (± 0.1 g weight) increased from between 1.0–1.4 per plant at 8% sucrose to between 1.6–2.6 per plant at 4% sucrose, with the highest numbers (1.8–2.6 per plant) produced under natural light for the cvs Desirée and King Edward. The mean % dry matter content of microtubers was reduced to 11.3% at 4% sucrose compared with 17.3% at 8% sucrose, but the survival rate of microtubers after 6 months storage was unaffected. Microtuber production under short days was improved at a higher intensity of natural light with culture ventilation in a partially‐shaded glasshouse cabinet, whilst using reduced inputs (lower sucrose supply and no lamps).     

Effects of Nitrogen Nutrition on Flowering in Carnation

Two varieties of perpetual flowering carnation were grown undervarious conditions of nitrogen supply, daylength, and temperature. In short days as compared with long, the number of leaves belowthe flower bud was always greater and the flower bud alwaysappeared later. At low levels of nitrogen, successive leaf pairs developed moreslowly and more leaves were formed below the flower, so thatflower initiation was delayed. This effect was more marked undershort days than under long days. The development of the flower bud from macroscopic appearanceto anthesis was affected primarily by temperature. Low temperaturesgenerally retarded development, this effect being most pronouncedin nitrogen deficient plants grown under short days.     

Normal and Abnormal Developments of the Stem Apex in Carnation

Normal and abnormal development of the stem apex is describedfor the carnation Dianthus caryophyllus, cultivated varieties.Abnormalities described include adventitious buds within theflower, carpel-like structures in the stamen whorl, excessivedevelopment of ovules, and axile secondary flower formations.Some comments are made on their occurrence and they are discussedin the light of present hypotheses concerning flower initiationand development.