The cells which are closely associated and interacting with guard cells are - (1) Transfusion tissue (2) Complementary cells (3) Subsidiary cells (4) Hypodermal cells
(3) Subsidiary cells Explanation: Guard cells interact physiologically and mechanically with subsidiary cells. Guard cells are those which have chloroplasts and control the opening of stomata. But, subsidiary cells are those which support the guard cells and they do not have chloroplasts.