You will find here a summary of numerous exploratory experiments. Their results highlight avenues worth pursuing or, conversely, avoiding in order not to “waste” time. These experiments can also help formulate hypotheses, which more formal experiments can later confirm or disprove. Researchers and students are encouraged to use this information to design their own protocols. This list of experiments will grow progressively.
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Exp 306 Commercial 30-10-10 Fertilizer
Objective: to determine whether a commercial fertilizer combined with tap water is sufficient to grow mycorrhizal fungi in dishes containing Hortasorb polymer.
Protocol
- Two-compartment dishes with Hortasorb superabsorbent polymer
- Commercial water-soluble 30-10-10 fertilizer, 150 mg/liter of tap water
- M2P nutrient solution
- Rhizophagus irregularis inoculum
- Funneliformis geosporus inoculum
- Host plant Plantago lanceolata
- 11 EU of Rhizophagus
- 12 EU of F. geosporus
Results/Observations
- 6/6 dishes inoculated with R. irregularis and irrigated with M2P colonized well
- 5/5 dishes inoculated with R. irregularis and irrigated with 30-10-10 colonized well (one seedling died and was removed from the experiment)
- 6/6 dishes inoculated with F. geosporus and irrigated with M2P colonized well
- 5/6 dishes inoculated with F. geosporus and irrigated with 30-10-10 colonized, some with weak development
- Polymer hydrated with the 30-10-10 solution swells by a factor of 127, compared to a factor of 75 for M2P
- Dishes hydrated with 30-10-10 dried out considerably faster than those hydrated with M2P
- Many dishes hydrated with 30-10-10 show necrotic root apices, a phenomenon not observed with M2P
Discussion/Conclusion
Plant growth was very rapid, and the dishes irrigated with 30-10-10 dried out (too) quickly, which appears to have harmed F. geosporus, which seems less “fast” than R. irregularis at colonizing roots. Once a root is colonized, both fungi grow rapidly and tolerate drought well. Several F. geosporus dishes showed a marked delay in colonization, likely due to drought; once that issue was resolved, hyphal and spore production returned to normal.
A few hypotheses emerge from this experiment:
- Growing mycorrhizal fungi is possible using a 30-10-10 fertilizer and tap water (City of Québec, Canada).
- Mycorrhizal fungi can be cultured with a wide range of nutrient solutions.
- Nutrient solutions and irrigation regimes affect fungi differently depending on the species.
- The hydration regime and frequency must be adapted to the fertilizer used, since early dehydration of the dishes can skew results.
- P. lanceolata appears sensitive to the type of fertilizer used. The 30-10-10 formulation seems to cause necrosis at the root apices, for reasons that remain unknown.
Survival After an Extended Stay in Refrigeration
An extended absence from the lab, with no one to look after the cultures, gave rise to an improvised experiment: numerous dishes covering different fungal species were placed in the refrigerator, in anticipation that the plants would die, with the intention of restarting the cultures from the colonized roots if necessary. The length of each stay is shown in the table below. Against all expectations, the plants did not perish. The old polymer was then removed and replaced with fresh polymer, to check whether the fungus could recolonize the new substrate. Here are the results and observations 46 days after returning the dishes to culture. Click on a fungus name for more details.
| Fungus | Time in Refrigerator | Observations and No. of Dishes Recolonized/Total |
|---|---|---|
| Funneliformis mossae | 58 days | 2 dishes intensely recolonized + 2 moderately = 4/4 |
| Gigaspora rosea | 46 days | 2 dishes weakly recolonized + 2 not recolonized = 2/4 |
| Funneliformis geosporus | 33 days | 3 dishes intensely recolonized with strong spore production = 3/3 |
| Diversispora varaderana | 53 days | 3 dishes intensely recolonized with spore production = 3/3 |
| Sclerocystis sp. | 53 days | Healthy plants, no new hyphae in the polymer = 0/2. (Update: after 82 days in culture, several hyphae are observable in one of the two dishes, so the result becomes = 1/2.) |
| Rhizophagus irregularis | 58 days | 3 dishes intensely recolonized with spore production = 3/3 |
| Rhizophagus sp. | 33 days | 1 dish densely recolonized, 1 dish lightly recolonized, and 2 dishes with no evidence of recolonization = 2/4 |