Some plants might be able to grow that way but a better way is to have the root structure in water and maintain humidity so the plant does best and doesnt dry out
yes and no. some plants can be grown emersed.... like swords or crypts. the roots kept wet leafs out of water. i think they need to be kept in water at all time.
i mean like i have this 3 gallon small tank. And i have this amazon sword type plant. i was going to use plant fert gravel from local stores as the gravel. and keep about half the tank full of water which the roots of the stem are still under water.