Specialized epidermal cells surrounding the guard cells are called:

As subsidiary cells and guard cells both are the modification of epidermal cells in which guard cells have chloroplasts which is absent in surrounding subsidiary cells. Subsidiary cells are the accessory cells to guard cells in the epidermis of plants. Two or four subsidiary cells are found surrounding the pair of guard cells. Subsidiary cells do not consist of chloroplasts. They provide support for the functioning of guard cells in the epidermis. Subsidiary cells play a role in ion channel-mediated opening and closing of guard cells.