A Simple Reliable Protocol for Cytogentically Stable Mass Propagation of Ornithogalum virens Lindl.

Ornithogalum virens is a plant of horticultural importance but recently researches are focused on its medicinal importance. A simple reliable protocol has been standardized for micropropagation of O. virens to produce a cytologically stable progeny with least polysomatic variation of chromosome number. Among different explants, bulb scales showed the maximum potential for organogenesis. From a single bulb scale 37 bulblets have been produced within 16 weeks of inoculation. A low concentration of auxin with different concentrations of cytokinin is suitable for organogenesis. A higher level of auxin induces callus formation. Bulblet production was the maximum in the medium supplemented with 0.5 mg/l NAA and 2 mg/l 2iP. O. virens normally has a chromosome number of 2n=6. In nature it shows a common occurrence of polysomaty. The somatic plates that deviate from normal 2n=6 specially 2n=12 are of quite common occurrence (approximately 18?25% per root tip). Strikingly the tissue culture regenerants show a uniform chromosome number 2n=6, frequency of polyploidy being negligible. RAPD profile of the explants and its regenerants are almost same. Five primer sets give more number of bands with explants’ DNA. Moreover, the intensity of the bands of source plant is sometimes more than that of the regenerants. This may coincides with the fact that in the source plant the somatic chromosome number is 2n=6 and 12, whereas in regenerants it is 2n=6.Plant Tissue Cult. & Biotech. 26(1): 1-14, 2016 (June)

Localization of actin in pollen tubes of Ornithogalum virens L.

The germinating pollen grain (in vivo on the stigma or in vitro in germination medium) forms a pollen tube which transports the vegetative nucleus and generative cell/two sperm cells participating in the process of double fertilization. The growth of the tube and the transport of organelles and the cells occur due to two major motor systems existing in the pollen tubes of higher plants: the tubuline-dynein/kinesin and the actin-myosin system. In pollen tubes of <em>Ornithogalum virens</em> the actin filaments were labelled with TRITC-phalloidin (2 µg/ml) in the PIPES buffer and the 10% sucrose, without the fixative and DMSO. Omission of the fixative and permeabilizing agent (DMSO) allowed better preservation of the structure, and the "fluorescence" of actin was observed in living pollen tubes. Observations in CLSM (confocal laser scanning microscope) showed that actin is distributed in the vicinity of the cell membrane. This could support the view that actin filaments and the plasmalemma form the pollen tube cortex along which the cytoplasmic movement of organelles, and cell transport occurs.

Specific end-to-end attachment of chromosomes in Ornithogalum virens

C-banding of nonhomologous chromosomes in haploid generative nuclei of Ornithogalum virens (n = 3) reveals a high degree of specificity with respect to end-to-end connexions. The centromeric end of chromosome 2 preferentially associates with the centromeric end of chromosome 3 and the telomeric end of chromosome 3 associates preferentially with the telomeric end of chromosome 1. This same association of nonhomologous chromosomes persists in prophase nuclei of diploid root tips. In addition, the telomeric ends of the 2 chromosome 2s are connected to one another as are the centromeric ends of the chromosome 1s. This results in a ring of chromosomes in which homologues lie opposite one another. Centromeric ends lie on one side of the nucleus and telomeric ends on the other. It is proposed that this specific association of chromosome ends reflects an order which was probably established at the preceding anaphase or telophase and which persists throughout interphase. The suggestion is made that the proximity of homologous ends and consequently homologous alignment may facilitate initiation of pairing at meiosis.