Apoplast

Apoplastic (red arrows) and symplastic (green) vehicles

Apoplast is an extracellular structure in higher plants composed of cell walls and intercellular spaces . In the apoplast, due to the capillary forces arising between the elements of the cell wall, soil and sediment moisture and all substances dissolved in it (for example, mineral salts and humic acids ) are transported. Apoplastic transport is blocked in the hydrophobic parts of the cell walls: Caspari belts , airways and cuticles . Unlike symplastic transport , apoplastic transport does not directly consume plant energy.