Previous studies have shown that Azospirillum or its culture filtrates induce root hairs in wheat seedlings to branch; this phenomenon is influenced by the bacterial genome at the strain level and by the plant genome at the cultivar level. Strain Sp245 caused most branching of root hairs; between wheat cultivars frequency of branching increased in the following order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Similarly, plant growth response to inoculation with Azospirillum, measured in mature plants, increased in the same order, suggesting that both phenomena (root hair branching and plant growth response) have a similar basis. In this study, the "branching substance" present in Azospirillum culture filtrate was found to be thermostable at 100 °C, removed by dialysis, present in the acidic nonpolar fraction of the cell-free extract, and co-chromatographed with authentic indole acetic acid on thin-layer chromatograms. Purified indole acetic acid caused branching of root hairs similar to that caused by the Azospirillum culture filtrates. Susceptibility of wheat cultivars to indole acetic acid induced branching increased in the order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Of five strains examined, strain Sp245 produced the most indole acetic acid in culture in the presence of tryptophan. The presence of indole acetic acid was confirmed by gas chromatography – mass spectrometry.
No takes yet. Share an insight, caveat, or question.
Jain et al. (1985) studied this question.