Seed structure (IMAGE) University of Zurich Caption Seed structure with a large central cell in the center (cell nucleus in yellow) surrounded by the tissue of the mother plant (purple). The mature central cell (left) is in a quiescent state until fertilization reactivates the cell cycle and the cell nucleus divides (right) to form the nutritive tissue. Credit Sara Simonini, University of Zurich Usage Restrictions none License Original 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.