Plants do not have such complex respiratory organs, in both animals and humans. However, they also breathe. This process is called gas exchange. He comes through special slits in the leaves and stems - stomata, as well as through cracks in the bark of trees. Once inside, the oxygen passes through the intercellular spaces, then dissolved in water, impregnating the cell wall and penetrate into the cells. With the exception of some species of aquatic plants like water lilies and pods): they have air cavities in their underwater parts.
The need for oxygen in plants less than in animals and humans, but they can experience its shortage. This is especially the case with large instances.
The stoma under the microscope