R. Van Parijs

Effect of Light on Nucleic-acid Synthesis and Polyploidy Level in Elongating Epicotyl Cells of Pisum sativum

The synthesis of DNA and RNA and the increase in dry matter were followed in the elongating cells of the epicotyl of peas (Pisum sativum L.) germinating in total darkness or in continuous light. The amounts of DNA and RNA per epicotyl were estimated by chemical methods, the amount of DNA per cell was measured by histophotometric techniques. The increase in DNA, RNA and dry matter in the epicotyl cells is much higher during germination in darkness than in light. During elongation in the dark most cortical epicotyl cells reach the 8C polyploidy level, in the light only the 4C polyploidy level is reached. A decrease in RNA synthesis is in agreement with a reduction in nuclear volume.SummaryThe synthesis of DNA and RNA and the increase in dry matter were followed in the elongating cells of the epicotyl of peas (Pisum sativum L.) germinating in total darkness or in continuous light. The amounts of DNA and RNA per epicotyl were estimated by chemical methods, the amount of DNA per cell was measured by histophotometric techniques. The increase in DNA, RNA and dry matter in the epicotyl cells is much higher during germination in darkness than in light. During elongation in the dark most cortical epicotyl cells reach the 8C polyploidy level, in the light only the 4C polyploidy level is reached. A decrease in RNA synthesis is in agreement with a reduction in nuclear volume.

Underreplication of repetitive DNA in polyploid cells of Pisum sativum

Abstract Earlier reported results of a difference in the amount of DNA between 2C meristematic plumula cells and 2C cortex cells of the epicotyls are confirmed by fluorometric Feulgen-DNA determinations. Renaturation experiments of isolated DNA suggest that this difference in DNA is probably correlated with an underreplication of some highly repetitive DNA sequences in cells preparing endomitosis.

A new uv-sensitive heterocyclic amino acid frott pea seedlings : 2-alanyl-3-isoxazoliin-5-one

Abstract A new α-amino (compound I) has been isolated and purified from pea seedlings. The chemical structure was analyzed by chemical methods and by spectroscopy. The structure was found to be 2-alanyl-3-isoxazolin-5-one. Some properties of this compound were compared to those of synthetic isoxazolin derivatives. The mono-acetyl derivative of I was synthesized. The compound is very sensitive to UV-irradiation.

The isolation and structure analysis of 2-(2-cyanoethyl)-3-isoxazolin-5-one, 2-(β,D-glucopyranosyl)-3-isoxazolin-5-one and 2-carboxymethyl-3-isoxazolin-5-one from Lathyrus odoratus

Three 2-substituted isoxazolin-5-ones have been isolated from Lathyrus odoratus seedlings. Structural analysis by spectrometric and chemical methods determined their formulas as 2-(2-cyanoethyl)-3-isoxazolin-5-one, 2-(β,D-glucopyranosyl)-3-isoxazolin-5-one and 2-carboxymethyl-3-isoxazolin-5-one. The structures of the first two compounds were confirmed by their chemical synthesis.

Effect of light on cell elongation, nucleic acid and protein synthesis in hypocotyls of Lupinus angustifolius

SummaryThe synthesis of DNA, RNA, protein and dry matter was followed in the elongating cells of hypocotyl of Lupinus (Lupinus angustifolius L.) germinating in total darkness or in continuous light. Light strongly inhibits the synthesis of DNA, RNA and protein. It was shown by histofluorometric DNA determinations that a reduced synthesis of DNA in continuous light is accompanied by a lower level of endomitosis in the cortex cells of the hypocotyl. In the dark cortex nuclei become 8 C while in the light they become only 4 C. The more pronounced differences between dark and light germinated hypocotyls of lupinus in comparison with pea epicotyls is explained to a great extent by mitotic growth.

Endomitosis and the effect of gibberellic acid in different Pisum sativum L. cultivars

The evolution of the total amount of DNA in epicotyls and of the amount of DNA per cell nucleus in epicotyl cortex cells during germination was followed in two closely related pea varieties, Pisum sativum cv. Finale and Pisum sativum cv. Rondo. Under etiolating conditions, growth of the cv. Rondo occurs only by cell elongation which is preceded by endomitotic DNA synthesis, while in the cv. Finale growth is the result of cell elongation accompanied by endomitotic DNA synthesis and cell division. The maximum C-level attained in both cultivars under etiolating conditions is 8 C (C=haploid amount of DNA in a gamete cell). Both the maximum C-level reached and the percentage of cells reaching this C-level seem to be under strict genetic control. In both cultivars, light inhibits the endomitotic DNA replication.Neither gibberellic acid (GA3), nor AMO 1618 alter the maximum C-level or the percentage distribution of the C-classes. Both growth regulators are effective, although in an opposite way, only in tissues where cell division occurs or where endomitotic DNA synthesis is blocked, as in light-grown pea epicotyls.

Isolation and characterization of 2-(β,D-glucopyranosyl)-4alanyl-3-Isoxazolin-5-one : A second UV-sensitive heterocyclic α-amino acid from Pisum sativum L.

Abstract In addition to 2-alanyl-3-isoxazolin-5-one (I) an other UV-sensitive heterocyclic α-amino acid (III) has been isolated and purified from pea seedlings. Some properties of III are compared with those of synthetic isoxazolinone derivatives and with those of I. The chemical structure was analyzed by chemical methods and by spectroscopy. The structure was found to be: 2-(β,D-glucopyranosyl)-4-alanyl-3-isoxazolin-5-one.

The origin of wound-induced satellite DNA in pea seedlings

DNA synthesis in wounded pea seedlings was studied by incorporation of [6-3H]-thymidine. It was shown that the satellite DNA, synthesized within the first two days after wounding, is not of plant origin, but produced by contaminating bacteria, although a strong sterilizing procedure was used. Main-band DNA synthesized after wounding seems to be the only plant DNA synthesized during the stress-period.

Characterization of the DNA Synthesized in Pea Seedlings after Wounding

Summary The characteristics of the newly synthesized main-band DNA in wounded and control pea seedlings were studied by analytical and preparative CsCl density gradient centrifugation in neutral and alkaline conditions, by Cs2SO4 gradient analysis in the absence or presence of Ag+ and Hg2+ in different concentrations, by examination of thermal denaturation, using the spectrophotometric technique or column chromatography on hydroxylapatite and by polyamino acid-kieselguhr column chromatography. The base composition calculated from the melting point is 43.2% GC and differs from the composition deduced from the density (35.7% GC). This discrepancy is caused by the presence of 4.9 to 5.3% 5-methylcytosine. All experiments show the similarity of the newly synthesized DNA (radioactivity profile) and the total DNA isolated from wounded and unwounded tissues (UV absorbancy) and point to the conclusion of a random base distribution in the pea genome. The presence of an AT or GC rich satellite DNA could not be demonstrated, even using selective Ag+ or Hg2+ complex formation and Cs2SO4 gradient centrifugation in conditions which reveal such DNA in other plant species.

New isoxazolinone amino acids from Lathyrus odoratus seedlings.

Abstract In addition to β-(isoxazolin-5-one-2-yl)-alanine (I) and β-(2-β-D-glucopyranosyl-isoxazolin-5-one-4-yl)-alanine (III), previously found in Pisum sativum seedlings, two new amino acids and an amine containing the same heterocyclic ring have been isolated from Lathyrus odoratus seedlings. Their structures were determined as α-amino-γ-(isoxazolin-5-one-2-yl)-butyric acid (VI), 2-aminoethyl-isoxazolin-5-one (VII) and the γ-glutamyl derivative of the latter (V).