Plants treated with diverse species of fungi that live on roots grew larger flowers, prompting bees to visit them more often and spend more time there.
鈥淸These fungi] might not only have benefits for the plant itself, or for the soil, but also for the pollinators,鈥� says at Stanford University in California.
Guzman and her colleagues grew squash plants (Cucurbita pepo) inoculated with four combinations of different species of mycorrhizal fungi. These fungi live on roots, giving the plant nutrients scavenged from the soil in exchange for carbon.
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Once the plants flowered, the researchers moved them from a greenhouse to an outdoor field. They then followed bees around the field for a week, counting their visits to each plant and how long they spent on them.
Plants inoculated with fungi received an average of 28 per cent more bee visits than plants that hadn鈥檛 been treated. The bees also spent 47 per cent more time on their flowers.
An increase in the treated plants鈥� flower size was the only trait clearly associated with more bee visits, the researchers found. Given that plants and mycorrhizal fungi have evolved together for hundreds of millions of years, it makes sense that the fungi could prompt the plants to grow larger flowers that are better at attracting pollinators. 鈥淚t鈥檚 no surprise that their role goes beyond plant growth,鈥� says Guzman.
Not every fungal treatment worked in the same way, though. The plants inoculated with the most diverse group of fungi saw the most bee visits, but other combinations had different effects. Some prompted the plant to divert nutrients away from flowers to their roots, resulting in fewer bee visits. Other treated plants grew more flowers and produced more nutritious pollen, but these changes weren鈥檛 linked to more bee visits.
鈥淚t鈥檚 nice to see that they found this variability among different types of fungi,鈥� says at the University of Saskatchewan in Canada. That there can be a trade-off between a plant attracting pollinators and supporting fungi suggests these two different symbiotic relationships could have influenced one another鈥檚 evolution, he says.
It could also be useful information for gardeners. 鈥淚f you鈥檙e going to create an inoculant, you want it to be diverse so you cover all your bases,鈥� says Guzman.
New Phytologist
