Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings.

Seeds of Pisum sativum L. cv Finale and Lathyrus odoratus L. cv Spencer were germinated aseptically in moistened sand in the dark. At several stages, the amino acid composition of the exudate and of the corresponding roots was analyzed. A number of common amino acids, including homoserine, were exuded by the growing seedling root in an early stage and were partly reabsorbed later. A number of uncommon amino acids, including several isoxazolin-5-one derivatives, uracil alanines, l-gamma-glutamyl-d-alanine, and alpha-aminoadipic acid were exuded at different rates.

A high amount of satellite DNA in the genome of Lupinus angustifolius L.

Embryo DNA, isolated from ungerminated seeds of Lupinus angustifolius L., contains an exceptionally high amount of guanine-cytosine-rich satellite DNA. The thermal denaturation curve of total embryo DNA is biphasic with an inflexion point at 62% denaturation, indicating the presence of satellite DNA. The satellite fraction could be separated from the mainband DNA by three successive preparative CsCl-gradient centrifugations. The densities of the DNA fractions are 1.7045 g cm(-3) and 1.6925 g cm(-3), respectively. The percentages of guanine-cytosine calculated from these densities are comparable to the percentages of GC calculated from the melting temperatures. Finally, ressociation studies prove that foldback DNA and highly repeated sequences are much more frequent in the satellite DNA fraction than in the mainband DNA.

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.

Stimulation of Endomitotic DNA Synthesis and Cell Elongation by Gibberellic Acid in Epicotyls Grown from Gamma-irradiated Pea Seeds.

Large doses of gamma-irradiation, given to air-dried pea seeds, inhibit the endomitotic DNA synthesis in pea epicotyls during germination in darkness. The cortex cells of the etiolated epicotyls reach only the 4 C DNA level, whereas cortex cells of unirradiated seeds reach the 8 C DNA level. Epicotyl elongation and cell elongation are also reduced.Application of gibberellic acid restores the endomitotic DNA synthesis and the cell elongation in epicotyls of irradiated seeds. The cortex cells reach again the 8 C DNA level in darkness.The results suggest that gamma-irradiation blocks endomitotic DNA synthesis and cell elongation by lowering the concentration of endogenous gibberellins.

The presence of minor histone components in the chromatin of Pisum sativum L. seedlings.

Two minor basic protein components (M1 and M2) were found in the histone extract from chromatin of pea seedlings. In the histone extract of pea cotyledons only one minor component (M1) was detected. These minor components show a high affinity for chromatin, have a molecular weight of 20.200 and 17.800 respectively and a basic amino acid composition. They are not contaminants of cytoplasmatic origin. Two similar minor components were found in the chromatin of Pisum arvense and Lens culinaris-seedlings, one component was present in the chromatin from cotyledons of these species.

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

The 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.

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.