Production of Plant Growth Substances by Azotobacter chroococcum

Abstract

S U M M A R YCultures of Azotobacter chroococcum strain A6 were grown for 14 days in a nitrogen-deficient mineral medium, the supernatant fluid and bacteria extracted and examined by paper partition chromatography with two solvent systems which separate authentic gibberellin (GA 3) and indolyl-3-acetic acid (IAA). Gibberellin-like substances were not detected on the chromatograms examined under ultraviolet (u.v.) radiation, but were detected when chromatograms were cut into ten equal strips representing a sequence of RF values and the eluates tested in dwarf pea and lettuce hypocotyl bioassays. Certain eluates applied to the roots of tomato seedlings also altered the later growth of stems, leaves and flowers. The Azotobacter cultures contained three gibberellin-like substances, of which probably the dominant was one with an RF value similar to that of GA 3 ; the other two were not identified. The average concentration of gibberellin/ml. culture was 0.03 pg. GA 3 equivalent. The gibberellins in Azotobacter cultures probably cause the reported effects on plant development and yield when seeds or roots are inoculated with Azotobacter. Plant growth may also be affected by synthesis of further gibberellins in the root zone when the Azotobacter inoculum colonizes developing roots.

In vitro establishment of nitrogen-fixing strawberry (Fragaria × ananassa) via artificial symbiosis with Azomonas insignis

“…Azomonas, like Azotobacters in general, provides reduced nitrogen source mainly as ammonia, amino acids, and vitamins (Newton et aI., 1953;Karube et al, 1981;Kuhla et al, 1985), but also exudes plant hormones (heteroauxins) (Brown and Burlingham, 1968). Plant cells may supply the bacteria with carbon and energy source, transforming the sugars presented in the media during the in vitro period and photosynthesizing later, in the ex vitro phase.…”

Differences in Endogenous Levels of Gibberellin-Like Substances in Nodules of Phaseolus lunatus L. Plants Inoculated with Two Rhizobium Strains

“…Free-living bacteria, including Rhizobium, have been shown to produce GA-like substances (1,11,23,25), and gibberellins may also be produced by plant roots (2,9,20).…”

Evaluation of Maize Nutrient Contents in a Maize/Cowpea Intercropping Systems in South Africa

“…However it doesn't produce any effect on the growth of the roots. 31 Brown et al, 32 have found that after treating tomato seeds or seedling roots with small amounts (0.5-0-01pg.) of commercially produced gibberellins GA 3, the plants responded in the same way as after treatments with 14-day cultures of Azotobacter chroococcumstrain A 6.…”