Iris leaf surface. Light micrograph of the surface of the leaf of an iris, Iris germanica. Several stomata are visible as yellow gaps between two kidney shaped orange guard cells. Long epidermal cells run diagonally across the image. Guard cells open and close the stomata depending on light, temperature and the internal water supply of the leaf. Open stomata allow gases to be exchanged by leaf tissues during photosynthesis. When closed, stomata can prevent water loss during dry periods. Irises are extremely popular garden plants and many varieties have been cultivated. Magnification: x85 at 35mm size.