A comparative biochemical and cytological characterization of normal and habituated sugarbeet calli

Abstract

Habituated sugarbeet callus examined by means of a light-microscope is characterized by absence of differentiated tracheary elements and of the reaction with syringaldazine. Habituated tissues also were found to exhibit low guaiacol- and syringaldazine-peroxidase activities, a deficiency of lignin as well as lower cellulose, dry mass and chlorophyll contents as compared to the normal auxin-requiring callus. These histological and cytological features led to consider this habituated callus as a vitrified tissue under stress. The question of a relationship between vitrification and habituation is posed

Long term in vitro‐cultured plant cells show typical neoplastic features at the cytological level

“…The role of such cell wall ingrowths in the cytoplasm is unclear but they have already been observed in cells, which are deficient in cellulose synthesis (Keller et al, 1994;.This correlates well with earlier studies showing that the HNO cell walls contains very few lignin and cellulose (Crèvecoeur et al, 1987).…”

“…Observations of samples at higher magnification revealed the presence of two types of protuberances at the surface of cells from both calli. The first type of protuberance is large and spherical Table 1 Characteristics, which indicate that cells from HNO callus are cancerous cells MORPHOLOGY Deficiency in cell wall differenciation (Crèvecoeur et al, 1992) Deficiency in chloroplast and mitochondria differenciation (Crèvecoeur et al, 1992) Nuclei with irregular shape and many nucleoli (Hagège et al, 1992a) BIOCHEMISTRY Hyperhydricity (Crèvecoeur et al, 1987) Deficiency of tetrapyrrole-containing compounds (Hagège et al, 1992b) Permanent oxydative stress (Arbillot et al, 1991) Accumulation of polyamines (Hagège et al, 1990 and is called "budding" (Fig. 2 C-D).…”

Vitrification in Micropropagation

“…Less dry weight and more water (Kevers et al 1984;Crevecoeur et al 1987). The additional water in vitrifying tissues was shown to be located in the extraprotoplastic space.…”

“…Less lignin (Daguin and Letouze 1985;Kevers and Gaspar 1985a;Kevers et al 1987). The lower lignification of vitreous plants was associated to lower activities of enzymes involved in the synthesis of lignin precursors and in their polymerization: phenylalanine ammonia lyase (Kevers and Gaspar 1985a;Hegedus and Phan 1987;Letouze and Daguin 1987), hydroxycinnamate CoA ligase (Phan and Letouze 1983;Hegedus and Phan 1987;Letouze and Daguin 1987), coniferyl alcohol dehydrogenase (Letouze and Daguin 1987), acidic and wall peroxidases (Kevers et al 1984;Kevers and Gaspar 1985a;Crevecoeur et al 1987;Letouze and Daguin 1987), flavonone synthase and hydroxyannamate CoA reductase (Hegedus and Phan 1987). Less cellulose , which was associated to a low c/N ratio favoring the synthesis of amino acids rather than the sugar units for cellulose (see below).…”

“…Most stomata of leaves from in vitro plantlets do not seem to have a closure mechanism and this may be the main cause of rapid water loss during acclimatization under low relative humidity (Brainerd and Fuchigami 1982;Dhawan and Bhojwani 1987;Ziv et al 1987). Watery callus types are constituted of parenchymatic cells without xylem elements (Crevecoeur et al 1987).…”