Leaf Pore of Grasses (IMAGE) University of Würzburg Caption Processes in a leaf pore (stoma) of grasses. When the leaves open and close, a shuttle service takes ions to and fro between guard cells and subsidiary cells. Credit (Picture: Dietmar Geiger) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.