Nutrient Transport from Root to Leaf

Mr. Barr,
I've read where terrestial plants and emersed plants use the mechanism of capillary action to pull water from roots to leaves. In one article (it may have been on the Tropica website) it was explained that as water evaporates from the leaf surface through exit pores at each "capillary" (there was probably a more scientic term) the vapor action pulled minute quantities of water up to fill the space voided by the evaporated water in the tube. By this action nutrients from the substrate is slowly "wicked" up to the leaves. I've always found it incredilble how tall trees pull tons of water from beneath the ground to distribute it several stories high without any moving parts.

In the case of submerged plants this mechanism clearly cannot function so could you offer any insights as to how aquatic plants move water and nutrients from their roots to their leaves?

This also begs the question of how the plant moves bouyant gases such as Oxygen from leaf downward to the roots?

Cheers,