Plant pore. Coloured scanning electron micrograph (SEM) of a closed stoma (dark green) on an anther. Other plant cells are seen around the stoma. A stoma is a pore that regulates the exchange of gases and water vapour into and out of the plant. The highest concentration of stomata is found on the leaves of a plant, but they are also found elsewhere, such as the anthers in this case. An anther, part of a flower, is part of the male reproductive structure of a plant. This stoma is from a chameleon plant (Houttuynia cordata).