How nutrients get into plants

We know about three mechanisms that roots use to absorb nutrients:

1> root interception: by growth, coming in direct contact with nutrients

2> flow into the plants vascular system (by terrestrial plants which
use evaporation at the leaf and capillary action; don't know if aquatic
plants have a similar process)

3> diffusion via concentration gradients in the local regions around
the rootlets.

How big are those rootlets? How fast do they grow?

Can these rootlets still use capillary action to induce flow even
under water? What makes capillary action work?

If the mechanism for transport into the rootlet is diffusion, wouldn't
this diffusion take place at the same rate as diffusion elsewhere in
the substrate? Does the rate of diffusion depend upon concentration
of ions?

If the edge of an aluminum silicate crystal has a negative charge,
could this act as a conduit for a stream of cations? Imagine a series
of steel bearings attached to a magnetic rod. As you pull one off the
end of the chain, the whole chain shuffles forward.

How does oxygen get transported into the root system? What function
does oxygen perform on behalf of plants in the substrate? Is this
something all aquatic plants do? What about terrestrial plants?