The effect of Azospirillum brasilense and auxin on root morphology in seedlings of Sorghum bicolor × Sorghum Sudanense

Ely Morgenstern, Yaacov Okon

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Abstract

The purpose of this work was to examine the effect of Azospirillum brasilense inoculation on root development in the hybrid Sorghum bicolor × Sorghum sudanense, and the possible involvement of auxin in this effect.Scanning electron photographs of inoculated roots revealed an increase in root diameter and in the density and length of root hairs. Inoculation of roots with 10s colony-forming units (cfu) per mL caused asymmetric growth of the root tips and shortened the distance between the first root hair formed and the root tip. In non-inoculated roots or roots inoculated with 105 cfu mL-1 the distance was longer.Experiments with suitable concentrations of indoleacetic acid produced changes in root morphology and root hair formation comparable to those produced by inoculation with Azospirillum. These results suggest a possible involvement of auxin in the effect of Azospirillum on root morphology.Root elongation and the rate of root elongation were inhibited by inoculation of germinated seeds with 108 cfu mL-4. IAA at concentration of 10~6 M also inhibited root elongation and the rate of root elongation. In both cases, inhibition began 24 h after tfeatment. Maximum decrease in the rate of root elongation was attained after 60 h.Similar effects on root elongation were obtained with a nif~ mutant of Azospirillum, indicating that nitrogen fixation is not involved in this effect on root morphology. Azospirillum stimulated the appearance of lateral roots.

Original languageEnglish
Pages (from-to)115-127
Number of pages13
JournalArid Soil Research and Rehabilitation
Volume1
Issue number2
DOIs
StatePublished - 1987

Keywords

  • Azospirillum brasilense
  • Indoleacetic acid
  • Root development
  • Root morphology
  • Sorghum bicolor x sorghum sudanense

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