We conducted an interesting experiment in our Mycology class recently. In one treatment, we inoculated potting soil with mycorrhizal fungi and planted seeds – cucumbers, beans, and corn. The control treatment was the same seeds planted in un-inoculated soil.
The results were dramatic – the inoculated soil resulted in earlier germination and much more rapid growth as you can see in the photographs below. The plants on the right were part of the group inoculated with mycorrhiza.
The root growth was also dramatically different on these bean plants:
Then we prepared slides from the different treatments to see if the differences could be traced to colonization by mycorrhizal fungi in plant root systems. Here is a root from the control treatment. You can clearly see the cell walls and the vascular cylinder in the center of the root that transports water and nutrients to the rest of the plant.
Mycorrhizal fungi have a symbiotic relationship with plants. The fungal hyphae form an underground network that absorbs nutrients, especially nitrogen and phosphorus from organic material in the soil. In exchange for providing access to these nutrients to to plants, the fungi receive energy that the plant produces by photosynthesis. The hyphae actually penetrate into the roots of plants, as you can see in the pictures we took.
This picture shows a root from the soil inoculated with mycorrhiza. The dark areas between the cells are the mycorrhizal hyphae:
The following slideshow explains some of the science behind the mycorrhizal relationship that is found in most plant species and is believed to have played an important role in the initial colonization of land by plants.
Here are some more pictures of mycorrhizal hyphae: