Genome plasticity during the acquisition of embryogenic competence.

Hypocotyl explants from carrot and other species experience concomitant segregation events and differentiation of homeotic structures during the first 20 days of culture on 2,4-dichlorophenoxyacetic acid (2,4-D). In addition to these cyto-morphological changes, significant amounts of nuclear DNA are lost, the molecular details of which we investigate in this paper. We have developed a slot-blot analysis assay to study the DNA content of a series of carrot samples; besides the leaves, this survey ranged over different culture timepoints: hypocotyls, cell lines, and somatic embryo stages.

Stimulation of carrot somatic embryogenesis by proline and serine.

Serine and proline, when added in a wide range of concentrations to Daucus carota cultures during pre-growth in the presence of 2,4-D(2,4-dichlorophenoxyacetic acid), extended in time and quantity the mitotic divisions and stimulated significantly the number of embryos regenerated when the hormone subsequently was omitted from the medium. A specific effect of these amino acids on regeneration is suggested, since proline (as hydroxyproline) and serine are the two major constituents of the cell wall glycoprotein, extensin, which thus may have a morphoregulatory function. The significant role of the conditions during pregrowth of the cultures in the presence of hormone is underlined by the effect of hydroxyproline and D-proline which also stimulate embryogenesis, but alter markedly the development of the embryos.

[Chromosomal variability of 2 species of Nicotiana in fluid culture].

The chromosomal number in relation with the age of suspension culture of nicotiana glauca (NG) and the non tumorous N. glauca x N. langsdorffii hybrid has been studied.

Genetic effects of griseofulvin on plant cell cultures.

Griseofulvin induces metaphase arrest and polyploidization in plant cells in culture; after which a process of chromosome segregation follows. During this process spontaneous or induced recessive mutations become expressed through the formation of homozygotes or monosomics. This finding can be of use whenever the isolation of recessive mutations is needed and haploid culture is difficult.