Component of the exocyst complex involved in the docking of exocytic vesicles with fusion sites on the plasma membrane during regulated or polarized secretion. Involved in polarized cell growth and organ morphogenesis. During cytokinesis, involved in cell plate initiation, cell plate maturation and formation of new primary cell wall. Probable component of an exocyst subcomplex specifically involved in autophagy-related, Golgi-independent membrane traffic to the vacuole. Regulates autophagosome formation and autophagy-related Golgi-independent import into the vacuole. Mediates ABCG36/PEN3 outer-membrane polarity at the periphery of lateral root cap and root epidermal cells (PubMed:27803190). The exocyst complex is composed of SEC3, SEC5, SEC6, SEC8, SEC10, EXO70A1 and EXO84B. Interacts with SEC6, SEC10, SEC15B and EXO70A1. Interacts with EXO70B1. Localized to globular structures in the perinuclear region (PubMed:19895414). During cytokinesis, localizes to the nascent cell plate and later to the cell plate insertion site and along the post-cytokinetic wall (PubMed:20870962). Polarized localization at the outermost side of root epidermal and cap cells, in the outer lateral membrane domain facing the environment (PubMed:27803190). Sterile plants with extreme dwarf phenotype and cytokinetic defects, and accumulation of vesicles in leaf epidermal cells (PubMed:20870962). Impaired trafficking and endocytic recycling of ABCG36/PEN3 between the trans-Golgi network and the plasma membrane in root epidermal and cap cells leading to a strong intracellular accumulation of ABCG36/PEN3 and lost ABCG36/PEN3 outer lateral plasma membrane polarity (PubMed:27803190). Belongs to the EXO84 family.