Not long ago I read an article that suggested that true symbiosis does not exist . . . that what we have thought to be mutually beneficial relationships between plants are actually mycorrhizal. I can't remember now whether I read it on the Forums or somewhere else and hoping that someone can give me a lead. I can't find anything so far on the web.
Both mycorrhizal and beneficial. Although they can spend part of their life cycle as free-living organisms, mycorrhizal fungi always associate with the roots of higher plants, indeed over 90% of plant species, including forest trees, wild grasses and many crops. Both partners benefit from the relationship: mycorrhizal fungi improve the nutrient status of their host plants, influencing mineral nutrition, water absorption, growth and disease resistance, whereas in exchange, the host plant is necessary for fungal growth and reproduction. Above excerpted from: Mechanisms underlying beneficial plant–fungus interactions in mycorrhizal symbiosis | Nature Communications .......................................................................... Insight into mycorrhizal relationships has been provided by Forum members, to wit and for example, our own Tom Hulse: Below excerpted from his post #7 on thread New to jade plants (and forums!) Discussion in 'Cacti and Succulents' started by cpainter30, Sep 24, 2020. Did you know that roots, by themselves, usually can't grow small and fine enough to take up the nutrients they need? They use fungus at the smallest level to grab those nutrients and make them available in what are called mycorrhizal associations with different kinds fungus. ----and our own Acerholic: Transplanting maples in Autumn/ Spring Discussion in 'Maples' started by Acerholic, Oct 10, 2020. Post#4: 8. Additives, yes I use an additive, it's Mycorrhizal to aid root growth. This is dusted over the root ball before potting up. Many references to this subject can be Forum-searched. Perhaps some of our knowledgeable members (Frog...?) may provide further insight and information.
I'm not sure I understand the question. Is it: do beneficial direct plant-to-plant relationships exist? Or are they always in association with a fungal intermediary? Mutualism (where both organisms benefit) is not common in plant-plant, but here's an example: Mutualism between co-occurring plant species in South Africa's Mediterranean climate heathland is mediated by birds - PubMed . Apparently there are other examples in dune environments, e.g., (PDF) Plant–Plant Interactions in Coastal Dunes (under the 13.2 Facilitation discussion) Commensalism (where one benefits and the other isn't negatively affected) is far more common.
Recent research into the mutualistic relationship between Beauvaria bassiana indicates a more complex relationship with plant roots than previously known. B bassiana is an entamopahogenic fungi that parasitizes insects and creates fruiting bodies on them to complete the reproductive cycle in favourable climates. This is of a commensual benefit to plants when the insects being parasitized are involved with herbivory. We now understand that this fungi has an endophytic relationship with plant roots with exchange of nutrients and photosynthates. So the fungi eats the bugs and feeds them to the plant. Pretty cool.