Question

Anyone know a good way to remember the difference between symplastic and apoplastic transport in a plant?

Answer 1

Remember the basic structure of the plant cell: cell surrounded by a cell wall. Plant cells are connected by plasmodesmata, and so share a common cytosol.

Now, think about this basic description, then look at the room your in. You are surrounded by walls, which then go to the door. The frame of the door is continuous with the wall, and will be continuous to the walls of the next room, right?

Now, the symplast is the actual living cell, and is defined by the cell MEMBRANE. The space between the membrane and cell WALL is the apoplast.

Now, back to your room. Imagine that your room wall filled with a giant balloon, with you in the balloon. It is blown up so that it touches all the walls. The space between the balloon and the wall is the apoplast. You, standing in the balloon, are in the symplast.

Now, apoplastic flow is the flow of water around the outside the cell membrane, in other words, in that space between the cell membrane and wall. It is a form of capillary flow.

Symplastic flow is movement within the cell. Remember the plant's cytosol is continous thanks to the plasmodesmata. So, materials in the symplast can move from one cell to the next within the cytosol.

So, apoplastic flow is movement on the outside of the cell membrane, while symplastic is flow within the cell membrane.