Takejiro Takamura

In vitro growth of Cymbidium plantlets cultured under superbright red and blue light-emitting diodes (LEDs)

SummaryThe effects of light generated by superbright blue and red LEDs on the growth of Cymbidium plantlets cultured in vitro have been studied. Leaf growth, chlorophyll content and shoot and root weights were affected by different LED irradiations. Red light promoted leaf growth but decreased chlorophyll content. This was reversed by blue light. The growth of Cymbidium plantlets in terms of increase in total shoot and root weights was comparable under red plus blue LEDs and the fluorescent systems. Generally, the response to different LED was similar for plantlets grown on sugar-free medium with or without CO2 enrichment and sugar-containing medium but without CO2 enrichment. The growth of Cymbidium plantlets was enhanced by CO2 enrichment. Our study demonstrates the effectiveness of a total irradiation system for Cymbidium plantlets growth in vitro. The significance of our findings in relation to the development of a suitable lighting system for plant tissue culture is discussed.

Colchicine induced tetraploids in yellow-flowered cyclamens and their characteristics

Abstract The possibility of obtaining tetraploids from diploid yellow-flowered cyclamen ‘Kage Yellow’ through colchicine treatment and the effects of polyploidization on the characteristics of yellow-flowered cyclamen were investigated. A 4-day treatment of tuber segments with 100 mg l −1 colchicine in vitro yielded two tetraploid plants. The petals of the tetraploids were larger and had a greater ability to accumulate chalcone than those of their diploid relatives. Polyploidization may therefore represent a useful method for the commercial breeding of deeper yellow-flowered cyclamen.

Somatic embryogenesis ofCyclamen persicum Mill. 'Anneke' from aseptic seedlings.

SummaryInCyclamen persicum ‘Anneke’, explants from the various vegetative organs of aseptic seedling formed embryoids. The optimal responses were recorded in Murashige and Skoog (MS) medium enriched with 5.0µM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.5µM kinetin and 3–6% sucrose. Embryogenesis was enhanced at higher temperature of 25–30°C. On the other hand, light inhibited embryogenesis. Histological and morphological studies confirmed that the embryoids were indeed somatic embryos.

In vitro shoot development ofEucalyptus citriodora on Rockwool in the film culture vessel under CO2 enrichment

An efficient system for growingin vitro plantlets ofEucalyptus citriodora Hook was developed. In the conventional closed system of culture with 2% sugar-containing gellan gum Murashige and Skoog (MS) medium supplemented with 0.02 mg/l indole-3-isobutyric acid, a serious defoliation of shoots was observed after three weeks. In contrast, plantlets grown on the sugar-free MS medium in the aerated bottle under 3,000 ppm CO2 enriched condition did not show any defoliation. A marked enhanced growth of plantlets and no defoliation were observed on rockwool with the sugar-free liquid MS medium in the “Culture Pack”, made of fluorocarbon polymer film, under CO2 enriched condition. CO2 enrichment for this sugar-free “Culture Pack”-Rockwool system was also found to contribute to an improved growth of the plants in acclimatization.

Effects of high temperature on flower colour and anthocyanin content in pink flower genotypes of greenhouse chrysanthemum (Chrysanthemum morifolium Ramat.)

Summary The relationship between the intensity of flower colour and changes in the content of the main anthocyanins under various controlled temperatures was examined in order to clarify the effects of high temperature on flower colouration in six pink flower genotypes of greenhouse chrysanthemum (Chrysanthemum morifolium Ramat.). Poor colouration of flowers was observed at 30°C in all genotypes except ‘Chatoo’. This genotype showed little difference in flower colour between different temperature treatments. The degree of change in flower colour differed depending on the genotype, whereas no clear differences in flower colouring were observed between Summer – Autumn flowering and Autumn-flowering genotypes. All genotypes showed lower contents of the two anthocyanins tested [cyanidin 3-O-(6’’-O-monomalonyl- -glucopyranoside) and cyanidin 3-O-(3’’,6’’-O-dimalonyl- -glucopyranoside)] at higher temperatures. Therefore, flower colour changes were attributable to changes in these two main anthocyanins. Differences in colouration between genotypes and temperature conditions were also detectable in values that were measured using a colorimeter. Changed parameters that were visually verifiable were the a* value, representing the degree of red colour, and the C* value, representing chroma. For ‘Sei-Monako’, which showed visually greater differences between temperature treatments, the a* and C* values were low under high temperature conditions. On the other hand, in ‘Chatoo’, the differences detected by eye and those in a* and C* values between temperature treatments were small. In addition, the present results indicate that mean temperature is more important than either day or night temperature in determining the degree of flower colouration.

Light Emitting Diodes (LEDs) as a Radiation Source for Micropropagation of Strawberry

Strawberry ‘Akihime’ shoot explants with three leaves were cultured in three different culture systems; (1) 500 ml bottle fitted with MilliSeal with sugar-free half-strength Murashige and Skoog agar medium, (2) the “Culture Pack”-rockwool (4 by 4 blocks) system, and (3) the “Miracle Pack”-rockwool (5 by 5 blocks) system with sugar-free half-strength MS liquid medium. These culture systems were placed in the “LED PACK3”, in which the red to blue light emitting-diodes (LED) ratio and the irradiation level were adjusted to 70% red +30% blue LED and 45 jumol.m-2.s-1, respectively. For comparison, they were also placed on the shelf under plant growth fluorescent lamps (PGF) in the culture room. In the “Culture Pack”-rockwool system, the number of leaves of plantlets under LEDs was higher than that of PGF. Shoot and root fresh weight of plantlets under LEDs were higher than that of PGF and the values were comparable to that of conventional culture systems. In the bottle culture and “Miracle Pack”-rockwool systems, the number of leaves and the total of shoot and root fresh weight of plantlets under LEDs was equal to that of PGF. Subsequent growth of plantlets cultured in the “Miracle Pack”-rockwool system under LEDs was examined after transferring to soil. The LED light source for in vitro culture of plantlets was found to contribute to an improved growth of the plants in acclimatization.

