Abstract: Apoplast is the plant cell compartment external to the plasma membrane which includes the cell walls, the intercellular space and the apoplastic fluid. Apoplast mainly consists of polysaccharides (cellulose, hemicelluloses and pectins), proteins and lignin, and has been demonstrated to be involved in response to different abiotic and biotic stresses. The paper summarizes the roles of apoplastic structural proteins, polysaccharide metabolism proteins, oxidation-reduction proteins and stress-responsive proteins in plant heavy metal tolerance to give a comprehensive understanding of the mechanisms of plant heavy metal tolerance. 

Key words: apoplastic protein, heavy metal tolerance； abiotic and biotic stress