Plant biologist Lena Mueller emerges from a brightly-lit room in a Salk Institute lab, holding a small plant rooted in a very small container of soil.
“This is our little legume that we work with and it looks very sad here because we don’t give it a lot of nutrients because we want it to interact with the fungus,” Mueller said.
But when fungus and plant interact, that’s when the plant gets a lot happier. And Mueller says its heightened exchange of nutrients could be an alternative to the heavy use of fertilizers in American farming.
Growing cash crops in the U.S. means accepting the environmental damage that comes with the use of fertilizer. A lot of it is washed into streams, bays and the ocean, causing algae growth, blocking sunlight and stealing oxygen from aquatic creatures.
The alternative seen in the Salk laboratory is a symbiotic relationship between plants and a soil fungus called arbuscular mycorrhiza — AM for short. The fungus delivers chemical nutrients to the plant, while the plant gives the fungus some of the carbon it pulls out of the air.
That symbiosis is well known but researchers believe they’ve found a way to make it work faster and better. The key is an activating molecule found in plants that drives that bond between plants and AM fungus.
Plant biologist Lena Mueller said they have learned to synthesize the molecule and give plants more of it, by adding it to the soil where it’s absorbed by the roots.
“And we find when we apply it, for example, it amplifies the symbiosis,” she said. “So roots become much more colonized by the fungus when that molecule is added.”
Plant roots can derive nutrients from soil all by themselves, of course, but the AM fungus does it a lot better. Mueller said upon boosting their plants’ activating molecule, they’ve found their leaves contain 200% more of the nutrient phosphate.
The activating molecule is called CLE16.
Mueller says 80% of plants can perform this interaction with fungus. These include corn, wheat, rice and soybeans. In fact, the legume her research team has been testing is very similar to a soybean plant.
The question is whether CLE16, the engine that drives that interaction, could be increased in those varieties of crops.
“We could test our already existing varieties that have been bred for yield (to see) if that molecule would work on them,” she said. “And that would be really exciting.”
Could fungal symbiosis actually eliminate the need for fertilizers? Mueller says probably not. But just reducing fertilizer use would be a strong step in the right direction.
