New roots function to take up water so root hairs which cannot be waxy and do their job. At different times of the year or different times of day the liquid in the same vessels may reverse direction. Photosynthate is moved from source to sink. In spring the source is the roots and the sink is the growing leaves, in summer and fall the source is the leaves and the sink is storage in roots, deposited in fruits and maturing seeds. For functions other than support the filling is considered to be random but cells take on the shape of bubbles in a cluster so physicists would say that this is not a random distribution.
Support function is carried out by cells in fibrous bundles.
Cells types may be discussed based on 1. This compartment has contact with the cell wall compartments of all cells around it and together the cell wall compartment forms a system continuous through out the plant. This compartment is isolated with in the cell. Plasmodesmata for integration and communication. A pore between the cells penetrating the cell walls of both cells, plasma membrane is continuous from cell to cell, cytoplasm streams between cells, diffusion of material can occur between cells without crossing membranes, and fingers of endoplasmic reticulum may extend through the plasmodesmata such that proteins manufactured in the endoplasmic reticulum of one cell may be release in the neighboring cell.