In vitro biological tests show that excreta or gross total and partial extracts of Lumbricus terrestris stimulate rhizogenesis and enhance root growth in young plants of the bean Phaseolus vulgaris. Similar results were obtained in experiments with worms freshly collected in the field and with worms previously deprived of food for 4 weeks. The rhizogenous substance produced by the worms is therefore not of exogenous origin, coming from the soil via the digestive tract. The similar effects of indol acetic acid at different concentrations and of excreta and gross extracts of worms in various dilutions indicate that the rhizogenous substance is similar to indol acetic acid, a well-known phytohormone in plants. Expressed as indol acetic acid equivalents, the quantity of the rhizogenous substance in worms would be approximately 18 × 103 ng/g, of which half (9 × 103 ng/g) is released in the excreta alone.[Journal translation]

In vitro application of total gross extract of earthworms (Lumbricus terrestris) in diverse dilutions stimulates rhizogenesis in young bean plants (Phaseolus vulgaris). The observed effect is similar to that of indol acetic acid, a well-known growth enhancer in plants, used here as a control in various concentrations. Fragmentation of worm extract by column chromatography results in three groups of fractions. Only the polar group of fractions has a significant rhizogenous effect, which is, however, inferior to that observed in the presence of total gross extract of worms or of indol acetic acid. Gross extract analyses using thin layer chromatography, with appropriate chromatography systems and reagents, revealed that indol acetic acid is not present, but is probably replaced by other indol-derived substances that have a neutral to basic chromatographic behaviour. These presumed indol-derived substances are identified as methyl-tryptophane, serotonin, and hydroxy-indol acetic acid. Analyses using mass spectrometry combined with gas chromatography, following fragmentation and purification of the group of rhyzogenous fractions, have revealed the presence of hydroxy-indol carboxylic acid, which seems to take the form of several isomeres.[Journal translation]

Earthworms have become a potential source of multi‐beneficial bacteria and effective bioinoculants. Seed biopriming is an efficient inoculation method to apply bacteria prior to sowing, which enhances the chances of bacterial candidates to colonize the rhizosphere and/or establish a liaison with the plant. In this study, we evaluated plant growth‐promoting traits of bacterial strains isolated from the earthworm’s Aporrectodea molleri chloragogenous tissue. In addition, we investigated their prospective use as biopriming agents to enhance Zea mays germination and seedling growth. Results were subjected to principal component analysis for potential correlations between the studied parameters. The bacterial strains displayed different in vitro plant growth‐promoting characteristics and were efficient when applied in vivo as they significantly increased maize germination rate (26–78%), root elongation (67–84%), seedlings fresh weight and dry weight. Aeromonas encheleia TC22 was the most significant strain to influence germination due to its high ability to produce indole‐3‐acetic acid, and along with Pseudomonas azotoformans TC1, they were the most proficient at enhancing seedling root elongation and biomass, which was significantly correlated with their in vitro plant growth‐promoting traits. Our findings indicate that isolates TC22 and TC1 are potent bio‐primers for maize seeds and should be tested further for their use as biopriming inoculants.

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