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The capability of Phalaenopsis to acclimate its photosynthetic capacity and metabolic activity to cool night temperature conditions is crucial for improving orchid production in terms of efficient greenhouse heating. The extent to which Phalaenopsis possesses acclimation potential and the mechanistic background of the metabolic processes involved, have, however, not been studied before. Plants were subjected to a direct and gradual shift from a day to night temperature regime of 28/28-28/16°C, the cold stress and cold acclimation treatment, respectively. In comparison with the cold stress treatment, the cold acclimation treatment led to a higher malate accumulation and a reduction in leaf net CO uptake. Consistently, the contribution of respiratory CO recycling to nocturnal malate synthesis was calculated to be 23.5 and 47.0% for the cold stress and cold acclimation treatment, respectively. Moreover, the lower levels of starch measured in the cold acclimated leaves confirmed the suggested enhanced respiratory CO recycling, implying that Phalaenopsis CAM operation evolved towards CAM idling. It is, however, plausible that this adjustment was not an effect of the low night temperature per se but a consequence of cool-root induced drought stress. Apart from that, at the start of the photoperiod, membrane stability showed a depression which was directly counteracted by an increased generation of glucose, fructose and sucrose. From these observations, it can be concluded that the observed plasticity in CAM operation and metabolic flexibility may be recognized as important steps in the low night temperature acclimation of Phalaenopsis. [ABSTRACT FROM AUTHOR]

We have developed an in vitro orchid ( Dendrobium grex Madame Thong-In) system as a model for investigating gene expression during floral transition. Total RNA was isolated from vegetative shoot apical meristems (VSAM) and transitional shoot apical meristems (TSAM). Using the mRNA differential display method, we identified 53 cDNA clones differentially expressed in VSAMs and 16 cDNA fragments specifically expressed in TSAMs. Northern blot analysis confirmed that, on the basis of their transcripts, 12 cDNAs decreased and 8 cDNAs increased during floral transition. Sequence analysis suggested that 5 clones are likely to be transcription factors, including one MADS-box gene of the AGL2 subfamily, one class 1 knox gene and one homolog of the Drosophila seven-up gene. Other clones showed homology with those coding for Arabidopsis SOD copper chaperone, CKI and the tobacco 21D7 protein. [ABSTRACT FROM AUTHOR]

Genetically transformed plants of a phalaenopsis orchid [ Doritaenopsis Coral Fantasy× Phalaenopsis (Baby Hat×Ann Jessica)] were regenerated after cocultivation of cell clumps with Agrobacterium tumefaciens strains LBA4404 (pTOK233) and EHA101 (pIG121Hm) that harbored genes for β-glucuronidase (GUS) and hygromycin resistance. The efficiency of transformation was markedly increased by 10 h cocultivation of cell clumps with A. tumefaciens that had been induced with 200 μ m acetosyringone, and by inclusion of 500 μ m acetosyringone in the cocultivation medium. Hygromycin-resistant cell clusters (0.5–3 mm in diameter) were selected from the infected cell clumps after 4–6 weeks of culture on agar (8 g/l)-solidified new Dogashima medium (NDM) containing 20 g/l sucrose, 0.1 mg/l naphthaleneacetic acid, 1.0 mg/l benzyladenine (BA), 50 mg/l hygromycin and 300 mg/l cefotaxime. The cell clusters proliferated 4 weeks after transfer onto the same medium. To induce callus greening, the carbon source was changed from sucrose to maltose. The green calli obtained produced protocorm-like bodies (PLBs) after 4 weeks of culture on phytohormone-free NDM medium. Regeneration of transgenic plantlets was enhanced by incubating PLBs on NDM medium supplemented with 0.1 mg/l abscisic acid, followed by partial desiccation for 10–30 min. Successful transformation was confirmed by histochemical GUS assay, PCR analysis and Southern hybridization of transformants. With this transformation system, more than 100 hygromycin-resistant phalaenopsis plantlets were produced about 7 months following infection of the cell aggregates. [ABSTRACT FROM AUTHOR]

Spathoglottis plicata seeds were encapsulated in 4-mm-diameter capsules of alginate-chitosan or alginate-gelatin and infected with the mycorrhizal fungus Rhizoctonia AM9. The encapsulated seeds were placed directly on Rhizoctonia culture. About 66% of the seeds encapsulated in sucrose-free chitosan-alginate established a symbiotic relationship with the mycorrhizal fungus after co-culturing for 2 weeks. The highest percentage of infection observed was about 84%. Addition of sucrose or using gelatin-alginate for encapsulation reduced the percentage of infection by about half. The growth of Rhizoctonia AM9 in sucrose-free alginate, chitosan and gelatin was found to be minimal. The advantages of germinating orchid seeds, encapsulated in sucrose-free polymers, through mycorrhizal infection is discussed. [ABSTRACT FROM AUTHOR]

A rapid and reliable micropropagation method was established for Spathoglottis plicata. Nodal and leaf explants dissected from 8-month-old pot-grown seedlings were cultured on charcoal-amended Murashige and Skoog medium supplemented with 16 combinations of α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BA) at concentrations of 0.54–10.74 µ m. Regeneration of protocorm-like bodies (PLBs) and subsequent plantlet development were observed from 98.5% of the nodal explants. Only 6.5% of leaf explants and occasionally some root segments (dissected from regenerated plantlets) were able to produce PLBs and then plantlets. The optimum plant growth regulator (PGR) combination for maximal PLB regeneration was 5.37 µ m NAA and 0.44 µ m BA. The best combination of PGR for plantlet development was 2.69–10.74 µ m NAA and 8.88 µ m BA. The NAA to BA ratios for maximal PLB induction and plantlet development were 12.2 and 0.3–1.2, respectively. Regenerated PLBs and plantlets, when cut into pieces of less than 1 mm and subcultured onto the above media, regenerated new PLBs and plantlets in another 3 months. [ABSTRACT FROM AUTHOR]

The seeds of a Japanese terrestrial orchid ( Bletilla striata Rchb.f.) were germinated and cultured on solidified new Dogashima (ND) medium for 10 days. These embryos were then precultured on ND medium supplemented with 0.3 m sucrose for 3 days at 25°C in continuous dark. The embryos were then overlaid with a mixture of 2 m glycerol and 0.4 m sucrose for 15 min at 25°C and finally dehydrated with highly concentrated vitrification solution (PVS2) for 3 h at 0°C prior to immersion into liquid nitrogen for 30 min. After rapid warming, the embryos were washed with liquid ND medium supplemented with 1.2 m sucrose for 20 min and then plated on ND medium. Successfully vitrified and warmed embryos developed into normal plantlets. The rate of plant regeneration amounted to about 60%. This vitrification method appears to be a promising technique for cryopreservation of orchids. [ABSTRACT FROM AUTHOR]