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Symplast - a) Symplast is the network of highly ordered, connected living axial and radial parenchyma cells in sapwood and inner bark. The symplast stores energy reserves. b) The symplast is the highly ordered, three-dimensional, connected webwork of living protoplasm in trees. It's like a webwork of jelly. The living protoplasm is contained in thin-walled cells called the parenchyma, which have small cell wall openings that act as tunnels where the protoplasm of one cell connects with the protoplasm of adjoining cells. The symplast stores energy reserves. The apoplast (dead fibers and tissues) stores bound water. Trees store their money (glucose), in the form of starch, in the symplast. As the symplast decreases, so does storage space. As storage of energy reserves decrease, so does the defense potential. Pathogens seem to know this very well. In other words, when the tree becomes symplastless, the tree or tree parts, has moved onto another ecological stage. (See TREE ANATOMY, SHIGO, 1994)
    Apoplast, Symplast - Apoplast dead, symplast living – think think think. Apoplast is the dead portions of the tree, the cell walls, the vessels in time, the tracheids in time. I say in time because they are all born alive, but in short time they all die.   Just like the fibers are born alive and the outer bark is born alive and then they die and become a part of the apoplast.
    The symplast –think living – everything is born alive. Then as it stays alive and works many, many, bodies inside the cells keep jiggling if you wish, moving if you wish –that’s what metabolism is all about –highly ordered movement inside the cell in order to utilize energy that is supplied to it.
    Think symplast the living webwork. And wood is living and dead, so what shall we call it? It is a duality of living and dead parts and dying. The living network is primarily the inner contents of the parenchyma cells, the thin walled cells that are still living and contain a nucleus and DNA and other substances. So as we put dyes and materials into trees and inject trees some of the materials move in the apoplast and some move in the symplast. This is the reason why any physiologist never should except a paper where someone injects a dye and then says this is the way the system goes. Because the dye can spread in the apoplast and the symplast. Symplast - living network and Apoplast - dead network.