Briefly describe the apoplast and symplast pathway.
Apoplast pathway - It is the system of adjacent cell walls that is continuous throughout the plant, except the casparian strips of the endodermis of the root. It does not involve crossing of the cell membrane. 

Symplast pathway - It is the system of the interconnected protoplasts. Neighbouring cells are connected  through the cytoplasmivc strands that extend through the plasmodesmata. It involves crossing of the cell membrane.