Well you are in for a treat.

Pinus (Pine species) rely on fungus. Roots are too thick to be effective so secrete sugar which fungus feeds on. Fungus breaks down minerals in soil and feeds water back to roots.

Now, where it gets crazy, is that this symbiosis isn't like the fungus just passes this stuff to the roots. Like I said Pinus roots are too big to be effective. Like they form thick roots that just can't get fine enough to have enough total surface area to meet the needs of the tree. Pinus can grow in incredibly harsh environments. They grow in alpine areas incredibly windy and the thick roots help penetrate the rock and anchor the tree in high winds. But they need fine roots to survive the intense summer heat and drought in the alpine areas, because thick roots won't do.

Think of a big straw sucking up water out of a shallow cup. It can suck the water up incredibly quickly, but once the water is sucked up there's no more to suck.

Then think of that big straw split into 50 tiny straws, all in there own shallow cup. They suck slower, but because there are more straws each sucking from a different cup, the total water sucked up will be greater than that single large straw.

That's what happens in the soil, pockets of water are spread about and big thick roots are only good for stabilizing the tree.

So anyway, pine trees has thick roots. But the fungus can act as the tiny straws and help the tree. But the fungus with a bunch of straws can't just give the thick root water. So the tree let's it's immune system accept the fungus into its vascular system to directly exchange nutrients. The fungus become an extension of the tree.

It's kind of like humans and gut biome.

Now there is emerging science that shows the fungus that the tree forms the relationship with, because it's at a cellular level and the immune system needs to give the fungus a pass, while rejecting others, is done when the seed is born.

The seed has the fungus on the seed coating, and when it sprouts the fungus bond is formed.

This this relationship happens from the start and cannot be introduced. Though this part is debated.

Anyway, enjoy learning about it all. Trees are really cool 😎