Introgression of unique characteristics of floral initiation under 24 hour day-length of Fragaria chiloensis ‘CHI-24-1’ into F. × ananassa

A unique flower initiation of the wild Junebearing strawberry strain ‘CHI-24-1’ in Fragaria chiloensis occurs under 24 h DL and high temperature conditions. To introduce the floral initiation characteristics of ‘CHI-24-1’ into cultivated strawberries of F. × ananassa, a cross pollination was conducted between ‘CHI-24-1’ and the Japanese short-day type strawberry cultivar ‘Nyoho’. The floral initiation of ‘CHI-24-1’ was induced in both parent and daughter plants linked with runners under a 24 h DL and 23/20 ∘C, but not 8 and 16 h DLs at the same temperatures. Of the 21 F1 hybrids grown under the 24 h DL, 12 showed flower truss production in the parent and/or daughter plants linked with runners. Among 64 F1 hybrids, 26 exposed to 8, 16 and 24 h DLs for 30 days produced no flower trusses. However, 32, one and five F1 hybrids produced flower trusses under the 24 h DL alone, 8 h DL alone and both the 8 and 24 h DLs, respectively. The results of the experiments indicated that none of the F1 hybrids were day-neutral plants, but approximately 60% had the characteristics of floral initiation under 24 h DL, which was inherited from the pollen parent of ‘CHI-24-1’. The importance of the unique floral initiation characteristics under 24 h DL with high temperature for strawberry breeding was discussed.

Inheritance of yellow-flowered characteristic and yellow pigments in diploid cyclamen (Cyclamen persicum Mill.) cultivars

Abstract The mode of inheritance of the yellow-flowered phenotype of yellow-flowered cyclamen was investigated. All F 1 progenies obtained by reciprocal crosses between yellow- and white-flowered cultivars were white-flowered and did not contain chalcone, the main pigment of yellow-flowered cyclamen. The segregation ratio of flower colors in most of F 2 and BC 1 progenies fitted the expected Mendelian ratio, showing that the yellow-flowered phenotype was controlled by a single recessive gene. The petals of all yellow-flowered plants in F 2 and BC 1 progenies contained chalcone. It is suggested that a single recessive gene causes the lack or defectiveness of chalcone-flavanone isomerase and determines the yellow-flowered phenotype.

Changes in pigment content and surface micro-morphology of in cut carnation flower petals under high-temperature conditions

Summary Senescence of carnation petals progresses gradually, even when climacteric ethylene production is blocked. The most distinct visible changes in the later stages of petal senescence are a fading of flower colour and a change in appearance (“freshness”). Cut carnation cv. Excerea flowers treated with silver thiosulphate were kept in vase solutions with or without 1% (w/v) sucrose under high-temperature conditions (32ºC). Changes in pigment content and the micro-morphology of epidermal cells in petals were monitored. The main pigment in ‘Excerea’ carnation petals was pelargonidin-3-malylglucoside (Pg3MG). A 48 – 70% reduction in Pg3MG occurred between day-5 and day-15 in petals kept under high-temperature conditions. Petal colour changes, as determined by lower C* and hº values using a colourimeter, were consistent with the reduction in Pg3MG content. Sucrose [1% (w/v)] in the vase water was effective at inhibiting the reduction in pigment content in petals kept under high-temperature conditions. An enlargement of epidermal cells occurred on both the abaxial and adaxial surfaces of petals between day-5 and day-15, irrespective of petal position, temperature conditions, or the composition of the vase solution. This enlargement in epidermal cells could cause the change in appearance of the flowers.

Ploidy Levels of Degenerated Embryos in the Crosses between Diploid and Tetraploid Cyclamen

In reciprocal crosses between diploid and tetraploid cyclamen, almost all zygotic embryos were degenerated. Ploidy levels of the degenerated embryos were, however, obscure. Therefore, embryo rescue by the ovule culture in the crosses were examined. A lot of progenies were obtained in the 2x x 4x crosses, when the ovule culture used medium with coconut water was done 28 days after pollination. Although almost all fruits were dropped 28 days after pollination in the 4x × 2x crosses, some progenies were obtained by the ovule culture at 7-28 days after pollination. Almost all progenies obtained by the ovule culture after the reciprocal crosses between the diploids and tetraploids were triploids, suggesting that many triploid zygotes were formed in the crosses. However, some tetraploid, pentaploid and hexaploid progenies were also obtained. Origin of the pentaploids was suggested the fertilization between a reduced gamete from a diploid plant and an unreduced gamete from a tetraploid plant. These results suggest that many triploid zygotes are formed in the crosses between diploid and tetraploid cyclamen, whereas development of the triploid embryo without the embryo rescue is inhibited. It also shows the possibility that pentaploids and hexaploids as well as triploids and tetraploids can be obtained in the crosses using the ovule culture, depending on the cross combination.