Roughly 90% of plant species form symbiotic relationships with mycorrhizal fungi. The fungal hyphae extend the plant's effective root surface area by orders of magnitude, trading mineral uptake for carbohydrates.
In forests, mycorrhizal networks connect trees of the same species and sometimes different species. Older trees ("mother trees") appear to preferentially feed seedlings through these networks — though the mechanism and the extent of intentionality (if any) is contested.
The popular "wood wide web" framing is evocative but may overstate the cooperative character of what is ultimately a network of resource exchanges under competitive pressure.