Rate of acetate and mevalonate incorporation by extracts of Pinus pinaster seedlings.
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Seven of ten strains studied produced cytokinin-like substances, mainly in 7 day old cultures. The cytokinin-like substances were most often located on chromatograms at Rf values 0.8 to 0.9, rarely at Rf 0.6 to 0.7.
It was found that synthesis of gibberellin-like substances by ten strains of Coryneform bacteria isolated from the roots of pine seedlings depended on both the composition of the medium and incubation time. More of these substances were produced in mineral medium with glucose in complex medium with casamino acids and yeast extract. Most gibberellin-like substances were found in 7 or 14-day old cultures. Culture supernatant fluids of most of the bacteria tested contained several gibberellin-like substances which on chromatograms run with the solvent system benzene, acetic acid (10:3, v/v) were located at Rf 0.0-0.3; 0.4-0.6 and 0.8-1.0.
It was found that in the presence of sodium succinate synthesis of auxins and gibberellin-like substances by microflora in the rhizosphere of pine seedlings was higher than in the presence of the other carbon sources. The smallest amounts of these substances were found in media with sodium pyruvate. The highest C-content (C:N = 60:1) was not optimal for the synthesis of plant growth regulators. Ammonia ions inhibited the production of gibberellin-like substances. The effect of different nitrogen sources and C:N ratio on the synthesis of auxins was different depending on bacterial strain used.
Cytokinin-like substances were produced in higher amounts by soil isolates than by those isolated from the rhizosphere and mycorrhizosphere. However more bacterial strains isolated from the rhizosphere and mycorrhizosphere were capable of synthesizing cytokinin-like compounds. A distinct effect of pH on the production of these substances was found. It is suggested that zeatin and zeatin riboside are likely to be among the cytokinin-like substances detected.
Among the bacteria studied Arthrobacter globiformis was predominating in the root zone, while in the non-rhizosphere soil most numerous were Bacillus circulans and A. globiformis. Ammonifiers were more numerous among the root zone bacteria than among the root free soil organisms. The reverse was noted with bacteria capable of hydrolysing starch, cellulose, pectin and chitin.
Casamino acids were found to be the best substrate for bacteria isolated from soil, rhizosphere and mycorrhizosphere of pine. Most active with this substrate were however the root zone bacteria. Glucose was oxidized similarly by the bacteria isolated from the three sources.
Studies were performed on the effect of culture medium and incubation time on the production of auxins by bacteria. The bacteria studied produced more auxins in the mineral medium containing glucose and tryptophan than in that enriched with casamino acids and yeast extract. The amount of auxins elaborated depended both upon the strain and the age of the culture. Some strains produced the largest amounts of these substances after 7 days of incubation while others required a longer period. Most of the substances showing auxin activity were located on the chromatograms at Rf 0.3-0.4 and 0.8-1.0.
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It has been found that IAA at the concentrations 0.1--10.0 ppm retards the pine root growth and decreases mitotic activity. All the applied concentrations of this hormone cause a decrease of the 3H-thymidine incorporation index and inhibit endomitotic polyploidization in suprameristematic segments. The mean time of the cell cycle prolongs and the heterogeneity of cellular populations increases in parallel with the increase of IAA concentration. The template activity of DNA decreases under the influence of the applied concentrations of IAA; this effect is being particularly strong in the meristematic root segment. IAA exerts also an inhibitory influence on protein synthesis, especially reducing the synthesis of histones.
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Fungi isolated from mycorrhizae of pine required tryptophan for auxin synthesis. More auxins were found in culture grown with pyrogallol than in those without this compound. The fungi studied produced also auxins from other than tryptophan compounds. Indole employed with serine was more suitable for the production of auxins than indole or anthranilic acid used separately. The active compounds showing auxin activity were located on the chromatograms at Rf 0.2--0.4 and 0.3--0.5 with the solvent system isopropanol, ammonia, water (10:1:1 v/v).
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The effect of ionizing irradiation on the viability of pine stands after the fallout from the damaged nuclear energy plant at Chernobyl (ChNPP) was shown within the territory of the 10-km zone. During the period 1986-1991, irradiated and damaged forest stands, so-called 'red forest', located in this area were systematically classified by observation. Mortality rate, re-establishment, development of tree canopies, reproduction anomalies and stand viability were shown to be dependent on absorbed irradiation dose, on the age of the stand and on forest composition. For pine stands in the acutely affected zone, doses of more than 60 Gy resulted in a massive mortality and no regeneration of pine trees since 1987. The injured trees had burned or had dried-up. The drying process was accelerated by a massive production of pathogenic insects invading the dying trees. Specifically, irradiation doses of 10-60 Gy, 1-10 Gy and 0.1-1 Gy caused high, medium and low injury to the forest stands, respectively. Doses of less than 0.1 Gy did not cause any visible damage to the trees. In 1987, repair processes were displayed by the tree canopies and practically the entire viability of the forest stands had recovered except for trees in the acute and highly affected zones. The young forest was reestablished in the same place as the perished trees and new pine saplings were planted on the reclaimed areas.
The production of gibberellin-like substances by bacteria and fungi was investigated. A considerable number of the microorganisms studied produced these substances (55 and 86% of bacterial and fungal isolates respectively). Most of the organisms tested synthesized biologically active substances located on the chromatograms with the solvent system benzene, acetic acid (10:3 v/v) at Rf 0.05--0.3. The ammount of gibberellin-like substances produced varied in the range 0.00007--0.00065 GA3 equivalents mug/ml in bacteria and 0.00014--0.00118 mug/ml in fungi.